All's not as it appears, this tale has many twists -
but if I wasn't here documenting the story
would that mean that the plot did not exist?

— Peter Hammill

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Even the Quiet Supermassive Black Holes are Blasting out Neutrinos and Gamma Rays

Wed, 09/29/2021 - 5:00pm

Is there anywhere in the Universe where we can escape from radiation? Certainly not here on Earth. And not in space itself, which is filled with diffuse radiation in the form of gamma rays and neutrinos. Scientists have struggled to explain where all those gamma rays and neutrinos come from. A trio of researchers is proposing a source for all that radiation in a new paper: resting black holes.

Supermassive Black Holes (SMBH) likely reside in the center of every large galaxy like the Milky Way. When those SMBHs are actively accreting matter they can spew out a lot of radiation across the entire spectrum, from radio waves to gamma rays. When that happens they’re called active galactic nuclei. But what about SMBHs that are quiet?

A new study says even quiescent SMBHs are emitting gamma rays and neutrinos. The discovery helps explain why the Universe is awash in energetic particles.

The title of the paper is “Soft gamma rays from low accreting supermassive black holes and connection to energetic neutrinos.” It’s published in the journal Nature Communications, and the lead author is Shigeo Kimura from Tohoku University in Sendai, Japan.

Active galaxy nuclei like this one spew out a lot of radiation. Astronomers think some of the Universe’s diffuse radiation comes from more sedate black holes. Credit: NASA/Dana Berry, SkyWorks Digital

Neutrinos are nearly massless subatomic particles and are electrically neutral, which is where they get their name. As a result, their gravitational interaction is near zero, and they don’t interact with the strong nuclear force either. They’re extremely difficult to detect, and they’re passing through your body right now.

Gamma rays, on the other hand, are not difficult to detect. They’re the most energetic photons in the Universe and you definitely don’t want any passing through your body. They’re released in atomic bomb detonations, among other things. Space-based detectors have found gamma rays with voltages in the gigaelectron range. If electron volt ranges aren’t your thing, just think of them as more energetic than visible light by orders of magnitude.

So scientists know a lot about both neutrinos and gamma rays, they just aren’t sure where they all come from. This research might have the answer. “The Universe is filled with a diffuse background of MeV gamma-rays and PeV neutrinos, whose origins are unknown. Here, we propose a scenario that can account for both backgrounds simultaneously,” the authors write.

Scientists think they know where powerful background gamma-rays in the gigaelectron volt (GeV) to teraelectron (TeV) volt ranges come from. They come from AGNs and probably star-forming galaxies. But the source of softer gamma-rays, those in the megaelectron volt (MeV) ranges are unknown. Same with many neutrinos.

This paper shows that low luminosity galactic nuclei could account for both the neutrinos and the gamma rays.

Computer simulation of plasma near a black hole. Credit: Hotaka Shiokawa / EHT

A black hole’s enormous mass and gravitational pull draws matter toward it. It forms an accretion disk of swirling matter, and eventually, the matter falls into the black hole. When that happens an enormous amount of gravitational energy is released. That energy heats up gas around the hole and creates plasma. In this case, the low-accreting black hole has insufficient cooling and the plasma’s temperature can reach tens of billions of degrees Celsius.

What happens is the plasma energizes protons to an extreme degree. They can be 10,000 times more energetic than what the Large Hadron Collider (LHC) can achieve, and the LHC is our most powerful particle accelerator. As these high-speed protons interact with matter and radiation, they produce neutrinos. This can account for the higher energy range neutrinos detected in space.

A similar mechanism produces gamma-rays. As the electrons reach extremely high temperatures, they become efficient producers of gamma-rays in the MeV range through a process called Comptonization.

This image from the study shows how mellow SMBHs can produce diffuse neutrinos and gamma rays that flood the Universe. Image Credit: Shigeo S. Kimura.

So the high-temperature plasma around quiet black holes can produce neutrinos and gamma-rays. Even though these types of black holes are dim and difficult to see, there are a lot of them. It’s reasonable to think they could account for background radiation in the form of gamma-rays and neutrinos.

But this is just a proposed mechanism. There’s no conclusive proof yet. Where will that come from?

Most of our gamma-ray detectors aren’t tuned to the MeV frequency. They’re tuned to higher energy levels. What’s needed is what the authors call a “multimessenger” detector. That’s a detector that detects both gamma-rays and neutrinos at the same time, in the right energy ranges. Proposed missions like e-ASTROGAM, the All-sky Medium Energy Gamma-ray Observatory (AMEGO), and the Gamma-Ray and AntiMatter Survey (GRAMS) should help.

More:

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Categories: Astronomy

Landsat 9 Joins a Fleet of Earth Observation Satellites

Wed, 09/29/2021 - 4:01pm

Earth has a new eye in orbit to monitor our changing planet.  

Landsat 9 launched on September 27, 2021 continuing the Landsat family of satellite’s nearly 50-year tradition of making critical observations to help with energy and water management, forest monitoring, human and environmental health, urban planning, disaster recovery and agriculture.

And… liftoff! ?

The #Landsat 9 satellite has lifted off from the Vandenberg Space Force Base in California aboard a @ULALaunch Atlas V rocket at 2:12pm ET. pic.twitter.com/O6YXhtf7kT

— NASA (@NASA) September 27, 2021

The mission launched from Vandenberg Space Force Base in California, on board an Atlas V rocket. The payload and booster reached orbit about 16 minutes after launch, and Landsat 9 separated from the rocket about an hour later, joining Landsat 8 – which has been in orbit since 2013 – along with the rest of NASA’s Earth-observing fleet.

Landsat is a joint mission between NASA and the U.S. Geological Survey (USGS). The first Landsat launched in 1972.

“The Landsat mission is like no other,” said Karen St. Germain, director of the Earth Science Division at NASA Headquarters. “For nearly 50 years, Landsat satellites observed our home planet, providing an unparalleled record of how its surface has changed over timescales from days to decades. Through this partnership with USGS, we’ve been able to provide continuous and timely data for users ranging from farmers to resource managers and scientists. This data can help us understand, predict, and plan for the future in a changing climate.”

Landsat 9 is now making its way to its final orbital altitude of 438 miles (705 kilometers). It will be in a near-polar, Sun-synchronous orbit.

 Combining the power of both Landsat 8 and 9, the two satellites can now photograph the entire Earth every eight days. Scientists and researchers use the images to monitor phenomena including agricultural productivity, forest extent and health, water quality, coral reef habitat health, and glacier dynamics. 

But anyone can look at or use the images, as Landsat data from over the years are available to view and download at this USGS website. You can also see other images of Earth from orbit at the NASA Earth Observatory website.

Landsat imagery is used to monitor natural disasters, such as these comparison images showing before and after images of flooding of the Ohio and Mississippi Rivers in 2011. Credit: NASA/USGS.

“[This] successful launch is a major milestone in the nearly 50-year joint partnership between USGS and NASA who, for decades, have partnered to collect valuable scientific information and use that data to shape policy with the utmost scientific integrity,” said Secretary of the Interior Deb Haaland. “As the impacts of the climate crisis intensify in the United States and across the globe, Landsat 9 will provide data and imagery to help make science-based decisions on key issues including water use, wildfire impacts, coral reef degradation, glacier and ice-shelf retreat, and tropical deforestation.”

Landsat 9 has two instruments on board: the Operational Land Imager 2 (OLI-2) and the Thermal Infrared Sensor 2 (TIRS-2). Working together, the two instruments can measure 11 wavelengths of light reflected or radiated off Earth’s surface, in the visible spectrum as well as other wavelengths beyond what our eyes can see. As the satellite orbits, these instruments will capture scenes across a swath of 115 miles (185 kilometers). Each pixel in these images represents an area about 98 feet (30 meters) across, about the size of a baseball infield. At that high a resolution, NASA says that resource managers will be able to identify most crop fields in the United States.

Earth orbiting satellites and missions, as of 2019. Credit: NASA

Further reading about the launch: NASA Earth Observatory, NASA blogs

The post Landsat 9 Joins a Fleet of Earth Observation Satellites appeared first on Universe Today.

Categories: Astronomy

Mars has Seasons, and They Might Have Revealed Where it’s Hiding its Water

Wed, 09/29/2021 - 1:34pm

The search for water on Mars has consumed a lot of data collection and research time.  Underground lakes have been found and then discounted again.  Melted ice has been proposed and then dismissed again.  All this attention focuses on one of the most important resources available to any future Martian explorers.  Water is critical to human life and can also be split into two crucial components for rocket fuel.  So finding an easily accessible cache of it is a prerequisite to any serious human mission to the red planet that expects to return its crew back home.

A team from the Lunar and Planetary Institute (LPI) thinks they might have found easily accessible reservoirs of water ice at much more temperate latitudes than had been traditionally thought.  Finding any significant water source near the equator would be cause for celebration, as most large known water deposits are located near the poles, which is even more inhospitable to human exploration than the rest of the planet.  

UT video discussing in-situ resource utilization on Mars.

Such a reservoir is precisely what Dr. Germán Martínez of LPI and his team think they have found.  To do so, they used data collected by Mars Odyssey’s Neutron Spectrometer.  They looked at sub-surface hydrogen levels, which have been studied before. But their novel contribution was to notice a pattern.  

There was a spike in hydrogen levels in certain parts of the planet, particularly in Hellas Planitia and Utopia Rupes in the southern and northern hemispheres, respectively.  That spike happened to be seasonal, which pointed to a type of source scientists hadn’t been able to differentiate before.

Map of Mars highlighting significant seasonal variations in surface hydrogen levels.
Credit – G. Martinez et al.

Water ice could potentially be the cause of the seasonality.  The spectrometer’s measured hydrogen signal increased during the colder months, which indicates that water ice could be freezing in the subterranean regions Odyssey was monitoring. During warmer months, the ice would sublimate, carrying away the hydrogen and leading to a drop in Odyssey’s readings.

Another finding lends even more credence to the hypothesis that relatively accessible water ice is the cause of the signal.  Odyssey found other areas with high levels of hydrogen, but they did not show the seasonality that the readings at Hellas Planitia and Utopia Rupes did.  In these cases, the water is probably deeper underground, less susceptible to sublimation in warmer months, and therefore less accessible for use in exploration missions.

Figure from the research paper showing the distribution of hydrogen.
Credit – Martinez et al.

Those exploration missions could include robotic rovers, which would likely be necessary to confirm or deny the presence of easily accessible waters in these areas.  Other remote sensings efforts can be brought to bear in the meantime. If the LPI team’s hypothesis turns out to be accurate, that new information could be a game-changer for the location of any future crewed Martian mission.

Learn More:
EuroPlanet Society – Scientists use seasons to find water for future Mars astronauts
UT – Does Mars Have Seasons?
UT – Nothing Says Springtime on Mars Like Explosions of Sand
LPI – Missing Water on Mars May Be Stored in the Crust

Lead Image:
Image of Mars from Viking Orbiter.
Credit – NASA / JPL -Caltech / USGS

The post Mars has Seasons, and They Might Have Revealed Where it’s Hiding its Water appeared first on Universe Today.

Categories: Astronomy

Dozens of Robots Competed to Race Through Underground Caves

Wed, 09/29/2021 - 12:22pm

America’s Defense Advanced Research Projects Agency (DARPA) is well known for its challenges.  It held a series of autonomous driving competitions back in the early 2000s that directly led to today’s self-driving cars.  Now that Grand Challenge has evolved into a new one – the Subterranean (SubT) challenge, which took place last week.  This new one also happens to be directly applicable to technologies that would be useful in space exploration.

Ostensibly, DARPA’s SubT challenge is to develop a robotic system capable of identifying and, and even potentially helping, victims of a natural disaster or other catastrophe.  The contest was broken into two overarching categories, and each category tackled three different types of terrain.  The two categories were the Systems track, which utilized physical robots, and the Virtual track, which concentrated on developing algorithms for searching a given area.

Video recap of Day 3 of the Cave Circuit Challenge.
Credit – DARPAtv YouTube Channel

The robots or algorithms for each category were then subject to three different terrains they had to master: a Tunnel Circuit, an Urban Circuit, and a Cave Circuit.  The Tunnel Circuit competition took place in August of 2019 in some abandoned mining tunnels around Pittsburgh, while the Urban Circuit was held in February 2020 at an abandoned power plant in Washington State.

Covid-19 threw a wrench into plans for the Cave Circuit, which was initially scheduled to take place in the fall of 2020.  Due to the pandemic, the competition, which was planned to take place in the Louisville Mega Cavern in Kentucky, was rescheduled to September of this year.

Unique “rollocopter” design from CoSTAR, a NASA-sponsored team, utilizes the capabilities of both a quadcopter and a two-wheeled rover.
Credit – NASA / JPL-Caltech

The goal in all three terrains, and for each category, is the same – find and identify as many targets of interest (i.e., potential victims) as possible and flag them for follow-up by first responders.  Accomplishing this is not as easy as it sounds and requires coordination by many robots scouting around the environment and talking to one another.  

Teams from all over the world took place in the competition. Some were funded by DARPA itself, while others were entirely self-funded. Ultimately, DARPA-funded CERBERUS won the systems competition. Team CERBERUS is a collaboration between various universities, including the University of Nevada, Reno, ETH Zurich, and UC Berkeley.  Their score of 23 tied another DARPA-funded team (CSIRO Data61) but they ultimately took home the $2 prize offered for winning the competition.  The Virtual Competition was led by Dynamo, a self-funded effort that took home the $750,000 prize for winning its virtual competition. 

Testing of the challenge robots has been ongoing for almost two years.
Credit – NASA / JPL-Caltech

Over the past two years, the technologies used in the systems have advanced dramatically.  CoSTAR, a team, partially run by roboticists from NASA’s Jet Propulsion Laboratory, was particularly happy about new AI and navigation systems that could be used in entirely different environments.

Those environments include lunar or Martian caves that could offer the most habitable places in those inhospitable locations.  If the original Autonomous Driving Grand Challenge is anything to go by, these new cave exploration technologies might be ready when they are needed for those lunar or Maritan exploration missions.

Learn More:
JPL – NASA Robots Compete in DARPA’s Subterranean Challenge Final
DARPA – Subterranean Challenge
DARPA – Stage is Set for DARPA’s Subterranean Challenge Final Event
DARPA – Team CERBERUS and Team Dynamo Win DARPA Subterranean Challenge Final Event
UT – MIT Claims they are Programming Humanoid Robots to help Explore Mars. But we all Know It’s Cylons!

Lead Image:
CoSTAR robot exploring a cave.
Credit – NASA / JPL-Caltech

The post Dozens of Robots Competed to Race Through Underground Caves appeared first on Universe Today.

Categories: Astronomy

Lunar Landers Could Spray Instant Landing Pads as They Arrive at the Moon

Wed, 09/29/2021 - 11:21am

Space exploration requires all kinds of interesting solutions to complex problems.  There is a branch of NASA designed to support the innovators trying to solve those problems – the Institute for Advanced Concepts (NIAC).  They occasionally hand out grant funding to worthy projects trying to tackle some of these challenges.  The results from one of those grants are now in, and they are intriguing.  A team from Masten Space Systems, supported by Honeybee Robotics, Texas A&M, and the University of Central Florida, came up with a way a lunar lander could deposit its own landing pad on the way down.

Lunar dust poses a significant problem to any powered landers on the surface.  The retrograde rockets needed to land on the moon’s surface softly will also kick dust and rock up into the air, potentially damaging the lander itself or any surrounding human infrastructure. A landing pad would lessen the impact of this dust and provide a more stable place for the landing itself.

Graphic showing the difference between landing with or without the deposition system.
Credit – Masten Space Systems

But constructing such a landing pad the traditional way would be prohibitively expensive.  Current estimates put the cost of building a lunar landing pad using traditional materials at approximately $120 million.  Any such mission also suffers from a chicken and egg problem.  How to get the materials to build the landing pad land in place if there is no landing pad, to begin with?

The technology Masten has developed is an ingenious solution to both of those problems.  Depositing a landing pad while descending would allow spacefarers to have a landing pad in place before a spacecraft ever touches down there.  It would also cost much less to install as all that is needed is a relatively simple additive to the rocket exhaust already being blasted into the surface.

Graphic showing the whole system process of the FAST particle injector.
Credit – Master Space Systems

Masten’s general idea is easy enough to understand.  Adding solid pellets into the rocket exhaust would allow that material to partially liquefy and deposit onto the exhaust’s blast zone, potentially hardening it to a point where dust is no longer a factor as it is encapsulated in a hard external shell.  Masten believed it could find the right material to add to rocket exhaust to do exactly that.

Success or failure would come down to the physical properties of the additive pellets.  Any additive with too much heat tolerance wouldn’t melt appropriately in the rocket exhaust, essentially bombarding the surface with tiny bullets.  On the other hand, any additive with too little heat tolerance could be completely melted by the rocket exhaust and vaporized into a useless cloud.

Example of how much dust can be kicked up even on Earth as one of Masten’s rockets is test fired.
Credit – Masten Space Systems

To find the perfect balance, Masten developed a two-tiered system, with relatively large (.5mm) alumina particles used to create a base layer of 1mm of melted lunar surface combined with alumina.  Then, as the lander got closer to the base layer, the additive would switch to a .024mm alumina particle, which would deposit at 650 m/s onto the base layer and create a 6m diameter landing pad that would cool in 2.5 seconds.

That all sounds like a pretty impressive idea, but it is still early days.  Like many federal grants, the NIAC grant focused on developing this depositable landing pad idea takes a phased approach. Most of the Phase I, which has just been completed, focused on proving the idea is feasible, which Masten believes it is.  

Example of the effects of an alumina plate, similar to what would be deposited on the moon’s surface in a fully scaled up system. An infrared image of the rocket exhaust can be seen to the right.
Credit – Masten Space Systems

Feasible is not the same as functional, but that is precisely what NIAC grants are supposed to support – wild ideas that might just fundamentally change some aspect of space exploration.  If Masten is correct and the approach is possible and can be scaled up, landing pads might be seen cropping up all over the lunar surface.  And eventually all over Mars as well.

Learn More:
MSS – Mitigating Lunar Dust: Masten Completes FAST Landing Pad Study
NASA – Instant Landing Pads for Artemis Lunar Missions

Lead Image:
Artist depiction of a lunar lander utilizes the FAST landing pad deposition technology.
Credit – Masten Space Systems

The post Lunar Landers Could Spray Instant Landing Pads as They Arrive at the Moon appeared first on Universe Today.

Categories: Astronomy

Aging White Dwarfs Become Even More Magnetic

Wed, 09/29/2021 - 11:13am

In a few billion years the Sun will end its life as a white dwarf. As the Sun runs out of hydrogen to fuse for energy it will collapse under its own weight. Gravity will compress the Sun until it’s roughly the size of Earth, at which point a bit of quantum physics will kick in. Electrons from the Sun’s atoms will push back against gravity, creating what is known as degeneracy pressure. Once a star reaches this state it will cool over time, and the once brilliant star will eventually fade into the dark.

Most stars in the universe will end as a white dwarf. Only the largest stars will explode as supernovae and become neutron stars or black holes. There are lots of white dwarfs in the Milky Way, but many of them can be difficult to study.

For one thing, white dwarfs don’t produce energy in their cores as regular stars do. They cool and fade as they age, so we tend to see the youngest and brightest white dwarfs. Observations of white dwarfs are also biased toward those with the smallest mass. That’s because the more massive a white dwarf is, the smaller it is. The reason for this has to do with the balance between electron degeneracy pressure and gravity. In a white dwarf, the electrons act as a sort of quantum gas. The more massive the white dwarf, the more tightly its gravity can squeeze the electrons, hence a smaller volume.

The most massive white dwarf is a bit larger than the Moon. Credit: Giuseppe Parisi

Fortunately, we’re getting better at studying smaller and cooler white dwarfs, as a recent study shows. The team used data from the Gaia spacecraft to find white dwarfs within 20 parsecs of Earth. In addition to known white dwarfs, the team identified about 100 white dwarfs that had never been cataloged. They then looked at the spectrum of these white dwarfs using ISIS spectrograph and polarimeter on the William Herschel Telescope. Since the spectrum of a white dwarf is affected by its magnetic field, the team was able to measure the strength of their magnetic fields.

They found an interesting result. There is a correlation between the age of a white dwarf and its magnetic field. The older a white dwarf is, the more likely it has a strong magnetic field. In other words, white dwarfs tend to become more magnetic as they age. This suggests that white dwarf magnetic fields are created through the cooling process of the star.

We aren’t sure how the cooling process magnetizes white dwarfs. The magnetic fields of larger and younger white dwarfs might be explained by a dynamo mechanism, similar to the process that generates Earth’s magnetic field. But the magnetic fields of old white dwarfs are often much larger than we think can be produced by a dynamo. So something strange is going on, and it will take more research to solve this mystery.

Reference: Bagnulo, S., and J. D. Landstreet. “New insight into the magnetism of degenerate stars from the analysis of a volume limited sample of white dwarfs.” arXiv preprint arXiv:2106.11109 (2021).

The post Aging White Dwarfs Become Even More Magnetic appeared first on Universe Today.

Categories: Astronomy

NASA’s Human Space Exploration Division is Being Split in Two

Tue, 09/28/2021 - 11:04pm

Large government organizations require lots of people to run them.  NASA is no exception.  America’s space agency has long been under pressure to organizationally support its ongoing Artemis program to return to the moon. Now, it has taken a step in that direction by announcing that its Human Exploration and Operations Mission Directorate will split into two new ones: the Exploration Systems Development Mission Directorate and the Space Operations Missions Directorate.

The announcement came on September 21st from Bill Nelson, NASA’s administration, who also announced a press conference to discuss the changes further.  In that press conference, NASA’s leadership team outlined some of the reasons for the change.  

Recording of the Town Hall meeting discussing the Human Spaceflight reorganization.
Credit – NASA

A big one was a “strong” recommendation from President Joe Biden.  That suggestion stemmed from politician’s frustrations in dealing with the agency’s budgetary processes.  With the same directorate handling both the Artemis program and ongoing work in the ISS, it was difficult for the people who control the purse strings to understand what that money was going towards.

Expanding a bureaucracy isn’t always the most efficient way to do something, however.  That will be no exception with this transition.  Pam Melroy, NASA’s deputy administrator, pointed out that “We’re actually not adding a whole new layer of people,” but that “the challenges that we have in coordinating across organizations is exactly the same as it is today.”

NASA’s description of the Artemis program.
Credit – NASA YouTube Channel

Those challenges include managing NASA’s increasingly complex human spaceflight programs.  With two separate directorates headed by two competent leaders, those programs will garner more specific attention.  The leaders they picked will have a significant impact how the success or failure of those programs.

NASA did select two very qualified individuals for those roles – Kathy Lueders was the current head of the predecessor directorate, where she was promoted to June of 2020. She previously had a leading role in the Commercial Crew Program, though she began her career in 1992 as a depot manager at the White Sands Test Facility after earning her B.S. in Industrial Engineering.  She’ll now lead the Space Operations Mission Directorate, taking over the ISS and other ongoing human spaceflight operations.

Kathy Lueders (right) will head the new Space Operations Mission Directorate, while Jim Free (left) will lead the new Exploration Systems Development Mission Directorate.
Credit – NASA / Aubrey Gemignani

To lead the Exploration Systems Development Mission Directorate, NASA brought back Jim Free, a former employee who had retired in 2017 as the technical deputy associate administrator for the directorate that is being separated.  After a stint in private industry, including as an Executive Vice President at Peerless Aerospace, Jim came back to the agency to help develop the Artemis program.  His career started back in 1990 as a propulsion engineer, and he has worked at a variety of NASA facilities in his almost 30-year career at the agency.  

Critics point out that the added bureaucracy will now require these two leaders to communicate effectively to maintain the same leadership present under Ms. Lueder’s leadership previously.  According to the agency, no changes will impact the various NASA centers located around the country, and the personnel switching will be primarily focused on the headquarters in Washington. With luck, this organizational shake-up will be a way to prioritize goals correctly and allow Congress and the American public to see more directly what their space exploration money is being spent on.

Learn More:
NASA – NASA Leadership Positions Agency for Future
SpaceNews.com – NASA splits human spaceflight directorate into two organizations
SpacePolicyOnline.com – NASA SPLITS HUMAN SPACEFLIGHT DIRECTORATE INTO TWO

Lead Image:
Artemis program graphic
Credit – NASA

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Categories: Astronomy

How Much Carbon Dioxide Snow Falls Every Winter on Mars?

Tue, 09/28/2021 - 10:24pm

Like Earth, Mars experiences climatic variations during the course of a year because of the obliquity of its rotational axis. This leads to the annual deposition/sublimation of the CO2 ice/snow, which results in the formation of the seasonal polar caps. Similarly, these variations in temperature result in interaction between the atmosphere and the polar ice caps, which has a seasonal effect on surface features.

On Mars, however, things work a little differently. In addition to water ice, a significant percentage of the Martian polar ice caps are made up of frozen carbon dioxide (“dry ice”). Recently, an international team of scientists used data from NASA’s Mars Global Surveyor (MGS) mission to measure how the planet’s polar ice caps grow and recede annually. Their results could provide new insights into how the Martian climate varies due to seasonal change.

The study that describes their findings was led by Haifeng Xiao, a research assistant with the Institute of Geodesy and Geoinformation Science at the Berlin Technical University. He was joined by researchers from Stanford University, the Université Paris-Saclay, the Institut Universitaire de France, and the German Aerospace Center’s (DLR) Institute of Planetary Research and Institute of Atmospheric Physics.

Time-lapse video showing the sublimation of the seasonal polar cap at the Martian North Pole. Credit: W.M. Calvin, et al. (2015)

What we know about the Martian polar ice caps indicates that they are composed of three parts. First, there is the Residual (or Permanent) Ice Cap, which consists of sheets of water ice several meters thick at the North Pole, and an 8-meter (~10 feet) thick sheet of frozen carbon dioxide at the South Pole. Beneath that are the Polar Layered Deposits (PLDs), which are 2 to 3 km (mi) thick and composed of water ice and dust.

Last is the Seasonal Ice Cap, a layer of frozen CO2 deposited on top of the permanent ice caps every winter. For the sake of their study, Haifeng and his colleagues focused on the Seasonal Ice Caps to reveal how they are affected by variations in seasonal temperatures and solar radiation – and how this is associated with annual variations in Mars’ climate. As Haifeng told Universe Today via email:

“Each Martian year, approximately 30% of the atmosphere’s CO2 mass is in vivid exchange with the polar surfaces through the seasonal deposition/sublimation. Temporal variations of levels and volumes of snow/ice associated with this process can put crucial constraints on the Mars climate system and volatile circulation models.

“In addition, the seasonal accumulation of the CO2 ice to form these seasonal polar caps can be affected by dust storms, cold spots, katabatic and orographic winds, and local shadowing. Thus, short and long-term variabilities of the seasonal polar caps could also indicate the variabilities of the Mars climate.”

During a Martian year, which lasts over 687 Earth days (or 668.5 Sols), seasonal changes lead to atmospheric carbon dioxide migrating from the North Pole to the South Pole (and vise versa). These seasonal actions are responsible for transporting large amounts of dust and water vapor, which leads to frosts and the formation of large cirrus clouds visible from space.

This image from the Mars Reconnaissance Orbiter (MRO) shows the “spiders” emerging from the carbon dioxide ice cap at the South Pole of Mars. Credit: NASA/JPL-Caltech

This process of sublimation and exchange between the poles is also responsible for notable geological features on Mars, such as the araneiform terrain (aka. “spiders”) near the South Pole and the way the dune fields in the northern planes become furrowed with the arrival of seasonals. As Haifeng explained, understanding the relationship between the seasonal polar caps and the formation of geological features on Mars could lead to a better understanding of the Martian environment.

Over the past two decades, measurements of the polar ice caps have been conducted using various methods – gravity variation, neutron, and gamma-ray flux – and modeled based on General Circulation and Energy Balance models. For their study, Haifeng and his colleagues relied on data obtained by the Mars Orbiter Laser Altimeter (MOLA) instrument aboard the MGS to obtain accurate measurements of the height and volume of Mars’s polar ice caps over time.

This consisted of reprocessing the MOLA Precision Experiment Data Records (PEDR) – or MOLA’s individual altimetry readings – using the latest available MGS orbit data and Mars rotational model. They then self-registered these profiles into a self-consistent Digital Terrain Model (DTM), which served as a static mean surface measurement for Mars. As Haifeng explained:

“We have proposed and validated the co-registration of local dynamic Mars Orbiter Laser Altimeter (MOLA) profile segments to static Digital Terrain Models (DTMs) as an approach for obtaining seasonal CO2 ice cover depth variations on Mars. In addition, we have also proposed a post-correction procedure based on the pseudo cross-overs of MOLA profiles to further improve the precision of the depth variation time series.”

“Furrowed” dunes in the cratered region near the Martian North Pole. Credit: NASA/JPL-Caltech/University of Arizona

From this, the team obtained a series of height-change measurements obtained at a test region over the residual polar cap of the South Pole where the deepest snow/ice can be expected.

with a precision of ~4.9 cm (1.93 inches) and peak-to-peak height variations of ~2.2 m (7.2 ft). The team also extended these results to the entire South Pole, which they hope to cover in greater detail in another soon-to-be-published study. Haifeng and his colleagues also plan to compare their results with radar altimetry data obtained by the SHAllow RADar sounder (SHARAD) aboard NASA’s Mars Reconnaissance Orbiter‘s (MRO).

“As the next step, We will try the SHARAD radar altimetry to cross-validate the MOLA measurements and to derive the long-term seasonal depth evolution of the seasonal polar caps of Mars, which will also be important for assessing the long-term stability of the underlying Martian Residual Polar Caps, especial the Residual South Polar Cap that is considered to be in a quasi-stable state,” said Haifeng.

These measurements will allow planetary scientists to learn a great deal more about the Martian climate and the annual changes it goes through. They will also help prepare future robotic and human exploration missions to the Red Planet, which are still anticipated for some time in the next decade.

Further Reading: arXiv

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Categories: Astronomy

Vera Rubin Observatory Should Find 5 Interstellar Objects a Year, Many of Which we Could Chase Down With Spacecraft

Tue, 09/28/2021 - 9:15pm

In a year (perhaps two), the Vera C. Rubin Observatory in Chile will become operational and commence its 10-year Legacy Survey of Space and Time (LSST). Using its 8.4-meter (27 foot) mirror and 3.2 gigapixel camera, this observatory is expected to collect 500 petabytes of images and data. It will also address some of the most pressing questions about the structure and evolution of the Universe and everything in it.

One of the highly-anticipated aspects of the LSST is how it will allow astronomers to locate and track interstellar objects (ISOs), which have become of particular interest since `Oumuamua flew through our system in 2017. According to a recent study by a team from the University of Chicago and the Harvard-Smithsonian Center for Astrophysics (CfA), the Rubin Observatory will detect around 50 objects during its 10-year mission, many of which we will be able to study up-close using rendezvous missions.

Their paper that describes their findings, which is being reviewed for publication in the Planetary Science Journal, was led by Devin Hoover, a researcher with the Dept. of Astronomy and Astrophysics at the University of Chicago. He was joined by Darryl Seligman, a T.C. Chamberlin Postdoctoral Fellow with the University of Chicago’s Dept. of Geophysical Sciences; and Matthew Payne, an SAO research scientist with the Harvard-Smithsonian Center for Astrophysics.

Ever since humanity got its first glimpse of an interstellar object on Oct. 19th, 2017, astronomers have contemplated the possibility of rendezvousing with future visitors. While astronomers had already theorized that our Solar System is visited by interstellar objects (ISOs) a few times a year, `Oumuamua the first such object ever observed. Moreover, the way it defied classification quickly led to the realization that this object was the first of its type ever to be observed.

This spawned no shortage of speculation of what it could be, with possibilities ranging from a hydrogen iceberg, a piece of a Pluto-like body, an interstellar “bust bunny,” and even an extraterrestrial solar sail. Regardless of its true nature, `Oumuamua’s mere existence confirmed that ISOs are statistically significant in our galaxy, which was bolstered by the detection of a second ISO (2I/Borisov) almost two years later.

As lead author Devin Hooper explained to Universe Today via email, the prospect of studying an ISO is extremely promising, given what they represent:

“Interstellar objects represent the building blocks and leftovers from the planet formation process in extrasolar systems. Just as the comets and asteroids in the Solar System have told us more about its formation than the planets themselves, interstellar objects will tell us more about planet and star formation than exoplanets and stars. Since these objects are passing through the Solar System, we can gain insights into the building blocks of extra-solar planets without traveling to other planetary systems.”

`Oumuamua (left) and 2I/Borisov (right) are the only two ISOs we know of for certain. Image Credit: ESO/M. Kornmesser; NASA, ESA, and D. Jewitt (UCLA)

For these reasons, the astronomical community is looking forward to the discovery of more interstellar objects. Several studies have already shown how new instruments will detect several such objects a year, which will allow astronomers to constrain the properties of this type of object and determine how `Oumuamua and 2I/Borisov fit into the overall population.

For instance, researchers have indicated that the Vera C. Rubin Observatory will detect several ISOs a year once the LSST begins. Similarly, there are proposals for rapid intercept missions capable of rendezvousing with some of these objects. To determine how many objects would be detectable and reachable, Hoover and his colleagues ran a series of computer simulations that generated an entire population of ISOs entering the Solar System.

The number density of the objects was based on what the detection of `Oumuamua and 2I/Borisov implied – i.e., 1026 in our galaxy, and one passing through the inner Solar System at any given time. To see which would be detectable by the LSST, said Hoover, they developed three detectability criteria:

“First, the ISO must have a minimum apparent magnitude below 24; in other words, it must be bright enough to be observed by the LSST. Second, the ISO must achieve an altitude above +30 degrees; in other words, it must be high enough in the sky… Finally, the Sun must have an altitude below -18 degrees; in other words, the Sun is below the horizon to make the sky sufficiently dark at the time of observation. The second and third criteria ensure that detectable ISOs are significantly distant from the Sun in the sky.”

An artist’s overview of the mission concept for the Comet Interceptor spacecraft, which will fly from the vicinity of Earth to rendezvous with a long-period comet or interstellar object inbound from the outer solar system. Credit: ESA

If any ISO passing through the inner Solar System satisfies all three of these criteria at any point along its trajectory (coincident with the LSST’s 10-year observation campaign), then it was considered detectable. They found that of their simulation ISO population, roughly 20% of those detectable by the LSST would also be reachable with a dedicated ISO rendezvous mission. This amounts to about one ISO being reachable per year between 2022/23 – 2032/33.

Looking to the near future, these results will allow researchers to devise observation strategies that will maximize the likelihood of detecting ISOs and help determine which future rendezvous missions are feasible. As Hoover put it:

“Specifically, 1.69% of the ISOs in our sample are both detectable and reachable by a rendezvous mission given 30 km/s of delta-v. We require both criteria because we know only the trajectories of detected ISOs, making it possible to send intercept missions to them. This, of course, hinges on the discovery of more ISOs. As the astronomical community enhances its detection capabilities, we will probe a vastly greater number of ISOs, allowing us to choose from a wider range of targets for a rendezvous mission.”

Right now, there are two missions in development – ESA’s Comet Interceptor mission and the NASA BRIDGE concept – both of which were considered in this study by Hoover and his colleagues. As Hoover indicated, these missions will have a delta-v of 15 km/s (54,000 km/h; 33,554 mph) and 2 km/s (7,200 km/h; 4,474 mph) respectively. This falls short of the delta-v requirements specified in their study, which narrows the population of reachable ISOs considerably.

The Vera C. Rubin Observatory is under construction at Cerro Pachon in Chile. Credit: Wil O’Mullaine/LSST

In fact, the results obtained by Hoover and his colleagues indicate that with these two missions, the percentage of reachable ISOs dwindled to 0.471% and 0.003% of their sample, respectively. Given the number density of ISOs in their simulation, this amounts to about 1 ISO per year that would be detectable and reachable with NASA’s BRIDGE concept. However, there are many proposals for intercept missions with higher delta-v capabilities, such as lightsails and directed-energy arrays. Even slower missions still stand a chance of making a rendezvous.

“Due to technological limitations, the delta-v capabilities of current missions are limited, but this does not make a rendezvous mission with an ISO impossible,” said Hoover. “Given the current estimate for the number density of ISOs within the Solar System, ~100 are within the 5 AU sphere at any given time. Given the time it takes for a typical ISO to cross the 5 AU sphere, we calculated that the LSST should detect ~10 reachable targets for BRIDGE within its 10-year observational campaign. Thus, I would not rule out the possibility of low delta-v intercept missions.”

Looking ahead, the results of this study will be of considerable use to astronomers and space agencies. Beyond offering updated estimates on how many ISOs will be detectable soon, these results will also allow researchers to devise observation strategies that maximize the likelihood of detecting ISOs. Furthermore, they underline the need for dedicated intercept missions capable of keeping up with ISOs that buzz our system!

Further Reading: arXiv

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Categories: Astronomy

China’s First Space Station Crew is Back From Orbit

Tue, 09/28/2021 - 8:08pm

On Friday, Sept. 17th, three Chinese astronauts returned safely from space following a three-month stay aboard the new Tiangong space station. This was a major milestone for the Chinese Manned Space (CMS) program, which beats its previous record for the longest crewed mission to space. Whereas the Shenzhou 11 mission (2016) lasted 33 days, the crew of Tang Hongbo, Nie Haisheng, and Liu Boming spent a total of 92 days in orbit.

The astronauts successfully landed in their Shenzou 12 capsule at the Dongfeng Landing Site, located in the Gobi Desert in the autonomous region of Inner Mongolia. According to a statement issued by the CMS, the astronauts safely exited the capsule and were in good physical condition. They were then flown to Beijing on a mission plane, where they were greeted by Li Shangfu, the commander of China’s crewed space project and the project leaders.

The search and rescue team inspecting the Shenzhou 12 capsule after the astronauts exited the vehicle. Credit: Xinhua

As the state-run Xinhua News Agency stated in a recent press release:

“Three Chinese astronauts, the first sent to orbit for space station construction, have completed their three-month mission and returned to Earth safely on Friday. The return capsule of the Shenzhou-12 manned spaceship, carrying astronauts Nie Haisheng, Liu Boming, and Tang Hongbo, touched down at the Dongfeng landing site in north China’s Inner Mongolia Autonomous Region, according to the China Manned Space Agency (CMSA).”

The three astronauts launched in June and were the first of four planned crewed missions to the station during the construction period (which is expected to be complete sometime in 2022). This was China’s first crewed mission to space in five years and represented multiple milestones for the China National Space Administration (CNSA). For one, the astronauts conducted several important station-related tasks while aboard the station.

“During the orbiting flight, two astronaut out-of-vehicle activities were carried out, and a series of space science experiments and technical tests were carried out,” said the CMS in another statement. “In orbit, the key technologies for the construction and operation of space stations such as rail repairs [sic]. The complete success of the Shenzhou 12 manned mission has laid a solid foundation for the construction and operation of the subsequent space station.”

The Shenzhou 12 space capsule landing in the Gobi desert. Credit: Xinhua

This mission was also the first time personnel were dispatched from the Dongfeng Landing Field to perform a search and recovery mission involving a crewed spacecraft. But most importantly, this was the first mission to the Tiangong (“Heavenly Palace”) space station since it was launched in April of 2021. This third-generation habitat builds on the experiences learned from the Tiangong-1 and Tiangong-2 stations.

The space station currently consists of the Tianhe Core Module (“Harmony of the Heavens”), which will be augmented with the addition of the Laboratory Cabin Modules (LCMs). These consist of the Wentian (“Quest for the Heavens”) and Mengtian (“Dreaming of the Heavens”) modules, which are scheduled to launch during the summer of 2022. Once these are integrated, China hopes to conduct a full range of scientific experiments and research in orbit.

These activities are meant to rival those that have been conducted aboard the International Space Station (ISS), which has been in orbit for 22 years and is due to be decommissioned by 2024 at the earliest. While it is unclear if the Tiangong space station will remain in orbit that long (or after the ISS retires), it is clear that China plans to maintain a space station in orbit indefinitely.

Further Reading: digitaltrends, Xinhua

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Categories: Astronomy

The Early Solar System was Messier and More Violent Than Previously Believed

Tue, 09/28/2021 - 5:45pm

Our conventional models of planet formation may have to be updated, according to a pair of new papers.

Accretion is the keyword in current planet formation theory. The idea is that the planets formed out of the solar nebula, the material left over after the Sun formed. They did this through accretion, where small particles accumulate into more massive objects. These massive boulder-sized objects, called planetesimals, continued to merge together into larger entities, sometimes through collisions. Eventually, through repeated mergers and collisions, the inner Solar System was populated by four rocky planets.

But the new research suggests that the collisions played out much differently than thought and that objects collided with each other several times, in a series of hit and runs, before merging. This research fills some stubborn holes in our current understanding.

The two new papers are published in The Planetary Science Journal. The first one looks at hit-and-runs in the late formation stages of Earth and Venus. It’s titled “Collision Chains among the Terrestrial Planets. II. An Asymmetry between Earth and Venus.” The lead author is Alexandre Emsenhuber, who was at the University of Arizona’s Lunar and Planetary Laboratory at the time this work was done.

The researchers relied on 3d simulations of giant impacts, and machine learning based on those impacts. They found that hit-and-runs or collision chains are as common as accretion events in the later stages of planetary formation, at least for Venus and Earth. And they also found that Earth acted as a kind of vanguard for Venus, helping to shepherd impactors into Venus.

The authors propose a hit-and-run-and-return model for the terrestrial planets, and have evidence to back it up. They say that the pre-planetary bodies would have spent a long time crashing into each, bouncing off, and returning to crash into each other again. Since the initial collision would have slowed them down, they’d be more likely to stick together in succeeding collisions. While the accretion model is often compared to a snowman with each snowball sticking to him, this model is more like billiards. There are successive collisions, with each collision at reduced velocities, until things calm down.

The central takeaway from the research is that giant impacts are not efficient planet-forming events.

“We find that most giant impacts, even relatively ‘slow’ ones, are hit-and-runs. This means that for two planets to merge, you usually first have to slow them down in a hit-and-run collision,” said Erik Asphaug, co-author from LPL at the University of Arizona. “To think of giant impacts, for instance the formation of the moon, as a singular event is probably wrong. More likely it took two collisions in a row.”

The first of the two papers focuses on Venus and Earth, often called “sister planets.” But for sister planets, there are some puzzling differences between the two when it comes to composition, geology, and satellite formation. The researchers think they know why.

“We think that during solar system formation, the early Earth acted like a vanguard for Venus.”

Alexandre Emsenhuber, Lead Author.

The early Solar System was a chaotic time, with objects smashing into each other. The new model shows that Earth and Venus had an unusual relationship. They say that Earth acted as a kind of vanguard for Venus. As objects struck Earth and bounced off they, many of them were sent toward Venus at a lower velocity. In this way, Venus accreted more objects from the outer Solar System.

“The Earth acts as a shield, providing a first stop against these impacting planets,” Asphaug said. “More likely than not, a planet that bounces off of Earth is going to hit Venus and merge with it.” Part of the reason for this is that the Solar System is like a gravity well. The closer an object gets to the Sun, the more likely it is to stay there. Since Venus is closer, more objects stuck to it after hitting Earth and bouncing off. “…an impactor that collides with Venus is pretty happy staying in the inner solar system, so at some point it is going to hit Venus again,” Asphaug explained.

Earth, Venus, Mars, and Mercury. According to ‘late stage accretion’ theory, Mars and Mercury (front left and right) are what’s left of an original population of colliding embryos, and Venus and Earth grew in a series of giant impacts. New research focuses on the preponderance of hit-and-run collisions in giant impacts, and shows that proto-Earth would have served as a ‘vanguard’, slowing down planet-sized bodies in hit-and-runs. But it is proto-Venus, more often than not, that ultimately accretes them, meaning it was easier for Venus to acquire bodies from the outer solar system. Image Credit: Lsmpascal – Wikimedia Commons

But Earth has no vanguard. There’s nothing to slow down interloping objects from the outer Solar System. As a result, many objects just bounced off. And since objects are drawn to the center of the gravity well, they’re not likely to encounter Earth again. Instead they encounter Venus. This discrepancy could account for the differences between Venus and Earth. In low-velocity hit-and-runs “… the runner is an identifiable remnant of the projectile (eg a mantle-stripped core, sometimes barely so)…” the authors write.

“The prevailing idea has been that it doesn’t really matter if planets collide and don’t merge right away, because they are going to run into each other again at some point and merge then,” Emsenhuber said. “But that is not what we find. We find they end up more frequently becoming part of Venus, instead of returning back to Earth. It’s easier to go from Earth to Venus than the other way around.”

In most hit-and-runs, most of the projectile survives the impact. But its velocity can be greatly reduced, and its trajectory changed. If the runner is slowed down enough, then both bodies can stay gravitationally bound to one another. In that case, the researchers call it a graze-and-merge.

The paper reached four related conclusions.

  1. The terrestrial planets weren’t isolated from each other during the later stages of planetary formation. Escaping runners from a hit-and-run with one planet are likely to collide with another planet.
  2. Long collision chains are less likely because the projectile needs such a high initial velocity, and high velocity runners are less likely to return.
  3. Earth served as a vanguard for Venus, slowing late stage projectiles and sending them toward Venus. Earth only accreted about half of the projectiles, at most, that collided with it.
  4. Runners from Earth are about equally as likely to collide with Venus as they are to return to Earth. But Venus retains the majority of its runners.
The Moon

The second paper deals with the Moon and its formation. It’s title is “Collision Chains among the Terrestrial Planets. III. Formation of the Moon.” It’s also published in The Planetary Science Journal. The lead author is Erik Asphaug, of the LPL at the University of Arizona.

The prevailing theory says that the young Earth was struck by a planet named Theia about 4.5 billion years ago. Earth has a larger core than it should have for its size, and that came from Theia. The impact destroyed Theia, and much of its mass was sent into orbit around Earth. Eventually it coalesced into the Moon.

But there are some unresolved problems in this scenario. The collision velocity would have to be very low, and the isotope composition of the Earth and the Moon are almost identical. A single low-velocity impact wouldn’t allow all the material to be mixed up enough for the isotope compositions to be so similar.

“The standard model for the moon requires a very slow collision, relatively speaking,” Asphaug said, “and it creates a moon that is composed mostly of the impacting planet, not the proto-Earth, which is a major problem since the moon has an isotopic chemistry almost identical to Earth.”

“The “graze-and-merge” collision strands a fraction of Theia’s mantle into orbit, while Earth accretes most of Theia and its momentum,” the authors write in their paper. “However, a Moon that derives mostly from Theia’s mantle, as angular momentum dictates, is challenged by the fact that O, Ti, Cr, radiogenic W, and other elements are indistinguishable in Earth and lunar rocks.”

The moon is thought to be the aftermath of a giant impact. According to a new theory, there were two giant impacts in a row, separated by about 1 million years, involving a Mars-sized ‘Theia’ and proto-Earth. In this image, the proposed hit-and-run collision is simulated in 3D, shown about an hour after impact. A cut-away view shows the iron cores. Theia (or most of it) barely escapes, so a follow-on collision is likely. Image Credit: A. Emsenhuber/University of Bern/University of Munich.

In the team’s new model, there’s not a single collision, but two. When Theia collides with Earth, it’s moving a bit faster, and bounces off Earth in a hit-and-run. About one million years later it returns. It collides with Earth again, in a giant impact similar to the existing model.

“The double impact mixes things up much more than a single event,” Asphaug said, “which could explain the isotopic similarity of Earth and moon, and also how the second, slow, merging collision would have happened in the first place.”

This figure from the study illustrates the hit-and-run and return scenario for the formation of the Moon. On the left is the first hit-and-run impact. Eventually Earth and Theis encounter each other again, in about one million years, and merge into one disk. The Earth and the Moon form from that homogenized disk. This model explains the near-identical isotopic composition of the Earth and the Moon. Image Credit: Asphaug et al 2021.

This new model of hit-and-run impacts and chains of collisions has the potential to explain some puzzling things about the terrestrial planets. If the standard accretion model is correct, why are the inner planets so different? Why doesn’t Venus have a moon of its own? Why does Earth have a strong magnetic shield and Venus such a weak one?

Asphaug says their research helps explain how these difference could have arisen.

“In our view, Earth would have accreted most of its material from collisions that were head-on hits, or else slower than those experienced by Venus,” he said. “Collisions into the Earth that were more oblique and higher velocity would have preferentially ended up on Venus.”

Common sense suggests that Earth would have more material from the outer Solar System because its closer to it than Venus is. But this research suggests the opposite. Projectiles from the outer Solar System would be likely travelling faster, so would bounce off Earth in a hit-and-run. Many of those projectiles would have found their way to Venus and become part of that planet. So Venus’ differences could be chalked up to its greater component of outer Solar System material.

“You would think that Earth is made up more of material from the outer system because it is closer to the outer solar system than Venus. But actually, with Earth in this vanguard role, it makes it actually more likely for Venus to accrete outer solar system material,” Asphaug said.

This research could also explain why Venus has no Moon, even though this hypothesis makes it more likely for the planet to acquire one. “While Venus may have been more likely than Earth to have acquired a massive satellite by our hypothesis, it may also have been more likely to have lost one,” the authors write. “For the same reason that Venus reaccretes a greater fraction of its runners, compared to Earth, it also reaccretes a greater fraction of its giant impact debris, of which it produces more for a given projectile.” Since Venus’ orbit is smaller than Earth, impact debris will collide with it sooner. All that returning debris could erode or even destroy any natural satellite that Venus may have acquired.

Overall, this research suggests a greater interconnectedness among the terrestrial planets. A greater understanding of the Moon’s geology, layering, and solidification could help confirm the new model. So could surface samples from Venus.

But that’s a ways off in the future.

More:

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Categories: Astronomy

No News Here, Just a Beautiful Globular Cluster Captured by Hubble. That is all.

Tue, 09/28/2021 - 9:41am

Here’s some beauty for your timeline: a stunning and ancient globular cluster captured by the venerable Hubble Space Telescope. The telescope’s Wide Field Camera 3 and Advanced Camera for Surveys was used to take this picture of ESO 520-21 (also known as Palomar 6), which is located about 25,000 light years away from Earth. Scientists say this globular cluster is probably about 12.4 billion years old.

Globular clusters are collections of tightly bound stars orbiting galaxies. Astronomers consider them as natural laboratories which enablie studies on the evolution of stars and galaxies. In particular, globular clusters could help researchers better understand the formation history and evolution of early type galaxies, as the origin of GCs seems to be closely linked to periods of intense star formation.

ESO 520-21 lies close to the center of the Milky Way, and from our vantage point on Earth, is in the constellation Ophiuchus. It’s location near the celestial equator is where interstellar gas and dust absorb starlight, which make observations more challenging.

NASA and ESA say that interstellar absorption affects some wavelengths of light more than others, changing the colors of astronomical objects by causing them to appear redder than they actually are. Astronomers call this process “reddening,” and it makes determining the properties of globular clusters close to the galactic center – such as ESO 520-21 – particularly difficult. A detailed study on the origins of this globular cluster was released in a paper earlier this month, which you can read here.

Another view of Palomar 6 from the VISTA Variables in The Via Lactea (VVV) public survey using the VISTA camera on the Very Large Telescope. Credit: Souza et al., 2021.

Source: NASA

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Categories: Astronomy

This is the Reactor That Could Make it Possible to Return From Mars

Tue, 09/28/2021 - 8:41am

Remember when engineers proposed one-way trips to Mars, because round trips are just too expensive to bring people back to Earth again?

Getting people home from Mars can only happen in two ways. One is to lug all the return fuel with you when you launch from Earth, which is prohibitively difficult and expensive. The second way is to make the return fuel in-situ from Martian resources. But how?

A group of researchers from the University of Cincinnati propose using a type of reactor that was used from 2010-2017 aboard the International Space Station, which scrubbed the carbon dioxide from air the astronauts breathe and generated water to drink, with methane as a biproduct. On Mars, this reactor, called a Sabatier reactor, could take carbon dioxide from Mars’ atmosphere and create methane for fuel.

“Right now if you want to come back from Mars, you would need to bring twice as much fuel, which is very heavy,” said professor Jingjie Wu, who is leading a group of students in this research. “And in the future, you’ll need other fuels. So we can produce methanol from carbon dioxide and use them to produce other downstream materials. Then maybe one day we could live on Mars.”

There’s another benefit to this research: it could also be used to convert greenhouse gases to fuel here on Earth, which could help address climate change.

Wu and his students, including lead author of a new paper and UC doctoral candidate Tianyu Zhang, are experimenting with different carbon catalysts in the the Sabatier reactor, which was named for the late French chemist Paul Sabatier. The Sabatier reactor was installed on the ISS in 2010 and was used until 2017. Contrary to some news reports regarding the research by Wu, Zhang and colleagues, the ISS system was never used to create fuel for orbital boosts.

“On the station, the water is recovered for use in the life support system,” explained Leah Cheshier, communications specialist at NASA’s Johnson Space Center. “The methane is vented to space given the station does not have a way to use it. The space station has not used this methane for orbital reboosts.”

UC chemical engineers are experimenting with different catalysts to convert carbon dioxide into methane and other fuels. Photo/Andrew Higley/UC Creative + Brand

The scientists outlined their research, published in Nature Communications, as they reviewed different catalysts to create different biproducts, such as methane and ethylene. They have had success using  graphene quantum dots — layers of carbon just nanometers big — that can increase the yield of methane.

“In the future we’ll develop other catalysts that can produce more products,” said Zhang, in a press release.

The team said the process is scalable for use in power plants that can generate tons of carbon dioxide. And it’s efficient since the conversion can take place right where excess carbon dioxide is produced, both on Earth and at Mars, where the atmosphere is composed almost entirely of carbon dioxide. Fuel could be created and stored for the return trip home, as well as for fuel to run generators or other life support systems on Mars.

“It’s like a gas station on Mars. You could easily pump carbon dioxide through this reactor and produce methane for a rocket,” Wu said.

The researchers said a lot of progress in Sabatier reactors have been made in recent years, and it could be very important for green energy for Earth.

“The process is 100 times more productive than it was just 10 years ago. So you can imagine that progress will come faster and faster,” Wu said. “In the next 10 years, we’ll have a lot of startup companies to commercialize this technique.”

NASA astronaut Doug Wheelock, Expedition 25 commander in 2010, works to install the Sabatier system that extracted water out of the International Space Station atmosphere. Credit: NASA

The Sabatier system on the space station was returned to ground in 2017 for assessment of its condition following its years of operation, NASA’s Cheshier told Universe Today. NASA has recently initiated an effort to perform design upgrades to Sabatier to improve performance and maintainability. An upgraded unit is planned to be launched to the space station in approximately 2025.

Lead image caption: UC chemical engineer Jingjie Wu holds up the reactor where a catalyst converts carbon dioxide into methane. UC’s research makes him optimistic that scientists will be able to remove carbon dioxide from the atmosphere. Photo/Andrew Higley/UC Creative + Brand

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Categories: Astronomy

What Happens to Interstellar Objects Captured by the Solar System?

Mon, 09/27/2021 - 6:36pm

Now that we know that interstellar objects (ISOs) visit our Solar System, scientists are keen to understand them better. How could they be captured? If they’re captured, what happens to them? How many of them might be in our Solar System?

One team of researchers is trying to find answers.

We know of two ISOs for certain: ‘Oumuamua and comet 2I/Borisov. There must’ve been others, probably many of them. But we’ve only recently gained the technology to see them. We’ll likely discover many more of them soon, thanks to new facilities like the Vera C. Rubin Observatory.

In a new paper submitted to The Planetary Science Journal, a trio of researchers have dug into the question of ISOs in our Solar System. The title of the paper is “On the Fate of Interstellar Objects Captured by our Solar System.” The first author is Kevin Napier from the Dept. of Physics at the University of Michigan.

As things stand now, there’s no reliable way to identify individual captured objects. If astronomers could catch an ISO in the process of being captured, that would be great. But the Solar System is awfully complex, and that makes identifying ISOs difficult. “Given the complex dynamical architecture of the outer Solar System, it is not straightforward to determine whether an object is of interstellar origin,” the authors write.

‘Oumuamua (L) and comet 2I/Borisov (R) are the only two ISOs we know of for certain. Image Credits: Left: By Original: ESO/M. KornmesserDerivative: nagualdesign – Derivative of http://www.eso.org/public/images/eso1737a/, shortened (65%) and reddened and darkened, CC BY-SA 4.0, https://commons.wikimedia.org/w/index.php?curid=64730303. Right: By NASA, ESA, and D. Jewitt (UCLA) – https://imgsrc.hubblesite.org/hvi/uploads/image_file/image_attachment/31897/STSCI-H-p1953a-f-1106×1106.png, Public Domain, https://commons.wikimedia.org/w/index.php?curid=83146132

There wasn’t much opportunity to study either ‘Oumuamua or Borisov. They were identified as ISOs by their hyperbolic excess velocity. That means an object has the right trajectory and a high enough velocity to escape a central object’s gravity. In this case, the central object is, of course, the Sun.

So, could ISOs be captured? Quite likely. “The first step in rigorously investigating this question is to calculate a capture cross-section for interstellar objects as a function of hyperbolic excess velocity…” the authors write.

But that’s just the first step, according to the authors. “Although the cross-section provides the first step toward calculating the mass of alien rocks residing in our solar system, we also need to know the lifetime of captured objects.” The researchers calculated the lifetime of the objects using simulations, tried to understand what happens to them over time in our Solar System, and then came up with a current inventory of captured ISOs.

The researchers identified three overall trends:

  • To survive for more than a few million years, captured objects must somehow lift their pericenters beyong Jupiter. (In this case, survival means staying bound to the Solar System.)
  • Objects on highly-inclined orbits tend to survive for longer than those on planar orbits.
  • No object achieved permanent trans-Neptunian status (ie q=30 AU.)

In the first case, if an ISO can’t lift its pericenter beyond Jupiter, it’ll probably be pulled into the gas giant and destroyed. In the second case, objects on highly inclined orbits are less likely to encounter a planet because most of the time they’re out of the Solar System’s plane. Objects on planar orbits are more likely to encounter a planet and be perturbed and sent back out into interstellar space. In the third case, it’s difficult for an ISO to achieve permanent trans-Neptunian status because it would take a very unlikely chain of events.

This figure from the study shows some simulation results. Each blue line is an individual ISO. The top represents the osculating pericenter distance in AUs. The bottom shows inclination in degrees. In their simulations, individual objects don’t become distinguishable until after about 100 million years. When a blue line ends, that ISO has left the Solar System. Image Credit: Napier et al 2021.

The simulations have some limitations, which the authors explain. They’ve only accounted for the Solar System’s four largest planets and the Sun. The smaller bodies are either not massive to have much effect, or what effect they would have is dwarfed by the Sun. They also ignore out-gassing, radiation pressure from the Sun, or drag from planetary atmospheres, which would be extremely rare anyway, and not likely to affect the results. “Each of these approximations is rather modest, so that including them would make relatively little difference to our conclusions,” they explain.

Overall, the simulation shows that over time most captured bodies would be ejected from the Solar System. It takes a while, though. That’s because most ISOs would simply pass through the system, and the ones that were captured into an unstable orbit of some type would go through many orbits, 30 in this work, before being ejected. That’s because captured objects typically have semi-major axes of 1000 AU with orbital periods of about 30,000 years. So it takes at least one million years before any captured ISOs could be ejected.

This figure from the study shows the surviving fraction of captured ISOs over time. The black points represent the data from the simulation, and the blue line is the best fit according to the equation. It takes at least about 1 million years before enough orbits take place for an ISO to be ejected. Image Credit: Napier et al 2021.

The researchers also calculated the populations of captured ISOs that might be in our Solar System currently. They point out that there are two distinct time periods when objects can be captured that are of interest. The first is in the early days of the Solar System when the Sun is still in its birth cluster of stars, and objects from within that cluster could be captured. The second is when the Sun resides in the field.

In their simulations, the trio of scientists used 276,691 synthetic captured interstellar objects. Of those, only 13 survived for 500 million years, and only three objects survived for one billion years. But these results come with detailed caveats that are best explained in the paper itself.

The authors point out that their simulations might be useful in understanding panspermia. If the chemicals necessary for life, or even life itself, can somehow travel between solar systems, the ISOs likely play a role. Maybe the most prominent role.

They also mention the Planet Nine scenario. One of the authors of this paper, Konstantin Batygin, along with Michael E. Brown, hypothesized a so-called Planet Nine. The Planet Nine hypothesis states that another planet about 5 to 10 times the mass of Earth is in a wide orbit with a semi-major axis of 400 to 800 AUs. Planet Nine, if it exists, would take between 10,000 and 20,000 years to complete one orbit around the Sun.

According to this paper, when included in the simulations, Planet Nine “…yielded rich dynamics that did not appear in the simulations including only the four known giant planets.”

More:

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Categories: Astronomy

Chefs on the Moon Will be Cooking up Rocks to Make air and Water

Mon, 09/27/2021 - 1:32pm

NASA has delayed their Artemis mission to the Moon, but that doesn’t mean a return to the Moon isn’t imminent. Space agencies around the world have their sights set on our rocky satellite. No matter who gets there, if they’re planning for a sustained presence on the Moon, they’ll require in-situ resources.

Oxygen and water are at the top of a list of resources that astronauts will need on the Moon. A team of engineers and scientists are figuring out how to cook Moon rocks and get vital oxygen and water from them. They presented their results at the Europlanet Science Congress 2021.

Professor Michèle Lavagna of Politecnico Milano led the experiments. A consortium of companies and agencies, including the ESA and the Italian Space Agency, is behind the work. Lavagna and others presented a laboratory demonstration of their work at EPSC2921.

When we talk about lunar soil, we mean lunar regolith, the layer of dust that coats the Moon. The same layer that confounded Apollo astronauts by finding its way into the lunar module, clogging mechanisms and interfering with instruments. The dust constitutes an ongoing hazard that space agencies are still trying to mitigate. But the same dust is also a critical resource.

An Apollo 17 astronaut digs in the lunar regolith to study the mechanical behaviour of moon dust. Credit: NASA

There’s lots of oxygen in the lunar regolith because oxygen readily reacts with other elements, especially group one elements. Lunar soil is rich in oxides, especially silicon dioxide, iron oxide, magnesium oxide, etc. According to the ESA, about 50% of lunar soil is iron and silicon dioxide, and about 26% of those compounds are oxygen. The trick is getting the oxygen out.

Lavagna demonstrated a two-step process that’s regularly used in industrial applications here on Earth. First, the simulated lunar regolith is vaporized in the presence of hydrogen and methane then washed with hydrogen gas. A furnace heats the minerals to 1,000 Celsius (1800 F), which turns them directly from a solid to a gas. By doing so, the minerals skip the liquid phase, making the entire process simpler.

Then the gases and the residual methane go to a catalytic converter and then a condenser which separates the water. After that, hydrolysis separates the oxygen, and the system recycles the hydrogen and methane by-products.

Engineers and scientists have been working on the challenge of extracting in-situ resources on the Moon for many years now. One method involves using molten salt electrolysis to extract oxygen. That method is adapted from mining, and it also produces useful metal alloys from lunar regolith.

But one of the critical features of this newer process, according to Lavagna, is it’s almost hands-off.

“Our experiments show that the rig is scalable and can operate in an almost completely self-sustained closed loop, without the need for human intervention and without getting clogged up,” said Professor Lavagna. 

This video shows water extracted by the process. Credit: Politecnico Milano, CC BY-NC-CD

The team is still working on optimizing the process in anticipation of an eventual fight test. They’re working with the furnace temperature, length and frequency of the washing, the ratio of the gas mixtures, and the size of soil batches. So far, they’ve learned that small batches of soil produce maximized yields when combined with the highest possible temperatures and long washing phases.

The system produces silica as a by-product. It also produces metals that require further processing before being used as in-situ resources.

‘The capability of having efficient water and oxygen production facilities on-site is fundamental for human exploration and to run high-quality science directly on the Moon,’ said Lavagna. ‘These laboratory experiments have deepened our understanding of each step in the process. It is not the end of the story, but it’s a very good starting point.’

More:

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Categories: Astronomy

Astronomers Detect Clouds on an Exoplanet, and Even Measure Their Altitude

Sun, 09/26/2021 - 7:26pm

The search for planets beyond our Solar System has grown immensely during the past few decades. To date, 4,521 extrasolar planets have been confirmed in 3,353 systems, with an additional 7,761 candidates awaiting confirmation. With so many distant worlds available for study (and improved instruments and methods), the process of exoplanet studies has been slowly transitioning away from discovery towards characterization.

For example, a team of international scientists recently showed how combining data from multiple observatories allowed them to reveal the structure and composition of an exoplanet’s upper atmosphere. The exoplanet in question is WASP-127b, a “hot Saturn” that orbits a Sun-like star located about 525 light-years away. These findings preview how astronomers will characterize exoplanet atmospheres and determine if they are conducive to life as we know it.

The research paper that describes their findings appeared in the December 2020 issue of Astronomy and Astrophysics. It was also the subject of a presentation made during the recent Europlanet Science Congress (EPSC) 2021, a virtual conference from September 13th to 24th, 2021. During the presentation, lead author Dr. Romain Allart showed how combining data from space-based, and ground-based telescopes detected clouds in WASP-127b’s upper atmosphere and measured their altitudes with unprecedented precision.

Some of the elements making WASP-127b unique, compared with the planets of our Solar System. Credits: David Ehrenreich/Université de Genève, Romain Allart/Université de Montréal.

Like many exoplanets discovered to date, WASP-127b is a gas giant that orbits very close to its parent star and has a very short orbital period – taking less than four days to complete a single orbit. The planet is also 10 billion years old, which is over twice as long as Earth (or “our” Saturn) has been around. Because of its close orbit, WASP-127b receives 600 times more irradiation than Earth and experiences atmospheric temperatures of up to 1,100°C (2012°F).

As a result, the planet’s atmosphere has expanded (or puffed up) to the point that it is 1.3 times as large as Jupiter but far less dense. In fact, WASP-127b is one of the least dense (or “fluffiest”) exoplanets discovered to date. This makes WASP-127b an ideal candidate for researchers working on atmospheric characterization, as the extended nature of fluffy exoplanets makes them easier to observe.

Using data obtained by the ESA/NASA Hubble Space Telescope (HST) and visible light measurements from the Very Large Telescope (VLT) at the ESO’s Paranal Observatory in Chile, the team observed WASP-127b as it made two passes in front of its star. Consistent with the Transit Method (aka. Transit Photometry), the team monitored WASP-127 for periodic dips in luminosity that indicated an exoplanet passing in front of the star (transiting) relative to the observation team.

Whereas Hubble obtained optical data that confirmed the transits, the VLT’s Echelle SPectrograph for Rocky Exoplanets and Stable Spectroscopic Observation (ESPRESSO) instrument obtained spectra from the light passing through WASP-127b’s upper atmosphere. Dr. Allart, a Trottier Postdoctoral Researcher at the Institute for Research on Exoplanets (iREX) at the Université de Montréal, led the study.

The Very Large Telescope in Chile firing a laser from its adaptive optics system. Credit: ESO

The combined data allowed the researchers to trace the altitude of the clouds to an atmospheric layer moving at speeds of about 13.5 to 17 km/s (48,600 km/h; 61,200 mph). They further estimated that the cloud deck altitude conformed to an atmospheric pressure range of between 0.3 and 0.5 millibars. Lastly, they detected signs of tenuous atomic sodium in the atmosphere, though there were no indications of other atomic species or water. As he explained in a recent Europlanet Society statement:

“First, as found before in this type of planet, we detected the presence of sodium, but at a much lower altitude than we were expecting. Second, there were strong water vapor signals in the infrared but none at all at visible wavelengths. This implies that water vapor at lower levels is being screened by clouds that are opaque at visible wavelengths but transparent in the infrared.

“We don’t yet know the composition of the clouds, except that they are not composed of water droplets like on Earth. We are also puzzled about why the sodium is found in an unexpected place on this planet. Future studies will help us understand not only more about the atmospheric structure but about WASP-127b, which is proving to be a fascinating place.”

The team’s ESPRESSO observations also showed that WASP-127b has a retrograde orbit, meaning that it orbits in the opposite direction of its star’s rotation and that it orbits on a different plane than the star’s equatorial. “Such alignment is unexpected for a hot Saturn in an old stellar system and might be caused by an unknown companion,” said Allart. “All these unique characteristics make WASP-127b a planet that will be very intensely studied in the future.”

TOI 1338 b is a circumbinary planet orbiting its two stars. It was discovered by TESS. Credit: NASA’s Goddard Space Flight Center/Chris Smith

These include space-based observatories like the James Webb Space Telescope (JWST) and the Nancy Grace Roman State Telescope (RST). Then there are ground-based observatories like the ESO’s Extremely Large Telescope (ELT), the Giant Magellan Telescope (GMT), and the Thirty Meter Telescope (TMT). With their combination of advanced imaging, coronagraphs, and/or adaptive optics, these facilities will allow astronomers to conduct detailed studies of exoplanet atmospheres.

Just as important is the fact that these studies will include rocky planets that orbit with the habitable zones (HZs) of their stars, not just gas giants with very distant or very close orbits (as was the case here). Since these “Earth-like” candidates are expected to be the most likely candidates for habitability, astrobiologists anticipate that it won’t be long before they find evidence of extraterrestrial life!

While the results of these studies are somewhat limited, the implications of the team’s research are anything but. In addition to demonstrating the effectiveness of combining data from multiple observatories, it also illustrates how astronomers are getting closer to the point where they can fully characterize an exoplanet’s atmosphere. With the introduction of next-generation observatories in the near future, these capabilities will become far greater.

Further Reading: Europlanet, Astronomy & Astrophysics

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Categories: Astronomy

Chang’e-5 Returned an Exotic Collection of Moon Rocks

Sun, 09/26/2021 - 4:08pm

Scientists have begun studying the samples returned from the Moon by China’s Chang’e-5 mission in December 2020, and a group of researchers presented their first findings at the Europlanet Science Congress (EPSC) last week.

“The Chang’e-5 samples are very diverse, and includes both local and exotic materials, including some glutenates [sharp, jagged lunar particles], silicas, salts, volcanic glasses, and impact glasses, along with different minerals and different rock types,” said Yuqi Qian, a PhD student at the China University of Geosciences, during his presentation at the EPSC virtual meeting.

A panoramic view from China’s Chang’e-5 probe shows the lunar terrain in front of the lander, including one of the landing legs in the foreground. (CNSA / CLEP Photo)

Chang’e-5 landed on the near side of the Moon in the Oceanus Procellarum, or Ocean of Storms, which is located on the western, central part of the Moon from our vantage point on Earth. It landed in an area not visited by the NASA Apollo or the Soviet Luna missions nearly 50 years ago. This area is also one of the youngest lunar surfaces, with an age of about 2 billion years old, and therefore these samples are different to those returned in the 1960s and 70s.

“The samples are very diverse, as we have known for a very long time that the formation of the lunar surface is a very complex process, including solar wind implantation, micrometeorite impacts, and condensation,” Qian said.

The “local” materials, which make up about 90 per cent of the returned samples, include young mare basalts, and local impact ejecta. The “exotic” materials, i.e., materials not native to the region, make up about 10 per cent of the Chang’e-5 samples and include distant impact ejecta, meteoritical materials, and volcanic glass beads. 

The Chang’e-5 lunar lander retrieved about 1.7 kilograms (3.81 pounds) of samples from the Moon. It used a drill to gather samples from the subsurface and robotic arm for surface samples. The Chang’e-5 sample return capsule landed in China’s Inner Mongolia region on December 16, 2020, successfully capping a 23-day odyssey that brought back the first lunar rocks since 1976.

Qian and colleagues from Brown University and the University of Münster have looked at the potential sources of the glass beads, and have traced these rapidly cooled glassy droplets to now-extinct volcanic vents known as ‘Rima Mairan’ and ‘Rima Sharp’ located roughly 230 and 160 kilometers southeast and northeast of the Chang’e-5 landing site. These fragments could give insights into past episodes of energetic, fountain-like volcanic activity on the Moon.

The team also looked at the potential sources of impact-related fragments. The young geological age of the rocks at the landing site narrows the search, as only craters with ages less than 2 billion years can be responsible, and these are relatively rare on the lunar near-side.

Image showing the location of the Chang’e-5 landing site (43.06°N, 51.92°W) and adjacent regions of the Moon, as well as impact craters that were examined as possible sources of exotic fragments among the recently returned lunar materials. Credit: Qian et al. 2021

The team modeled what craters could be responsible for the exotic materials and found that some materials could have been ejected from as far as 1,300 km away from the Chang’e-5 landing site. They found that Harpalus, located farther north of Chang’e-5’s site, is a significant contributor of many exotic fragments among the samples, along with craters to the south and southeast (Aristarchus, Kepler, and Copernicus), and northwest (Harding).

Modelling and review of work by other teams has linked other exotic pieces of rock to domes rich in silica or to highland terrains that surround the landing site.

“All of the local and exotic materials among the returned samples of Chang’e-5 can be used to answer a number of further scientific questions,” said Qian, in a press release. “In addressing these we shall deepen our understanding of the Moon’s history and help prepare for further lunar exploration.”

You can read the team’s findings here.

Lead image caption: Image of the Chang’e-5 sample “CE5C0400” from the Moon’s surface. This fraction of lunar materials returned to Earth by Chang’e-5 weighs nearly 35 grams and was collected by a robotic arm. Credit: CNSA (China National Space Administration) / CLEP (China Lunar Exploration Program) / GRAS (Ground Research Application System).

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Categories: Astronomy

A Tiny, Inexpensive Satellite Will be Studying the Atmospheres of hot Jupiters

Sat, 09/25/2021 - 7:05pm

The Colorado Ultraviolet Transit Experiment (aptly nicknamed CUTE) is a new, NASA-funded mission that aims to study the atmospheres of massive, superheated exoplanets – known as hot Jupiters – around distant stars. The miniaturized satellite, built by the Laboratory for Atmospheric and Space Physics (LASP) at the University of Colorado Boulder, is set to launch this Monday, September 27th on an Atlas V rocket.

Small-sized satellites like CUTE, known as CubeSats, are nothing new. They’ve long been a staple of collaborative university student projects, as cheap ways to get engineering experience in space. But lately, researchers have been pushing the boundaries of what CubeSats are capable of, putting them to the test with more and more ambitious projects. In 2018, for example, the first interplanetary CubeSats (MarCO-A and-B) left low earth orbit and traveled to Mars with NASA’s InSight lander, providing communications and telemetry for the lander as it descended towards the planet. CUTE, on the other hand, will remain in Earth orbit, but the scope of its ambition is equally lofty for such a small spacecraft.

Its primary mission is to understand the volatile physics around hot Jupiters. These enormous exoplanets have no analog in our solar system: they are similar in size to our gas giants, but orbit much closer to their stars, and can reach temperatures of over 7,800 degrees Fahrenheit.

CUTE principal investigator Kevin France explains that “because these planets are parked so close to their parent stars, they receive a tremendous amount of radiation.” That radiation heats the planets, causing their atmospheres to inflate and expand. Some of the gas eventually escapes and streams away from the planet.

Taking the carpool lane to space! When #Landsat 9 launches, we’ve got CubeSats riding along. CuPID and CUTE are hitching a ride to study exoplanet atmospheres and interactions between the Sun’s plasma and Earth’s magnetosphere. ??? https://t.co/aZfTfeVska pic.twitter.com/SVbzvsFdYz

— NASA Earth (@NASAEarth) September 24, 2021 University of Colorado graduate student Arika Egan leads installation of the CUTE CubeSat into the EFS dispenser system at Vandenberg Space Force Base on July 23, 2021. Credit: NASA / WFF

CUTE will spend its 7-month mission observing as many hot Jupiters as it can (10 at minimum), and measuring how quickly gas is escaping from them. Atmospheric escape is a process that happens to all planets, Earth included, but nothing like as quickly or on such large scales as on these hot Jupiters. Still, understanding how it works on these giants can help researchers understand how it works on rocky worlds too. If successful, the data CUTE gathers will be used to understand the processes of atmospheric escape on a wide range of different planet types.

This is the first time a NASA-funded CubeSat has been used to study exoplanets. LASP Director Daniel Baker is excited by what these tiny spacecraft can accomplish. “As little as a decade ago,” he said, “many in the space community expressed the opinion that CubeSat missions were little more than ‘toys. There was recognition that small spacecraft could be useful as teaching and training tools, but there was widespread skepticism that forefront science could be done with such small platforms. I am delighted that LASP and the University of Colorado have led the way in demonstrating that remarkable science can be done with small packages.”

The launch of CUTE from Vandenberg Air Force base in California can be watched live on September 27th, with liftoff planned for 2:12 PM EDT.

Learn More:

Daniel Strain, “New cereal box-sized satellite to explore alien planetsCU Boulder Today.

Featured Image: Artist impression of gases being blown away from KELT-9b, one of the hot Jupiters being studied by CUTE. Credit: LASP; NASA/JPL-Caltech/

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Categories: Astronomy

Astronomers Find a Giant Cavity in Space, Hollowed out by an Ancient Supernova

Sat, 09/25/2021 - 12:11pm

Star formation is a topic astronomers are still trying to fully understand. We know, for example, that stars don’t form individually, but rather are born within vast interstellar molecular clouds. These stellar nurseries contain gas dense enough for gravity to trigger the formation of stars. In spiral galaxies, these molecular clouds are most commonly found within spiral arms, which is why stars are most often born in spiral arms.

We can observe several of these molecular clouds in our local neighborhood of the Milky Way. The most famous one is the Orion nebula, which is part of the Orion Molecular Cloud Complex, but there are other well-known molecular clouds, such as the molecular clouds of Perseus and Taurus. We can see stars forming within these clouds.

One part of the story we don’t fully understand is how these dense molecular clouds form in the first place. Since they are often found along spiral arms, one idea is that they form within pressure waves along the arms as stars bunch up like a traffic jam. Another idea is that their formation is triggered by supernovae. These massive explosions create shockwaves in interstellar gas and dust, causing them to bunch together. But proving this idea is hard because it’s extremely difficult to pin down the location of a molecular cloud. We can see where it is in the sky, but determining the distance is difficult. But a new study has pinned down the locations of the Perseus and Taurus clouds, and the result supports the supernova model.

A bubble exists between the Taurus molecular cloud (blue) and the Perseus molecular cloud (red). Credit: Jasen Lux Chambers/Center for Astrophysics | Harvard & Smithsonian

Using data from the Gaia spacecraft, the team was able to map the Perseus and Taurus molecular clouds in 3-D. They also mapped other, fainter clouds in the region, and found they were all part of a single structure. They all lie along the surface of a bubble about 500 light-years across. The spherical structure is very clear, and the team has even created an augmented reality version you can check out. Based on the structure of the bubble, the team estimates it was formed by a large supernova or series of supernovae that occurred about 10 million years ago. The clouds we see now, and the stars forming within them, are the result of supernova shock waves.

This work shows that supernovae can play a significant role in the formation of stars, beyond their contribution of heavier elements. With 3-D maps such as this one, we can now compare them to simulation models to better understand both cloud formation and star formation.

Reference: Bialy, Shmuel, et al. “The Per-Tau Shell: A Giant Star-forming Spherical Shell Revealed by 3D Dust Observations.” The Astrophysical Journal Letters 919.1 (2021): L5.

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Categories: Astronomy

Galactic Panspermia. How far Could Life Spread Naturally in a Galaxy Like the Milky Way?

Fri, 09/24/2021 - 6:25pm

Can life spread throughout a galaxy like the Milky Way without technological intervention? That question is largely unanswered. A new study is taking a swing at that question by using a simulated galaxy that’s similar to the Milky Way. Then they investigated that model to see how organic compounds might move between its star systems.

The central question in science is probably “How did life begin?” There’s no larger question, and there’s no answer, so far. A secondary question is more approachable: “Can life spread from star to star?” That’s the theory of panspermia, in a nutshell.

Earth’s history poses an important question when it comes to panspermia. Scientists think there wasn’t enough time between when the Earth cooled enough to become habitable and the appearance of life. Not all scientists think that, of course. There’s a range of thoughts on the matter. But the question remains: Was there enough time for DNA-based life to get going independently on Earth, or did panspermia play a role?

While much of the talk around panspermia concerns simple lifeforms somehow moving between stars, more serious talk concerns the movement of organic compounds necessary for life. Scientists have found some of those compounds on comets and elsewhere out in space. We now know they’re not necessarily rare. So can those compounds move around from solar system to solar system?

The new study is titled “Panspermia in a Milky Way-like Galaxy.” The lead author is Raphael Gobat, from Instituto de Física, Valparaíso, Chile. The paper is available on the pre-print site arxiv.org.

So, is panspermia a thing? Inside a solar system like ours, it seems possible. Meteorites from Mars have landed on Earth, which is pretty solid evidence. If rocks can make the trip, why not chemicals in or on those rocks? Could spores make the interstellar trip between star systems?

The team of researchers set out to answer that question. They worked with a simulated galaxy from MUGS, the McMaster Unbiased Galaxy Simulations. MUGS is a set of 16 simulated galaxies created by researchers in the early 2000s. In 2016, Gobat et al added a modified galactic habitability model, called GH16.

Their chosen galaxy is g15784. It’s a little more massive than the Milky Way and has a history of quiescent mergers. It hasn’t merged with anything very massive in a long time, and it’s orbited by several spherical galaxies.

Here it is, the simulated galaxy called g15784. Two spheroidal galaxies are seen in the image, one above the galactic plane and one below. Image Credit: Gobat et al 2021.

The team computed a level of habitability for each star particle in the galaxy. In this case, that means the number of main sequence low-mass stars with terrestrial planets within their habitable zones. They followed GH16 to do that. GH16 takes into account stellar metallicity, minimum and maximum mass, formation history, and the inner and outer ranges of its habitability zone (HZ.)

They also considered the effect of supernovae explosions on habitability. The galactic core is the most densely populated part of the galaxy. So even though there are more potentially habitable planets there, there are also more deadly supernovae. The higher density of stars in the core means each habitable planet has a higher chance of being rendered uninhabitable by a supernova. The higher metallicity in the core also reduces habitability, according to the authors. That makes the central region a tough place for panspermia.

The group also looked at the spiral arms of g15784. While star density is also high there, and so are supernova rates (SNR), they didn’t affect habitability the same as in the bulge. They also looked at the galactic disk and halo.

A three-panel figure from the paper showing a projected column at z = 0 and in a 1 kpc-wide slice passing through the center of g15784. The top shows the median value for natural habitability, the middle shows the fraction of possible cradles in the simulated galaxy, and the bottom shows the fraction of possible colonization targets. The magenta star shows where the Sun would be if this were the Milky Way. Image Credit: Gobat et al 2021.

The study shows that panspermia is at least possible, though there’s no simple answer to the question. They found that while median habitability increases with galactocentric radius, while the probability for panspermia is inverse. That’s because of the higher star density in the galactic bulge.

But panspermia probability is low in the central disk. That’s because of higher supernova rates and a lower escape fraction due to higher metallicity. Natural habitability doesn’t vary much throughout the galaxy, whereas panspermia probability varies widely, by several orders of magnitude.

The team found no correlation between the probability of panspermia and the habitability of the receiving particle. (In this study, particle refers to a high number of stars, due to the simulation’s low resolution.)

Lastly, they found that panspermia is less effective than in-situ prebiotic evolution, although they say that they can’t quantify that precisely.

In their conclusion, the authors point out several caveats for the work. “… first, it includes several factors that we have regarded as unknown constants (e.g., the capture fraction of spores by target planets, the relation between habitability and the presence of life, the typical speed of interstellar objects, and the absolute value of escape fraction of the interstellar organic compounds from source planets).” As a result, they consider their results to be “… naturally more qualitative than quantitative.”

They also caution that while a real galaxy like the Milky way is dynamic and changing, their simulated galaxy is just a snapshot. “As such, these results only apply if the typical timescale for panspermia is much shorter than the dynamical timescale of a galaxy.”

There are other differences between the simulated galaxy and the Milky Way. “For example, our mock galaxy has a larger value of bulge-to-disc light ratio than the actual Milky Way, and the galactic bulge has been suggested to be well-suited for panspermia.” Finally, they point out that MUGS is a low-resolution simulation, and a higher-resolution simulation could produce some differences in the results.

We’ve recently been visited by two interstellar objects: ‘Oumuamua and comet 2L/Borisov. So we know that objects are travelling between star systems. There’ve probably been many more interstellar visitors that we weren’t technologically capable of seeing. And we know that organic building blocks are present out in space.

That doesn’t prove that organic building blocks can travel between stars, but it seems possible. Thanks to this research, we might know a little more about how likely it is, and where in a galaxy it might take place.

More:

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Categories: Astronomy