Universe Today

It’s a measure of human ingenuity and curiosity that scientists debate the possibility of life on Venus. They established long ago that Venus’ surface is absolutely hostile to life. But didn’t scientists find a biomarker in the planet’s clouds? Could life exist there, never touching the planet’s sweltering surface?

It seems to depend on who you ask.

We’ll start with phosphine.

Phosphine is a biomarker, and in 2020, researchers reported the detection of phosphine in Venus’ atmosphere. There should be no phosphine because phosphorous should be oxidized in the planet’s atmosphere. According to the paper, no abiotic source could explain the quantity found, about 20 ppb.

Subsequently, the detection was challenged. When others tried to find it, they couldn’t. Also, the original paper’s authors informed everyone of an error in their data processing that could’ve affected the conclusions. Those authors examined the issue again and mostly stood by their original detection.

At this point, the phosphine issue seems unsettled. But if it is present in Venus’ atmosphere and is biological in nature, where could it be coming from? Venus’s surface is out of the question.

That leaves Venus’ cloud-filled atmosphere as the only abode of life. While the idea might seem ridiculous at first glance, researchers have dug into the idea and generated some interesting results.

In a new paper, researchers examine the idea of microscopic life that lives and reproduces in water droplets in Venus’s clouds. The title is “Necessary Conditions for Earthly Life Floating in the Venusian Atmosphere.” The lead author is Jennifer Abreu from the Department of Physics and Astronomy, Lehman College, City University of New York. The paper is currently in pre-print.

Spacecraft have struggled to contend with the harsh conditions on Venus’s surface. The Soviet Venera 13 lander captured this image of the planet’s surface in March of 1982. NASA/courtesy of nasaimages.org

“It has long been known that the surface of Venus is too harsh an environment for life,” the authors write. “Contrariwise, it has long been speculated that the clouds of Venus offer a favourable habitat for life but regulated to be domiciled at an essentially fixed altitude.” So, if life existed in the clouds, it wouldn’t be spread throughout. Only certain altitudes appear to have what’s needed for life to survive.

The type of life the authors envision aligns with other thinking about Venusian atmospheric life. “The archetype living thing <being> the spherical hydrogen gasbag isopycnic organism,” they state. (Isopycnic means constant density; the other terms are self-explanatory.)

Here’s how the authors think it could work.

Venus is shrouded in clouds so thick we can only see the surface with radar. The clouds reach all the way around the globe. The cloud base is about 47 km (29 miles) from the surface, where the temperature is about 100 C (212 F.) At equatorial and mid-latitudes, they extend up to a 74 km (46 miles) altitude, and at the poles, they extend up to about 65 km (40 miles.)

Cloud structure in the Venusian atmosphere in 2016, revealed by observations in two ultraviolet bands by the Japanese spacecraft Akatsuki. Image Credit: Kevin M. Gill

The clouds can be subdivided into three layers based on the size of aerosol particles: the upper layer from
56.5 to 70 km altitude, the middle layer from 50.5 to 56.5 km, and the lower layer from 47.5 to 50.5 km. The smallest droplets can float in all three layers. But the largest droplets, which the authors call type 3 droplets with a radius of 4 µm, are only present in the middle and lower layers.

“It has long been suspected that the cloud decks of Venus offer an aqueous habitat where microorganisms can grow and flourish,” the authors write. Everything life needs is there: “Carbon dioxide, sulfuric acid compounds, and ultraviolet (UV) light could give microbes food and energy.”

Because of temperature, life in Venus’ clouds would be restricted to a specific altitude range. At 50 km, the temperature is between 60 and 90 degrees Celsius (140 and 194 degrees Fahrenheit). The pressure at that altitude is about 1 Earth atmosphere.

This figure from the research shows the temperature and pressure throughout Venus’s atmosphere. Image Credit: Image Credit: S. Seager et al. 2021. doi:10.1089/ast.2020.2244

There’s a precedent for life existing in the clouds. It happens here on Earth, where scientists have observed bacteria, pollen, and even algae at altitudes as high as 15 km (9.3 miles.) There’s even evidence of bacteria growing in droplets in a super-cooled cloud high in the Alps. The understanding is that these organisms were carried aloft by wind, evaporation, eruptions, or even meteor impacts. But there’s an important difference between Earth’s and Venus’ clouds.

Earth’s clouds are transient. They form and dissolve constantly. But Venus’ clouds are long-lasting. They’re a stable environment compared to Earth’s clouds. In Earth’s clouds, aerosol particles are sustained for only a few days, while in Venus’ clouds, the particles can be sustained for much longer periods of time.

Add it all up, and you get stable cloud environments where aerosol particles can sustain themselves in an environment where energy and nutrients are available. The researchers say that though eventually aerosol particles and the life within them will fall to the surface, they have time to reproduce before that happens.

This image shows the cycle of Venusian aerial microbial life. Image Credit: S. Seager et al. 2021. doi:10.1089/ast.2020.2244

The idea of a microbial life cycle in Venusian clouds was developed by other researchers in their 2021 paper “The Venusian Lower Atmosphere Haze as a Depot for Desiccated Microbial Life: A Proposed Life Cycle for Persistence of the Venusian Aerial Biosphere.”

There are five steps in Venus’s proposed cloud lifecycle:

1. Dormant desiccated spores (black blobs) partially populate the lower haze layer of the atmosphere.
2. Updrafts transport them up to the habitable layer. The spores could travel up to the clouds via gravity waves.
3. Shortly after reaching the (middle and lower cloud) habitable layer, the spores act as cloud condensation nuclei, and more and more water gathers into a single droplet. Once the spores are surrounded by liquid with the necessary chemicals, they germinate and become metabolically active.
4. Metabolically active microbes (dashed blobs) grow and divide within liquid droplets (shown as solid circles in the figure). The liquid droplets continue to grow by coagulation.
5. Eventually, the droplets are large enough to settle out of the atmosphere gravitationally; higher temperatures and droplet evaporation trigger cell division and sporulation. The spores are smaller than the microbes and resist further downward sedimentation. They remain suspended in the lower haze layer (a depot of hibernating microbial life) to restart the cycle.

In this new work, the researchers focus on time.

“One of the key assumptions of the aerial life cycle put forward in Seager et al. 2021 is the timescale on which droplets would persist in the habitable layer to empower replication,” the authors write. “It is this that we now turn to study.”

This table from the research shows generation times for some common Earth bacteria. Image Credit: Abreu et al. 2024.

The authors used E. Coli generation times under optimal conditions in their work. In aerobic and nutrient-rich conditions, E. Coli can reproduce in 20 minutes. So, the E. Coli population will double three times in one hour. Bacteria must reproduce faster than they fall to the surface to sustain itself. They need to form a colony.

The researchers calculated that to sustain itself, the time it takes for bacteria to fall from the habitable part of the atmosphere to the inhabitable has to be longer than half an Earth day. As droplet size increases, the droplets would begin to sink. “As the droplet size approaches 100 µm, the droplets would start sinking to the lower haze layers,” they explain. However, their detailed calculations show that reproduction outpaces the fallout rate.

According to the team’s work, a population of bacteria could sustain itself in Venus’ clouds.

There are, obviously, still some questions. How certain are we that nutrients are available? Is there enough energy? Are there updrafts that can loft spores into the right layer of the atmosphere?

But the real big question is how was this all set in motion?

“An optimist might even imagine that the microbial life actually arose in a good-natured surface habitat, perhaps in a primitive ocean, before the planet suffered a runaway greenhouse, and the microbes lofted into the clouds,” the authors write. If that’s the case, this unique situation arose billions of years ago. Is there any other possibility? Could life have originated in the clouds?

Much scientific investigation into Venus, phosphine, clouds, and life relies on scant evidence. Few are willing to go out on a limb and proclaim that Venus can and does support life. We need more evidence.

For that, we have to wait for missions like the Venus Life Finder Mission. It’s a private mission being developed by Rocket Lab and a team from MIT. Who knows what VLF and other missions like DAVINCI and VERITAS will find? Stronger evidence of phosphine? Better data on Venus’ atmospheric layers and the conditions in them?

Life itself?

Artist’s impression of the Rocket Lab Mission to Venus. Credit: Rocket Lab

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Pink Floyd was wrong, there is no dark side to the Moon. There is however, a far side. The tidal effects between the Earth and Moon have caused this captured or synchronous rotation. The two sides display very different geographical features; the near side with mare and ancient volcanic flows while the far side displaying craters within craters. New research suggests the Moon has turned itself inside out with heavy elements like titanium returning to the surface. It’s now thought that a giant impact on the far side pushed titanium to the surface, creating a thinner more active near side. 

There have been a number of theories for the formation of the Moon; the capture theory and the accretion theory to name two of them. Perhaps the most accepted theory now is the giant impact theory which suggests Earth was struck by a large object, causing a lot of debris to be ejected into orbit. This material eventually coalesced to form the Moon we know and love today. 

In the decades that followed the Apollo missions, scientists studied the rocks returned by the astronauts. The studies revealed that many of the surface rocks contained unexpectedly high concentrations of titanium. More surprisingly was that satellite observations revealed these titanium rich minerals were far more common on the nearside and absent on the far-side. What is known is that the Moon formed fast and hot and would have been covered for a short period in an ocean of molten magma. The magma cooled and solidified forming the Moon’s crust but trapped below was the more dense material including titanium and iron. 

Sample collection on the surface of the Moon. Apollo 16 astronaut Charles M. Duke Jr. is shown collecting samples with the Lunar Roving Vehicle in the left background. Image: NASA

The dense material should have sunk to greater depths inside the Moon however over the years that followed something strange seems to have happened. The denser material did indeed sink, mixed with mantle but melted and returned to the surface as titanium rich lava flows. Debates have been raging whether this is exactly what happened but a new piece of research by a team at the University of Arizona Lunar and Planetary Laboratory offer more details about the process and how the interior of the Moon evolved.

It has already been suggested that the Moon may have suffered a giant impact on the far side causing the heavier elements to be forced over to the near side but the new study highlighted supporting evidence from gravitational anomalies. The team measured tiny variations in the Moon’s gravitational field from data from the GRAIL mission. GRAIL – or Gravity Recovery and Interior Laboratory – orbited the Moon to create the most accurate gravitational map of the Moon to date. Using GRAIL data the team discovered that titanium-iron oxide minerals had migrated to the near side and sunk to the interior in sheetlike cascades. This was consistent with models suggesting the event occurred more than 4.22 billion years ago. 

Global map of the Moon, as seen from the Clementine mission, showing the differences between the lunar near- and farside. Credit: NASA.

As paper co-author and LPL associate professor Jeff Andrews-Hanna said “The moon is fundamentally lopsided in every respect.” The near side feature known as Oceanus Procellarum is a great example. It is lower in elevation and has a lava flow covered thinner crust with high concentrations of titanium rich elements. This is very different on the far side. The strange and unique structure of the region is thought to be key in understanding the event that happened billions of years ago to shape the Moon we see today.

Source : How the Moon turned itself inside out

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There’s a lot we don’t know about the planet nearest to us. Venus is shrouded in clouds, making speculation about what’s happening on its surface a parlor game for many planetary scientists for decades. But one idea that always seems to come up in those conversations – volcanoes. It’s clear that Venus has plenty of volcanoes – estimates center around about 85,000 of them in total. However, science is still unclear as to whether there is any active volcanism on Venus or not. A new set of missions to the planet will hopefully shed some light on the topic – and a new paper from researchers from Europe looks at how we might use information from those missions to do so.

The authors break the question of whether there is active volcanism on Venus into two distinct approaches. First, can Venus maintain its current atmospheric composition without adding gases from volcanic sources? Second, is there any evidence for “transient” effects that would only be possible if active volcanoes existed? 

Let’s explore the first approach first. One major data point to consider with this approach is the variability of sulfur dioxide in the atmosphere over periods as long as decades. Some researchers have pointed to this variability as clear evidence of volcanism. Still, some take a more nuanced view and point out that the variability could be caused by unknown surface-atmosphere interactions or even interactions between two layers of the atmosphere itself.

Fraser has a particular interest in Venus – here’s why.

Transient effects in the atmosphere could include any number of features, ranging from water vapor to particulate matter (e.g., volcanic ash). So far, data collected on this has been limited and mainly done with remote sensing missions. However, at least a few of the new missions to Venus will involve taking data as they descend through the atmosphere. 

One of those – DAVINCI – plans to take measurements in situ in the atmosphere. It will come with a couple of spectrometers, inertial measurement units, and high-tech cameras to collect data in the planet’s lower atmosphere. The spectrometers themselves should be able to directly and clearly detect trace volcanic gases in the atmosphere. Ionic concentrations, such as the deuterium/hydrogen ratio, would also indicate ongoing volcanic outgassing.

But what about gases higher up in the atmosphere? EnVision, another mission, will specialize in that area of the planet using different types of near-IR and ultraviolet spectroscopy. It might help solve some mysteries in Venus’ cloud tops, including where an unknown reservoir of sulfur dioxide is located, as it seems to be a feedstock to an unknown process taking place in the clouds that defies current modeling efforts.

Venera was one of the previous efforts to map the surface of Venus. Fraser discusses its history here.

Though it is beyond the scope of the current paper, another potentially interesting sensor on a cloud-based platform would be an infrasound sensor – as it would be able to directly detect pressure differences caused by volcanic eruptions. Unfortunately, no current planned mission would maintain position in the atmosphere for long enough for such a sensor to do its work, though a few have been proposed in recent years.

There’s still going to be a long wait time before any of these analytical techniques can be put to good use. Of the three main missions heading to Venus shortly, the earliest – DAVINCI – isn’t planned to launch for at least another five years, with arrival at Venus a few years later. That’s plenty of time for theorists to fine-tune their ideas about what the mission might find. And hopefully, it will help us answer the question of volcanism on our closest neighbor once and for all.

Learn More:
Wilson et al. – Possible Effects of Volcanic Eruptions on the Modern Atmosphere of Venus
UT – Potentially Active Volcanoes Have Been Found on Venus
UT – We Now Have a Map of all 85,000 Volcanoes on Venus
UT – Volcanoes on Venus May Still Be Active

Lead Image:
Maat Mons Volcano on Venus
Credit – NASA / JPL

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In 2009, NASA launched the Lunar Reconnaissance Orbiter (LRO.) Its ongoing mission is to map the lunar surface in detail, locating potential landing sites, resources, and interesting features like lava tubes. The mission is an ongoing success, another showcase of NASA’s skill. It’s mapped about 98.2% of the lunar surface, excluding the deeply shadowed regions in the polar areas.

But recently, the LRO team’s skill was on display for another reason: it captured images of another satellite speeding over the lunar surface.

The Republic of Korea, or what most of us call South Korea, launched their Danuri lunar orbiter in August 2022. It’s the nation’s first lunar orbiter, and its mission is to develop and test technologies—including the space internet—and make a topographic map of the lunar surface. The map will help select future landing sites and identify resources such as uranium, helium-3, silicon, aluminum, and water ice. Danuri carries a suite of instruments, including a spectrometer, a magnetometer, and different cameras. Significantly, it contains a camera that will allow it to image the shadowed polar regions beyond the LRO’s capabilities.

A rendering of South Korea’s Danuri, Korean Pathfinder Lunar Orbiter (KPLO). Image Credit: Korean Aerospace Research Institute.

NASA contributed to the Korea Aerospace Research Institute’s (KARI) Danuri mission. NASA built the Shadowcam instrument that images the shadowed regions at the lunar poles.

As a sort of high-five to their fellow space-faring nation, the LRO captured images of Danuri as it sped by under the LRO.

On March 5th and 6th, the pair of orbiters sped by each other at a combined velocity of 11,500 km/h (7,200 mp/h). There were three orbits that put the LRO in a position to capture images of the swiftly moving Danuri. During each orbit, the vertical separation between the two was different.

The LRO was 5 km (3 miles) above Danuri in the first image. The LRO had to change its angle. To catch Danuri, it had to aim 43 degrees down from its usual angle.

Danuri looks like a streak in this LRO image taken 5 km above it. Image Credit: NASA/Goddard/Arizona State University

On the second orbit, only 4 km (2.5 miles) separated the pair of orbiters.

During the second orbit, the LRO captured this image of Danuri from only 4 km (2.5 miles) above it. The LRO was oriented 25 degrees toward the South Korean orbiter. Image Credit: NASA/Goddard/Arizona State University

On the third and final orbit, the separation between the two spacecraft was greater: 8 km (5 miles.) This time, the LRO was oriented at a 60-degree angle.

In the image on the right, the Danuri pixels are unsmeared. The LRO was 8 km (5 miles) above Danuri when it captured this image. The image is rotated 90 degrees to look like what a person would see if they onboard the LRO and looking out a window. Image Credit: NASA/Goddard/Arizona State University

Danuri is difficult to see in the final image.

NASA says Danuri is in the white box near the right-hand corner of the image. If you can see it, you should consider becoming a citizen scientist. For perspective, the crater above the white box is 12 km (7.5 miles) wide. Image Credit: NASA/Goddard/Arizona State University

This isn’t the first time the pair of orbiters have played the imaging game. Back in April 2023, it was Danuri’s turn to take a picture of the LRO. At the time, the Korean spacecraft passed about 18 km (11 miles) above the LRO and imaged it with its ShadowCam instrument.

Danuri captured this image of the LRO when the NASA satellite was 18 km (11 miles) below it. The combined velocity of both spacecraft was 11,000 km/h (7,000 mp/h.) Image Credit: NASA/KARI/Arizona State University

This isn’t the first time lunar orbiters have captured each other’s portraits. In 2014, the LRO captured NASA’s Lunar Atmosphere and Dust Environment Explorer (LADEE) before it was sent to impact the lunar surface. Read about it here.

The post US Satellite Photographs a South Korean Satellite from Lunar Orbit appeared first on Universe Today.

On Monday, April 8th, people across North America witnessed a rare celestial event known as a total solar eclipse. This phenomenon occurs when the Moon passes between the Sun and Earth and blocks the face of the Sun for a short period. The eclipse plunged the sky into darkness for people living in the Canadian Maritimes, the American Eastern Seaboard, parts of the Midwest, and northern Mexico. Fortunately for all, geostationary satellites orbiting Earth captured images of the Moon’s shadow as it moved across North America.

One such satellite was the Geostationary Operational Environmental Satellite-16 (GOES-16), part of the Earth observation network jointly run by NASA and the National Oceanic and Atmospheric Administration (NOAA). The GOES-16 (GOES-East) satellite is the first of the series, regularly monitoring space weather and providing continuous imagery and atmospheric measurements of Earth’s western hemisphere. From its orbit at a distance of 36,000 km (~22,370 mi) from Earth, GOES-16 captured the passage of the eclipse across North America from approximately 10:00 A.M. to 05:00 P.M. EST (07:00 A.M. to 02:00 P.M. PST).

Solar eclipses take several forms, which include what many residents in North America witnessed yesterday (i.e., the Moon completely blocking the face of the Sun). There’s also an annual eclipse, which happens when the Moon passes between the Sun and Earth when it is at or near its farthest point from Earth. As a result, the face of the Sun is not completely obscured and is visible as a bright ring in the sky. There’s also a partial eclipse, which happens when the Sun, Moon, and Earth are not perfectly lined up, making the Sun appear crescent-shaped.

There’s also what is known as a hybrid solar eclipse, which can appear to shift between annular and total (due to Earth’s curvature) as the Moon’s shadow moves across the globe. A total eclipse, however, is the rarest of these events, where people located directly in the center of the Moon’s shadow will see only the Sun’s outer atmosphere (the corona). The next total eclipse is not expected to occur until August 12th, 2026, and will be visible to residents in Greenland, Iceland, Spain, Russia, and a small area of Portugal. For people in Europe, Africa, and North America, the same eclipse will appear as a partial one.

The passage of the Moon’s shadow across Earth’s surface is known as the “path of totality.” As the images show, this path spanned across the North American continent from Mexico to the eastern tip of Canada. Aside from GEOS-16, images were also taken by the European Space Agency’s (ESA) Copernicus Sentinel-3 mission using its Sea and Land Surface Temperature Radiometer (SLSTR). This satellite monitors Earth’s oceans, land, glaciers, and atmosphere to monitor and improve our understanding of global weather dynamics.

In addition to providing a rare glimpse at what a total eclipse looks like from space, the combined images are also an effective tool for researching how an eclipse influences Earth’s weather. As the Moon obscures light and heat from the Sun, air temperatures drop in the path of totality and can cause cloud formations to evolve in different ways. Data from GOES-16, Sentinel-3, and other Earth Observation satellites is now being used to explore these effects.

Further Reading: ESA

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In 2013, the Hubble Space Telescope spotted water vapour on Jupiter’s moon Europa. The vapour was evidence of plumes similar to the ones on Saturn’s moon Enceladus. That, and other compelling evidence, showed that the moon has an ocean. That led to speculation that the ocean could harbour life.

But the ocean is obscured under a thick, global layer of ice, making the plumes our only way of examining the ocean. The plumes are so difficult to detect they haven’t been confirmed.

The lead author of the paper presenting Hubble’s 2013 evidence is Lorenz Roth of Southwest Research Institute. He said, “By far, the simplest explanation for this water vapour is that it erupted from plumes on the surface of Europa. If those plumes are connected with the subsurface water ocean we are confident exists under Europa’s crust, then this means that future investigations can directly investigate the chemical makeup of Europa’s potentially habitable environment without drilling through layers of ice. And that is tremendously exciting.”

It is, but first, scientists have to find the plumes.

“We pushed Hubble to its limits to see this very faint emission. These could be stealth plumes because they might be tenuous and difficult to observe in visible light,” said Joachim Saur of the University of Cologne, co-author of the 2013 paper.

This artist’s illustration shows plumes erupting through Europa’s icy surface. Gigantic Jupiter lurks in the background. Image Credit: NASA/ESA/K. Retherford/SWRI

Describing them as tenuous stealth plumes turned out to be prophetic.

Recently, a team of researchers went looking for the plumes. Their results are in a presentation given to the IAU Symposium 383 titled “ALMA Spectroscopy of Europa: A Search for Active Plumes.” The lead author is M.A. Cordiner from the Solar System Exploration Division at NASA’s Goddard Space Flight Center.

“The subsurface ocean of Europa is a high-priority target in the search for extraterrestrial life, but direct investigations are hindered by the presence of a thick exterior ice shell,” the authors write. The researchers used ALMA to search for molecular emissions from atmospheric plumes. They were investigating processes under the ice that could help them understand Europa’s ocean and its chemistry.

The Solar System is full of icy bodies, including comets, Kuiper Belt Objects, dwarf planets, and moons like Europa. Europa has a high density compared to other icy bodies, indicating a substantial rocky interior. Its ocean makes up about 10% of the moon and is covered by an icy shell of uncertain thickness. It could be several tens of kilometres thick. Scientists learned much of this from NASA’s Galileo mission.

In recent years, Europa and its ocean have leapt to the top of the list of targets in the search for life. The reasons aren’t obscure: liquid water is an irresistible beacon in our search for habitable places. The plumes from Europa’s ocean are our only way to study the ocean and its potential habitability.

This illustration shows what the interior of Europa might look like. Geysers might erupt through cracks and fissures in the ice. Image Credit: NASA/JPL-Caltech/Michael Carroll)

Over the years, different telescopes have examined Europa, searching for more evidence of the plumes. They’ve found potential intermittent plume activity near the moon’s south pole. But confirmation of the plumes the Hubble spotted in 2013 is elusive. In 2023, the JWST examined Europa. Those observations “found no evidence for active plumes, indicating that any present-day activity must be localized and weak; robust confirmation of the initial HST plume results also remains challenging,” the authors write.

In an attempt to find the plumes, the authors employed ALMA, the Atacama Large Millimeter/submillimeter Array. They observed Europa on four separate days to cover the moon’s surface. Unfortunately, they found no plumes.

These are four ALMA images of Europa. The researchers observed the moon on four different days so they could image almost the entire surface. They found no plumes. Image Credit: Cordiner et al. 2024.

“Despite near-complete coverage of both Europa’s leading and trailing hemispheres, we find no evidence for gas phase molecular absorption or emission in our ALMA data,” the researchers write. “Using ALMA’s unique combination of high spectral/spatial resolution and sensitivity, our observations have enabled the first dedicated search for HCN, H2CO, SO2 and CH3OH in Europa’s exosphere and plumes. No evidence was found for the presence of these molecules.”

Finding no evidence doesn’t quite mean that those molecules aren’t there. Rather, it means that if they are there, their concentrations are so low they’re below the detection threshold. In this case, some concentrations would be lower than those detected in Enceladus’ plumes, which are confirmed.

One chemical in particular illustrates this point: CH3OH (methanol.) “For the CH3OH abundance, on the
other hand, our ALMA upper limit of < 0.86% would not have been sensitive enough to detect this molecule at the Enceladus plume abundance of 0.02%,” the authors write.

There are some interesting relationships between Europa and other icy objects in the Solar System. It has to do with abundance limits. The researchers established upper limits for H2CO (formaldehyde) on Europa. “Indeed, our H2CO abundance upper limit is significantly lower than measured by Cassini in the Enceladus plume, implying a possible chemical difference.”

Despite the fact that it didn’t find any plumes, the observations were still valuable. By setting detection limits it helps subsequent efforts to search for them. And this won’t be scientists’ final attempt at finding plumes. Anything that provides clues to Europa’s ocean is too tantalizing to ignore, and this research shows that ALMA is suited to this type of investigation.

“Our results show that ALMA is a powerful tool in the search for outgassing from icy bodies within the Solar System and that follow-up searches for other molecules at additional epochs (on Europa and other icy bodies) are justified,” the researchers conclude.

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NASA’s Parker Solar Probe has been in studying the Sun for the last six years. In 2021 it was hit directly by a coronal mass ejection when it was a mere 10 million kilometres from the solar surface. Luckily it was gathering data and images enabling scientists to piece together an amazing video. The interactions between the solar wind and the coronal mass ejection were measured giving an unprecedented view of the solar corona. 

The Sun is a fascinating object and as our local star, has been the subject of many studies. There are still mysteries though and it was hoping to unravel some of these that the NASA Parker Solar Probe was launched. It was sent on its way by the Delta IV heavy back in 2018 and has flown seven times closer to the Sun than any spacecraft before it. 

Illustration of the Parker Solar Probe spacecraft approaching the Sun. Credits: Johns Hopkins University Applied Physics Laboratory

By the time Parker completes its seven year mission it will have completed 24 orbits of the Sun and flown to within 6.2 million kilometres to the visible surface. For this to happen, its going to get very hot so the probe has a 11.4cm thick carbon composite shield to keep its components as cool as possible in the searing 1,377 Celsius temperatures. 

Flying within the Sun’s outer atmosphere, the corona, the probe picked up turbulence inside a coronal mass ejection as it interacted with the solar wind. These events are eruptions of large amounts of highly magnetised and energetic plasma from within the Sun’s corona. When directed toward Earth they can cause magnetic and radio disruptions in many ways from communications to power systems. 

Image of a coronal mass ejection being discharged from the Sun. (Credit: NASA/Goddard Space Flight Center/Solar Dynamics Observatory)

Using the Wide Field Imager for Parker Solar Probe (WISPR) and its prime position inside the solar atmosphere, unprecedented footage was captured (click on this link for the video). The science team from the US Naval Research Laboratory revealed what seemed like turbulent eddies, so called Kelvin-Helmholtz instabilities (KHIs) in one of the images. Turbulent eddy structures like these have been seen in the atmosphere of terrestrial planets. Strong wind shear between upper and lower cloud levels causes thin trains of crescent wave like clouds. 

Member of the WISPR team Evangelos Paouris PhD was the eagle eyed individual that spotted the disturbance. Paouris and team analysed the structure to verify the waves. The discovery of these rare features in the CME have opened up a whole new field of investigations.  

The KHIs are the result of turbulence which plays a key role in the movement of CMEs as they flow through the ambient solar wind. Understanding the CMEs and their dynamics of CMEs and a more fuller understanding of the Sun’s corona. This doesn’t just help us understand the Sun but also helps to understand the effect of CMEs on Earth and our space based technology.

Source : WISPR Team Images Turbulence within Solar Transients for the First Time

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In a couple billion years, our Sun will be unrecognizable. It will swell up and become a red giant, then shrink again and become a white dwarf. The inner planets aren’t expected to survive all the mayhem these transitions unleash, but what will happen to them? What will happen to the outer planets?

Right now, our Sun is about 4.6 billion years old. It’s firmly in the main sequence now, meaning it’s going about its business fusing hydrogen into helium and releasing energy. But even though it’s about 330,000 times more massive than the Earth, and nearly all of that mass is hydrogen fuel, it will eventually run out.

In another five billion years or so, its vast reservoir of hydrogen will suffer depletion. As it burns through its hydrogen, the Sun will lose mass. As it loses mass, its gravity weakens and can no longer counteract the outward force driven by fusion. A star is a balancing act between the outward expansion of fusion and the inward force of gravity. Eventually, the Sun’s billions-of-years-long balancing act will totter.

With weakened gravity, the Sun will begin to expand and become a red giant.

This illustration shows the current-day Sun at about 4.6 billion years old. In the future, the Sun will expand and become a red giant. Image Credit: By Oona Räisänen (User:Mysid), User:Mrsanitazier. – Vectorized in Inkscape by Mysid on a JPEG by Mrsanitazier (en:Image: Sun Red Giant2.jpg). CC BY-SA 3.0, https://commons.wikimedia.org/w/index.php?curid=2585107

The Sun will almost certainly consume Mercury and Venus when it becomes a red giant. It will expand and become about 256 times larger than it is now. The inner two planets are too close, and there’s no way they can escape the swelling star. Earth’s fate is less certain. It may be swallowed by the giant Sun, or it may not. But even if it isn’t consumed, it will lose its oceans and atmosphere and become uninhabitable.

The Sun will be a red giant for about one billion years. After that, it will undergo a series of more rapid changes, shrinking and expanding again. But the mayhem doesn’t end there.

The Sun will pulse and shed its outer layers before being reduced to a tiny remnant of what it once was: a white dwarf.

An artist’s impression of a white dwarf star. The material inside white dwarfs is tightly packed, making them extremely dense. Image credit: Mark Garlick / University of Warwick.

This will happen to the Sun, its ilk, and almost all stars that host planets. Even the long-lived red dwarfs (M-dwarfs) will eventually become white dwarfs, though their path is different.

Astronomers know the fate of planets too close to the stars undergoing these tumultuous changes. But what happens to planets further away? To their moons? To asteroids and comets?

New research published in The Monthly Notices of the Royal Astronomical Society digs into the issue. The title is “Long-term variability in debris transiting white dwarfs,” and the lead author is Dr. Amornrat Aungwerojwit of Naresuan University in Thailand.

“Practically all known planet hosts will evolve eventually into white dwarfs, and large parts of the various components of their planetary systems—planets, moons, asteroids, and comets—will survive that metamorphosis,” the authors write.

There’s lots of observational evidence for this. Astronomers have detected planetary debris polluting the photospheres of white dwarfs, and they’ve also found compact debris disks around white dwarfs. Those findings show that not everything survives the main sequence to red giant to white dwarf transition.

“Previous research had shown that when asteroids, moons and planets get close to white dwarfs, the huge gravity of these stars rips these small planetary bodies into smaller and smaller pieces,” said lead author Aungwerojwit.

This Hubble Space Telescope shows Sirius, with its white dwarf companion Sirius B to the lower left. Sirius B is the closest white dwarf to the Sun. Credit: NASA, ESA, H. Bond (STScI) and M. Barstow (University of Leicester).

In this research, the authors observed three white dwarfs over the span of 17 years. They analyzed the changes in brightness that occurred. Each of the three stars behaved differently.

When planets orbit stars, their transits are orderly and predictable. Not so with debris. The fact that the three white dwarfs showed such disorderly transits means they’re being orbited by debris. It also means the nature of that debris is changing.

“The unpredictable nature of these transits can drive astronomers crazy—one minute they are there, the next they are gone.”

Professor Boris Gaensicke, University of Warwick

As small bodies like asteroids and moons are torn into small pieces, they collide with one another until nothing’s left but dust. The dust forms clouds and disks that orbit and rotate around the white dwarfs.

Professor Boris Gaensicke of the University of Warwick is one of the study’s co-authors. “The simple fact that we can detect the debris of asteroids, maybe moons or even planets whizzing around a white dwarf every couple of hours is quite mind-blowing, but our study shows that the behaviour of these systems can evolve rapidly, in a matter of a few years,” Gaensicke said.

“While we think we are on the right path in our studies, the fate of these systems is far more complex than we could have ever imagined,” added Gaensicke.

This artist’s illustration shows the white dwarf WD J0914+1914 (Not part of this research.) A Neptune-sized planet orbits the white dwarf, and the white dwarf is drawing material away from the planet and forming a debris disk around the star. Image Credit: By ESO/M. Kornmesser – https://www.eso.org/public/images/eso1919a/, CC BY 4.0, https://commons.wikimedia.org/w/index.php?curid=84618722

During the 17 years of observations, all three white dwarfs showed variability.

The first white dwarf (ZTF J0328?1219) was steady and stable until a major catastrophic event around 2011. “This might suggest that the system underwent a large collisional event around 2011, resulting in the production of large amounts of dust occulting the white dwarf, which has since then gradually dispersed, though leaving sufficient material to account for the ongoing transit activity, which implies continued dust production,” the researchers explain.

The second white dwarf (ZTF J0923+4236) dimmed irregularly every couple of months and displayed chaotic variability on the timescale of minutes. “These long-term changes may be the result of the ongoing disruption of a planetesimal or the collision between multiple fragments, both leading to a temporarily increased dust production,” the authors explain in their paper.

The third star (WD 1145+017) showed large variations in numbers, shapes and depths of transits in 2015. This activity “concurs with a large increase in transit activity, followed by a subsequent gradual re-brightening,” the authors explain, adding that “the overall trends seen in the brightness of WD?1145+017 are linked to varying amounts of transit activity.”

But now all those transits are gone.

“The unpredictable nature of these transits can drive astronomers crazy—one minute they are there, the next they are gone,” said Gaensicke. “And this points to the chaotic environment they are in.”

But astronomers have also found planetesimals, planets, and giant planets around white dwarfs, indicating that the stars’ transitions from main sequence to red giant don’t destroy everything. The dust and debris that astronomers see around these white dwarfs might come from asteroids or from moons pulled free from their giant planets.

“For the rest of the Solar System, some of the asteroids located between Mars and Jupiter, and maybe some of the moons of Jupiter may get dislodged and travel close enough to the eventual white dwarf to undergo the shredding process we have investigated,” said Professor Gaensicke.

When our Sun finally becomes a white dwarf, it will likely have debris around it. But the debris won’t be from Earth. One way or another, the Sun will destroy Earth during its red giant phase.

“Whether or not the Earth can just move out fast enough before the Sun can catch up and burn it is not clear, but [if it does] the Earth would [still] lose its atmosphere and ocean and not be a very nice place to live,” explained Professor Gaensicke.

The post What Happens to Solar Systems When Stars Become White Dwarfs? appeared first on Universe Today.

Galactic collisions, meteor impacts and even stellar mergers are not uncommon events. neutron stars colliding with black holes however are a little more rare, in fact, until now, we have never observed one. The fourth LIGO-Virgo-KAGRA observing detected gravitational waves from a collision between a black hole and neutron star 650 million light years away. The black hole was tiny though with a mass between 2.5 to 4.5 times that of the Sun. 

Neutron stars and black holes have something in common; they are both the remains of a massive star that has reached the end of its life. During the main part of a stars life the inward pull of gravity is balanced by the outward push of the thermonuclear pressure that makes the star shine. The thermonuclear pressure overcomes gravity for low mass stars like the Sun but for more massive stars, gravity wins. The core collapses compressing it into either a neutron star or a black hole (depending on the progenitor star mass) and explodes as a supernova – in the blink of an eye. 

In May 2023, as a result of the fourth observing session of the LIGO-Virgo-KAGRA (Laser Interferometer Gravitational Wave Observatory-Virgo Gravitational Wave Interferometer and Kamioka Gravitational Wave Detector) network, gravitational waves were picked up from a merger event. The signal came from an object 1.2 times the mass of the Sun and another slightly more massive object. Further analysis revealed the likelihood that one was a neutron star and the other a low mass black hole. The latter falls into the so called ‘mass gap’, more massive than the most massive neutron star and less massive than the least massive black hole.

Interactions between objects can generate gravitational waves. Before they were detected back in 2015, stellar mass black holes were typically found through X-ray observations. Neutron stars on the other hand, were usually found with radio observations. Between the two, was the mass gap with objects lacking between three and five solar masses. 

It has been the subject of debate among scientists with the odd object found which fell within the gap, fuelling debate about its existence. The gap has generally been considered to separate the neutron stars from the black holes and items in this mass group have been scarce. This gravitational wave discovery suggests maybe objects in this gap are not so rare after-all. 

One of the challenges of detecting mass gap objects and mergers between them is the sensitivity of detectors. The LIGO team at the University of British Columbia researchers are working hard to improve the coatings used in mirror production. Enhanced performance on future LIGO detectors will further enhance detection capabilities. It’s not just optical equipment that is being developed, infrastructure changes are also being addressed including data analysis software too. Improving sensitivity in all aspects of the gravity wave network is sure to yield results in future runs. However for now, the rest of the first half of the observing run needs analysing with 80 more candidate signals to study. 

Source : New gravitational wave signal helps fill the ‘mass gap’ between neutron stars and black holes

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Sometimes, the easy calculations are the most interesting. A recent paper from Balázs Bradák of Kobe University in Japan is a case in point. In it, he takes an admittedly simplistic approach but comes up with seven known exoplanets that could hold the key to the biggest question of them all – are we alone?

Dr. Bradák starts with a simple premise – there is a chance that life on Earth might have started via panspermia. There is also a case that panspermia was intention – an advanced civilization could theoretically have purposefully sent a biological seed ship to our local solar system to spread life here, essentially from scratch.

With those admittedly very large assumptions in place, Dr. Bradák works out a few characteristics about the planets that could have been the starting point for such a civilization. First, he assumes, as much of the astrobiological community does, that for an advanced civilization to arise on a planet, that planet has to be at least partially covered in an ocean. 

Sun-like stars aren’t the only potential hosts for habitable planets, as Fraser discusses here.

To meet that requirement, the planet has to be both the right size and the right temperature. The two size categories of exoplanets that Dr. Bradák originally selected were “terrestrial” – planets similar to Earth, including so-called “Super-Earths” – and “sub-Neptunes” – planets that are significantly larger than Earth but smaller than the ice giant in the outer fringes of our solar system.

Any such exoplanet also has to be in the habitable zone of its parent star. That alone dramatically narrows the potential field of planetary candidates. For simplicity’s sake, Dr. Bradák also eliminates sub-Neptunes as a potential planetary class. However, one other factor comes into play as well: age.

We know it took around 4.6 billion years for life to evolve to a point where it could theoretically send objects to other star systems – as we have now with Voyager. Since the original planet would also have to have evolved such a civilization, it would be double the time for its minimum age – or 9.2 billion years old.

The idea of panspermia has been around for decades, as Fraser discusses.

Dr. Bradák adds some additional argument that lowers the required age of the system – and he also assumes that the planetary system of a star forms at a similar time gap as our planetary system did. The distance to most of these stars is inconsequential on the scale of billions of years, so the travel time for the seed ship was discounted in this calculation. 

After all that pruning, Dr. Bradák turned to NASA’s Exoplanet Archive, which currently contains 5271 known exoplanets. Of those 5271, only 7 meet the specified age, size, and habitable zone placement criteria. In other words, according to our current knowledge of exoplanets and how life evolved, only a few planets could potentially have been the starting point for an intentional panspermia campaign.

One planet in particular stands out – Kepler-452 b, which has a star similar to ours and an orbit similar to ours. That system is only 1,400 light years away, relatively close by astronomical standards. If nothing else, it points to that system as a potentially interesting focal point for exoplanet surveys, including assessments of exoplanet atmospheres. However, we’ll likely have to wait for the next generation of grand telescopes.

For now, this was an interesting, though brief, speculative exercise. Astronomers are always looking for exciting things, and this paper contributes to the arguments about why it’s so important to spend time looking in detail at some of the exoplanets we already know about.

Learn More:
B. Bradák – A BOLD AND HASTY SPECULATION ABOUT ADVANCED CIVILIZATION-BEARING PLANETS
APPEARING IN EXOPLANET DATABASES
UT – A Super-Earth (and Possible Earth-Sized) Exoplanet Found in the Habitable Zone
UT – A New Place to Search for Habitable Planets: “The Soot Line.”
UT – Want to Find Life? Compare a Planet to its Neighbors

Lead Image:
Artist’s illustration of a habitable planet.
Credit – Wikipedia / VP8/Vorbis

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You’ve likely heard of the Breakthrough Starshot (BTS) initiative. BTS aims to send tiny gram-scale, light sail picospacecraft to our neighbour, Proxima Centauri B. In BTS’s scheme, lasers would propel a whole fleet of tiny probes to the potentially water-rich exoplanet.

Now, another company, Space Initiatives Inc., is tackling the idea. NASA has funded them so they can study the idea. What can we expect to learn from the effort?

Proxima b may be a close neighbour in planetary terms. But it’s in a completely different solar system, about four light-years away. That means any probes sent there must travel at relativistic speeds if we want them to arrive in a reasonable amount of time.

That’s why Space Initiatives Inc. proposes such tiny spacecraft. With their small masses, direct lasers can propel them to their destination. That means they must send a swarm of hundreds or even one thousand probes to get valuable scientific results.

This is much different than the architecture that missions usually conform to. Most missions are a single spacecraft, perhaps with a smaller attached probe like the Huygens probe attached to the Cassini spacecraft. How does using a swarm change the mission? What results can we expect?

“We anticipate our innovations would have a profound effect on space exploration.”

Thomas Eubanks, Space Inititatives Inc.

A new presentation at the 55th Lunar and Planetary Science Conference (LPSC) in Texas examined the idea. It’s titled “SCIENTIFIC RETURN FROM IN SITU EXPLORATION OF THE PROXIMA B EXOPLANET.” The lead author is T. Marshall Eubanks from Space Initiatives Inc., a start-up developing 50-gram femtosatellites that weigh less than 100 grams (3.5 oz.)

Tiny probes like these can only do flybys. They’re too tiny and low-mass for anything else. When designing a mission like this, the first consideration is whether the probes will operate as a dispersed or coherent swarm. In a dispersed swarm, the probes reach their destination sequentially. In a coherent swarm, the probes are together when they do their flyby. Both architectures have their merits.

In either case, these tiny solar sail probes will be very thin. But thanks to technological advances, they can still gather high-resolution images by working together.

The image below shows 247 probes forming an array as they fly by Proxima b. Together, they have the light-collecting area of a three-meter telescope. This arrangement should enable sub-arc-second resolutions at optical wavelengths. Spectroscopy should be equally as fine.

“While both erosion by the Interstellar Medium (ISM) and image smearing will degrade imaging, we anticipate these systems will enable sub-arcsecond resolution imaging and spectroscopy of the target planet,” the authors write.

This image from the presentation shows how the probe swarm would arrive at Proxima b. (Note that the planned swarm dispersion is much smaller than is indicated here.) Image Credit: Eubanks et al. 2024.

These tiny spacecraft could do some course correction, but not much. So, getting the navigation right is critical. Unfortunately, our data on Proxima b’s orbit is not as well-understood as the planets in our own Solar System. It all comes down to ephemeris.

Ephemeris tables show the trajectory of planets and other objects in space. But in Proxima b’s case, the ephemeris error is potentially quite large.

Added to that is the distance. If the probes can travel at 20% of light speed, reaching the planet will take over 21 years. The authors calculate that if they can restrict Proxima b’s ephemeris error to 100,000 km and send 1,000 probes, at least one will come within 1,000 km of the planet. “Meeting this ephemeris error goal will require improved astrometry of the Proxima system,” the authors write.

The probes would perform science observations on their way to Proxima b. As they travel, the swarm would have dozens or even hundreds of opportunities to use microlensing to study stellar objects. A stellar mass microlensing event requiring one month on Earth would only take one hour.

“It is now possible to predict lensing events for nearby stars; BTS probe observations of dozens or hundreds of predicted microlensing events by nearby stars will offer both a means of observing these systems and a novel means of interstellar navigation,” the authors explain.

The swarm would be only the third mission to leave our Solar System. The Voyage spacecraft left the heliosphere, but only inadvertently. So, the swarm could observe the interstellar medium (ISM) during its 20+ year journey. One of the questions we have about the local ISM concerns clouds. We only have poor data on the nature of these clouds, and scientists aren’t certain if our Solar System is in the Local Interstellar Cloud (LIC.)

“In situ observation of the properties of these clouds will be a primary scientific goal for mission science during the long interstellar voyage,” the researchers write.

There are clouds in the ISM near our Solar System. But we don’t know much about them, including if our Solar System is in the LIC or if it’s leaving it. Image Credit: Interstellar Probe/JHUAPL

Opportunistic science during the voyage is great, but arrival at Proxima b is the meat of the mission. One day before the probes arrive, they would still be 35 AU away. At that point, the mission could begin imaging. Proxima b would still only be several pixels across, but it’s enough to see any visible moons.

“At this point, it would be worth turning some probes to face forward and begin imaging the Proxima system to search for undiscovered planets, moons and asteroids in the system, and to begin a Proxima b approach video,” the researchers explain.

Upon arrival at Proxima Centauri b, a one-meter aperture telescope 6,000 km away from the planet could attain a six-meter resolution on the surface. That’s an idealistic number, as not all of the planet’s surface could be imaged at that resolution. PCb is also tidally locked to its star, meaning one side is in darkness. Because of that, the mission should be designed to gather low-light and infrared images of the night side. “Night-side illumination imagery might also be the most conclusive technosignature from an initial Proxima mission,” the authors write.

As probes pass through Proxima b’s shadow, they could use the light from the star to perform spectroscopy. Probes passing behind Proxima b could use the Earth laser system for spectrometry, and if the probes are in a coherent swarm, they could use the lasers from pairs of probes on either side of the planet.

“Transmission spectroscopy, which for Proxima b cannot be done from Earth,” the researchers explain, “will likely provide the best means of determining the existence of a biology or even a technological society on Proxima b through the search for the spectral lines of biomarkers and technomarkers.”

As humanity’s first mission to Proxima Centauri b, the swarm would face some hurdles and uncertainties. But in a coherent swarm architecture, the mission could also be almost too successful. “A BTS mission, especially with a coherent swarm, may collect more data than can be returned to Earth,” the authors write. If the data returned has to be selected autonomously by the swarm itself, that could be more demanding than deciding what data to collect in the first place.

Scientists have many questions about Proxima Centauri b. Should the swarm ever be launched, any amount of data it returns will be valuable. Even though it’ll take over four years for the data to be sent back to Earth.

An artist’s conception of a violent flare erupting from the red dwarf star Proxima Centauri. Such flares can obliterate the atmospheres of nearby planets. Credit: NRAO/S. Dagnello.

Scientists don’t know how hot the planet is. They’re not certain if it even has liquid water. It looks like the planet is just over one Earth mass and has a slightly higher radius. But those measurements are uncertain. Scientists are also uncertain about its composition. The star it orbits is a flare star, which means the planet could be subjected to extremely powerful bursts of radiation. That’s a lot of uncertainty.

But it’s the nearest exoplanet, the only one we could feasibly reach in a realistic amount of time. That alone makes it a desirable target.

There’s no final plan for a mission like this. It’s largely conceptual. But the technology to do it is coming along. NASA has funded a mission study, so it definitely has merit.

“Fortunately, we don’t have to wait until mid-century to make practical progress – we can explore and test swarming techniques now in a simulated environment, which is what we propose to do in this work,” said report lead author Thomas Eubanks from Space Initiatives Inc. “We anticipate our innovations would have a profound effect on space exploration, complementing existing techniques and enabling entirely new types of missions, for example, picospacecraft swarms covering all of cislunar space or instrumenting an entire planetary magnetosphere.”

Eubanks also points out how a swarm of probes could investigate interstellar objects that pass through our inner Solar System, like Oumuamua.

But the main mission would be the one to Proxima Centauri b. According to Eubanks, that would happen sometime in the third quarter of this century.

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