Astronomy

NASA astronauts Stephen Bowen, left, Frank Rubio, Warren Hoburg, and UAE (United Arab Emirates) astronaut Sultan Alneyadi, right, pose for a photo wearing solar glasses, Tuesday, March 19, 2024, at the Mary W. Jackson NASA Headquarters building in Washington. Bowen, Hoburg, and Alneyadi spent 186 days aboard the International Space Station as part of Expedition 69; while Rubio set a new record for the longest single spaceflight by a U.S. astronaut, spending 371 days in orbit on an extended mission spanning Expeditions 68 and 69.

At the Kitt Peak National Observatory in Arizona, an instrument with 5,000 tiny robotic eyes scans the night sky. Every 20 minutes, the instrument and the telescope it’s attached to observe a new set of 5,000 galaxies. The instrument is called DESI—Dark Energy Survey Instrument—and once it’s completed its five-year mission, it’ll create the largest 3D map of the Universe ever created.

But scientists are getting access to DESI’s first data release and it suggests that dark energy may be evolving.

DESI is the most powerful multi-object survey spectrograph in the world, according to their website. It’s gathering the spectra for tens of millions of galaxies and quasars. The goal is a 3D map of the Universe that extends out to 11 billion light-years. That map will help explain how dark energy has driven the Universe’s expansion.

DESI began in 2021 and is a five-year mission. The first year of data has been released, and scientists with the project say that DESI has successfully measured the expansion of the Universe over the last 11 billion years with extreme precision.

“The DESI team has set a new standard for studies of large-scale structure in the Universe.”

Pat McCarthy, NOIRLab Director

DESI collects light from 5,000 objects at once with its 5,000 robotic eyes. It observes a new set of 5,000 objects every 20 minutes, which means it observes 100,000 objects—galaxies and quasars—each night, given the right observing conditions.

This image shows Stu Harris working on assembling the focal plane for the Dark Energy Spectroscopic Instrument (DESI) at Lawrence Berkeley National Laboratory in 2017 in Berkeley, Calif. Ten petals, each containing 500 robotic positioners that are used to gather light from targeted galaxies, form the complete focal plane. DESI is attached to the 4-meter Mayall Telescope at Kitt Peak National Observatory. Image Credit: DESI/NSF NOIRlab

DESI’s data creates a map of the large-scale structure of the Universe. The map will help scientists unravel the history of the Universe’s expansion and the role dark energy plays. We don’t know what dark energy is, but we know some force is causing the Universe’s expansion to accelerate.

“The DESI instrument has transformed the Mayall Telescope into the world’s premier cosmic cartography machine,” said Pat McCarthy, Director of NOIRLab, the organization behind DESI. “The DESI team has set a new standard for studies of large-scale structure in the Universe. These first-year data are only the beginning of DESI’s quest to unravel the expansion history of the Universe, and they hint at the extraordinary science to come.”

DESI measures dark energy by relying on baryonic acoustic oscillations (BAO.) Baryonic matter is “normal” matter: atoms and everything made of atoms. The acoustic oscillations are density fluctuations in normal matter that date back to the Universe’s beginnings. BAO are the imprint of those fluctuations, or pressure waves, that moved through the Universe when it was all hot, dense plasma.

As the Universe cooled and expanded, the density waves froze their ripples in place, and where density was high, galaxies eventually formed. The ripple pattern of the BAO is visible in the DESI leading image. It shows strands of galaxies, or galaxy filaments, clustered together. They’re separated by voids where density is much lower.

The deeper DESI looks, the fainter the galaxies are. They don’t provide enough light to detect the BAO. That’s where quasars come in. Quasars are extremely bright galaxy cores, and the light from distant quasars creates a shadow of the BAO pattern. As the light travels through space, it interacts with and gets absorbed by clouds of matter. That lets astronomers map dense pockets of matter, but it took over 450,000 quasars. That’s the most quasars ever observed in a survey like this.

Because the BAO pattern is gathered in such detail and across such vast distances, it can act as a cosmic ruler. By combining the measurements of nearby galaxies and distant quasars, astronomers can measure the ripples across different periods of the Universe’s history. That allows them to see how dark energy has stretched the scale over time.

It’s all aimed at understanding the expansion of the Universe.

In the Universe’s first three billion years, radiation dominated it. The Cosmic Microwave Background is evidence of that. For the next several billion years, matter dominated the Universe. It was still expanding, but the expansion was slowing because of the gravitational force from matter. But since then, the expansion has accelerated again, and we give the name dark energy to the force behind that acceleration.

So far, DESI’s data supports cosmologists’ best model of the Universe. But there are some twists.

“We’re incredibly proud of the data, which have produced world-leading cosmology results,” said DESI director and LBNL scientist Michael Levi. “So far, we’re seeing basic agreement with our best model of the Universe, but we’re also seeing some potentially interesting differences that could indicate dark energy is evolving with time.”

Levi is referring to Lambda Cold Dark Matter (Lambda CDM), also known as the standard model of Big Bang Cosmology. Lambda CDM includes cold dark matter—a weakly interacting type of matter—and dark energy. They both shape how the Universe expands but in opposite ways. Dark energy accelerates the expansion, and regular matter and dark matter slow it down. The Universe evolves based on the contributions from all three. The Lambda CDM does a good job of describing what other experiments and observations find. It also assumes that dark energy is constant and spread evenly throughout the Universe.

This data is just the first release, so confirmation of dark energy evolution must wait. By the time DESI has completed its five-year run, it will have mapped over three million quasars and 37 million galaxies. That massive trove of data should help scientists understand if dark energy is changing.

Whatever the eventual answer, the question is vital to understanding the Universe.

“This project is addressing some of the biggest questions in astronomy, like the nature of the mysterious dark energy that drives the expansion of the Universe,” says Chris Davis, NSF program director for NOIRLab. “The exceptional and continuing results yielded by the NSF Mayall telescope with DOE DESI will undoubtedly drive cosmology research for many years to come.”

DESI isn’t the only effort to understand dark energy. The ESA’s Euclid spacecraft is already taking its own measurements to help cosmologists answer their dark energy questions.

In a few years, DESI will have some more powerful allies in the quest to understand dark energy. The Vera Rubin Observatory and Nancy Grace Roman Space Telescope will both contribute to our understanding of the elusive dark energy. They’ll perform surveys of their own, and by combining data from all three, cosmologists are poised to generate some long-sought answers.

But for now, scientists are celebrating DESI’s first data release.

“We are delighted to see cosmology results from DESI’s first year of operations,” said Gina Rameika, associate director for High Energy Physics at the Department of Energy. “DESI continues to amaze us with its stellar performance and how it is shaping our understanding of dark energy in the Universe.”

The post A New Map Shows the Universe’s Dark Energy May Be Evolving appeared first on Universe Today.

Humans have been digging underground for millennia – on the Earth. It’s where we extract some of our most valuable resources that have moved society forward. For example, there wouldn’t have been a Bronze Age without tin and copper – both of which are primarily found under the ground. But when digging under the ground on celestial bodies, we’ve had a much rougher time. That is going to have to change if we ever hope to utilize the potential resources that are available under the surface. A paper from Dariusz Knez and Mitra Kahlilidermani of the University of Krakow looks at why it’s so hard to drill in space – and what we might do about it.

In the paper, the authors detail two major categories of difficulties when drilling off-world – environmental challenges and technological challenges. Let’s dive into the environmental challenges first.

One obvious difference between Earth and most other rocky bodies that we would potentially want to drill holes into is the lack of an atmosphere. There are some exceptions – such as Venus and Titan, but even Mars has a thin enough atmosphere that it can’t support one fundamental material used for drilling here on Earth – fluids.

The ocean on Europa is a common destination for a exploration mission that will require some drilling. Fraser explores how we would do it.

If you’ve ever tried drilling a hole in metal, you’ve probably used some cooling fluid. If you don’t, there is a good chance either your drill bit or your workpiece will heat up and deform to a point where you can no longer drill. To alleviate that problem, most machinists simply spray some lubricant into the drill hole and keep pressing through. A larger scale version of this happens when construction companies drill into the ground, especially into bedrock – they use liquids to cool the spots where they’re drilling.

That isn’t possible on a celestial body with no atmosphere. At least not using traditional drilling technologies. Any liquid exposed to the lack of atmosphere would immediately sublimate away, providing little to no cooling effect to the work area. And given that many drilling operations occur autonomously, the drill itself – typically attached to a rover or lander – has to know when to back off on its drilling process before the bits melt. That’s an added layer of complexity and not one that many designs have yet come up with a solution.

A similar fluid problem has limited the adoption of a ubiquitous drill technology used on Earth – hydraulics. Extreme temperature swings, such as those seen on the Moon during the day/night cycle, make it extremely difficult to provide a liquid for use in a hydraulic system that doesn’t freeze during cold nights or evaporate during scorching days. As such, hydraulic systems used in almost every large drilling rig on Earth are extremely limited when used in space.

Here’s a detailed look at a drill used on Mars by Smarter Every Day.
Credit – Smarter Every Day YouTube Channel

Other problems like abrasive or clingy regolith can also crop up, such as a lack of magnetic field when orienting the drill. Ultimately, these environmental challenges can be overcome with the same things humans always use to overcome them, no matter what planetary body they’re on – technology.

There are plenty of technological challenges for drilling off-world as well, though. The most obvious is the weight constraint, a crucial consideration for doing anything in space. Large drilling rigs use heavy materials, such as steel casings, to support the boreholes they drill, but these would be prohibitively expensive using current launch technologies. 

Additionally, the size of the drilling system itself is the limiting factor of the force of the drill – as stated in the paper, “the maximum force transmitted to the bit cannot exceed the weight of the whole drilling system.” This problem is exacerbated by the fact that typical rover drills are leveraged out on a robotic arm rather than placed directly underneath where the maximum amount of weight can be applied. This force limitation also limits the type of material the drill can get through – it will be hard-pressed to drill through any significant boulder, for example. While redesigning rovers with drill location in mind could be helpful, again, the launch weight limitation comes into play here.

Curiosity has a unique drilling technique, as described in this JPL video.
Credit – NASA JPL YouTube Channel

Another technological problem is the lack of power. Hydrocarbon-fueled engines power most large drilling rigs on Earth. That isn’t feasible off of Earth, so the system must be powered by solar cells and the batteries they provide. These systems also suffer from the same tyranny of the rocket equation, so they are typically relatively limited in size, making it difficult for drilling systems to take advantage of some of the benefits of entirely electric systems over hydrocarbon-powered ones – such as higher torque.

No matter the difficulties these drilling systems face, they will be vital for the success of any future exploration program, including crewed ones. If we ever want to create lava cave cities on the Moon or get through Enceladeus’ ice sheet to the ocean within, we will need better drilling technologies and techniques. Luckily, there are plenty of design efforts to come up with them.

The paper details four different categories of drill designs:

1. Surface drills – less than 10 cm depth
2. Shallow-depth drills – less than 1m depth
3. Medium-depth drills – between 1m and 10m depth
4. Large-depth drills – greater than 10m depth 

For each category, the paper lists several designs at various completeness stages. Many of them have novel ideas about how to go about drilling, such as using an “inchworm” system or using ultrasonics. 

CNET describes another Martian mission that used a drill – InSight.
Credit – CNET YouTube Channel

But for now, drilling off-world, and especially on asteroids and comets, which have their own gravitational challenges, remains a difficult but necessary task. As humanity becomes more experienced at it, we will undoubtedly get better at it. Given how important this process is for the grand plans of space explorers everywhere, the time when we can drill effectively into any rocky or icy body in the solar system can’t come soon enough.

Learn More:
Knez & Khalilidermani – A Review of Different Aspects of Off-Earth Drilling
UT – Drill, Baby, Drill! – How Does Curiosity ‘Do It’
UT – Cylindrical Autonomous Drilling Bot Could Reach Buried Martian Water
UT – Perseverance Drills Another Hole, and This Time the Sample is Intact

Lead Image:
Curiosity’s arm with its drill extended.
Credit – NASA/JPL/Ken Kremer/kenkremer.com/Marco Di Lorenzo

The post Why is it so hard to drill off Earth? appeared first on Universe Today.

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