A CubeSat Mission to Phobos Could Map Staging Bases for a Mars Landing

The moons of Mars are garnering increased attention, not only because they could provide a view of the solar system’s past but also because they could provide invaluable staging areas for any future human settlement on Mars itself. However, missions specifically designed to visit Phobos, the bigger of the two moons, have met with varying stages of failure. So why not make an inexpensive mission to do so – one that could launch multiple copies of itself if necessary? That’s the idea behind a CubeSat-based mission to Phobos, known as Perseus, which was initially described back in 2020.

Phobos is interesting for several reasons, but so far, we’ve only gotten relatively grainy pictures of this small moon, whose total diameter is the size of a medium-sized city. Most of those pictures have come from Mars orbiters, such as MRO, who occasionally turn their instruments on the other bodies in the system. Several planned missions to visit directly, such as Phobos 1 and 2 and, more recently, Phobos Grunt, have failed in space, limiting our understanding of this potentially helpful moon to secondary scraps from larger missions.

Enter a new mission concept—Perseus (which, surprisingly, appears to not be an acronym for anything) is designed as a 27U CubeSat that inherits several commercial-off-the-shelf (COTS) systems used in other interplanetary CubeSat missions, including its own propulsion system and remote sensing kit. Depending on the funding the mission receives, it could branch into one of two different potential interaction styles with Phobos.

MMX is another mission to collect actual samples from Phobos, though its launch has been delayed until 2026 at the earliest.

First, the mission design preferred by the mission designers, who mainly come from the University of Arizona and Arizona State University, would involve capturing Perseus in a co-orbit with Mars and Phobos. This would allow the CubeSat to pass by the moon every day, with about a 6-minute encounter time. This would allow Perseus to capture multiple images of multiple sides of Phobos, some of which have never been seen before from such a short vantage point.

The other mission concept would put Perseus on a hyperbolic trajectory past Phobos itself. In this concept, Perseus would only get a single 2-minute flyby with the moon but could get much closer, and therefore higher resolution, images of a specific area it chose to fly by. It would then be flung into the solar system, eventually running out of fuel. Saving the cost of the larger fuel load for the orbital mission concept is the main reason for designing the less scientifically exciting flyby option.

With the orbital mission concept, Perseus could collect visible light images of the surface of Phobos down to 5m per pixel and thermal images of 25 m per one pixel, as its scientific payload would consist of visible light and thermal imagers. That is about 6 times better in visible light than the 30 m / pixel, which is the best information we have from an image from HiRISE on the Mar Reconnaissance Orbiter.

Fraser makes the case for sending humans to the Martian moons first.

That level of resolution could further explore some features of Phobos, such as the “grooves” that dominate its surface. Additionally, Perseus could scout potential landing sites for future human missions to prepare for a visit to the Red Planet.

However, the real benefit of Perseus is that it is relatively cheap. While relatively large by CubeSat standards at 54 kg and a 27U configuration, many components’ flight heritage means it would be relatively cheap to assemble and test. However, the mission has not been granted any funding so far, and a brief literature search doesn’t show any additional work on the project in the last several years. But, it fits well with the trend towards smaller, less risky, and less expensive missions. Maybe someday, a similar one will get the green light, and we can finally start collecting some detailed light from one of the most important moons in the solar system.

Learn More:
Nallapu et al. – Trajectory design of perseus: A cubesat mission concept to Phobos
UT – What Could We Learn From a Mission to Phobos?
UT – How Mars’ Moon Phobos Captures Our Imaginations
UT – Did An Ancient Icy Impactor Create the Martian Moons?

Lead Image:
Engineering Model of the Perseus Spacecraft.
Credit – Nallapu et al.

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Interstellar Objects Can't Hide From Vera Rubin

We have studied the skies for centuries, but we have only found two objects known to come from another star system. The first interstellar object to be confirmed was 1I/2017 U1, more commonly known as ?Oumuamua. It was discovered with the Panoramic Survey Telescope and Rapid Response System (Pan-STARRS) and stood out because of its large proper motion. Because ?Oumuamua swept through the inner solar system, it was relatively easy to distinguish. The second interstellar object, 2I/Borisov, stood out because it entered the inner solar system from well above the orbital plane. But while we have only discovered two alien visitors so far, astronomers think interstellar objects are common. It’s estimated that several of them visit our solar system each year, and there may be thousands within the orbit of Neptune on any given day. They just don’t stand out, so we don’t notice them. But that could soon change.

The Vera C. Rubin Observatory is scheduled to come online in 2025. Unlike many large telescopes, Rubin Observatory isn’t designed to focus on specific targets in the sky. Its mirror can capture a patch of sky seven Moons wide in a single image. It will capture more than a petabyte of data every night, capturing images of solar system bodies every few days. This will allow astronomers to track even faint and slow-moving bodies with precision. The orbit of any interstellar object will stand out clearly. IF astronomers can find them. Which is where a new study comes in.

With so much data being gathered, there is no way to go through the data by hand. Some things, such as supernovae and variable stars, will be easy to distinguish, but interstellar bodies in the outer solar system will pose a particular challenge. In any given image, they will appear as a common asteroid or comet. It’s only after months or years of tracking that their unique orbits will reveal their true origins.

The fieldview of Rubin’s image compared to the Moon. Credit: SLAC National Accelerator Laboratory

So the authors of this new work propose using machine learning. To demonstrate how this would work, the team created a database of simulated solar system bodies. Some of them were given regular orbits, while others were given interstellar paths. Based on this data, they trained algorithms to distinguish the two. They found that some machine learning methods worked better than others. In this case, the Random Forest approach, where one classifies decision trees statistically, and the Gradient Boosting method, which prioritizes “weak learners” to strengthen them, seem to work the best. The more commonly known Neural Network method was less effective.

Overall, the team found that machine learning can detect interstellar objects with great efficiency, and the number of false positives should be small enough that they could be effectively managed. While the approach won’t find all the interstellar bodies in our solar system, it should be able to find hundreds of them within the first year of Rubin’s operation. And that will give us plenty of data to better understand these enigmatic visitors.

Reference: Cloete, Richard, Peter Vereš, and Abraham Loeb. “Machine learning methods for automated interstellar object classification with LSST.” Astronomy & Astrophysics 691 (2024): A338.

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The Early Earth Wasn’t Completely Terrible

Earth formed 4.54 billion years ago. The first period of the history of the Earth was known as the Hadean Period which lasted from 4.54 billion to 4 billion years ago. During that time, Earth was thought to be a magma filled, volcanic hellscape. It all sounds rather inhospitable at this stage but even then, liquid oceans of water are thought to have existed under an atmosphere of carbon dioxide and nitrogen. Recent research has shown that this environment may well have been rather more habitable than once thought. 

The name ‘Hadean’ comes from Hades, the Greek god of the underworld. It nicely reflects the hot, hostile climate of the early Earth. During this period, Earth was largely a molten, chaotic world with volcanic eruptions a common sight on the landscape. Overhead, there would be regular visitors from space with meteorites and comets impacting the surface as the crust is still forming. Despite these conditions, it seems that water also began to accumulate as the planet cooled, possibly having been delivered by comets or released from outgassing from giant volcanoes. By the end of the era, the crust had solidified enough to form two early continents separated by forming oceans. 

Artist concept of Earth during the Late Heavy Bombardment period. Credit: NASA’s Goddard Space Flight Center Conceptual Image Lab.

In a paper published by a team of researchers from the University of California they confirm this conclusion that, far from being in hospitable, early Earth was actually far less tumultuous. The team, led by Christopher K Jones explore the evolution of the Earth from formation to the evolution of life. They review a number of different pathways for the origins of life during the Hadean in the context of the large-scale planetary environment at the time, including Earth’s position in the Solar System.

This view of Earth from space is a fusion of science and art, drawing on data from multiple satellite missions and the talents of NASA scientists and graphic artists. This image originally appeared in the NASA Earth Observatory story Twin Blue Marbles. Image Credits: NASA images by Reto Stöckli, based on data from NASA and NOAA.

In order to complete their work, the team look at the a number of critical aspects across different disciplines that included microbiology, atmospheric chemistry, geochemistry and planetary science. The relationships between life’s beginnings and the processes and state of the environment at the time is also assessed in their paper including the formation of the crust and evolution of the atmosphere. 

The paper also explores a number of different atmospheric processes from wet-dry and freeze-thaw cycles to hydrothermal vent systems. This is not just assessed on Earth but in the Solar System at large to see if there is any correlation or overlaps. The impact of comets too are considered and how they would impact on the atmospheric chemistry. 

According to a new study, a comet impact triggered massive wildfires and a temporary cooling 12,800 years ago. Credit: NASA/Don Davis

The team conclude that Earth, during the Hadean period, most likely had liquid water. The debate still rages on however about the existence of continents and their composition. This uncertainty has an impact on just how organic life could have got a foothold on Earth. However it did, life would have taken a hold by the end of the Hadean era and started to leave evidence in the geological records of the Archean period that followed. 

Unfortunately the paper is far from conclusive, leaving a number of questions unanswered but it does make a fabulous start to fill in the gaps at just how life began on this planet we call home.

Source : Setting the stage: Building and maintaining a habitable world and the early conditions that could favour life’s beginnings on Earth and beyond

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Globular Clusters Evolve in Interesting Ways Over Time

Globular clusters are among the oldest objects in the Universe. The early Universe was filled with dwarf galaxies and its just possible that globular clusters are the remains of these ancient relics. Analysis of the stars in the clusters reveals ages in the region of 12-13 billion years old. A new paper just published shows that the globular clusters are home to two distinct types of stars; the primordial ones with normal chemical composition and those with unusual heavy amounts of heavier elements. 

Globular clusters are dense, spherical collections of stars that orbit the outer regions of galaxies, usually in the galactic halo. They contain hundreds of thousands, sometimes millions of stars bound together by gravity. They differ from open clusters, which are younger and less tightly bound and found in the main body of a galaxy. Globular clusters in contrast, are ancient with ages typically in the regions of 10 to 13 billion years old. 

M13 – Credit: R. Jay GaBany

There stellar components are mostly composed of low-mass, metal-poor stars, suggesting they formed early in the history of the universe before the heavier elements appeared. Studying globular clusters can reveal lots about stellar evolution, the formation of galaxies and even dark matter. Our own Galaxy the Milky Way is home to over 150 known globular clusters like well known M13 in the northern hemisphere or Omega Centauri in the southern hemisphere.

Omega Centauri is the brightest globular cluster in the night sky. It holds about 10 million stars and is the most massive globular cluster in the Milky Way. It’s possible that globulars and nuclear star clusters are related in some way as a galaxy evolves. Image Credit: ESO.

In a paper recently published in Astronomy and Astrophysics, a team of researchers have advanced our understanding of these clusters by revealing more about their formation and dynamical evolution. The team led by Emanuele Dalessandro from the National Institute for Astrophysics (INAF) explored multiple populations of stars in the clusters. They studied the change in positions of the stars and their velocity in the first 3D kinematic analysis of 16 globular clusters. 

The team used data from ESA’s Gaia telescope the European Southern Observatory Very Large Telescope and Multi Instrument Kinematic Survey to measure the 3D velocity of stars within the clusters. This was a combination of proper motion (motion across the sky) and radial velocity (motion towards and away from us.) To gather the measurements, spectroscopic survey data was used.

Artist’s impression of the Gaia spacecraft detecting artificial signals from a distant star system. In this synchronization scheme, the star system’s inhabitants send the signal shortly after witnessing a supernova, which is also seen by telescopes on Earth. (Credit: Danielle Futselaar / Breakthrough Listen)

The formation and evolution of globular clusters has been one of the most hotly debated questions for the last few decades. The significance of understanding them is huge explains Dalessandro,’because they not only help us to test cosmological models of the formation of the Universe due to their age but also provide natural laboratories for studying the formation, evolution, and chemical enrichment of galaxies.’ Understanding the physical processes behind their formation was key to understanding how they evolve. This was the goal of their study which revealed for the first time that globular cluster form through multiple star formation events. 

Source : The first 3D view of the formation and evolution of globular clusters

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A Superfast Supercomputer Creates the Biggest Simulation of the Universe Yet

Scientists at the Department of Energy’s Argonne National Laboratory have created the largest astrophysical simulation of the Universe ever. They used what was until recently the world’s most powerful supercomputer to simulate the Universe at an unprecedented scale. The simulation’s size corresponds to the largest surveys conducted by powerful telescopes and observatories.

The Frontier Supercomputer is located at the Oak Ridge National Laboratory in Tennessee. It’s the second-fasted supercomputer in the world, behind only El Capitan, which pulled ahead in November, 2024. Frontier is the world’s first exascale supercomputer, though El Capitan has joined the ranks of exascale supercomputing.

The new Frontier simulation is record-breaking and is now the largest simulation of the Universe ever conducted. Its exascale computing allows it to simulate a level of detail that was unreachable prior to its implementation. Exascale is so advanced that it’s difficult to fully exploit its capabilities without new programming paradigms.

Frontier is a significant leap in astrophysical simulations. It covers a volume of the Universe that’s 10 billion light years across. It incorporates detailed physics models for dark matter, dark energy, gas dynamics, star formation, and black hole growth. It should provide new insights into some of the fundamental processes in the Universe, such as how galaxies form and how the large-scale structure of the Universe evolves.

“There are two components in the universe: dark matter—which as far as we know, only interacts gravitationally—and conventional matter, or atomic matter.” said project lead Salman Habib, division director for Computational Sciences at Argonne.

“So, if we want to know what the universe is up to, we need to simulate both of these things: gravity as well as all the other physics including hot gas, and the formation of stars, black holes and galaxies,” he said. “The astrophysical ‘kitchen sink’ so to speak. These simulations are what we call cosmological hydrodynamics simulations.”

Cosmological hydrodynamics simulations combine cosmology with hydrodynamics and allow astronomers to examine the complex interrelationships between gravity and things like gas dynamics and stellar processes that have shaped and continue to shape our Universe. They can only be conducted with supercomputers because of the level of complexity and the vast number of numerical equations and calculations involved.

The sheer amount of energy needed for Frontier to perform these simulations is staggering. It consumes about 21 MW of electricity, enough to power about 15,000 single-family homes in the US. But the payoff is equally as impressive.

“For example, if we were to simulate a large chunk of the universe surveyed by one of the big telescopes such as the Rubin Observatory in Chile, you’re talking about looking at huge chunks of time — billions of years of expansion,” Habib said. “Until recently, we couldn’t even imagine doing such a large simulation like that except in the gravity-only approximation.”

“It’s not only the sheer size of the physical domain, which is necessary to make direct comparison to modern survey observations enabled by exascale computing,” said Bronson Messer, Oak Ridge Leadership Computing Facility director of science. “It’s also the added physical realism of including the baryons and all the other dynamic physics that makes this simulation a true tour de force for Frontier.”

The Exascale-class HPE Cray EX Supercomputer (Frontier) at Oak Ridge National Laboratory. Image Credit: By OLCF at ORNL – https://ift.tt/W6Tvyip, CC BY 2.0, https://ift.tt/HXTV0P6

Frontier simulates more than just the Universe. In June, researchers working with it achieved another milestone. They simulated a system of 466 billion atoms in a simulation of water. That was the largest system ever modeled and more than 400 times larger than its closest competition. Since water is a primary component of cells, Frontier is paving the way for an eventual simulation of a living cell.

Frontier promises to make advancements in multiple other areas as well, including nuclear fission and fusion and large-scale energy transmission systems. It’s also been used to generate a quantum molecular dynamics simulation that’s 1,000 times greater in size and speed than any of its predecessors. It also has applications in modelling diseases, developing new drugs, better batteries, better materials including concrete, and predicting and mitigating climate change.

Astrophysical/cosmological simulations like Frontier’s are powerful when they’re combined with observations. Scientists can use simulations to test theoretical models compared to observational data. Changing initial conditions and parameters in the simulations lets researchers see how different factors shape outcomes. It’s an iterative process that allows scientists to update their models by identifying discrepancies between observations and simulations.

Frontier’s huge simulation is just one example of how supercomputers and AI are taking on a larger role in astronomy and astrophysics. Modern astronomy generates massive amounts of data, and requires powerful tools to manage. Our theories of cosmology are based on larger and larger datasets that require massive computing power to simulate.

Frontier has already been superseded by El Capitan, another exascale supercomputer at the Lawrence Livermore National Laboratory (LLNL). However, El Capitan is focused on managing the nation’s nuclear stockpile according to the LLNL.

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How Much Are Asteroids Really Worth?

Popular media love talking about asteroid mining using big numbers. Many articles talk about a mission to Psyche, the largest metallic asteroid in the asteroid belt, as visiting a body worth $10000000000000000000, assumedly because their authors like hitting the “0” key on their keyboards a lot. But how realistic is that valuation? And what does it actually mean? A paper funded by Astroforge, an asteroid mining start-up based in Huntington Beach, and written by a professor at the Colorado School of Mine’s Space Resources Program takes a good hard look at what metals are available on asteroids and whether they’d genuinely be worth as much as the simple calculations say that would be.

The paper divides metals on asteroids into two distinct types—those that would be worth returning to Earth and those that wouldn’t. Really, the only metals judged to be worthy of returning to Earth are the platinum-group metals (PGMs), which are known for their extraordinarily high cost, relatively low supply, and high usefulness in a variety of modern-day technology. That includes catalytic converters, which is why they are commonly the target of thieves.

The other category would be metals used for in-space construction, such as iron, aluminum, and magnesium. While these might not be economically viable to send back to Earth because of their relatively low prices on our home planet, they are useful up in space for constructing large structures, such as space stations or solar power arrays. However, given the chicken-and-egg problem of not having any demand for these space-sourced metals because they are so expensive, it is hard to quantify how much they are worth. Its competition (i.e. launching the material from Earth), is priceable though, and at $10,000 / kg, plus $100 / kg for a common material such as iron.

Fraser talks about whether we would mine asteroids.

Those prices aren’t anywhere near the $500,000 / kg that a PGM such as Rhodium has ever back on Earth, but it could still make mining asteroids for iron economically viable if the material is used in space. So what do all those calculations mean for the actual value of the asteroids that we might mine?

First and most importantly, recent research suggests that asteroids made out of “pure metal,” such as Psyche is assumed to be, are likely pure fiction. While that might not be great news for any single benign asteroid worth a lot, the other part of that research is that even asteroids that were originally thought to be relatively low in metal content actually have reasonable quantities that could be economically extracted.

To prove the point, the paper looked in detail at a series of meteorite studies, which are the equivalent of left-over asteroids, and compared the “grades” of 83 different elements with ores found on or near the Earth’s surface. Since remote sensing has difficulty distinguishing between some of those elements, meteorite samples that can be subjected to advanced analysis techniques are our best bet at accurately calculating the chemical composition of asteroids, other than the few samples of in-tact asteroids that have been returned so far.

Isaac Arthur also discusses the prospects of asteroid mining.
Credit – Isaac Arthur YouTube Channel

That data showed that PGMs, while lower in concentration than considered initially (because of an assumption in a foundational paper on the composition of asteroids), are still in much higher concentrations than the equivalent terrestrial ores. In particular, a material known as a refractory metal nugget (RMN) could have concentrations of PGMs orders of magnitude higher than anything found on Earth or other types of asteroidal material.

RMNs are primarily found in a calcium aluminum inclusion (CAI) structure, mainly on L-type asteroids. L-types are relatively uncommon asteroids with a reddish tint, but we haven’t yet visited them. They might be made up of more than 30% CAIs, though, in which case, they could contain a significant amount of extractable PGMs without additional processing.

However, RMNs themselves are very small, at the micron to sub-micron range, making them extremely hard to process in the first place. So, bulk extraction from asteroidal regolith could range up to hundreds of ppm, which is already a few orders of magnitude greater than their concentration in Earth’s regolith.

Fraser talks about mining Psyche, the largest “metallic asteroid” in the asteroid belt.

When looking at the metals for use in space, they are about as abundant as initially predicted, but they face challenges in processing them out of their oxidized states. Typically, this requires some high-energy procedure, such as molten regolith electrolysis, to break off the elemental metal, which is needed for further processing. Again, there’s the chicken and egg problem of having a power source that is large enough to perform these processes, but building it would require the material that would require the power source.

Eventually, that problem will disappear if companies like AstroForge have their way. Remember that the company funded this study, and its two co-founders and Kevin Cannon, the professor at CSM, were co-authors. The company plans to launch its next mission, a rendezvous with near-Earth asteroids, to try to tell if they’re “metallic” in January. Perhaps that mission will help contribute to our growing understanding of the composition and value of the asteroids surrounding us.

Learn More:
Cannon, Gialich, Acain – Precious and structural metals on asteroids
UT – What Are Asteroids Made Of?
UT – What Is The Difference Between Asteroids and Meteorites?
UT – Asteroids: 10 Interesting Facts About These Space Rocks

Lead Image:
Asteroid mining concept.
Credit: NASA/Denise Watt

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Magnetic Tornado is Stirring up the Haze at Jupiter’s Poles

Jupiter is a stunning planet to observe. Whether it be visible light or any other wavelength. In a stunning new image released by the University of California -Berkley, Jupiter is seen in ultraviolet light. The familiar Great Red Spot appears as a blue oval as do many of the familiar belt features. Around the polar regions are revealed a brown haze which is thought to be caused by a high altitude vortex mixing up the atmosphere. The jury is still out on the mechanism behind this though but it may be an interaction between Jupiter’s strong magnetic field which pierces the atmosphere near the poles. 

Jupiter is the largest planet in the Solar System, a gas giant with powerful storms. With a diameter of 143,000 km, Jupiter is 11 times wider than Earth and capable of swallowing all of the other planets in the Solar System and still have room to spare. It is composed or hydrogen and helium and lacks a solid surface. It’s atmosphere has bands of alternating colour with strong winds, hurricanes and lightning storms. The Great Red Spot is one of its most well known features, a hurricane system three times the size of Earth. It’s also home to a family of satellites including the four well known Galilean moons Io, Europa, Ganymede and Callisto. 

Side-by-side images show the opposite faces of Jupiter. The largest storm, the Great Red Spot, is the most prominent feature in the left bottom third of this view. Credit: NASA, ESA, Amy Simon (NASA-GSFC).

The atmosphere of Jupiter is a complex system of thick clouds, storms and high winds. The hydrogen makes up about 90% of the atmosphere with helium the bulk of the remainder plus trace amounts of methane, water vapour and other compounds. The belts in the atmosphere appear to alternate between lighter and darker colours driven by different temperatures, chemical compositions and wind speeds that reach up to 640 km/hr. Lower down, beneath the visible layer, the atmosphere becomes denser, hotter and eventually becomes fluid. Other phenomenon have been observed from lightning storms, aurora and ice crystal clouds. 

Europa and Io move across the face of Jupiter, with the Great Red Spot behind them. Image: NASA/JPL/Cassini, Kevin M. Gill

The newly released ultraviolet image reveals strange features around the polar regions. The oval shaped features are Earth-sized and only visible in the ultraviolet wavelengths. The ovals seems to consistently appear at a slightly lower latitude than the auroral zones around the poles. In the image, the ovals seem dark in colour due to absorption of ultraviolet radiation, more so than the brighter surrounding regions. 

The Hubble Space Telescope orbits Earth at an altitude of 540 km and takes yearly images of Jupiter and the other planets. Hubble was the first telescope to capture the so called UV ovals and they have since been detected by the Cassini spacecraft. The team at UC Berkeley discovered that the ovals were more common around the south pole (appearing in 75% of images around south pole and only 12% around north pole.) 

This image of NASA’s Hubble Space Telescope was taken on May 19, 2009 after deployment during Servicing Mission 4. NASA

The team spoke with planetary atmospherics experts Tom Stallard (Northumbria University in UK) and Xi Zhang (from UC Santa Cruz) to try and understand the mechanism. They theorise that Jupiter’s strong magnetic field lines experience friction in the ionosphere leading to the establishment of a vortex (a rotating, spinning flow of fluid or air.) It is the vortex that drives the dark ovals. 

Source : Magnetic tornado is stirring up the haze at Jupiter’s poles

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The Holiday Fireplace Video We Needed

There’s a new contender for your holiday fireplace video. This one comes from NASA, and features rocket engines and boosters to light up your days with Space Launch System holiday cheer.

Say goodbye to the crackling logs in fireplace videos of Christmas past. We’ll miss the anticipation of the fire burning down to embers and the next log being placed in the fireplace.

Instead, we can gaze contentedly as the Space Launch System’s four RS-25 engines and pair of boosters light up our video hearths.

Enjoy the warm glow of liquid hydrogen and liquid oxygen as their combustion casts a calming, flickering glow. Thrill to the intense white-hot gases from the solid boosters as their aluminum powder and ammonium perchlorate oxidizer, bound together by polybutadiene acrylonitrile, is set ablaze.

NASA created this 8-hour-long looping video from the November 2022 launch of Artemis 1 to the Moon. The holiday video is a somewhat sanitized version of the real launch. The real launch was a thunderous, bellowing spectacle featuring a towering maelstrom of light and thorax-vibrating sound. Below is the real launch.

Traditionalists might scoff at this updated holiday fireplace video, and tradition is fine. But progress is also good, so why not spend some time thinking about humanity’s frontiers, and our return to the Moon, while tucking into some turkey and eggnog?

Merry Christmas, and Happy Thanksgiving to our American friends.

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An AI Chemist Made A Catalyst to Make Oxygen On Mars Using Local Materials

Breaking oxygen out of a water molecule is a relatively simple process, at least chemically. Even so, it does require components, one of the most important of which is a catalyst. Catalysts enable reactions and are linearly scalable, so if you want more reactions quickly, you need a bigger catalyst. In space exploration, bigger means heavier, which translates into more expensive. So, when humanity is looking for a catalyst to split water into oxygen and hydrogen on Mars, creating one from local Martian materials would be worthwhile. That is precisely what a team from Hefei, China, did by using what they called an “AI Chemist.”

Unfortunately, the name “AIChemist” didn’t stick, though that joke might vary depending on the font you read it in. Whatever its name, the team’s work was some serious science. It specifically applied machine learning algorithms that have become all the rage lately to selecting an effective catalyst for an “oxygen evolution reaction” by utilizing materials native to Mars. 

To say it only chose the catalyst isn’t giving the system the full credit it’s due, though. It accomplished a series of steps, including developing a catalyst formula, pretreating the ore to create the catalyst, synthesizing it, and testing it once it was complete. The authors estimate that the automated process saved over 2,000 years of human labor by completing all of these tasks and point to the exceptional results of the testing to prove it.

Depiction of the process the AI Chemist went through to create the test catalyst.
Credit – Zhu et al.

Before we get to that, though, let’s start with the “initial conditions.” The team developed an “all-in-one” robotic AI chemist capable of performing all these tasks. It was initially based on work done by more limited AI chemists who could read synthetic chemistry literature and estimate the efficacy of different chemical compounds for different tasks. After they built the model, they needed to feed it with some data.

For that data, they selected five different common rocks from the surface of Mars. They estimated that there would be 3,764,376 possible combinations to come out of the elements present in those rocks, depending on how the combinations were manufactured. So, the first task of the AI Chemist was to select one that could act as a catalyst for splitting off oxygen. Part of that dataset was built with 30,000 other theoretical datasets and the results of 243 experiments. The result is a “polymetallic” material composed of manganese, iron, nickel, magnesium, aluminum, and calcium. 

Next, a sample of the catalyst would be manufactured for testing. The AI is equipped with a robot arm that took physical samples of meteorites that had been dissolved in hydrochloric acid and attempted to synthesize the suggested catalyst out of those materials. This process involved pretty extreme processes like centrifuging the samples at 7,500g for 5 minutes to separate out the necessary materials and drying out the resultant material. Impressively, all of this was seemingly done without human intervention.

Fraser goes into detail about how a potential mission to Mars will happen in the near future – including creating oxygen using catalysts.

After some of the material had been synthesized, the research team tested it by actually performing the reduction process it was designed to do. More importantly, they did so under Martian ambient conditions. The material performed admirably, similar to existing catalysts already used.

So, effectively, an AI just developed and tested a catalyst for use on Mars using local materials. And potentially saved over 2,000 years of intensive human labor in doing so. That is a testament to how effective AI is at finding patterns in existing data and extrapolating them using new data. It remains to be seen, though, if this catalyst will ever see the light of day on Mars, as the catalyst itself must be integrated with the rest of the system to perform the reduction reaction to split oxygen from water effectively. Given the complexity of the process used to create that catalyst, it might be easier for us to ship one directly from Earth, even if it doesn’t use Martian materials.

Learn More:
Zhu et al. – Automated synthesis of oxygen-producing catalysts from Martian meteorites by a robotic AI chemist
UT – A Single Robot Could Provide a Mission To Mars With Enough Water and Oxygen
UT – What is ISRU, and How Will it Help Human Space Exploration?
UT – A new way to Make Oxygen on Mars: Using Plasma

Lead Image:
Series of images of the robotic arm used in the experiments running the catalyst synthesis process.
Credit – Zhu et al.

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An Insanely High-Resolution Image of the Sun

Our local star the Sun has been the source of many studies from ground based telescopes to space based observatories. The ESA Solar Orbiter has been approaching the Sun, capturing images along the way in unprecedented detail. It arrived at its halfway point in March last year and captured a series of 25 images. They have now been stitched together to reveal an astonishingly high resolution image. You can even zoom in to see individual granules in the solar photosphere. 

In comparison to Earth, the Sun is massive but in when it comes to other stars, it’s pretty average. It provides energy to sustain life through the process of nuclear fusion deep in its core.  The hydrogen atoms are fused into helium generating so much energy that heat and light bathes our planet. Like all other stars, the Sun is a great big ball of electrically charged gas with a visible surface temperature of about 5,500°C. It measures a staggering 1.39 million km across and lies at an average distance of 150 million km from us. It accounts for 99% of the mass of the Solar System and it is this which is responsible for its immense gravitational pull which has kept planets, asteroids and comets in orbit for the last 4.6 billion years!

The Sun on November 1, 2023 with the eQuinox 2 telescope by Unistellar and Smart Solar Filter. Credit: Nancy Atkinson.

Without a doubt it is the most prominent astronomical object to grace our skies and so it is no surprise it has been the target of many, many studies. ESA’s Solar Orbiter is one of those space based observatories that has started to unveil some of the mysteries of our nearest star. It was launched in February 2020 and was designed to capture images of the Sun’s poles along with measuring its magnetic fields and the solar wind. The orbit followed by Solar Orbiter is very specific following an elliptical orbit that takes it to within 42 million km of the Sun. 

Solar Orbiter

On board Solar Orbiter are instruments to probe the dynamics of the Sun. The most exciting of these are those designed to observe the Sun directly and includes the Extreme Ultraviolet Imager (EUI) and the Polarimetric and Helioseismic Imager (PHI) which when combined can with other on board instruments can create some fabulously high resolution images. With Solar Orbiter already half way to the Sun ESA have released a stunning new image of our nearest star derived from data from both EUI and PHI.

At the time the images were taken, Solar Orbiter was 74 million km away from the Sun (Mercury is approximately 50 million km away) and was too close to be able to capture one image of the whole Sun. Instead, 25 images were taken over a few hours and then stitched together to create the mosaic that has just been released. The finished result can be seen here and has a resolution of around 175 km per pixel. Previous observations have gone deeper for example the Gregor Solar Telescope on Tenerife has achieved a resolution of just 50 km per pixel but this was only ever of a small section of the Sun.

Large mosaics were never possible due to the turbulence in the atmosphere making it impossible to stitch sufficient images together.  The image is stunning. If you zoom in you can see the pattern of granulation all over the Sun’s photosphere and even a few sunspots in super high resolution. 

Source : The Solar Fire Up Close

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The Hubble and FU Orionis: a New Look at an Old Mystery

In 1936 astronomers watched as FU Orionis, a dim star in the Orion constellation, brightened dramatically. The star’s brightness increased by a factor of 100 in a matter of months. When it peaked, it was 100 times more luminous than our Sun.

Astronomers had never observed a young star brightening like this.

Since then, we’ve learned that FU Orionis is a binary star. It’s surrounded by a circumstellar disk and the brightness episodes are triggered when the star accretes mass from the disk. There are other young stars similar to FU Orionis, and it’s now the namesake for an entire class of variable young stars that brighten in the same manner. FU Ori stars are a sub-class of T-Tauri stars, young, pre-main sequence stars that are still growing.

Astronomers have modelled FU Ori’s accretion and brightness episodes with some success. But the nature of the disk-star interface has remained a mystery. Attempts to image the boundary between the two haven’t been successful. Until now.

Astronomers used the Hubble Space Telescope to observe FU Ori with the telescope’s COS (Cosmic Origins Spectrograph) and STIS (Space Telescope Imaging Spectrograph) instruments. Their results are published in The Astrophysical Journal Letters. The research is “A Far-ultraviolet-detected Accretion Shock at the Star–Disk Boundary of FU Ori” and the lead author is Adolfo Carvalho. Carvalho is an Astronomy PhD candidate at Caltech.

FU Ori stars are T-Tauri stars that represent the most actively accreting young stellar objects (YSOs). The outward magnetic pressure from T-Tauri stars prevents the disk from touching the star. Astronomers think that classical T-Tauri stars accrete material along their magnetic field lines and deposit on the poles in a process called magnetospheric accretion.

This schematic shows how magnetospheric accretion works on T-Tauri stars. Image Credit: Adapted from Hartmann et al. (2016).

However, FU Ori stars are different. They’ve undergone disk instability either because the disk is so much larger than the star, because of the presence of a binary, or from infalling material. The instability leads to rapid changes in the accretion rate. The increased rate of accretion upsets the balance between the star’s magnetic field and the inner edge of the accretion disk. The spectra of FU Ori stars is dominated by absorption features from the inner disk. Excess emissions from those stars is understood as matter shocking onto the star’s photosphere. However, for FU Ori stars, astronomers are uncertain about the detailed structure of the accretion boundary layer.

The researchers focused on the inner edge of FU Ori’s accretion disk in an attempt to confirm the accretion disk model and understand the boundary layer more completely.

“We were hoping to validate the hottest part of the accretion disk model, to determine its maximum temperature, by measuring closer to the inner edge of the accretion disk than ever before,” said Lynne Hillenbrand of Caltech in Pasadena, California, a co-author of the paper. “I think there was some hope that we would see something extra, like the interface between the star and its disk, but we were certainly not expecting it. The fact we saw so much extra — it was much brighter in the ultraviolet than we predicted — that was the big surprise.”

In FU Ori stars, the accretion disk is closer than in T-Tauri stars. This, combined with the enhanced infall rate, makes them much brighter than T-Tauris. In fact, during an outburst, the disk actually outshines the star. The disk is orbiting faster than the star rotates, and this means there should be a region where the disk impacts the star. The impact slows the material down and heats it up.

This artist’s image helps illustrate FU Ori’s accretion and flaring. Left panel: Material from the dusty and gas-rich disk (orange) plus hot gas (blue) mildly flows onto the star, creating a hot spot. Middle panel: The outburst begins – the inner disk is heated, more material flows to the star, and the disk creeps inward. Right panel: The outburst is in full throttle, with the inner disk contacting the star. Image Credit: Caltech/T. Pyle (IPAC)

The new Hubble UV observations show that the region is there and that it’s much hotter than thought.

“The Hubble data indicates a much hotter impact region than models have previously predicted,” said lead author Carvalho. “In FU Ori, the temperature is 16,000 kelvins [nearly three times our Sun’s surface temperature]. That sizzling temperature is almost twice the amount prior models have calculated. It challenges and encourages us to think of how such a jump in temperature can be explained.”

That means that the scientific model of FU Ori stars, called the viscous disk accretion model, needs to be updated. The team’s revised model says that as material from the accretion disk approaches the star and reaches its surface, it produces a hot shock that emits ultraviolet light. The temperature of the shock suggests that the material is moving at 40 km/s at the boundary, which is in line with simulations of the accretion process.

“The measured temperature and the size of the FUV emission region are consistent with expectations for a shock at the disk–star boundary,” the authors explain in their research. “The shock arises from the collision of the highly supersonic disk surface accretion flow with the stellar photosphere.”

One question scientists have concerns exoplanet formation around young stars. Researchers think that planets start to form when stars are very young. Is this hot flaring a detriment to planet formation? Does it affect their evolution? The extreme UV accretion flaring that FU Ori stars undergo could affect the chemistry of planets.

“Our revised model based on the Hubble data is not strictly bad news for planet evolution, it’s sort of a mixed bag,” explained Carvalho. “If the planet is far out in the disk as it’s forming, outbursts from an FU Ori object should influence what kind of chemicals the planet will ultimately inherit. But if a forming planet is very close to the star, then it’s a slightly different story. Within a couple outbursts, any planets that are forming very close to the star can rapidly move inward and eventually merge with it. You could lose, or at least completely fry, rocky planets forming close to such a star.”

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China Tests a Reusable Inflatable Module in Space

Inflatable space modules are not a new concept, NASA have been exploring the possibility since the 1960’s. The Chinese Space Agency is now getting in on the act and is testing its new inflatable module which is part of its Shijian-19 satellite launch. To get it into orbit the capsule was compressed and folded and then inflated once in orbit. Following completion of the tests, it re-entered the atmosphere, landing in the Gobi Desert on 10th October. The goal is for this to be used to extend its space station in the same way NASA have been exploring expansion of ISS. 

The idea of inflatable space capsules offers a lightweight solution which simplifies the launch process. Their development began back in the 1960’s but real progress was seen with projects like TransHub that looked at new advanced materials. Even though TransHub was cancelled it was a precursor to ventures like the Bigelow Aerospace module known as BEAM. It was tested in 2016 on the ISS and proved the concept could work making them an invaluable part of the future of space exploration. 

This computer rendering shows the Bigelow Expanded Activity Module in its fully expanded configuration. Image: NASA

The Chinese National Space Administration (CNSA) has now started experimentation with inflatable modules. They have been a major player on the global space stage since it was founded in 1993. Among their successes have been the Chang’e lunar missions and the Tianwen-1 Mars explorers. Since 2021, the Tiangong space station has been in orbit high above the Earth and there are now plans for crewed lunar missions. 

A recovery team member checks the Chang’e-6 probe’s sample return capsule after its landing in Inner Mongolia. (Credit: CGTN / CNSA)

On 27th September, the CNSA launched their Shijian-19 retrievable satellite from Jiuquan in China. A test inflatable module was developed and manufactured by the China Academy of Space Technology (CAST) as a landmark step in getting an inflatable module in orbit. They confirmed that the inflatable flexible sealed module completed a successful orbital test. The module is a sealed structure made from composite materials much like the Bigelow Aerospace BEAM module. 

Launch is completed by compressing and folding the module and then inflating upon reaching orbit. The technique makes construction relatively cheap and the launch process far more efficient. Following on from the successful test, CAST promise that larger-scale modules are the next step marking an important step forward in sealed module technology. To arrive at this stage in the development of inflatable technology, CAST completed ground based tests that confirmed they were air tight, could deal with extreme pressures and vibrations and would be capable of with standing impact from space debris. 

A rendering of the Chinese Tiangong space station. Credit: CMSA

The CNSA have confirmed they plan to expand their Tiangong space station and are now exploring the possibility of using inflatable modules as part of their plans. The next likely module to be added is likely to be a multifunctional capsule that will allow other modules to be added. The success of the inflatable module opens up a number of possibilities and opportunities for the Chinese agency, not just for Tiangong but for other space exploration habitats. 

Source : China’s inflatable space capsule passes in-orbit test

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OKEANOS – A Mission That Would Have Retrurned Samples From the Trojan Asteroids

Getting a mission to the point of officially being accepted for launch is an ordeal. However, even when they aren’t selected for implementation, their ideas, and in some cases, their technologies, can live on in other missions. That was the case for the Oversize Kite-craft for Exploration and AstroNautics in the Outer Solar system (OKEANOS) project, originally planned as a Japanese Aerospace Exploration Agency (JAXA) mission. Despite not receiving funding to complete its entire mission, the project team released a paper that details the original plan for the mission, and some of those plans were incorporated into other missions that are still under development.

OKEANOS sought to build on JAXA’s success in returning samples from asteroids to Earth. Its most well-known mission in that regard was Hayabusa-2, which returned samples from the asteroid Ryugu in 2020 and has been the subject of dozens of scientific papers since. Ryugu is a near-earth asteroid, which means its origins in the solar system are dramatically different from those of other asteroids farther out from the Sun, which is where OKEANOS came in.

The original plan for OKEANOS was to launch a sample return mission to one of the Jupiter Trojan asteroids that sit in the Lagrange points in front of and behind Juptier and its orbital path. Scientists believe these asteroids originated outside of Neptune’s orbit in the Kuiper belt but were brought closer to the Sun due to gravitational fluctuations caused by the migration of the gas giant planets. Since they would hold clues to the early solar system, astronomers are interested in their composition, and some space exploration enthusiasts are interested in the materials they hold for in-situ resource utilization purposes. But so far, no missions have visited them yet.

A solar panel, like the one shown in the video, would have been a key component of the OKEANOS missions.
Credit – The Japan Times YouTube Channel

That is about to change, though, with Lucy, a NASA mission that launched in 2021 to visit them. However, Lucy will simply do remote observations and lacks the equipment to sample them directly, let alone return a sample back to Earth. The project team had hoped OKEANOS would do just that.

Several novel technologies would be used to enable OKEANOS’ scientific objectives. One of the most interesting was a combination solar sail and ion drive known as a solar power sail. A solar power sail combines the solar pushing power of a solar sail with flexible photovoltaic solar collectors that can collect a significant amount of energy while deployed in a sail-like configuration. JAXA has also successfully tested a similar system with its IKAROS mission, demonstrating the technology in 2010.

Since solar sails have tiny thrust out near Jupiter, OKEANOS relies entirely on an ion engine and simply deploys its “sails” to deploy the solar panels that collect energy to power the ion drive. But once it reached its destination, it would utilize its second interesting technology—a lander.

Fraser talks about Lucy, the first mission to explore the Trojan asteroids.

The two main asteroid sample return missions – OSIRIS-REx and Hayabusa-2 – directly touched down on the surface of their respective asteroids. However, there have been deployed landers that have at least attempted to land on an asteroid before – Philae, the lander that accompanied ESA’s Rosetta mission, is probably the most famous. But never before has a mission attempted to land a lander, collect a sample, and return it to a “mothership” that would then transport that sample back to Earth. Doing so out at the Trojan asteroids would add a new difficulty level of having significant communications lag time, making it difficult to troubleshoot any problems with the mission.

Given JAXA’s track record, it seemed likely that they could pull off that technical challenge. However, the mission was never fully funded due to a “cost issue,” according to the paper. JAXA selected a project known as LiteBIRD to study the cosmic microwave background as its large-class mission for this decade instead. Despite that, the technical details of some of the instrumentation have been described in other papers, and the project team feels confident that future asteroid sample return missions will adopt at least some of them. We’ll be sure to see more of those in the future as interest grows in understanding the roots of our solar system and how we might utilize the readily available resources on asteroids.

Learn More:
Takao et al. – Sample return system of OKEANOS—the solar power sail for Jupiter Trojan exploration
UT – Lucy Adds Another Asteroid to its Flyby List
UT – Separation Camera Takes Full Images and ‘Movie’ of IKAROS Solar Sail
UT – Tiny Fragments of a 4-Billion Year Old Asteroid Reveal Its History

Lead Image:
Concept images of the OKEANOS mission.
Credit – Takao et al.

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Fantastic New Image of the Sombrero Galaxy From Webb

NGC 4594 is an unusual galaxy. It was discovered in 1781 by Pierre Méchain, and is striking because of a symmetrical ring of dust that encircles the visible halo of the galaxy. Images taken of the galaxy in 2003 show this dusty ring in detail, where it almost resembles the brim of a large hat. So it’s understandable that NGC 4594 is more commonly known as the Sombrero Galaxy. Now the James Webb Space Telescope has captured an amazingly sharp image of the galaxy, and it’s revealing some interesting surprises.

The famous Sombrero galaxy. The prominent dust lane and halo of stars and globular clusters give this galaxy its name. Credit: NASA/ESA and The Hubble Heritage Team (STScI/AURA)

Although Hubble’s view of the Sombrero Galaxy is stunning, it is bound by the limits of the optical spectrum. In the Hubble image, the thick dust ring obscures any stars that may be forming within it, and the brilliance of the active black hole at the heart of the galaxy outshines any details at the center of the galaxy. Given what we know about galaxies and star formation, it was thought that the dust ring could hide stellar nurseries where new stars are being born. And the central region of the galaxy likely held a bulge of stars similar to that of other galaxies.

The JWST image reveals a very different story. This particular image was captured by Webb’s Mid-Infrared Instrument (MIRI), which can peer through much of the galaxy’s dust. It reveals clumps of warm molecular gas within the brim of the galaxy, but surprisingly few young stars. It appears that the dust ring is not a significant source of star formation. The image also unveils the central region of the galaxy. Rather than a halo of stars surrounding the black hole, there is a flat disk. While the central black hole is active, it is a low luminosity galactic nucleus, which is again surprising given that it does produce jets of plasma like more active galactic nuclei.

Overall, the Sombrero Galaxy is much more unusual than we expected, and while these are only the first detailed images from the Webb, they already promise to yield a wealth of data. Future observations will likely focus on the globular clusters of the galaxy. There are about 2,000 globular clusters within the Sombrero Galaxy, which is unusually high for a galaxy of its size. This could help explain why NGC 4594 is so different from other galaxies.

You can find more images of the Sombrero Galaxy on the Webb Space Telescope website.

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We’re Living in an Abnormal Galaxy

Astronomers often use the Milky Way as a standard for studying how galaxies form and evolve. Since we’re inside it, astronomers can study it in detail with advanced telescopes. By examining it in different wavelengths, astronomers and astrophysicists can understand its stellar population, its gas dynamics, and its other characteristics in far more detail than distant galaxies.

However, new research that examines 101 of the Milky Way’s kin shows how it differs from them.

One powerful way to understand things is to compare and contrast them with others in their class, a technique we learn in school. Surveys are an effective tool to compare and contrast things, and astronomical surveys have contributed an enormous amount of foundational data towards the effort. The Sloan Digital Sky Survey (SDSS), the Two Micron All Sky Survey (2MASS), and the ESA’s Gaia mission are all prominent examples.

The Satellites Around Galactic Analogs (SAGA) Survey is another, and its third data release features in three new studies. The studies are all based on 101 galaxies similar in mass to the Milky Way, and each study tackles a different aspect of comparing those galaxies to ours.

• The SAGA Survey. III. A Census of 101 Satellite Systems around Milky Way–mass Galaxies
• The SAGA Survey. IV. The Star Formation Properties of 101 Satellite Systems around Milky Way–mass Galaxies
• The SAGA Survey. V. Modeling Satellite Systems around Milky Way–Mass Galaxies with Updated UniverseMachine

Research shows that galaxies form inside gigantic haloes of dark matter, the elusive substance that doesn’t interact with light. 85% of the Universe’s matter is mysterious dark matter, while only 15% is normal or baryonic matter, the type that makes up planets, stars, and galaxies. Though we can’t see these massive haloes, astronomers can observe their effects. Their gravity draws normal together to create galaxies and stars.

Dark matter haloes are part of the Large-Scale Structure of the Universe, the cosmic web of dark matter and galaxy clusters and superclusters that make up the Universe’s backbone. Simulated Image Credit: Ralf Kaehler/SLAC National Accelerator Laboratory

SAGA is aimed at understanding how dark matter haloes work. It examines low-mass satellite galaxies around galaxies similar in mass to the Milky Way. These satellites can be captured and drawn into the dark matter haloes of larger galaxies. SAGA has found several hundred of these satellite galaxies orbiting 101 Milky Way-mass galaxies.

“The Milky Way has been an incredible physics laboratory, including for the physics of galaxy formation and the physics of dark matter,” said Risa Wechsler, the Humanities and Sciences Professor and professor of physics in the School of Humanities and Sciences. Wechsler is also the co-founder of the SAGA Survey. “But the Milky Way is only one system and may not be typical of how other galaxies formed. That’s why it’s critical to find similar galaxies and compare them.”

The comparison between the Milky Way and the 101 others revealed some significant differences.

“Our results show that we cannot constrain models of galaxy formation just to the Milky Way,” said Wechsler, who is also professor of particle physics and astrophysics at the SLAC National Accelerator Laboratory. “We have to look at that full distribution of similar galaxies across the universe.”

The SAGA Survey’s third data release includes 378 satellites found in 101 MW-mass systems, and the first paper focuses on the satellites. Only a painstaking search was able to uncover them. Four of them belong to the Milky Way, including the well-known Large and Small Magellanic Clouds.

This figure shows how SAGA compares to other efforts to find satellite galaxies. Image Credit: Mao et al. 2024.

“There’s a reason no one ever tried this before,” Wechsler said. “It’s a really ambitious project. We had to use clever techniques to sort those 378 orbiting galaxies from thousands of objects in the background. It’s a real needle-in-the-haystack problem.”

SAGA found that the number of satellites per galaxy ranges from zero to 13. According to the first paper, the mass of the most massive satellite is a strong predictor of the abundance of satellites. “One-third of the SAGA systems contain LMC-mass satellites, and they tend to have more satellites than the MW,” the paper states. The Milky Way is an outlier in this regard, which is one reason it’s atypical.

The second study focuses on star formation in the satellites. The star formation rate (SFR) is an important metric in understanding galaxy evolution. The research shows that star formation is still active in the satellite galaxies, but the closer they are to the host, the slower their SFR. Is it possible that the greater pull of the dark matter halo close to the galaxy is quenching star formation?

“Our results suggest that lower-mass satellites and satellites inside 100 kpc are more efficiently quenched in a Milky Way–like environment, with these processes acting sufficiently slowly to preserve a population of star-forming satellites at all stellar masses and projected radii,” the second paper states.

However, in the Milky Way’s satellites, only the Magellanic Clouds are still forming stars, with radial distance playing a role. “Now we have a puzzle,” Wechsler said. “What in the Milky Way caused these small, lower-mass satellites to have their star formation quenched? Perhaps, unlike a typical host galaxy, the Milky Way has a unique combination of older satellites that have ceased star formation and newer, active ones – the LMC and SMC – that only recently fell into the Milky Way’s dark matter halo.”

This figure from the research shows the SFR (left) and the specific SFR (right) for the satellite galaxies in the study. The specific SFR differs from the SFR in that it’s divided by the total stellar mass of the galaxy. The specific SFR basically tells astronomers how quickly the galaxy is growing relative to its size. It’s used to compare star formation efficiency across different size galaxies. The grey squares the SAGA hosts and the stars are the Large and Small Magellanic Clouds. Image Credit: Geha et al. 2024.

This is another reason that our galaxy is atypical.

What about the smaller dark matter haloes around the satellite galaxies? What role do they play?

“To me, the frontier is figuring out what dark matter is doing on scales smaller than the Milky Way, like with the smaller dark matter halos that surround these little satellites,” Wechsler said.

The third paper compares SAGA’s third data release with computer simulations. The authors developed a new model for quenching in galaxies with less-than-or-equal-to 10⁹ solar masses. Their model is constrained by the SAGA data on the 101 galaxies, and the researchers then compared it to isolated field galaxies from the Sloan Digital Sky Survey.

The model successfully reproduced the stellar mass function of the satellites, their average SFRs, and the quenched fractions in the satellites. It also maintained the SFR in more isolated satellite galaxies and observed enhanced quenching in closer satellites.

This figure from the research shows the distribution of stellar mass vs. halo mass, with the grey contours representing 2,500 mock Saga-like hosts. It shows that their model successfully reproduces much of what SAGA found. Image Credit: Wang et al. 2024.

The model needs more testing with observations, and the authors point out that spectroscopic surveys are a logical next step. Those surveys can hopefully answer questions about the role internal feedback plays in the lower-mass satellites, about their mass and gas accretion and the influence dark matter has on them, as well as gas processes specific to the satellites.

“SAGA provides a benchmark to advance our understanding of the universe through the detailed study of satellite galaxies in systems beyond the Milky Way,” Wechsler said. “Although we finished our initial goal of mapping bright satellites in 101 host galaxies, there’s a lot more work to do.”

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