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By NASA
2 min read
Preparations for Next Moonwalk Simulations Underway (and Underwater)
ESI24 Haghighi Quadchart
Azadeh Haghighi
University of Illinois, Chicago
In-space manufacturing and assembly are vital to NASA’s long-term exploration goals, especially for the Moon and Mars missions. Deploying welding technology in space enables the assembly and repair of structures, reducing logistical burdens and supply needs from Earth. The unique challenges and extreme conditions of space–high thermal variations, microgravity, and vacuum–require advanced welding techniques and computational tools to ensure reliability, repeatability, safety, and structural integrity in one-shot weld scenarios. For the first time, this project investigates these challenges by focusing on three key factors: (1) Very low temperatures in space degrade the weldability of high thermal conductivity materials, like aluminum alloys, making it harder to achieve strong, defect-free welds. (2) The extreme vacuum in space lowers the boiling points of alloying elements, altering the keyhole geometry during welding. This selective vaporization changes the weld’s final chemical composition, affecting its microstructure and properties. (3) Microgravity nearly eliminates buoyancy-driven flow of liquid metal inside the molten pool, preventing gas bubbles from escaping, which leads to porosity and defects in the welds. By examining these critical factors using multi-scale multi-physics models integrated with physics-informed machine learning, and forward/inverse uncertainty quantification techniques, this project provides the first-ever real-time digital twin platform to evaluate welding processes under extreme space/lunar conditions. The models are validated through Earth-based experiments, parabolic flight tests, and publicly available data from different databases and agencies worldwide. Moreover, the established models will facilitate extendibility to support in-situ resource utilization on the Moon, including construction and repair using locally sourced materials like regolith. The established fundamental scientific knowledge will minimize trial-and-error, enable high-quality one-shot welds in space, and reduce the need for reworks, significantly reducing the costs and time needed for space missions.
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SSC and USC partnered up to pair USC Trojans with SSC Guardians to work within real USSF programs. This partnership team acted as a “living laboratory” to identify strategies for implementing agile development into complex defense projects.
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By NASA
Earth (ESD) Earth Home Explore Climate Change Science in Action Multimedia Data For Researchers 14 Min Read NASA’s Brad Doorn Brings Farm Belt Wisdom to Space-Age Agriculture
This image shows corn cultivation patterns across the U.S. Midwest in 2020, with lands planted in corn marked in yellow. Credits:
NASA Earth Observatory/ Lauren Dauphin Bradley Doorn grew up in his family’s trucking business, which hauled milk and animal feed across the sprawling plains of South Dakota. Home was Mitchell, a small town famous for its Corn Palace, where murals crafted from corn kernels and husks have adorned its facade since 1892—a tribute to the abundance of the surrounding farmland.
Trucking was often grueling work for the family, the day breaking early and ending in headlights. Like farming, driving a truck wasn’t just a job; it was the engine of daily life, thrumming through nearly every conversation and decision.
Brad loved the outdoors, and by the time he started college in the early 1980s, studying geological engineering felt like a natural fit. “I wanted to be out in the field somewhere, working under the big skies of the West,” Brad recalled. But in his sophomore year at the South Dakota School of Mines and Technology, the tuition money dried up.
Dean Doorn, Brad Doorn’s father, stands beside a milk truck used in the family’s business of hauling milk across South Dakota in the 1960s and ’70s. Credit: B. Doorn Doorn found himself at a crossroads familiar to many in rural America: return to the certainty of a family trade or chart a new route. “That’s when the Army stepped in,” he said. The ROTC program offered a way to continue with school and a path into the world of remote sensing—a field that would come to define his career.
Brad’s choice to join the Army would eventually place him at the forefront of a mapping revolution, equipping him to see and analyze Earth in ways never possible before the advent of satellites. But more than the technical skills, the military showed him the allure of a life anchored to mission and team.
Even as his career took him far from Mitchell, Doorn would remain connected to his rural America roots. Today, he leads NASA’s agriculture programs within the agency’s Earth Science Division. “My family wasn’t made up of farmers, but farming was a part of everything growing up,” said Brad. “Even now, working with NASA, that connection to the land—the sense of how weather, crops, and people are tied together—it’s still in everything I do.”
Amid the dazzle of NASA’s feats exploring the solar system and universe, it’s easy to miss the agency’s quiet work in fields of soy and wheat. But for more than 60 years, the agency has harnessed the power of its satellites to deliver crucial data on temperature, precipitation, crop yields, and more to farmers, policymakers, and food security experts worldwide.
The Landsat 9 satellite captured this false-color image of Louisiana rice fields in February 2023. Dark blue shows flooded areas, while green indicates vegetation. Grid-like levees separate fields pre-planting. Louisiana is the third largest producer of rice in the U.S. Credit: NASA Earth Observatory/ Lauren Dauphin From orbit, satellites beam down streams of data—numbers and pixels that, when paired with farmers’ knowledge of the land, can guide growers as they adjust irrigation levels or plan for the next planting. But the satellites don’t just yield data; they tell stories that call for action, enabling nations to brace for droughts, floods, and the prospect of empty grain silos.
“Under Brad’s guidance, NASA’s agriculture program has become a global leader for satellite-driven solutions, tackling food security and sustainability head-on,” said Lawrence Friedl, the senior engagement officer for NASA Earth Science. Reflecting on years of collaboration, he added: “I am so impressed and grateful for what he and his teams have accomplished.”
Boots Meet Satellites in the First Gulf War
Long before Brad began guiding NASA’s agricultural initiatives, he was already navigating tricky terrain, both literal and figurative, with satellite imagery. His career in remote sensing didn’t start with crops, but with the deserts of Iraq and Kuwait.
As part of the Army’s 18th Airborne Corps, Brad led a company at Fort Bragg (now Fort Liberty) in North Carolina that had just returned from operations in the First Gulf War, in the early 1990s. “I loved being part of a unit, part of something bigger than just me,” Brad recalled. “It felt good to have that purpose and mission.”
Far from the combat zone, Doorn’s company became cartographers of the invisible. Their task: merge data from the Landsat satellite with the gritty reality of desert warfare depicted on military maps.
Brad Doorn, then a U.S. Army officer, sits at his desk during his early career in remote sensing. His military experience would later shape his work at NASA, applying satellite technology to real-world challenges. Credit: B. Doorn Landsat, a civilian satellite built by NASA and operated by the U.S. Geological Survey, could see what the soldiers on the ground could not. Its thermal infrared sensor—a camera with a penchant for temperature and moisture—read the desert floor like an ancient script, picking out the cold, soggy signature of mud lurking beneath the desert’s deceptive crust. Each pixel of satellite data became a brushstroke in a new kind of map, keeping tanks out of the mire and the missions on track.
“It was so neat to see the remote sensing techniques I’d learned about in school actually making a difference,” Doorn said.
With this knowledge, he helped guide his unit’s shift from analog maps—paper grids and grease pencils—to the emerging world of digital mapping, a leap that sharpened the military’s ability to read the landscape and steer clear of trouble.
From Desert Muck to Farm Fields
Brad’s military experience gave him an early look at how satellite data could address tangible, on-the-ground challenges. In the Army, he saw how integrating satellite data into military maps could offer soldiers critical information. That experience set the foundation for his later work at NASA, where he would help develop technology with lasting, practical impacts.
Consider OpenET, a NASA-funded initiative that uses Landsat data to give farmers insights into water use and irrigation needs at field scale. The ET in OpenET stands not for the little alien who phoned home, but for evapotranspiration. It’s a combination of water evaporating from the ground and water released by plants into the air.
The program relies on the same thermal technology Doorn used during the Gulf War. Just as cooler, wetter areas in the desert hint at muddy spots, cooler patches in farm fields show where there’s more moisture or plants are releasing more water. These data are key to managing water resources wisely and keeping crops healthy.
“OpenET has transformed our understanding of water demand,” explained Doorn.
To better manage water, state officials and farmers in California are using satellite data through OpenET to track evapotranspiration. Here, the colors represent total evapotranspiration for 2023 as the equivalent depth of water in millimeters. Dark blue regions have higher evapotranspiration rates, such as in the Central Valley. Credit: NASA Earth Observatory using openetdata.org In the late 2000s, when a new generation of Landsat satellites was being planned, the thermal infrared imagers were initially left off the drawing board. “Landsat 8’s design caused a lot of consternation in some Western states that were beginning to use the instrument for measuring and monitoring water use,” said Tony Willardson, the executive director of the Western States Water Council, a government entity that advises western governors on water policy.
Brad played a key role in conveying to NASA the critical need for this technology, both for agriculture and water management, Willardson said. The thermal imager was eventually reinstated and has since “helped to close a gap in western water management.”
“A lot of the technologies that we are using more and more were developed by NASA,” said Willardson. “We need NASA to be doing even more in Earth science.”
Sowing Global Food Stability from Space
Brad ended up serving in the Army for nearly a decade. “You hit that 10-year mark in the military, and you sort of have to decide if you’re staying in for 20 or if you’re getting out,” said Brad. “My wife, Kristen, was able to manage her career as a registered dietician through the first four moves in six years, but eventually it was too much. So, I told her: ‘Your choice. You decide where we go next.’”
She chose southern Pennsylvania to be closer to her family. Brad was 32 years old, and the couple had two small children at the time—one of whom had had open-heart surgery at 6 weeks old to fix a heart defect. They would go on to have another child.
In the late 1990s, within a few years of leaving the military, Doorn found himself someplace he had never imagined: sitting behind a desk at the U.S. Department of Agriculture. For a boy who had grown up driving trucks across the plains of South Dakota—who had vowed never to work in an office, much less live east of the Mississippi—this was an unexpected detour. But he had long since learned that the best paths are often the ones you don’t see coming.
At USDA, he moved forward not with a grand plan, but with an instinctive trust in where curiosity and challenge might lead. He rose through the ranks, from a programmer to directing the agency’s international food production analysis program. He was increasingly driven by a conviction that satellite data, if used the right way, could transform how we see the land and the way we feed the world.
While at USDA, and later at NASA, which he joined in 2009, Brad was instrumental in developing and overseeing the Global Agricultural Monitoring (GLAM) system. This real-time interactive satellite platform delivers massive amounts of ready-to-use satellite data directly to USDA crop analysts, eliminating the burden of data processing and enabling them to focus on rapid crop analysis across the globe. It was a pioneering tool, said Inbal Becker-Reshef, a research professor at University of Maryland’s Department of Geographical Sciences, who played a central role in developing the GLAM system.
At a 2022 Kansas gathering, Brad Doorn presents to farmers about NASA’s Earth Science Division and its activities supporting agriculture. Credit: A. Whitcraft GLAM set the stage for GEOGLAM, a separate, international initiative launched in 2011 by agriculture ministers from the G20—a group of the world’s major economies—partly as a response to global food price volatility. GEOGLAM, which stands for Group on Earth Observations Global Agricultural Monitoring, uses satellite data to monitor global crop conditions, from drought stress to excessive rain, around the world.
Joseph Glauber, a former USDA chief economist, noted that there was initial uncertainty within USDA about the initiative’s longevity, but he credited Brad’s background with rallying support. Today, GEOGLAM’s monthly crop assessments, produced by over 40 organizations including USDA and NASA, serve as a global consensus on crop conditions, helping governments and humanitarian organizations anticipate food shortages.
“Even today, the G20 points to GEOGLAM and its sister initiative, the Agricultural Market Information System—which tracks how crop conditions affect markets—as major successes,” Glauber said.
Harvesting Data Amid Conflict
Doorn’s work crosses continents. When war broke out between Russia and Ukraine in 2022, it rattled global food markets. The Ukrainian government turned to NASA Harvest—a global food security and agriculture consortium led by the University of Maryland and funded by NASA—for help. As manager of NASA’s agriculture program, Brad was a driving force behind the launch of NASA Harvest in 2017, envisioning it as a program that would harness satellite data to provide timely, actionable insights for global agriculture.
From orbit, satellites could observe the sown and the harvested wheat, sunflowers, and barley, offering some of the only reliable estimates for fields in the war zone. Satellite imagery revealed that, despite the conflict, more cropland had been planted and harvested in Ukraine than anyone had expected, a finding that helped stabilize volatile global food prices.
“Brad and the team recognized that providing that type of rapid agricultural assessment for policy support is what NASA Harvest exists for,” said Becker-Reshef, who is the director of the consortium.
NASA Harvest’s reach stretches well beyond Europe. In sub-Saharan Africa, the consortium collaborates with local and international partners, tracking the health of crops and the creeping spread of drought. This information helps equip governments, aid organizations, and farmers to act before disaster strikes, making each data point a crucial defense against hunger.
NASA Harvest has since been joined by NASA Acres, founded in 2023 to provide satellite data and tools that help farmers make well-informed decisions for healthier crops and soil in the United States. One project, for example, involves working with farmers in Illinois to manage nitrogen use more effectively, leveraging satellite data to enhance crop yields while reducing environmental impact.
This image shows corn cultivation patterns across the U.S. Midwest in 2020, with lands planted in corn marked in yellow. The map was built from the Cropland Data Layer product provided by the National Agricultural Statistics Service, which includes data from the USGS National Land Cover Database and from satellites such as Landsat 8. Credit: NASA Earth Observatory/ Lauren Dauphin Friedl noted that Doorn understands the missions of both NASA and the USDA, and with his agricultural roots, he knows the needs of farmers and agricultural businesses firsthand. “Often in meetings, Brad would remind us that the margins for a farmer are in the pennies,” Friedl said. “They wouldn’t be able to afford remote sensing,” so making sure NASA’s satellite information was free and accessible was that much more important.
“It’s hard to imagine that NASA would have the agriculture program it does without somebody like Brad continuing to advocate and push for this to exist,” said Alyssa Whitcraft, the director of NASA Acres. “He knows how critical it is for satellite data to be accessible and useful to those on the ground. He makes sure we never lose sight of that.”
An Emissary Between Worlds
Colleagues say Doorn’s strength lies in his ability to bridge worlds, whether it’s making connections between agencies like NASA and USDA, or connecting such agencies to state water councils or farming communities. His fluency in translating complex science into simple terms makes him equally at ease in whichever world he finds himself.
“There’s NASA language and there’s farm language,” says Lance Lillibridge, who farms about 1,400 acres of corn and soybeans in Benton County, Iowa, and has helped lead the Iowa Corn Growers Association. “Sometimes you need an interpreter, and Brad’s that guy.” He recalled a meeting where some farmers were skeptical, wary of NASA’s “big brother” eyes in the sky, “but Brad had a way of putting people at ease, keeping everyone focused on the shared goal of better data for better decisions.”
Brad Doorn speaks during NASA’s “Space for Ag” roadshow in Iowa, July 2023, highlighting NASA’s role in supporting sustainable farming practices. Credit: N. Pepper “One of my favorite memories of Brad,” said Forrest Melton, the OpenET project scientist at NASA’s Ames Research Center, “is an afternoon spent visiting with farmers in western Nebraska, drinking iced tea and talking with them about the challenges facing their family farm.”
Colleagues describe Brad as a nearly unflappable guide, one who knows the agricultural landscape so well that he makes the impossible seem manageable. They say his calm, approachable style, paired with a ready smile, puts people at ease whether in Washington conference rooms or Midwestern barns. And he listens closely to understand where there may be opportunities to help.
“Few people in the water and agriculture communities, from the small-scale farmer to the federal government appointee, aren’t familiar with some aspect of the work Brad has enabled over the decades,” said Sarah Brennan, a former deputy program manager for NASA’s water resources programs. “He has supported the development of some of the greatest advancements in using remote sensing in these communities.”
It’s About the People and the Team
Doorn’s leadership is less about issuing directives, colleagues say, and more about cultivating growth—in crops, in data systems, and in people. Like a farmer tending to his fields, he nurtures the potential in every project and person he encounters. “Almost everyone who has worked for Brad can point back to the opportunities he provided them that launched their successful careers,” said Brennan.
Over the years, he’s added layers to this work of creating paths for others to succeed: as president of the American Society of Photogrammetry and Remote Sensing, as an adjunct professor at Penn State, and as a youth basketball league director.
“What I’ve learned, probably in the military and I’ve carried it forward, is that it’s the people that matter,” Brad said. “I had great mentors who believed it’s just as important to help others grow as it is to meet the day’s demands. Those roles shift your focus toward the people around you, and often, the more you give of your time, the more you end up getting back.”
Young Brad Doorn (front center) stands with his siblings, capturing a family moment in 1960s South Dakota. His youngest brother isn’t pictured. Credit: B. Doorn It has been a long journey from hauling milk and animal feed across the South Dakota plains to surveying them now as a scientist. The tools of his career have changed—from truck routes to satellite orbits, from paper maps to digital data—but his mission remains the same: helping farmers feed the world.
“Growing up in South Dakota, I saw firsthand the challenges farmers face. Today, I’m proud to help provide the tools and data that can make a real difference in their lives,” Doorn added. “Whether it’s a farmer, an economist, or a military analyst, if you give them the right tools, they’ll take them to places you never even thought about. That’s what excites me—seeing where they go.”
By Emily DeMarco
NASA’s Earth Science Division, Headquarters
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By NASA
5 min read
Preparations for Next Moonwalk Simulations Underway (and Underwater)
A prototype of a robot designed to explore subsurface oceans of icy moons is reflected in the water’s surface during a pool test at Caltech in September. Conducted by NASA’s Jet Propulsion Laboratory, the testing showed the feasibility of a mission concept for a swarm of mini swimming robots.NASA/JPL-Caltech In a competition swimming pool, engineers tested prototypes for a futuristic mission concept: a swarm of underwater robots that could look for signs of life on ocean worlds.
When NASA’s Europa Clipper reaches its destination in 2030, the spacecraft will prepare to aim an array of powerful science instruments toward Jupiter’s moon Europa during 49 flybys, looking for signs that the ocean beneath the moon’s icy crust could sustain life. While the spacecraft, which launched Oct. 14, carries the most advanced science hardware NASA has ever sent to the outer solar system, teams are already developing the next generation of robotic concepts that could potentially plunge into the watery depths of Europa and other ocean worlds, taking the science even further.
This is where an ocean-exploration mission concept called SWIM comes in. Short for Sensing With Independent Micro-swimmers, the project envisions a swarm of dozens of self-propelled, cellphone-size swimming robots that, once delivered to a subsurface ocean by an ice-melting cryobot, would zoom off, looking for chemical and temperature signals that could indicate life.
Dive into underwater robotics testing with NASA’s futuristic SWIM (Sensing With Independent Micro-swimmers) concept for a swarm of miniature robots to explore subsurface oceans on icy worlds, and see a JPL team testing a prototype at a pool at Caltech in Pasadena, California, in September 2024. NASA/JPL-Caltech “People might ask, why is NASA developing an underwater robot for space exploration? It’s because there are places we want to go in the solar system to look for life, and we think life needs water. So we need robots that can explore those environments — autonomously, hundreds of millions of miles from home,” said Ethan Schaler, principal investigator for SWIM at NASA’s Jet Propulsion Laboratory in Southern California.
Under development at JPL, a series of prototypes for the SWIM concept recently braved the waters of a 25-yard (23-meter) competition swimming pool at Caltech in Pasadena for testing. The results were encouraging.
SWIM Practice
The SWIM team’s latest iteration is a 3D-printed plastic prototype that relies on low-cost, commercially made motors and electronics. Pushed along by two propellers, with four flaps for steering, the prototype demonstrated controlled maneuvering, the ability to stay on and correct its course, and a back-and-forth “lawnmower” exploration pattern. It managed all of this autonomously, without the team’s direct intervention. The robot even spelled out “J-P-L.”
Just in case the robot needed rescuing, it was attached to a fishing line, and an engineer toting a fishing rod trotted alongside the pool during each test. Nearby, a colleague reviewed the robot’s actions and sensor data on a laptop. The team completed more than 20 rounds of testing various prototypes at the pool and in a pair of tanks at JPL.
“It’s awesome to build a robot from scratch and see it successfully operate in a relevant environment,” Schaler said. “Underwater robots in general are very hard, and this is just the first in a series of designs we’d have to work through to prepare for a trip to an ocean world. But it’s proof that we can build these robots with the necessary capabilities and begin to understand what challenges they would face on a subsurface mission.”
Swarm Science
A model of the final envisioned SWIM robot, right, sits beside a capsule holding an ocean-composition sensor. The sensor was tested on an Alaskan glacier in July 2023 through a JPL-led project called ORCAA (Ocean Worlds Reconnaissance and Characterization of Astrobiological Analogs). The wedge-shaped prototype used in most of the pool tests was about 16.5 inches (42 centimeters) long, weighing 5 pounds (2.3 kilograms). As conceived for spaceflight, the robots would have dimensions about three times smaller — tiny compared to existing remotely operated and autonomous underwater scientific vehicles. The palm-size swimmers would feature miniaturized, purpose-built parts and employ a novel wireless underwater acoustic communication system for transmitting data and triangulating their positions.
Digital versions of these little robots got their own test, not in a pool but in a computer simulation. In an environment with the same pressure and gravity they would likely encounter on Europa, a virtual swarm of 5-inch-long (12-centimeter-long) robots repeatedly went looking for potential signs of life. The computer simulations helped determine the limits of the robots’ abilities to collect science data in an unknown environment, and they led to the development of algorithms that would enable the swarm to explore more efficiently.
The simulations also helped the team better understand how to maximize science return while accounting for tradeoffs between battery life (up to two hours), the volume of water the swimmers could explore (about 3 million cubic feet, or 86,000 cubic meters), and the number of robots in a single swarm (a dozen, sent in four to five waves).
In addition, a team of collaborators at Georgia Tech in Atlanta fabricated and tested an ocean composition sensor that would enable each robot to simultaneously measure temperature, pressure, acidity or alkalinity, conductivity, and chemical makeup. Just a few millimeters square, the chip is the first to combine all those sensors in one tiny package.
Of course, such an advanced concept would require several more years of work, among other things, to be ready for a possible future flight mission to an icy moon. In the meantime, Schaler imagines SWIM robots potentially being further developed to do science work right here at home: supporting oceanographic research or taking critical measurements underneath polar ice.
More About SWIM
Caltech manages JPL for NASA. JPL’s SWIM project was supported by Phase I and II funding from NASA’s Innovative Advanced Concepts (NIAC) program under the agency’s Space Technology Mission Directorate. The program nurtures visionary ideas for space exploration and aerospace by funding early-stage studies to evaluate technologies that could transform future NASA missions. Researchers across U.S. government, industry, and academia can submit proposals.
How the SWIM concept was developed Learn about underwater robots for Antarctic climate science See NASA’s network of ready-to-roll mini-Moon rovers News Media Contact
Melissa Pamer
Jet Propulsion Laboratory, Pasadena, Calif.
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melissa.pamer@jpl.nasa.gov
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By NASA
5 Min Read Making Mars’ Moons: Supercomputers Offer ‘Disruptive’ New Explanation
A NASA study using a series of supercomputer simulations reveals a potential new solution to a longstanding Martian mystery: How did Mars get its moons? The first step, the findings say, may have involved the destruction of an asteroid.
The research team, led by Jacob Kegerreis, a postdoctoral research scientist at NASA’s Ames Research Center in California’s Silicon Valley, found that an asteroid passing near Mars could have been disrupted – a nice way of saying “ripped apart” – by the Red Planet’s strong gravitational pull.
The team’s simulations show the resulting rocky fragments being strewn into a variety of orbits around Mars. More than half the fragments would have escaped the Mars system, but others would’ve stayed in orbit. Tugged by the gravity of both Mars and the Sun, in the simulations some of the remaining asteroid pieces are set on paths to collide with one another, every encounter further grinding them down and spreading more debris.
Many collisions later, smaller chunks and debris from the former asteroid could have settled into a disk encircling the planet. Over time, some of this material is likely to have clumped together, possibly forming Mars’ two small moons, Phobos and Deimos.
To assess whether this was a realistic chain of events, the research team explored hundreds of different close encounter simulations, varying the asteroid’s size, spin, speed, and distance at its closest approach to the planet. The team used their high-performance, open-source computing code, called SWIFT, and the advanced computing systems at Durham University in the United Kingdom to study in detail both the initial disruption and, using another code, the subsequent orbits of the debris.
In a paper published Nov. 20 in the journal Icarus, the researchers report that, in many of the scenarios, enough asteroid fragments survive and collide in orbit to serve as raw material to form the moons.
“It’s exciting to explore a new option for the making of Phobos and Deimos – the only moons in our solar system that orbit a rocky planet besides Earth’s,” said Kegerreis. “Furthermore, this new model makes different predictions about the moons’ properties that can be tested against the standard ideas for this key event in Mars’ history.”
Two hypotheses for the formation of the Martian moons have led the pack. One proposes that passing asteroids were captured whole by Mars’ gravity, which could explain the moons’ somewhat asteroid-like appearance. The other says that a giant impact on the planet blasted out enough material – a mix of Mars and impactor debris – to form a disk and, ultimately, the moons. Scientists believe a similar process formed Earth’s Moon.
The latter explanation better accounts for the paths the moons travel today – in near-circular orbits that closely align with Mars’ equator. However, a giant impact ejects material into a disk that, mostly, stays close to the planet. And Mars’ moons, especially Deimos, sit quite far away from the planet and probably formed out there, too.
“Our idea allows for a more efficient distribution of moon-making material to the outer regions of the disk,” said Jack Lissauer, a research scientist at Ames and co-author on the paper. “That means a much smaller ‘parent’ asteroid could still deliver enough material to send the moons’ building blocks to the right place.”
It’s exciting to explore a new option for the making of Phobos and Deimos – the only moons in our solar system that orbit a rocky planet besides Earth’s.
Jacob Kegerreis
Postdoctoral research scientist at NASA’s Ames Research Center
Testing different ideas for the formation of Mars’ moons is the primary goal of the upcoming Martian Moons eXploration (MMX) sample return mission led by JAXA (Japan Aerospace Exploration Agency). The spacecraft will survey both moons to determine their origin and collect samples of Phobos to bring to Earth for study. A NASA instrument on board, called MEGANE – short for Mars-moon Exploration with GAmma rays and Neutrons – will identify the chemical elements Phobos is made of and help select sites for the sample collection. Some of the samples will be collected by a pneumatic sampler also provided by NASA as a technology demonstration contribution to the mission. Understanding what the moons are made of is one clue that could help distinguish between the moons having an asteroid origin or a planet-plus-impactor source.
Before scientists can get their hands on a piece of Phobos to analyze, Kegerreis and his team will pick up where they left off demonstrating the formation of a disk that has enough material to make Phobos and Deimos.
“Next, we hope to build on this proof-of-concept project to simulate and study in greater detail the full timeline of formation,” said Vincent Eke, associate professor at the Institute for Computational Cosmology at Durham University and a co-author on the paper. “This will allow us to examine the structure of the disk itself and make more detailed predictions for what the MMX mission could find.”
For Kegerreis, this work is exciting because it also expands our understanding of how moons might be born – even if it turns out that Mars’ own formed by a different route. The simulations offer a fascinating exploration, he says, of the possible outcomes of encounters between objects like asteroids and planets. These events were common in the early solar system, and simulations could help researchers reconstruct the story of how our cosmic backyard evolved.
This research is a collaborative effort between Ames and Durham University, supported by the Institute for Computational Cosmology’s Planetary Giant Impact Research group. The simulations used were run using the open-source SWIFT code, carried out on the DiRAC (Distributed Research Utilizing Advanced Computing) Memory Intensive service (“COSMA”), hosted by Durham University on behalf of the DiRAC High-Performance Computing facility.
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Members of the news media interested in covering this topic should reach out to the NASA Ames newsroom.
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