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Desert Field Test With NASA Advanced Rover Prototype
NASA/JPL-Caltech Photojournal Navigation Downloads Desert Field Test With NASA Advanced Rover Prototype
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Description
A prototype four-wheel rover developed at NASA’s Jet Propulsion Laboratory with advanced mobility and robotic autonomy capabilities trundled across the Colorado Desert near Plaster City, California, during a field test in March 2026. Called ERNEST (Exploration Rover for Navigating Extreme Sloped Terrain), the rover served here as a testbed for autonomy software developed for a potential lunar mission requiring higher speeds and much greater mileage than can be achieved with current planetary rovers.
ERNEST was trailed by engineers as it traveled about 16 miles over the course of 37 hours of drive time. That’s more than 10 times the speed at which NASA’s Perseverance rover can navigate on Mars. The team also tested how well the rover traveled at dusk, dawn, and nighttime to simulate the experience of large terrain shadows in polar regions on the Moon.
Figure A
Figure A shows the rover traveling toward its shadow.
Figure B
Figure B shows two team members setting up illuminators on the rover at night.
Figure C
Figure C shows three team members observing the rover during its long-range traverse.
Figure D
Figure D shows the rover with one wheel up on a rock.
Work on ERNEST began in 2022 and was initially supported by JPL internal research and development funds. It is currently funded by NASA’s Mars Exploration Program and the agency’s Exploration Science Strategy Integration Office under its Science Mission Directorate in Washington. Caltech in Pasadena, California, manages JPL for NASA.
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Desert Field Test With NASA Advanced Rover Prototype
NASA/JPL-Caltech Photojournal Navigation Downloads Desert Field Test With NASA Advanced Rover Prototype
PNG (27.94 MB)
PIA26701 Figure A
JPEG (26.03 MB)
PIA26701 Figure B
JPEG (951.75 KB)
PIA26701 Figure C
JPEG (16.03 MB)
PIA26701 Figure D
JPEG (16.46 MB)
Description
A prototype four-wheel rover developed at NASA’s Jet Propulsion Laboratory with advanced mobility and robotic autonomy capabilities trundled across the Colorado Desert near Plaster City, California, during a field test in March 2026. Called ERNEST (Exploration Rover for Navigating Extreme Sloped Terrain), the rover served here as a testbed for autonomy software developed for a potential lunar mission requiring higher speeds and much greater mileage than can be achieved with current planetary rovers.
ERNEST was trailed by engineers as it traveled about 16 miles over the course of 37 hours of drive time. That’s more than 10 times the speed at which NASA’s Perseverance rover can navigate on Mars. The team also tested how well the rover traveled at dusk, dawn, and nighttime to simulate the experience of large terrain shadows in polar regions on the Moon.
Figure AFigure A shows the rover traveling toward its shadow.
Figure BFigure B shows two team members setting up illuminators on the rover at night.
Figure CFigure C shows three team members observing the rover during its long-range traverse.
Figure DFigure D shows the rover with one wheel up on a rock.
Work on ERNEST began in 2022 and was initially supported by JPL internal research and development funds. It is currently funded by NASA’s Mars Exploration Program and the agency’s Exploration Science Strategy Integration Office under its Science Mission Directorate in Washington. Caltech in Pasadena, California, manages JPL for NASA.
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NASA Testing Advanced Capabilities for Moon, Mars Rovers
On a bleak stretch of the Colorado Desert in Southern California, a compact four-wheeled rover recently trundled about 16 miles (26 kilometers) with minimal intervention from the team of engineers trailing it. Called ERNEST (Exploration Rover for Navigating Extreme Sloped Terrain), this prototype is being used by NASA to advance both robotic autonomy and the ability to traverse challenging landscapes.
Developed at NASA’s Jet Propulsion Laboratory in Southern California, ERNEST is 4 feet (1.2 meters) long. Not only can it lift each of its mesh wheels to get past obstacles that would stymie Curiosity and Perseverance, NASA’s six-wheeled Mars rovers, but the prototype also has enhanced independent decision-making capabilities. These mobility and autonomy advances could be infused into future missions that will venture to previously inaccessible areas of the Red Planet or the Moon.
ERNEST serves as a testbed for a potential future lunar rover mission requiring high speeds and extreme distances. In a recent field test, the prototype traveled 16 miles over the course of 37 hours, going an order of magnitude above the top speed at which NASA’s current Mars rovers can navigate. Credit: NASA/JPL-CaltechIn the field, ERNEST served as a testbed for a potential future lunar mission requiring higher speeds and much greater mileage than can be accomplished by current rovers. This technology could be used to inform future designs for exploration efforts on the Moon and beyond.
“This testing is helping us refine the mobility hardware and autonomy software to navigate extreme distances across a wide range of terrain and lighting conditions anticipated on the Moon,” said Issa Nesnas, a principal technologist at JPL who led the recent testing as head of autonomy for a NASA mission concept for a potential future long-range lunar rover.
Engineers from JPL set up illuminators after transporting ERNEST for a pre-sunrise test during a seven-day desert field campaign.NASA/JPL-Caltech
Nesnas’ team is using ERNEST to demonstrate it is possible to build a rover that’s twice as big as the prototype and capable of a long-distance Moon mission. During the recent campaign, ERNEST traveled at speeds up to 0.6 mph (1 kph) over 37 hours of driving, across seven days of intermittent testing. That’s an order of magnitude above the top speed Perseverance and Curiosity can navigate.
“You could do a science road trip across the Moon — or Mars — with this vehicle,” said James Keane, a JPL planetary scientist working on lunar missions.
The initial goal of the team that developed ERNEST was mechanical: to design a relatively simple, low-cost rover that advances the trusted rocker-bogie suspension system featured on every Mars rover since NASA’s Sojourner. This passive system keeps relatively constant weight on all six wheels, thanks to pivot points and struts that enable each one to adapt to the changing surface.
The mobility and autonomy advances developed at JPL for the ERNEST prototype rover could be infused into future NASA missions to previously inaccessible areas of the Red Planet or the Moon. Credit: NASA/JPL-CaltechOn ERNEST, the active suspension lets the rover manage weight distribution among its wheels. Two powered joints in front articulate a gimbal that allows the rover to drive using different gaits like squirming, wheel-walking, and obstacle-climbing. With a clutch mechanism, it can switch between active and passive suspension, which is less terrain capable but more energy efficient. With four steerable wheels, it can drive in any direction, including sideways.
“We started by postulating that we could do better in designing a planetary surface robotic mobility system,” said Hari Nayar, a JPL principal technologist leading the ERNEST team. “While the rocker-bogie system has been very successful over the past 30 years, there’s been a lot of research in that time on mobility and understanding terrain interaction.”
Before arriving at today’s version of ERNEST, the team built two earlier prototypes, each about 2 feet (0.6 meters) long, to test 11 active suspension configurations. In a trailer filled with lunar regolith simulant, they ran experiments at different slope angles over several months before landing on a final design.
Then the team scaled up, including adding a rectangular head mounted on a 4.5-foot-tall (1.4-meter-tall) mast. The hardware was completed in September 2024, but the rover still needed a human operator to joystick it, sending commands to instruct the rover on how to move over obstacles.
In order to train the rover to think on its own, the ERNEST team turned to reinforcement learning, a type of artificial intelligence where the robot learns by interacting with its environment. The Dynamics and Real-Time Simulation Laboratory at JPL developed a high-fidelity virtual testing environment that replicates the rover’s behavior. The team fed the simulator data collected by engineers who documented the response of the actual rover hardware to a variety of terrain types. On a high-performance computing cluster, the team ran many simulations at once, sometimes completing thousands of hours of tests over a single weekend.
After months of virtual training, the ERNEST team was ready to see if the rover could use its new autonomous algorithms to figure out how to drive over terrain features that would halt a passive-suspension rover. They set up an obstacle course with sand ripples, rubble piles, steps, and steep slopes in JPL’s Mars Yard, an outdoor terrain proving ground. Then they watched as the rover maneuvered the terrain on its own. Since then, ERNEST has completed many such courses.
Nayar’s team is starting a new autonomy project which involves integrating the rover’s ability to determine when and how to use its active suspension with longer-range intelligent navigation. The goal is to enable ERNEST to plan an efficient path so that it can tackle surmountable obstacles and circumnavigate hazardous ones. These capabilities could contribute to potential future rover missions encountering formidable landscapes on Mars or more rugged areas of the Moon.
Work on ERNEST began in 2022 was initially supported by JPL internal research and development funds. It is currently funded by NASA’s Mars Exploration Program and the agency’s Exploration Science Strategy and Integration Office in its Science Mission Directorate at NASA Headquarters in Washington. Caltech in Pasadena, California, manages JPL for NASA.
Media Contacts
Karen Fox / Molly Wasser
NASA Headquarters, Washington
240-285-5155 / 240-419-1732
karen.c.fox@nasa.gov / molly.l.wasser@nasa.gov
Melissa Pamer
Jet Propulsion Laboratory, Pasadena, Calif.
626-314-4928
melissa.pamer@jpl.nasa.gov
2026-040
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NASA Testing Advanced Capabilities for Moon, Mars Rovers
On a bleak stretch of the Colorado Desert in Southern California, a compact four-wheeled rover recently trundled about 16 miles (26 kilometers) with minimal intervention from the team of engineers trailing it. Called ERNEST (Exploration Rover for Navigating Extreme Sloped Terrain), this prototype is being used by NASA to advance both robotic autonomy and the ability to traverse challenging landscapes.
Developed at NASA’s Jet Propulsion Laboratory in Southern California, ERNEST is 4 feet (1.2 meters) long. Not only can it lift each of its mesh wheels to get past obstacles that would stymie Curiosity and Perseverance, NASA’s six-wheeled Mars rovers, but the prototype also has enhanced independent decision-making capabilities. These mobility and autonomy advances could be infused into future missions that will venture to previously inaccessible areas of the Red Planet or the Moon.
ERNEST serves as a testbed for a potential future lunar rover mission requiring high speeds and extreme distances. In a recent field test, the prototype traveled 16 miles over the course of 37 hours, going an order of magnitude above the top speed at which NASA’s current Mars rovers can navigate. Credit: NASA/JPL-CaltechIn the field, ERNEST served as a testbed for a potential future lunar mission requiring higher speeds and much greater mileage than can be accomplished by current rovers. This technology could be used to inform future designs for exploration efforts on the Moon and beyond.
“This testing is helping us refine the mobility hardware and autonomy software to navigate extreme distances across a wide range of terrain and lighting conditions anticipated on the Moon,” said Issa Nesnas, a principal technologist at JPL who led the recent testing as head of autonomy for a NASA mission concept for a potential future long-range lunar rover.
Engineers from JPL set up illuminators after transporting ERNEST for a pre-sunrise test during a seven-day desert field campaign.NASA/JPL-CaltechNesnas’ team is using ERNEST to demonstrate it is possible to build a rover that’s twice as big as the prototype and capable of a long-distance Moon mission. During the recent campaign, ERNEST traveled at speeds up to 0.6 mph (1 kph) over 37 hours of driving, across seven days of intermittent testing. That’s an order of magnitude above the top speed Perseverance and Curiosity can navigate.
“You could do a science road trip across the Moon — or Mars — with this vehicle,” said James Keane, a JPL planetary scientist working on lunar missions.
The initial goal of the team that developed ERNEST was mechanical: to design a relatively simple, low-cost rover that advances the trusted rocker-bogie suspension system featured on every Mars rover since NASA’s Sojourner. This passive system keeps relatively constant weight on all six wheels, thanks to pivot points and struts that enable each one to adapt to the changing surface.
The mobility and autonomy advances developed at JPL for the ERNEST prototype rover could be infused into future NASA missions to previously inaccessible areas of the Red Planet or the Moon. Credit: NASA/JPL-CaltechOn ERNEST, the active suspension lets the rover manage weight distribution among its wheels. Two powered joints in front articulate a gimbal that allows the rover to drive using different gaits like squirming, wheel-walking, and obstacle-climbing. With a clutch mechanism, it can switch between active and passive suspension, which is less terrain capable but more energy efficient. With four steerable wheels, it can drive in any direction, including sideways.
“We started by postulating that we could do better in designing a planetary surface robotic mobility system,” said Hari Nayar, a JPL principal technologist leading the ERNEST team. “While the rocker-bogie system has been very successful over the past 30 years, there’s been a lot of research in that time on mobility and understanding terrain interaction.”
Before arriving at today’s version of ERNEST, the team built two earlier prototypes, each about 2 feet (0.6 meters) long, to test 11 active suspension configurations. In a trailer filled with lunar regolith simulant, they ran experiments at different slope angles over several months before landing on a final design.
Then the team scaled up, including adding a rectangular head mounted on a 4.5-foot-tall (1.4-meter-tall) mast. The hardware was completed in September 2024, but the rover still needed a human operator to joystick it, sending commands to instruct the rover on how to move over obstacles.
In order to train the rover to think on its own, the ERNEST team turned to reinforcement learning, a type of artificial intelligence where the robot learns by interacting with its environment. The Dynamics and Real-Time Simulation Laboratory at JPL developed a high-fidelity virtual testing environment that replicates the rover’s behavior. The team fed the simulator data collected by engineers who documented the response of the actual rover hardware to a variety of terrain types. On a high-performance computing cluster, the team ran many simulations at once, sometimes completing thousands of hours of tests over a single weekend.
After months of virtual training, the ERNEST team was ready to see if the rover could use its new autonomous algorithms to figure out how to drive over terrain features that would halt a passive-suspension rover. They set up an obstacle course with sand ripples, rubble piles, steps, and steep slopes in JPL’s Mars Yard, an outdoor terrain proving ground. Then they watched as the rover maneuvered the terrain on its own. Since then, ERNEST has completed many such courses.
Nayar’s team is starting a new autonomy project which involves integrating the rover’s ability to determine when and how to use its active suspension with longer-range intelligent navigation. The goal is to enable ERNEST to plan an efficient path so that it can tackle surmountable obstacles and circumnavigate hazardous ones. These capabilities could contribute to potential future rover missions encountering formidable landscapes on Mars or more rugged areas of the Moon.
Work on ERNEST began in 2022 was initially supported by JPL internal research and development funds. It is currently funded by NASA’s Mars Exploration Program and the agency’s Exploration Science Strategy and Integration Office in its Science Mission Directorate at NASA Headquarters in Washington. Caltech in Pasadena, California, manages JPL for NASA.
Media Contacts
Karen Fox / Molly Wasser
NASA Headquarters, Washington
240-285-5155 / 240-419-1732
karen.c.fox@nasa.gov / molly.l.wasser@nasa.gov
Melissa Pamer
Jet Propulsion Laboratory, Pasadena, Calif.
626-314-4928
melissa.pamer@jpl.nasa.gov
2026-040
Explore More 4 min read El Niño Is UnderwaySatellite observations of sea surface height indicated that the 2026 event continued to strengthen in…
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NASA’s Lucy Reveals Wobbling, Peanut-Shaped Asteroid
Even small asteroids lead complex lives. During its flyby of the asteroid Donaldjohanson last year, NASA’s Lucy spacecraft revealed the asteroid to be a wobbly, peanut-shaped body that has undergone a lot of activity in its relatively short history. Formed as fragments coalesced after a violent collision 155 million years ago, the asteroid was transformed by the small but inexorable force of the Sun’s radiation, all while retaining signs of the brief presence of liquid water in its distant past.
Zooming through the main asteroid belt toward one of the Jupiter Trojan asteroid groups, the Lucy spacecraft collected the first close-up images and other data at Donaldjohanson on April 20, 2025, as it passed 650 miles away from the asteroid. The data revealed that, instead of spinning simply around one axis like most other asteroids and planets, Donaldjohanson has a more complicated two-axis rotation. Scientists also saw Donaldjohanson’s peanut shape and the craters and ridges on its surface.
To view this video please enable JavaScript, and consider upgrading to a web browser that supports HTML5 video
A timelapse video made from images taken by NASA’s Lucy spacecraft as it approached the asteroid Donaldjohanson on April 20, 2025. The L’LORRI (Lucy Long Range Reconnaissance Imager) instrument, the spacecraft’s high-resolution black-and-white imager, collected these images over two hours as the spacecraft rapidly closed in on the asteroid from an initial separation of more than 58,000 miles (93,000 km), until the spacecraft passed a mere 650 miles (1000 km) from the 5-mile- (8 km-) wide asteroid.NASA/Goddard/SwRI/JHU-APLLucy’s encounter with the asteroid was planned as a dress rehearsal for the spacecraft and mission team before its primary asteroid encounters, which begin with Lucy’s flyby of the Trojan asteroid Eurybates on Aug. 12, 2027. The instruments performed as expected, and, as a bonus, scientists got a rare opportunity to study a previously unexplored asteroid up close and to compare it to two asteroids with similar compositions but different histories: Bennu, the target of NASA’s OSIRIS-REx sample-return mission, and Ryugu, the site of JAXA’s (Japan Aerospace Exploration Agency) Hayabusa2 sample-return mission.
Here’s what Lucy’s science team has learned so far from Lucy’s encounter with Donaldjohanson, as reported on June 18 in the journal Science.
Wobbling rotationWith Earth-based telescopes, observers saw fluctuations in the light Donaldjohanson reflects, regular patterns of peaks and valleys, typical of an elongated object rotating once every 10.5 Earth days. But Lucy’s data revealed another pattern: Donaldjohanson appears to be rotating like a wobbly top. Paper authors reported that the asteroid rotates end-over-end once every 10.5 Earth days, and wobbles back and forth around its long axis once every 26.5 days.
To view this video please enable JavaScript, and consider upgrading to a web browser that supports HTML5 video
The asteroid Donaldjohanson is shown slowly rotating in a tumbling, non-principal axis motion, with its angular momentum vector and rotation axes indicated. The surface is colored by gravity slope, which measures the angle between the local surface and the direction of gravity. Higher values (warmer colors) indicate steeper terrain relative to the local gravitational pull. Regions with limited stereo image coverage have been masked out where the shape model is less well constrained.Kel Elkins/NASA’s Science Visualization Studio/DLR Peanut shapeWhile the Earth-based observations hinted at Donaldjohanson’s elongated shape, the Lucy flyby revealed a “bilobate” structure: two lobes connected by a neck, like a peanut. These lobes are likely two fragments from an asteroid collision that gently came together afterward by their mutual gravity.
Donaldjohanson likely rotated at least 10 times faster when it formed, having slowed to its current rate in the last 20 to 60 million years, the team estimates. As it slowed, the balance between the centrifugal force pushing things apart and gravity pulling things together changed and loose rocky material slid down slopes creating the worn-down appearance of many craters, as the flyby images showed.
The paper’s authors say that the asteroid’s slowing rotation is likely caused by a subtle consequence of solar heating known as the YORP effect. Each part of the asteroid’s Sun-warmed surface radiates heat away as infrared light, and that radiation imparts a tiny recoil force to the surface. Because the asteroid’s shape isn’t symmetric, this results in a net torque, or twist, that can change the asteroid’s rotation. Thus, YORP can slow asteroid spins down or speed them up, as in the case of Bennu (once every four hours) and Ryugu (once about every seven hours), which both likely used to rotate much slower than they do today.
Fleeting waterAs it passed by Donaldjohanson at 30,000 mph, Lucy recorded the signatures of iron-rich clay minerals on the surface. These clays must have formed in the distant past with the help of liquid water. However, the exposure must have been brief, Lucy scientists concluded, because iron in clays tends to be replaced with other elements, such as magnesium, as water lingers.
Indeed, scientists saw magnesium-rich clays at Bennu and Ryugu, which suggested prolonged water exposure, perhaps lasting millions of years, when they were still part of larger asteroids.
This difference in water exposure history, and other characteristics, may mean that the parent bodies of these asteroids formed at different times or in different regions of the solar system before relocating to the main belt.
Compare, contrastDonaldjohanson is thought to be made from rocky remnants of a larger, carbon- and water-rich asteroid that collided with another object in the main asteroid belt. Bennu and Ryugu are thought to have formed in the same way and in the same region.
But Donaldjohanson is different. At 155 million years old, it is much younger than Bennu and Ryugu, which formed 1 to 2 billion years ago. Donaldjohanson also has remained in the asteroid belt since birth, while its wandering cousins migrated into orbits around the Sun that bring them close to Earth’s orbit about once a year (which made them perfect close targets for sample return missions).
During its April 20, 2025, encounter with the main-belt asteroid Donaldjohanson, NASA’s Lucy spacecraft discovered evidence for iron-rich clays on the surface using its infrared spectrometer. These clays, which are similar to those found in carbon-rich meteorites such as QUE 97990, indicate that water was briefly present in the asteroid during the distant past.NASA/Goddard/SwRI/Dan Gallagher
“It’s helpful for scientists to compare Donaldjohanson with asteroids like Bennu and Ryugu, which are seemingly similar asteroids, because every subtle difference is another clue to our origin story,” said Simone Marchi, Lucy deputy principal investigator and lead author of the study at the Boulder, Colorado, office of the Southwest Research Institute.
“Once we start learning more about the Trojans, a completely different population of space rocks with very different histories, our understanding of solar system formation is destined to be challenged,” said Marchi.
Named after a fossilized skeleton of a human ancestor discovered in Ethiopia in 1974, NASA’s Lucy will be the first mission to explore Jupiter’s Trojan asteroids, a population of well-preserved space rocks that formed early in our solar system’s history and could help scientists understand how the planets formed and moved around before settling in their current configuration.
Download story graphics from NASA’s Scientific Visualization Studio.
About Lucy:Lucy’s principal investigator is based out of the Boulder, Colorado, branch of Southwest Research Institute, headquartered in San Antonio. NASA’s Goddard Space Flight Center in Greenbelt, Maryland, provides overall mission management, systems engineering, and safety and mission assurance. Lockheed Martin Space in Littleton, Colorado, built the spacecraft. Lucy is the 13th mission in NASA’s Discovery Program. NASA’s Marshall Space Flight Center in Huntsville, Alabama, manages the Discovery Program for the agency’s Science Mission Directorate in Washington.
For more information on NASA’s Lucy mission, visit:
LucyNASA’s Goddard Space Flight Center, Greenbelt, Md.
and
Katherine Kretke
Southwest Research Institute, Boulder, Colo.
Media Contacts:Karen Fox / Molly Wasser
Headquarters, Washington
240-285-5155 / 240-419-1732
karen.c.fox@nasa.gov / molly.l.wasser@nasa.gov
Sarah Frazier
NASA’s Goddard Space Flight Center, Greenbelt, Md.
202-853-7191
sarah.frazier@nasa.gov
Zooming through the main asteroid belt toward one of the Jupiter Trojan asteroid groups, the Lucy spacecraft collected the first close-up images and other data at Donaldjohanson on April 20, 2025, as it passed 650 miles away from the asteroid. The data revealed that, instead of spinning simply around one axis like most other asteroids and planets, Donaldjohanson has a more complicated two-axis rotation. Scientists also saw Donaldjohanson’s peanut shape and the craters and ridges on its surface.
NASA’s Lucy Reveals Wobbling, Peanut-Shaped Asteroid
Even small asteroids lead complex lives. During its flyby of the asteroid Donaldjohanson last year, NASA’s Lucy spacecraft revealed the asteroid to be a wobbly, peanut-shaped body that has undergone a lot of activity in its relatively short history. Formed as fragments coalesced after a violent collision 155 million years ago, the asteroid was transformed by the small but inexorable force of the Sun’s radiation, all while retaining signs of the brief presence of liquid water in its distant past.
Zooming through the main asteroid belt toward one of the Jupiter Trojan asteroid groups, the Lucy spacecraft collected the first close-up images and other data at Donaldjohanson on April 20, 2025, as it passed 650 miles away from the asteroid. The data revealed that, instead of spinning simply around one axis like most other asteroids and planets, Donaldjohanson has a more complicated two-axis rotation. Scientists also saw Donaldjohanson’s peanut shape and the craters and ridges on its surface.
To view this video please enable JavaScript, and consider upgrading to a web browser that supports HTML5 video
A timelapse video made from images taken by NASA’s Lucy spacecraft as it approached the asteroid Donaldjohanson on April 20, 2025. The L’LORRI (Lucy Long Range Reconnaissance Imager) instrument, the spacecraft’s high-resolution black-and-white imager, collected these images over two hours as the spacecraft rapidly closed in on the asteroid from an initial separation of more than 58,000 miles (93,000 km), until the spacecraft passed a mere 650 miles (1000 km) from the 5-mile- (8 km-) wide asteroid.NASA/Goddard/SwRI/JHU-APLLucy’s encounter with the asteroid was planned as a dress rehearsal for the spacecraft and mission team before its primary asteroid encounters, which begin with Lucy’s flyby of the Trojan asteroid Eurybates on Aug. 12, 2027. The instruments performed as expected, and, as a bonus, scientists got a rare opportunity to study a previously unexplored asteroid up close and to compare it to two asteroids with similar compositions but different histories: Bennu, the target of NASA’s OSIRIS-REx sample-return mission, and Ryugu, the site of JAXA’s (Japan Aerospace Exploration Agency) Hayabusa2 sample-return mission.
Here’s what Lucy’s science team has learned so far from Lucy’s encounter with Donaldjohanson, as reported on June 18 in the journal Science.
Wobbling rotationWith Earth-based telescopes, observers saw fluctuations in the light Donaldjohanson reflects, regular patterns of peaks and valleys, typical of an elongated object rotating once every 10.5 Earth days. But Lucy’s data revealed another pattern: Donaldjohanson appears to be rotating like a wobbly top. Paper authors reported that the asteroid rotates end-over-end once every 10.5 Earth days, and wobbles back and forth around its long axis once every 26.5 days.
To view this video please enable JavaScript, and consider upgrading to a web browser that supports HTML5 video
The asteroid Donaldjohanson is shown slowly rotating in a tumbling, non-principal axis motion, with its angular momentum vector and rotation axes indicated. The surface is colored by gravity slope, which measures the angle between the local surface and the direction of gravity. Higher values (warmer colors) indicate steeper terrain relative to the local gravitational pull. Regions with limited stereo image coverage have been masked out where the shape model is less well constrained.Kel Elkins/NASA’s Science Visualization Studio/DLR Peanut shapeWhile the Earth-based observations hinted at Donaldjohanson’s elongated shape, the Lucy flyby revealed a “bilobate” structure: two lobes connected by a neck, like a peanut. These lobes are likely two fragments from an asteroid collision that gently came together afterward by their mutual gravity.
Donaldjohanson likely rotated at least 10 times faster when it formed, having slowed to its current rate in the last 20 to 60 million years, the team estimates. As it slowed, the balance between the centrifugal force pushing things apart and gravity pulling things together changed and loose rocky material slid down slopes creating the worn-down appearance of many craters, as the flyby images showed.
The paper’s authors say that the asteroid’s slowing rotation is likely caused by a subtle consequence of solar heating known as the YORP effect. Each part of the asteroid’s Sun-warmed surface radiates heat away as infrared light, and that radiation imparts a tiny recoil force to the surface. Because the asteroid’s shape isn’t symmetric, this results in a net torque, or twist, that can change the asteroid’s rotation. Thus, YORP can slow asteroid spins down or speed them up, as in the case of Bennu (once every four hours) and Ryugu (once about every seven hours), which both likely used to rotate much slower than they do today.
Fleeting waterAs it passed by Donaldjohanson at 30,000 mph, Lucy recorded the signatures of iron-rich clay minerals on the surface. These clays must have formed in the distant past with the help of liquid water. However, the exposure must have been brief, Lucy scientists concluded, because iron in clays tends to be replaced with other elements, such as magnesium, as water lingers.
Indeed, scientists saw magnesium-rich clays at Bennu and Ryugu, which suggested prolonged water exposure, perhaps lasting millions of years, when they were still part of larger asteroids.
This difference in water exposure history, and other characteristics, may mean that the parent bodies of these asteroids formed at different times or in different regions of the solar system before relocating to the main belt.
Compare, contrastDonaldjohanson is thought to be made from rocky remnants of a larger, carbon- and water-rich asteroid that collided with another object in the main asteroid belt. Bennu and Ryugu are thought to have formed in the same way and in the same region.
But Donaldjohanson is different. At 155 million years old, it is much younger than Bennu and Ryugu, which formed 1 to 2 billion years ago. Donaldjohanson also has remained in the asteroid belt since birth, while its wandering cousins migrated into orbits around the Sun that bring them close to Earth’s orbit about once a year (which made them perfect close targets for sample return missions).
During its April 20, 2025, encounter with the main-belt asteroid Donaldjohanson, NASA’s Lucy spacecraft discovered evidence for iron-rich clays on the surface using its infrared spectrometer. These clays, which are similar to those found in carbon-rich meteorites such as QUE 97990, indicate that water was briefly present in the asteroid during the distant past.NASA/Goddard/SwRI/Dan Gallagher“It’s helpful for scientists to compare Donaldjohanson with asteroids like Bennu and Ryugu, which are seemingly similar asteroids, because every subtle difference is another clue to our origin story,” said Simone Marchi, Lucy deputy principal investigator and lead author of the study at the Boulder, Colorado, office of the Southwest Research Institute.
“Once we start learning more about the Trojans, a completely different population of space rocks with very different histories, our understanding of solar system formation is destined to be challenged,” said Marchi.
Named after a fossilized skeleton of a human ancestor discovered in Ethiopia in 1974, NASA’s Lucy will be the first mission to explore Jupiter’s Trojan asteroids, a population of well-preserved space rocks that formed early in our solar system’s history and could help scientists understand how the planets formed and moved around before settling in their current configuration.
Download story graphics from NASA’s Scientific Visualization Studio.
About Lucy:Lucy’s principal investigator is based out of the Boulder, Colorado, branch of Southwest Research Institute, headquartered in San Antonio. NASA’s Goddard Space Flight Center in Greenbelt, Maryland, provides overall mission management, systems engineering, and safety and mission assurance. Lockheed Martin Space in Littleton, Colorado, built the spacecraft. Lucy is the 13th mission in NASA’s Discovery Program. NASA’s Marshall Space Flight Center in Huntsville, Alabama, manages the Discovery Program for the agency’s Science Mission Directorate in Washington.
For more information on NASA’s Lucy mission, visit:
LucyNASA’s Goddard Space Flight Center, Greenbelt, Md.
and
Katherine Kretke
Southwest Research Institute, Boulder, Colo.
Media Contacts:Karen Fox / Molly Wasser
Headquarters, Washington
240-285-5155 / 240-419-1732
karen.c.fox@nasa.gov / molly.l.wasser@nasa.gov
Sarah Frazier
NASA’s Goddard Space Flight Center, Greenbelt, Md.
202-853-7191
sarah.frazier@nasa.gov
Zooming through the main asteroid belt toward one of the Jupiter Trojan asteroid groups, the Lucy spacecraft collected the first close-up images and other data at Donaldjohanson on April 20, 2025, as it passed 650 miles away from the asteroid. The data revealed that, instead of spinning simply around one axis like most other asteroids and planets, Donaldjohanson has a more complicated two-axis rotation. Scientists also saw Donaldjohanson’s peanut shape and the craters and ridges on its surface.
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Stages of Star Formation
Stages of Star Formation
This image, captured by NASA’s James Webb Space Telescope and released on June 5, 2026, shows just a small portion of one of the Orion Molecular Clouds, a long and massive filament of cold gas and dust beyond the Orion Nebula. Every stage of star formation — from the youngest stellar embryos to protoplanetary discs to newly-minted pre-main sequence stars — is contained within this scene which stretches 150 light-years across.
Image credit: ESA/Webb, NASA & CSA, T. Megeath, M. Zamani (ESA/Webb); Acknowledgement: M. H. Özsaraç
Stages of Star Formation
This image, captured by NASA’s James Webb Space Telescope and released on June 5, 2026, shows just a small portion of one of the Orion Molecular Clouds, a long and massive filament of cold gas and dust beyond the Orion Nebula. Every stage of star formation — from the youngest stellar embryos to protoplanetary discs to newly-minted pre-main sequence stars — is contained within this scene which stretches 150 light-years across.
Image credit: ESA/Webb, NASA & CSA, T. Megeath, M. Zamani (ESA/Webb); Acknowledgement: M. H. Özsaraç
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