In April, the world watched as four humans circled the Moon for the first time in over 50 years with NASA’s Artemis II mission. On Saturday, Sept. 19, the public is invited to look up again with NASA events across the country, including the International Observe the Moon Night celebration held at NASA’s Goddard Space Flight Center Visitor Center in Greenbelt, Maryland.

International Observe the Moon Night is an annual celebration that brings people together to learn about the Moon and explore our connection to Earth’s nearest celestial neighbor. Since the program began in 2010, people around the world have participated through lunar observations, hands-on activities, artwork, music, and more.
 
At NASA Goddard, this year’s celebration will highlight the agency’s ongoing exploration of the Moon, including the historic Artemis II mission. Visitors can peer behind the scenes to learn more about what it took to make Artemis II’s journey around the Moon a success and discover how Goddard scientists and engineers are helping advance our understanding of the Moon, solar system, and beyond.
 
The event will run from 6 p.m. to 9 p.m. EDT.
 
Throughout the event at NASA Goddard, visitors can take part in interactive hands-on activities, create artwork and crafts, and capture selfies at a photo kiosk. Telescopes will also be set up outside (depending on weather), giving attendees an opportunity to observe the Moon and other astronomical objects up close. Inside the Visitor Center, guests can even see a real Apollo 14 Moon rock on display.

• At 6:30 p.m., Dr. Amanda Nahm, planetary scientist at NASA Headquarters, will explore the lunar science and Moon joy from Artemis II.
• At 7:30 p.m., Ernie Wright, scientific visualizer at NASA Goddard, will offer a more technical look at how scientists use real data to create videos and visualizations of the Moon.

The event will also offer a chance to learn more about the groundbreaking research happening at NASA Goddard as scientists work to unlock the secrets of the Moon with missions like the Lunar Reconnaissance Orbiter (LRO) and explore our solar system and the universe beyond.
 
International Observe the Moon Night at Goddard is free and family friendly. Registration is not required, although registering in advance will help the Visitor Center team plan for the event. The event will take place rain or shine, and free parking is available at the Visitor Center.
 
Additional event details, including registration, accessibility and other logistics: https://www.nasa.gov/goddard/visitor-center/events-and-programs/.
 
For people who cannot travel to Greenbelt, there are opportunities to participate in International Observe the Moon Night from all around the planet. Join lunar observers around the world by observing the Moon with friends and family, attending a virtual event or finding an event in your area. Learn more and register your participation at go.nasa.gov/ObserveTheMoon.
 
International Observe the Moon Night is sponsored by NASA’s LRO mission and the Solar System Exploration Division of NASA’s Goddard Space Flight Center, with support from many partners. The celebration is a way for people to pause and look up at our future destination, as NASA prepares for deep space missions to the Moon and beyond.
 
To learn about NASA’s Artemis program, visit:
https://www.nasa.gov/artemis
 
To learn about LRO, visit:
https://www.nasa.gov/lro

Dr. Delia Santiago-Materese

Program Scientist

Dr. Delia Santiago-Materese wants things to get complex

From terrestrial animals to experiments in microgravity and Martian clouds, this NASA program scientist’s career path links diverse challenges. Today, she supports a mission to Saturn’s moon Titan, a world teeming with organic molecules that could hold valuable clues about the origin of life.

When novelty is your hobby, you already have a large part of the recipe for a career full of challenges. That is why Dr. Delia Santiago-Materese describes her path within NASA as “meandering.” Her diverse roles have taken her to low Earth orbit, to the clouds of Mars, and to the surroundings of Jupiter. Now, they are also bringing her closer to the surface of Titan, an intriguing moon of Saturn. Woven together by her exploring spirit and a perennial curiosity, all these experiences have one point in common: life.

Today, Santiago-Materese is part of the Planetary Science Division at NASA Headquarters in Washington. The main decoration in her office is a model of Jupiter, larger than a basketball, resting next to a scale model of the spacecraft exploring it, Juno. Small black and red pins with the inscription “Dragonfly” rest in the center of a round table. Several framed diplomas cover a wall. From here, Santiago-Materese does “a little bit of everything” on any given workday as a program scientist for the Juno and Dragonfly missions, and for the Discovery program, which features a portfolio of several missions in our cosmic neighborhood.

This medley of roles is no coincidence. Santiago-Materese describes herself as someone who does not pursue a single goal, but rather diverse interests that she discovers along the way. “I am always looking for something new to add to my experiences,” she says, “because I think I also get bored easily.”

The daughter of a military family, Santiago-Materese was born in Spain by coincidence. Her roots are actually on another continent: her mother is Mexican-American and her father is Puerto Rican. From her time in Spain, she only keeps some baby photos; she lived part of her life in Texas and then in California, which she considers her home—despite having spent her childhood summers in San Sebastián, Puerto Rico. It was in the Golden State where she first imagined herself as a veterinarian and decided to study Biological Sciences. And it was during her studies at Stanford University, “just around the corner” from NASA’s Ames Research Center in California’s Silicon Valley, that Santiago-Materese discovered astrobiology.

This elective course brought her closer to a discipline that, to some extent, was in its infancy. Today, NASA’s Astrobiology Program investigates life in the universe on many levels: how it began, how it evolved here on Earth, and where it might exist elsewhere. And that was how Santiago-Materese realized that biology and space were not two isolated things, she recounts.

Rodents, Insects, and Martian Clouds

After finishing her studies, Santiago-Materese completed a one-year internship at the San Francisco Zoo. But the unknown that astrobiology presents continued to intrigue her, so she went back to one of her professors to inquire more about it. She asked around and found someone at Lockheed Martin, a company that often contracts with NASA on space projects. They were looking for people for a new project studying the nutrition of the food bars for rodents traveling to space aboard the space shuttle.

Santiago-Materese has applied that formula ever since: identifying what truly interests her and finding the right person to ask questions. If people “don’t know what you’re interested in, they can’t help you,” she explains. After experience with the Space Shuttle Program, including managing databases for science payloads aboard the space shuttle, she went on to work with the International Space Station, which was then beginning its legacy of over 25 years in Earth orbit. She supported the development of biological experiments in microgravity, this time with fruit flies. But Santiago-Materese wanted to keep moving farther from Earth and investigate future space destinations.

This curiosity led her to the Martian sky. As part of her graduate studies at the University of California, Santa Cruz, Santiago-Materese investigated the Martian atmosphere, focusing on ice in the clouds and the development of climate models for the Red Planet. She earned her master’s degree and would later return to complete her doctorate under the NASA Pathways program, which is one of the agency’s primary early-career hiring pathways. She would defend her thesis six months after giving birth to her first daughter (one of the achievements she is most proud of, she says). That is why, although she loves the “weird” planets of the outer solar system, she is “more of a Mars person,” by training.

At NASA Ames, Santiago-Materese held various roles, ranging from social media and open science to lunar sciences. She then became a program officer for the Solar System Workings program in the Planetary Science Division at NASA Headquarters as part of a detail, or temporary assignment. And then, she took off for Maryland along with her family.

Enabling Science

Santiago-Materese sums up her current role as a program scientist as the “science liaison” between NASA Headquarters and a mission. “When you do program scientist work, you might not be specialized or an expert in the exact science, but you need to be able to understand it and talk about it, to understand its importance,” she explains. “In general, we are supporting other people so they can do science.” In this endeavor, being someone who “gets more energy from working with people” is useful… and necessary: “You are having conversations all day long” with colleagues from different disciplines— from science and engineering to finance.

The Juno mission, in orbit around Jupiter since 2016, and Dragonfly, which is scheduled to launch no earlier than July 2028, are part of NASA’s New Frontiers program. Santiago-Materese also oversees the array of missions in the Discovery program, which includes ongoing science missions like Psyche and Lucy—heading to different asteroids—and future missions to Venus.

For Santiago-Materese, sharing her unconventional path can be valuable for students and youth in general, especially those who are unsure of what they want to do. “Your dream job,” she says, “you might not know it exists, or maybe it doesn’t exist today.” Beyond that, this zigzagging path has led her to accumulate experiences and relationships with different people, which she treasures even as she sets off for her next destination.

An Alien World

About two years out from Dragonfly’s launch, it is no surprise that this robotic mission takes up much of Santiago-Materese’s time. “Dragonfly feels like a combination of all my different experiences over time,” she reflects. And it signifies, to some extent, a return to her roots: it is an astrobiology mission. Although not designed to detect life, Dragonfly will investigate prebiotic chemistry: the chemical processes that could have led to the emergence of life on Earth.

Dragonfly will embark on a journey of about six years to the surface of Titan. The spacecraft will carry an array of science instruments and will be the first NASA science mission to explore another world by flying from location to location. This car-sized rotorcraft will touch down at various geological sites of interest to analyze the moon’s composition and its habitability potential.

When it arrives at Titan, it will encounter a landscape that is strange and familiar at the same time: it could be a window into Earth’s remote past. This frozen world has a thick atmosphere and clouds drifting across the sky; dunes, lakes, rivers, canyons and mountains. Titan even has a process equivalent to our water cycle. However, on Titan, it is not water that flows but hydrocarbons, primarily methane and ethane. “It’s a more methane-based chemistry, so it is very alien, and that is what I really love about Titan,” says Santiago-Materese. And on this moon, organic molecules abound.

These molecules contain carbon and are used by all known forms of life. They are fundamental to understanding the origin of life, as they can be produced by both biological and non-biological processes. On Titan, these organic molecules fall to the surface and form dense deposits over its bedrock of water ice. Scientists believe that the complex chemistry precursor to life could be triggered there if provided with a little liquid water, such as that generated by an asteroid impact.

Santiago-Materese is especially excited about what the Dragonfly Mass Spectrometer (DraMS) instrument will help discover. DraMS, designed and built at NASA’s Goddard Space Flight Center in Greenbelt, Maryland, will analyze samples from Titan’s surface. “The more complex things get, the more interesting things happen,” she says. “So I’m curious: just how complex do the molecules get? Will we find any interesting patterns?”

But in science, every time you ask a question, a new one arises. Dragonfly will try to answer several of them. “When you have a planet with complex chemistry but not life, what happens? What is there before life?” the program scientist wonders.

Titan, a valuable natural laboratory, “is going to completely change our understanding of what another world can be like,” she anticipates. In addition to what the scientific community expects to discover thanks to Dragonfly, Santiago-Materese is interested in the potential unexpected findings. “There are very defined science goals, but a lot of it is exploratory work,” she explains. “It is kind of nice to know that there is a big range [of possibilities], that we could be very surprised.”

By Noelia González, NASA’s Goddard Space Flight Center, Greenbelt, Maryland

Lee esta historia en español aquí.

The post Dr. Delia Santiago-Materese appeared first on NASA Science.

A solar eclipse, the Perseids, bright Venus after sunset, and a deep partial lunar eclipse highlight August’s skywatching.

Skywatching Highlights

• Aug. 5: Last Quarter Moon
• Aug. 12: Total solar eclipse across northern Russia, Greenland, Iceland, northern Spain, and part of Portugal; partial eclipse in parts of the U.S.; New Moon
• Aug. 12-13: Perseid meteor shower peak under dark skies
• Aug. 14-16: Venus reaches greatest eastern elongation and shines low in the west after sunset
• Aug. 27-28: Partial lunar eclipse visible from much of North and South America and parts of Europe and Africa

Transcript

A solar eclipse, one of the year’s best meteor showers, Venus at its brightest in the evening sky, and a lunar eclipse to close out the month.

That’s “What’s Up” for August.

On Aug. 12, a total solar eclipse crosses northern Russia, Greenland, Iceland, and northern Spain, with a small corner of Portugal inside the path of totality.

In parts of the United States, from Alaska to North Carolina, the eclipse is partial. The Moon will take only a small bite out of the Sun, and the amount of coverage will vary with location.

Remember to watch safely. Use certified eclipse glasses or a safe solar viewer any time any part of the Sun is visible. Regular sunglasses are not safe. And never use binoculars, a telescope, or a camera without a solar filter made for the front of the optics.

Later that same night, the Perseid meteor shower will light up the sky, peaking the evening of Aug. 12 into the early morning hours of the 13th. And with a New Moon arriving on the 12th, the skies will be ideally dark.

The Perseids happen every year when Earth passes through a debris stream left behind by Comet Swift-Tuttle. As those tiny bits of comet dust hit our atmosphere at high speed, they burn up as bright streaks of light.

To view this meteor shower, look toward the northeast once it’s fully dark and watch for the constellation Perseus to clear the horizon. This is where the meteors originate, but let your eyes wander, because they can flash across any part of the sky.

For the best view, stay out late as the stars climb higher, find a dark open spot, and give your eyes 30 minutes to adjust.

Aug. 14-16, Venus reaches its greatest eastern elongation, which is its widest apparent separation from the Sun during this evening appearance.

Look low in the western sky shortly after sunset for the bright object that will outshine every star around it. Through a telescope after sunset, Venus will look close to half lit, like a tiny lunar phase.

On the night of Aug. 27, continuing into Aug. 28 for some time zones, the Full Moon slips through Earth’s shadow, resulting in a partial lunar eclipse. It will be visible from much of North and South America and parts of Europe and Africa.

At maximum eclipse, about 93% of the Moon’s diameter will be inside Earth’s dark central shadow, called the umbra. The Moon will not be completely covered, but it can look dramatically darkened, with a rusty, coppery tint along the covered edge.

Unlike a solar eclipse, a lunar eclipse is safe to watch with just your eyes. Binoculars or a small telescope can give you a closer view of Earth’s curved shadow moving across the Moon.

Here are the phases of the Moon for August.

You can stay up to date on all of NASA’s missions exploring the solar system and beyond at science.nasa.gov. I’m Raquel Villanueva from NASA’s Jet Propulsion Laboratory, and that’s What’s Up for this month.

Keep Exploring

Discover More Topics From NASA

What’s Up

Skywatching

Galaxies

Stars

The post What’s Up: August 2026 Skywatching Tips from NASA appeared first on NASA Science.

A solar eclipse, the Perseids, bright Venus after sunset, and a deep partial lunar eclipse highlight August’s skywatching.

Skywatching Highlights

• Aug. 5: Last Quarter Moon
• Aug. 12: Total solar eclipse across northern Russia, Greenland, Iceland, northern Spain, and part of Portugal; partial eclipse in parts of the U.S.; New Moon
• Aug. 12-13: Perseid meteor shower peak under dark skies
• Aug. 14-16: Venus reaches greatest eastern elongation and shines low in the west after sunset
• Aug. 27-28: Partial lunar eclipse visible from much of North and South America and parts of Europe and Africa

Transcript

A solar eclipse, one of the year’s best meteor showers, Venus at its brightest in the evening sky, and a lunar eclipse to close out the month.

That’s “What’s Up” for August.

On Aug. 12, a total solar eclipse crosses northern Russia, Greenland, Iceland, and northern Spain, with a small corner of Portugal inside the path of totality.

In parts of the United States, from Alaska to North Carolina, the eclipse is partial. The Moon will take only a small bite out of the Sun, and the amount of coverage will vary with location.

Remember to watch safely. Use certified eclipse glasses or a safe solar viewer any time any part of the Sun is visible. Regular sunglasses are not safe. And never use binoculars, a telescope, or a camera without a solar filter made for the front of the optics.

Later that same night, the Perseid meteor shower will light up the sky, peaking the evening of Aug. 12 into the early morning hours of the 13th. And with a New Moon arriving on the 12th, the skies will be ideally dark.

The Perseids happen every year when Earth passes through a debris stream left behind by Comet Swift-Tuttle. As those tiny bits of comet dust hit our atmosphere at high speed, they burn up as bright streaks of light.

To view this meteor shower, look toward the northeast once it’s fully dark and watch for the constellation Perseus to clear the horizon. This is where the meteors originate, but let your eyes wander, because they can flash across any part of the sky.

For the best view, stay out late as the stars climb higher, find a dark open spot, and give your eyes 30 minutes to adjust.

Aug. 14-16, Venus reaches its greatest eastern elongation, which is its widest apparent separation from the Sun during this evening appearance.

Look low in the western sky shortly after sunset for the bright object that will outshine every star around it. Through a telescope after sunset, Venus will look close to half lit, like a tiny lunar phase.

On the night of Aug. 27, continuing into Aug. 28 for some time zones, the Full Moon slips through Earth’s shadow, resulting in a partial lunar eclipse. It will be visible from much of North and South America and parts of Europe and Africa.

At maximum eclipse, about 93% of the Moon’s diameter will be inside Earth’s dark central shadow, called the umbra. The Moon will not be completely covered, but it can look dramatically darkened, with a rusty, coppery tint along the covered edge.

Unlike a solar eclipse, a lunar eclipse is safe to watch with just your eyes. Binoculars or a small telescope can give you a closer view of Earth’s curved shadow moving across the Moon.

Here are the phases of the Moon for August.

You can stay up to date on all of NASA’s missions exploring the solar system and beyond at science.nasa.gov. I’m Raquel Villanueva from NASA’s Jet Propulsion Laboratory, and that’s What’s Up for this month.

Keep Exploring

Discover More Topics From NASA

What’s Up

Skywatching

Galaxies

Stars

Born on July 25, 1920, Chushiro Hayashi graduated from the University of Tokyo with a degree in physics in 1942. After World War II service in the navy, he returned to school, finishing his doctorate in 1954 and becoming a professor at Kyoto University in 1957. An innovator, he applied fundamental physics to astronomy andContinue reading "July 25, 1920: The birth of Chushiro Hayashi"

The post July 25, 1920: The birth of Chushiro Hayashi appeared first on Astronomy Magazine.

NASA MAVEN (Mars Atmosphere and Volatile Evolution) mission scientists have uncovered a key puzzle piece in understanding certain types of auroras on Mars, finding that they form in a similar way to Earth-based auroras.
 
Results published Thursday in Nature Communications show the same mechanism that circulates and catapults charged particles into Earth’s atmosphere is happening at Mars on much smaller scales because of differences in the two planets’ magnetic fields.
 
The MAVEN spacecraft, in orbit around Mars, experienced a loss of signal with ground stations on Earth on Dec. 6, 2025. On June 3, NASA declared the mission had concluded after finding the spacecraft to be unrecoverable. However, data from the mission is still being used to inform NASA science and future missions to Mars.
 
When the Sun’s magnetic field lines get close to Earth’s magnetosphere, the large magnetic bubble protecting the planet, they can reconnect and inject energy and mass throughout Earth’s magnetosphere and magnetotail, ultimately firing electrons back into the atmosphere to generate Earth’s auroras. This process, called the Dungey cycle, drives electrical currents, accelerates charged particles that create auroras, and controls the circulation of plasma in Earth’s magnetosphere and ionosphere.
 
This new study shows that a miniature version of the Dungey cycle is happening over Mars’ strong crustal magnetic fields, which gives scientists a better look into the physics of Martian auroras.
 
“We knew that magnetic reconnection was happening at Mars but did not expect it to be like the Dungey cycle,” said Shaosui Xu, lead author of the study and associate research physicist at the Space Sciences Laboratory at the University of California, Berkeley.
 
Mars does not have a global magnetic field like Earth. Earth’s magnetic field is created by our planet’s churning core, while Mars has numerous miniature magnetospheres that arise from intensely magnetized crust scattered around the planet.  These regions were formed around 4 billion years ago when lava cooled in the presence of Mars’ ancient global magnetic field, which has since disappeared due to intense solar wind stripping the planet’s atmosphere.
 
The MAVEN mission has observed highly localized auroras over these crustal fields, similar to Earth’s auroras at the poles, but it wasn’t until now that scientists could fully understand the physics of how they form. The study used several instruments aboard the MAVEN spacecraft to build up a picture of the Dungey-like behavior: the Magnetometer and Solar Wind Electron Analyzer instruments, which were used to determine the magnetic configuration and derive electrical currents, and the STATIC (Suprathermal and Thermal Ion Composition) instrument, which was used to measure plasma flows in the ionosphere.
 
“We really pushed the limit of STATIC to get the data we needed,” said Xu. “It was the final piece to the puzzle in understanding these localized auroras.”
 
The realization that a Dungey-like cycle was happening within these crustal magnetic fields answered the question of how the electrons were being energized to create the auroras. It also shows that a Dungey-like mechanism can happen on both large and small scales, giving more insight into where in the solar system this process could be taking place.
 
“This is a remarkable result that changes how we think of Martian auroras and is another important step toward understanding why Mars and Earth have evolved so differently despite being governed by the same underlying physics.” said Shannon Curry, MAVEN’s principal investigator and a research scientist at the Laboratory for Atmospheric and Space Physics at the University of Colorado Boulder. “I am incredibly proud of our team’s work on this discovery and excited to uncover new insights into the Red Planet and its evolution.”
 
By finding out more about this process, scientists also are gaining a better understanding of how the solar environment interacts with the Red Planet as a whole, which is essential for future robotic and crewed missions.
 
“I remember in graduate school discussing with my advisor how the cycling of crustal magnetic fields could work at Mars,” said Xu. “It’s incredible to be part of the team that found the answer to that question.”
 
The MAVEN mission is part of NASA’s Mars Exploration Program portfolio. The mission’s principal investigator is based at the Laboratory for Atmospheric and Space Physics at the University of Colorado Boulder, which also is responsible for managing science operations and public outreach and communications. NASA’s Goddard Space Flight Center in Greenbelt, Maryland, manages the MAVEN mission. Lockheed Martin Space built the spacecraft and is responsible for mission operations. NASA’s Jet Propulsion Laboratory in Southern California provides navigation and Deep Space Network support.
 
For more information on NASA’s MAVEN mission, visit:
 
https://science.nasa.gov/mission/maven/
 
Karen Fox / Alana Johnson
Headquarters, Washington
240-285-5155 / 202-672-4780
karen.c.fox@nasa.gov / alana.r.johnson@nasa.gov
 
Lonnie Shekhtman
NASA’s Goddard Space Flight Center, Greenbelt, Md.
lonnie.shekhtman@nasa.gov

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.

Lucy’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 rotation

With 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.

Peanut shape

While 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 water

As 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, contrast

Donaldjohanson 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).

“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:

By Lonnie Shekhtman

NASA’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

The post NASA’s Lucy Reveals Wobbling, Peanut-Shaped Asteroid appeared first on NASA Science.

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.

Lucy’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 rotation

With 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.

Peanut shape

While 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 water

As 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, contrast

Donaldjohanson 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).

“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:

By Lonnie Shekhtman

NASA’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