New research led by scientists at NASA’s Jet Propulsion Laboratory in Southern California has revealed the identity of a puzzling near-Earth object by precisely tracking its motion through space and using powerful observatories that image faint celestial objects.

This object has a dual personality: Past images hadn’t revealed obvious cometlike activity, suggesting it might be an asteroid, but its motion recently proved to be irregular like that of a comet. The scientists detailed their findings in a study published in the journal Nature Astronomy.

The puzzle began on Aug. 28, 2025, when the object, provisionally known as the asteroid 1998 SH2, passed safely within 2 million miles (3 million kilometers) of our planet during its 4½-year orbit around the Sun. Researchers looking to observe 1998 SH2 with NASA’s Deep Space Network (DSN) planetary radar system had calculated its position using data from previous orbits and factored in the effects that the gravity of the Sun and planets would have on its path. But when 1998 SH2 didn’t show up where they expected, they realized that something unanticipated had been influencing the object’s motion.

Object tracking

By using optical astrometry to precisely measure the object’s position in the sky, the researchers were able to identify the cause.

“After we measured the nongravitational perturbations affecting the motion of 1998 SH2 and recognized they weren’t compatible with the object being an asteroid, we suspected the object could be an active comet,” said Davide Farnocchia, a navigation engineer with NASA’s Center for Near-Earth Object Studies at JPL and study lead.

Although 1998 SH2’s orbit around the Sun had been well-tracked from 1998 to 2016, the object had completed two solar orbits without additional observations by telescopes until the 2025 DSN attempts. Analyzing all observations collected since the object’s discovery in 1998, researchers determined the perturbations to 1998 SH2’s motion and hypothesized that the object may be generating a small thrust by venting gas into space, causing it to deviate from its predicted path.

This venting results from the Sun heating ice mixed with rocky material, turning the ice into a gas. With regular comets, this activity forms a trademark bright tail and coma — the gas and dust surrounding a comet’s nucleus. But when an object produces gas and dust in much smaller quantities, its tail and coma may not be detectable to most observatories.

Tail, coma emerge

The August 2025 close approach to Earth of 1998 SH2 provided the perfect opportunity for the paper’s authors to gather observational evidence of visible cometary activity. They reached out to astronomers at the Canada-France-Hawaii Telescope, a 3.6-meter (12-foot) optical/infrared telescope near the summit of Mauna Kea, Hawaii, and the 1.5-meter (5-foot) European Southern Observatory’s Danish Telescope in La Silla, Chile, to observe. Astronomers at the powerful European Southern Observatory’s 8.2-meter (27-foot) Very Large Telescope on the Chilean mountain Cerro Paranal also tracked the object.

“The images we collected from these observatories showed a weak but clear tail, thus confirming that 1998 SH2 is, in fact, a comet,” said Olivier Hainaut, an astronomer with the European Southern Observatory and coauthor of the study. “That’s how science works — you form a hypothesis, and you set out to test it. This data is exactly what was needed to confirm our hypothesis that 1998 SH2 was a comet.”

As an outcome of the investigation, 1998 SH2 will receive an additional comet provisional designation, P/1998 SH2.

Planetary defense implications

The research also sheds light on another, even more unusual, class of objects called dark comets. Like 1998 SH2, dark comets exhibit significant irregularities, or perturbations, in their trajectory but lack other visible evidence of comet activity — there’s no coma, tail, or visible outgassing. These enigmatic objects fall into two distinct populations: larger ones with orbits similar to those of Jupiter-family comets (short period comets with highly elliptical, or eccentric, orbits), and smaller ones that orbit closer to the Sun. Since the 2016 discovery of the first dark comet, about a dozen more have been identified.

The paper’s authors suggest that many of the larger dark comets, which have orbits like 1998 SH2’s, could turn out to be regular comets if astronomers get the right opportunity to observe them with powerful telescopes capable of imaging incredibly faint objects. And by analyzing the motion of all near-Earth objects using precision astrometry data, researchers may reveal more comets that were previously designated as asteroids if they exhibit cometlike nongravitational perturbations. 

“This work shows the importance of continuously tracking near-Earth objects,” said Farnocchia. “Because of outgassing, the motion of comets is more significantly perturbed than that of asteroids. Detecting these perturbations can be an important diagnostic tool for planetary defense that will help understand which objects may be comets rather than asteroids, how their orbits evolve, and how that influences their Earth impact risks.”

Hunting for near-Earth objects

NASA’s upcoming Near-Earth Object (NEO) Surveyor will collect data that can be used to support this effort. The first space survey telescope to be built for planetary defense, this next-generation mission will seek out some of the hardest-to-find near-Earth objects, such as dark asteroids and comets that don’t reflect much visible light.

NASA’s Center for Near Earth Object Studies, the Goldstone Solar System Radar Group, and NEO Surveyor all are managed by JPL and supported by the agency’s Planetary Defense Coordination Office in Washington. Caltech in Pasadena manages JPL for NASA. The DSN receives programmatic oversight from the SCaN (Space Communications and Navigation) program office, also at NASA headquarters.

More information about planetary radar, NASA’s Center for Near Earth Object Studies, and near-Earth objects can be found at:

https://www.jpl.nasa.gov/asteroid-watch

News Media Contacts

Ian J. O’Neill
Jet Propulsion Laboratory, Pasadena, Calif.
818-354-2649
ian.j.oneill@jpl.nasa.gov

Karen Fox / Molly Wasser
NASA Headquarters, Washington
202-358-1600
karen.c.fox@nasa.gov / molly.l.wasser@nasa.gov

2026-046

A meteorite recovered immediately upon its fall to Earth on July 16, 2024, is helping NASA scientists uncover new clues about ancient water, the chemical evolution of primitive asteroids, and the ingredients that may have helped make life possible throughout the early solar system.

This rapid recovery began when an amateur astronomer in New Jersey quickly recognized that a newly fallen meteorite had landed on his property. Recognizing its scientific value and wearing protective gloves, he collected the fragments and stored them in aluminum foil and glass containers, which preserved delicate minerals and organic compounds that are often altered by moisture, weather, and contamination.

As the meteorite fell to Earth, cameras across New Jersey captured its fiery passage through the atmosphere. Scientists used these observations to reconstruct the fireball’s trajectory and, after recovering the meteorite, combined this data with laboratory analyses to determine where in the solar system the rock most likely originated. In a study published Wednesday in the journal Science Advances, researchers found evidence that ancient salty water altered minerals within the meteorite’s parent asteroid, preserving unique minerals and a rich inventory of organic compounds.

“When we have both a documented fireball and a quick recovery of its meteorite, we can learn not only what the rock is made of, but where it came from in the asteroid belt,” said Peter Jenniskens, meteor astronomer at both NASA’s Ames Research Center in California’s Silicon Valley and the SETI Institute, and lead author of the study.

Named for the township where it was recovered, the Hillsborough meteorite belongs to a class of carbon-rich meteorites known as CM carbonaceous chondrites. These primitive rocks preserve some of the oldest materials in the solar system, recording the chemical processes that shaped asteroids more than 4.5 billion years ago.

While examining the unusually pristine meteorite, researchers found a mosaic of tiny broken-up rocks and noticed that some contained unusually high concentrations of sodium — an unexpected finding for this type of meteorite. The surprising signal prompted a closer investigation using powerful electron microscopes that allowed scientists to examine the meteorite from the millimeter scale down to individual atoms. By combining observations across multiple scales, researchers reconstructed the history of the minerals and the fluids that once flowed through them.

These analyses revealed microscopic fractures filled with sodium-rich material left behind by ancient brines. Unlike pure water, brines contain dissolved salts that allow them to transport elements and chemically alter the rocks they move through. In the case of the Hillsborough sample, those ancient fluids altered the asteroid’s minerals and left behind chemical evidence that remained preserved for billions of years.

Scientists were also able to detect fragile sodium-carbonate salts that normally react with moisture in Earth’s atmosphere before they can be studied. Jangmi Han, a paper co-author and mineralogist at NASA’s Johnson Space Center in Houston, identified evidence of ancient brines preserved within microscopic fractures. Similar salts were identified in samples returned from the asteroids Bennu and Ryugu by NASA’s OSIRIS-REx mission and JAXA’s (Japan Aerospace Exploration Agency) Hayabusa2 mission. However,Hillsborough marks the first time the salts have been identified in a CM carbonaceous chondrite meteorite, offering a new glimpse into the surfaces of the primitive asteroids that produced these meteorites.

Together, these findings suggest that ancient, salt-rich brines were more widespread among primitive asteroids than previously recognized, and provide scientists with new opportunities to compare how water altered different asteroid bodies across the early solar system.

“The chips of the most salt-rich bits of this meteorite are quite comparable to the samples returned by the Hayabusa2 and OSIRIS-REx missions,” said Mike Zolensky, a meteorite researcher at NASA Johnson and co-author of the study. “They’re not identical. They’re different in some very interesting ways, but they’ve seen very similar processes.”

Scientists expected Hillsborough to contain a rich suite of organic compounds because it is a CM carbonaceous chondrite. What made the meteorite exceptional was how quickly it was recovered, allowing researchers to study those compounds before prolonged exposure to Earth’s environment could contaminate the sample.

“One of the big surprises for me when we analyzed a small chip of the Hillsborough meteorite was the complexity of amino acids and other organic compounds,” said Danny Glavin, senior scientist in the Astrobiology Analytical Laboratory at NASA’s Goddard Space Flight Center in Greenbelt, Maryland, and co-author of the study.

Its diversity of amino acids and other organic compounds is, comparable to the Murchison meteorite, a nearly 100-kilogram carbonaceous chondrite that fell in Australia in 1969 and became the benchmark for extraterrestrial organic chemistry.

“It’s just more proof that the chemical building blocks of life could have been delivered — and are still being delivered — to Earth today by these carbonaceous asteroid fragments,” said Glavin, who was a co-investigator on OSIRIS-REx, leading an international team that studied the organic composition of the samples delivered to Earth from asteroid Bennu in 2023.

Understanding the Hillsborough meteorite required expertise from multiple scientific disciplines.

Astronomers reconstructed the meteorite’s journey through space, finding evidence that it may have originated from the Erigone asteroid family in the inner asteroid belt, home to the asteroid Donaldjohanson, which was visited in 2025 by NASA’s Lucy spacecraft. Mineralogists identified evidence of ancient brines preserved within microscopic fractures, while organic chemists analyzed the meteorite’s inventory of amino acids and other organic compounds.

“Together, those complementary studies are helping scientists build one of the clearest pictures yet of how primitive asteroids such as the asteroid Erigone evolved chemically over billions of years,” said Jenniskens.

Researchers continue to study the Hillsborough meteorite, revealing new details about how water transformed primitive asteroids and shaped the early solar system.

By tracing the history of water on primitive asteroids, scientists are learning how water and the chemical ingredients for life were distributed throughout the early solar system.

“If you follow the water through the solar system, you’re actually following life,” Zolensky said. “Following the history of water through the solar system is an essential part of understanding the origin of life.”

For more information on NASA’s astromaterials research and exploration, visit:

https://science.nasa.gov/astromaterials

Karen Fox / Molly Wasser
Headquarters, Washington
240-285-5155 / 240-419-1732
karen.c.fox@nasa.gov / molly.l.wasser@nasa.gov

Victoria Segovia
NASA’s Johnson Space Center, Houston 281-483-5111
victoria.segovia@nasa.gov

NASA’s Perseverance Mars rover has uncovered evidence that a 245-foot-thick (75-meter-thick) stack of ancient rock on the rim of Jezero Crater was built by repeated asteroid impacts. Referred to as the “Broom Point member” by the rover’s science team, this sequence of layered bedrock is likely more than 3.9 billion years old, making it among the oldest terrain ever examined by a Mars rover.  

Released Wednesday in the Journal of Geophysical Research: Planets, the findings offer a window into one of the most tumultuous chapters in the history of the solar system.  

“Since leaving Jezero, Perseverance has been exploring a brand-new frontier, both geographically and geologically — a chapter of Martian time that predates the crater itself,” said Ken Farley, Perseverance deputy project scientist at Caltech in Pasadena, California. “On Earth, our earliest geologic history has been fundamentally broken up, deformed, and erased by plate tectonics. Because Mars lacks plate tectonics to recycle its crust, this ancient record remains intact, giving us a rare glimpse into a geological time period that doesn’t exist on our own planet.” 

Reading between layers 

After ascending the western rim of Jezero Crater in late 2024, Perseverance began examining surrounding locations with its science instruments. Their data at Broom Point revealed six distinct rock types, including breccias — rocks composed of angular fragments — alternating with layers of fine-grained, pulverized rock dust. Rock fragments within the breccias are pocked with gas-bubble cavities, indicating they were once molten. 

The presence of tiny, dark, glassy beads within the layers offered an important clue about how these rocks formed. While volcanoes can produce similar glassy droplets, they rarely occur in such high abundance, pointing to asteroid impacts, instead, as the primary architect. In fact, the largest beads rival those flung out by the dinosaur-killing Chicxulub asteroid’s impact on Earth. 

The repetition of these distinct rock types multiple times throughout this thick sequence of rock indicates that high-energy impact events happened again and again across this region of early Mars. 

“The different rock layers are a record of variable-sized impacts occurring at different distances from where this rock sequence was accumulating,” said Alex Jones, a Ph.D. student in planetary geology at Imperial College London and lead author of the paper. “Some large impacts took place very far away, some small impacts nearby. Their debris all ended up landing here, constructing this thick section of rock.”  

How these layers formed may suggest an interaction with water or ice. Several of the layers look like they may have been formed by fast, ground-hugging debris flows. On Earth, these powerful, fluidlike surges can occur when molten rock hits water or ice that instantly flashes into steam.  

Cosmic one-two punch 

Some of Broom Point’s layers tilt at angles exceeding 80 degrees — nearly vertical — which is far too steep to be caused by the impact that created Jezero Crater.  

Instead, scientists suspect a cosmic “one-two punch” shaped this landscape long ago. First, a colossal asteroid impact created the 1,200-mile-wide (1,900-kilometer-wide) Isidis Basin, one of the largest impact basins on Mars, upending and tilting the once-flat rock layers. Later, a second asteroid likely struck, forming Jezero Crater, which measures 28 miles (45 kilometers) across. This second impact fractured and uplifted the already-tilted rocks into the dramatic formations the rover sees today.  

To pin down exactly when these events took place, the Perseverance team collected two core samples, dubbed “Bell Island” and “Main River.” If a future mission were to return them to Earth, laboratory dating could determine when and how often impacts were occurring on early Mars — and, by extension, the infant Earth, whose own early impact record has been erased by billions of years of plate tectonics. 

“During this violent era, it wasn’t rain or snow falling from the sky, but an almost constant barrage of molten rock droplets and pulverized dust kicked up by asteroid impacts,” said Jones. “If we can pin down the ages of these layers, it would be like reading a cosmic weather report from 4 billion years ago.” 

More about Perseverance 

NASA’s Jet Propulsion Laboratory in Southern California, which is managed for the agency by Caltech, built and manages operations of the Perseverance rover on behalf of the agency’s Science Mission Directorate in Washington, as part of NASA’s Mars Exploration Program portfolio. Arizona State University leads the operations of the rover’s Mastcam-Z instrument, working in collaboration with Malin Space Science Systems in San Diego, on the design, fabrication, testing, and operation of the cameras. SuperCam is led by Los Alamos National Laboratory in New Mexico, where the instrument’s Body Unit was developed. The rover’s SHERLOC (Scanning Habitable Environments with Raman and Luminescence for Organics and Chemicals) instrument was built at NASA JPL, and its WATSON (Wide Angle Topographic Sensor for Operations and eNgineering) camera was built at Malin Space Science Systems.

For more information on NASA’s Perseverance, visit:

https://science.nasa.gov/mission/mars-2020-perseverance

News Media Contacts

DC Agle 
Jet Propulsion Laboratory, Pasadena, Calif.
818-393-9011
agle@jpl.nasa.gov  

Karen Fox / Alana Johnson
NASA Headquarters, Washington
240-285-5155 / 202-672-4780
karen.c.fox@nasa.gov / alana.r.johnson@nasa.gov

2026-045