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 NASA’s Juno mission has provided the first measurements of the temperature below the surface of Jupiter’s moon Io, revealing significant heating within the shallow subsurface of the most volcanically active world in the solar system. Collected during two close flybys, the data also shows that most of Io’s surface is remarkably smooth and composed of material of very low density.

Published Wednesday in the Journal of Geophysical Research: Planets, these findings break new observational ground for both fiery and icy worlds beyond our planet.

Io’s extreme volcanism is powered by tidal heating. The moon is constantly stretched and squeezed by Jupiter’s immense gravity as it travels its slightly elliptical orbit, generating internal heat output many times greater than Earth’s. Until now, virtually everything known about that heat came from infrared observations, which sense only the temperature of the top surface. The latest findings are derived from data collected by the spacecraft’s Microwave Radiometer (MWR) instrument.

“The Juno Microwave Radiometer directly observed Io’s heat output by looking below the surface,” said Scott Bolton, study coauthor and Juno’s principal investigator at Southwest Research Institute in San Antonio. “The surprising discovery that we could see below a rocky moon’s surface has important implications for studying Earth’s volcanoes. Juno has taught us that if we look with an MWR-type instrument near a volcano on Earth, we might see a similar signature in the subsurface temperature gradient, providing new information on how terrestrial volcanoes work.”

Fire, ice

Juno’s Microwave Radiometer was designed by Bolton to peer beneath Jupiter’s cloud tops to investigate the dynamics and composition of the gas giant’s deep atmosphere. The MWR’s six microwave antennas serve as a single instrument, simultaneously detecting microwaves at a wide range of wavelengths, from about half an inch to 20 inches (1.3 to 51 centimeters). During the mission’s extended phase, the MWR instrument has provided the opportunity to observe three of the planet’s Galilean moons: Ganymede, Europa, and Io.

“The technique is novel in that each wavelength explores different depths, providing a new way to characterize the deep atmosphere of giant planets and the subsurface crusts of icy and rocky moons,” said Bolton. “At Ganymede and Europa, we explored tens of miles below the surface, assuming their ice shells were mostly pure water, but the ability to probe into the volcanic rock at Io was an unexpected discovery.”

During flybys on Dec. 30, 2023, and Feb. 3, 2024, the solar-powered Juno spacecraft came within about 930 miles (1,500 kilometers) of the moon’s surface.

“The instrument measured Io’s thermal emission at depths ranging from a few inches down to tens of feet. Everywhere we looked, we found the temperature rising by more than 40 degrees Fahrenheit just several feet into the surface — a gradient far steeper than solar heating alone can explain,” said Shannon Brown, the paper’s lead author at NASA’s Jet Propulsion Laboratory in Southern California.

The data suggests two possible explanations. First, heat could be rising steadily through a conductive crust. While this background heat flow — measured at 1 to 3 watts per square meter — is relatively gentle on a local scale (roughly equivalent to a small nightlight glowing under every square yard), across the entire moon it represents a release of energy up to 30 times Earth’s average. Alternatively, the signal could be coming from cooling lava flows, capped by roughly 30 to 35 feet (9 to 11 meters) of solidified crust, that cover about 10% of the moon’s surface at any given time.

“Io provides a unique window into learning how tidal heating works throughout the cosmos, a fundamental process that provides energy and heat to worlds that are far from their parent star,” said Bolton. “This process can not only create the most volcanic body in the solar system, in the case of Io, but also fuels the subsurface oceans on the moons of giant planets, such as Europa and Ganymede. Up until this point we could only observe the heat escaping at the surface or through eruptions. Now we can characterize how the heat is moving from the interior toward the surface.”

Great plains of Io

Another big insight gained from the two flybys is just how smooth Io is. Prior to the recent findings, the moon was known for its tall mountains, but the MWR indicates that apart from this visible topography, the surface features expansive smooth patches that stretch for 60 miles (100 kilometers) or more. Because Juno flew by overlapping regions of Io at different angles, the team was able to map how the surface reflects microwaves, much like an airline passenger might see the ocean flash with sunlight only at specific angles.

“Away from its mountains, the surface is more like the Great Plains of North America, and even though Io is a rocky body, the surface material has a very low density — more like pumice or a fluffy volcanic ash than solid rock,” said Brown.

More about Juno

A division of Caltech in Pasadena, California, JPL manages the Juno mission for the principal investigator, Scott Bolton, of the Southwest Research Institute. Juno is part of NASA’s New Frontiers Program, which is managed at the agency’s Marshall Space Flight Center in Huntsville, Alabama, for the NASA’s Science Mission Directorate in Washington. Lockheed Martin Space in Denver built and operates the spacecraft. More information about Juno is at:

https://science.nasa.gov/mission/juno

News Media Contacts

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

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

Deb Schmid 
Southwest Research Institute, San Antonio 
210-522-2254 
dschmid@swri.org 

2026-050

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

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

July 8, 2026

C.13

NASA Awards Contracts for Mars Advanced Surface Mobility Technology

NASA has selected seven companies for contract awards under the Mars Exploration Program’s Science Transport and Robotic Innovation for Deployment and Exploration, or STRIDE, initiative to advance next-generation commercial robotic surface mobility for future Mars exploration.

The STRIDE awards will support the development of innovative robotic mobility systems that may enable future Mars missions to access more challenging terrain, travel greater distances, and investigate scientifically valuable regions that are difficult to reach with current mobility systems.

The STRIDE awards have a total potential value of approximately $17 million with a period of work targeted to begin in Fall of 2026.

Contract awardees are:

• AeroVironment, Arlington, Virginia
• Astrobotic, Pittsburgh, Pennsylvania
• Venturi Astrolab (Astrolab), Hawthorne, California
• Ground Control Robotics, Atlanta, Georgia
• Honeybee Robotics, Longmont, Colorado
• Intuitive Machines, Houston, Texas
• MEI Technologies, Webster, Texas

STRIDE demonstrates NASA’s commitment to strong public-private partnerships, allowing the agency to explore new approaches for Mars surface exploration while identifying key capability gaps and development needs for commercial systems that could operate and traverse realistic Martian environments.

For more information about NASA’s Mars Exploration, visit:

https://science.nasa.gov/planetary-science/programs/mars-exploration

Following its longest hibernation period ever of nearly a year, NASA’s New Horizons spacecraft has emerged in good health and is ready to begin transmitting science data gathered in the distant Kuiper Belt far beyond Pluto.

On June 23, flight controllers at the Johns Hopkins Applied Physics Laboratory (APL) in Laurel, Maryland, confirmed New Horizons, acting on stored commands uplinked to its main computer last July, had safely awakened from a 321‑day hibernation period that began Aug. 7. With the spacecraft now approximately 5.9 billion miles (9.5 billion kilometers) from Earth, the radio signals carrying that confirmation took about 8 hours and 52 minutes to reach the APL Mission Operations Center via NASA’s Deep Space Network station near Madrid, Spain.

The mission team typically places New Horizons in resource‑saving hibernation mode during long cruise periods. While the spacecraft is hibernating, operators do not send commands or retrieve data, but the spacecraft continues gathering and storing data around the clock from its heliospheric plasma sensors, Solar Wind at Pluto and the Pluto Energetic Particle Spectrometer Science Investigation, as well as its space dust detector, the Venetia Burney Student Dust Counter.

Alice Bowman, the New Horizons mission operations manager at APL, said the spacecraft reported back to Earth, via the Deep Space Network, with a weekly status beacon. “Every status report through this hibernation period was ‘green,’ meaning all was well aboard New Horizons each and every week,” she said.

As New Horizons resumes active operations, Bowman noted, the team will begin downlinking spacecraft health and safety data, followed by data from the three scientific instruments. In about three weeks, the spacecraft’s onboard Alice ultraviolet spectrograph will look at the hydrogen gas distribution in the outer heliosphere, while the Solar Wind at Pluto, the Pluto Energetic Particle Spectrometer Science Investigation, and the Venetia Burney Student Dust Counter instruments continue their measurements, and the ground team conducts a series of spacecraft and instrument checkouts.

The team also is completing upgrades to the ground‑system software that will make it easier to maintain operations of the spacecraft. Tests are already underway and are expected to continue through the year.

New Horizons is operating on updated autonomy logic designed for operations farther from the Sun and to accommodate the expected reduction in power and the naturally occurring increase in radio‑signal travel time.

The NASA spacecraft’s exploration of this distant region of the solar system marks the latest step in a journey that began in January 2006 with the fastest launch on record; a flyby of Jupiter in February 2007 that included stunning views of the gas giant and its moons; the first exploration through the Pluto system in July 2015; the first exploration of a Kuiper Belt object, Arrokoth, in January 2019, and unique studies of the Sun’s outer heliosphere and dozens of additional Kuiper Belt objects since then.

For more information on NASA’s New Horizons mission, visit:

https://science.nasa.gov/mission/new-horizons/

NASA’s Perseverance rover has spent five years traversing Jezero Crater looking for the chemical leftovers of whatever processes were at work on Mars billions of years ago. The rover has found organic carbon, but it has mostly been inside rocks that had to be drilled or abraded to expose it. But now, at an outcrop on the edge of an ancient river channel named Neretva Vallis, Perseverance detected complex macromolecular carbon sitting right on the rock’s surface.

“To our knowledge, that’s the shallowest detection of organic matter on Martian surface to date,” said Ashley E. Murphy, a researcher at the Planetary Institute in Tucson, Arizona, and lead author of the study of the rock, which was found at a site called Bright Angel. On Earth, this much macromolecular carbon usually suggests a biological origin. But to learn what this Bright Angel carbon is and where it came from, we might need to bring samples back to Earth.

Carbon on the rocks

The detection of Bright Angel carbon came from SHERLOC (Scanning Habitable Environments with Raman and Luminescence for Organics and Chemicals), a UV Raman spectrometer fitted on Perseverance’s robotic arm. SHERLOC fires a deep-ultraviolet laser at a target and reads the light that bounces back at shifted energies, a signal that enables scientists to identify specific molecular bonds.

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