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Month Long Evolution of the D/G Jupiter Impact Sites from Comet P/Shoemaker-Levy 9
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By NASA
Explore This Section Overview Science Science Findings Juno’s Orbits Spacecraft People Stories Multimedia JunoCam Images Jupiter hosts the brightest and most spectacular auroras in the Solar System. Near its poles, these shimmering lights offer a glimpse into how the planet interacts with the solar wind and moons swept by Jupiter’s magnetic field. Unlike Earth’s northern lights, the largest moons of Jupiter create their own auroral signatures in the planet’s atmosphere — a phenomenon that Earth’s Moon does not produce. These moon-induced auroras, known as “satellite footprints,” reveal how each moon interacts with its local space environment.
Juno capturing the marks on Jupiter of all four Galilean moons. The auroras related to each are labeled Io, Eur (for Europa), Gan (for Ganymede), and Cal (for Callisto). NASA/JPL-Caltech/SwRI/UVS team/MSSS/Gill/Jónsson/Perry/Hue/Rabia Before NASA’s Juno mission, three of Jupiter’s four largest moons, known as Galilean moons — Io, Europa, and Ganymede — were shown to produce these distinct auroral signatures. But Callisto, the most distant of the Galilean moons, remained a mystery. Despite multiple attempts using NASA’s Hubble Space Telescope, Callisto’s footprint had proven elusive, both because it is faint and because it most often lies atop the brighter main auroral oval, the region where auroras are displayed.
NASA’s Juno mission, orbiting Jupiter since 2016, offers unprecedented close-up views of these polar light shows. But to image Callisto’s footprint, the main auroral oval needs to move aside while the polar region is being imaged. And to bring to bear Juno’s arsenal of instruments studying fields and particles, the spacecraft’s trajectory must carry it across the magnetic field line linking Callisto and Jupiter.
These two events serendipitously occurred during Juno’s 22nd orbit of the giant planet, in September 2019, revealing Callisto’s auroral footprint and providing a sample of the particle population, electromagnetic waves, and magnetic fields associated with the interaction.
Jupiter’s magnetic field extends far beyond its major moons, carving out a vast region (magnetosphere) enveloped by, and buffeted by, the solar wind streaming from our Sun. Just as solar storms on Earth push the northern lights to more southern latitudes, Jupiter’s auroras are also affected by our Sun’s activity. In September 2019, a massive, high-density solar stream buffeted Jupiter’s magnetosphere, briefly revealing — as the auroral oval moved toward Jupiter’s equator — a faint but distinct signature associated with Callisto. This discovery finally confirms that all four Galilean moons leave their mark on Jupiter’s atmosphere, and that Callisto’s footprints are sustained much like those of its siblings, completing the family portrait of the Galilean moon auroral signatures.
An international team of scientists led by Jonas Rabia of the Institut de Recherche en Astrophysique et Planétologie (IRAP), CNRS, CNES, in Toulouse, France, published their paper on the discovery, “In situ and remote observations of the ultraviolet footprint of the moon Callisto by the Juno spacecraft,” in the journal Nature Communications on Sept. 1, 2025.
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Close-Up Views of NASA’s DART Impact to Inform Planetary Defense
Photos taken by the Italian LICIACube, short for the LICIA Cubesat for Imaging of Asteroids. These offer the closest, most detailed observations of NASA’s DART (Double Asteroid Redirection Test) impact aftermath to date. The photo on the left was taken roughly 2 minutes and 40 seconds after impact, as the satellite flew past the Didymos system. The photo on the right was taken 20 seconds later, as LICIACube was leaving the scene. The larger body, near the top of each image is Didymos. The smaller body in the lower half of each image is Dimorphos, enveloped by the cloud of rocky debris created by DART’s impact. NASA/ASI/University of Maryland On Sept. 11, 2022, engineers at a flight control center in Turin, Italy, sent a radio signal into deep space. Its destination was NASA’s DART (Double Asteroid Redirection Test) spacecraft flying toward an asteroid more than 5 million miles away.
The message prompted the spacecraft to execute a series of pre-programmed commands that caused a small, shoebox-sized satellite contributed by the Italian Space Agency (ASI), called LICIACube, to detach from DART.
Fifteen days later, when DART’s journey ended in an intentional head-on collision with near-Earth asteroid Dimorphos, LICIACube flew past the asteroid to snap a series of photos, providing researchers with the only on-site observations of the world’s first demonstration of an asteroid deflection.
After analyzing LICIACube’s images, NASA and ASI scientists report on Aug. 21 in the Planetary Science Journal that an estimated 35.3 million pounds (16 million kilograms) of dust and rocks spewed from the asteroid as a result of the crash, refining previous estimates that were based on data from ground and space-based observations.
While the debris shed from the asteroid amounted to less than 0.5% of its total mass, it was still 30,000 times greater than the mass of the spacecraft. The impact of the debris on Dimorphos’ trajectory was dramatic: shortly after the collision, the DART team determined that the flying rubble gave Dimorphos a shove several times stronger than the hit from the spacecraft itself.
“The plume of material released from the asteroid was like a short burst from a rocket engine,” said Ramin Lolachi, a research scientist who led the study from NASA’s Goddard Space Flight Center in Greenbelt, Maryland.
The important takeaway from the DART mission is that a small, lightweight spacecraft can dramatically alter the path of an asteroid of similar size and composition to Dimorphos, which is a “rubble-pile” asteroid — or a loose, porous collection of rocky material bound together weakly by gravity.
“We expect that a lot of near-Earth asteroids have a similar structure to Dimorphos,” said Dave Glenar, a planetary scientist at the University of Maryland, Baltimore County, who participated in the study. “So, this extra push from the debris plume is critical to consider when building future spacecraft to deflect asteroids from Earth.”
The tail of material that formed behind Dimorphos was prominent almost 12 days after the DART impact, giving the asteroid a comet-like appearance, as seen in this image captured by NASA’s Hubble Space Telescope in October 2022. Hubble’s observations were made from roughly 6.8 million miles away. NASA, ESA, STScI, Jian-Yang Li (PSI); Image Processing: Joseph DePasquale DART’s Star Witness
NASA chose Dimorphos, which poses no threat to Earth, as the mission target due to its relationship with another, larger asteroid named Didymos. Dimorphos orbits Didymos in a binary asteroid system, much like the Moon orbits Earth. Critically, the pair’s position relative to Earth allowed astronomers to measure the duration of the moonlet’s orbit before and after the collision.
Ground and space-based observations revealed that DART shortened Dimorphos’ orbit by 33 minutes. But these long-range observations, made from 6.8 million miles (10.9 million kilometers) away, were too distant to support a detailed study of the impact debris. That was LICIACube’s job.
After DART’s impact, LICIACube had just 60 seconds to make its most critical observations. Barreling past the asteroid at 15,000 miles (21,140 kilometers) per hour, the spacecraft took a snapshot of the debris roughly once every three seconds. Its closest image was taken just 53 miles (85.3 km) from Dimorphos’ surface.
The short distance between LICIACube and Dimorphos provided a unique advantage, allowing the cubesat to capture detailed images of the dusty debris from multiple angles.
The research team studied a series of 18 LICIAcube images. The first images in the sequence showed LICIACube’s head-on approach. From this angle, the plume was brightly illuminated by direct sunlight. As the spacecraft glided past the asteroid, its camera pivoted to keep the plume in view.
This animated series of images was taken by a camera aboard LICIACube 2 to 3 minutes after DART crashed into Dimorphos. As LICIACube made its way past the binary pair of asteroids Didymos, the larger one on top, and Dimorphos, the object at the bottom. The satellite’s viewing angle changed rapidly during its flyby of Dimorphos, allowing scientists o get a comprehensive view of the impact plume from a series of angles. ASI/University of Maryland/Tony Farnham/Nathan Marder As LICIACube looked back at the asteroid, sunlight filtered through the dense cloud of debris, and the plume’s brightness faded. This suggested the plume was made of mostly large particles — about a millimeter or more across — which reflect less light than tiny dust grains.
Since the innermost parts of the plume were so thick with debris that they were completely opaque, the scientists used models to estimate the number of particles that were hidden from view. Data from other rubble-pile asteroids, including pieces of Bennu delivered to Earth in 2023 by NASA’s OSIRIS-REx spacecraft, and laboratory experiments helped refine the estimate.
“We estimated that this hidden material accounted for almost 45% of the plume’s total mass,” said Timothy Stubbs, a planetary scientist at NASA Goddard who was involved with the study.
While DART showed that a high-speed collision with a spacecraft can change an asteroid’s trajectory, Stubbs and his colleagues note that different asteroid types, such as those made of stronger, more tightly packed material, might respond differently to a DART-like impact. “Every time we interact with an asteroid, we find something that surprises us, so there’s a lot more work to do,” said Stubbs. “But DART is a big step forward for planetary defense.”
The Johns Hopkins Applied Physics Laboratory in Laurel, Maryland, managed the DART mission and operated the spacecraft for NASA’s Planetary Defense Coordination Office as a project of the agency’s Planetary Missions Program Office.
By Nathan Marder, nathan.marder@nasa.gov
NASA’s Goddard Space Flight Center, Greenbelt, Md.
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Preparations for Next Moonwalk Simulations Underway (and Underwater)
Dwarf planet Ceres is shown in these enhanced-color renderings that use images from NASA’s Dawn mission. New thermal and chemicals models that rely on the mission’s data indicate Ceres may have long ago had conditions suitable for life.NASA/JPL-Caltech/UCLA/MPS/DLR/IDA The dwarf planet is cold now, but new research paints a picture of Ceres hosting a deep, long-lived energy source that may have maintained habitable conditions in the past.
New NASA research has found that Ceres may have had a lasting source of chemical energy: the right types of molecules needed to fuel some microbial metabolisms. Although there is no evidence that microorganisms ever existed on Ceres, the finding supports theories that this intriguing dwarf planet, which is the largest body in the main asteroid belt between Mars and Jupiter, may have once had conditions suitable to support single-celled lifeforms.
Science data from NASA’s Dawn mission, which ended in 2018, previously showed that the bright, reflective regions on Ceres’ surface are mostly made of salts left over from liquid that percolated up from underground. Later analysis in 2020 found that the source of this liquid was an enormous reservoir of brine, or salty water, below the surface. In other research, the Dawn mission also revealed evidence that Ceres has organic material in the form of carbon molecules — essential, though not sufficient on its own, to support microbial cells.
The presence of water and carbon molecules are two critical pieces of the habitability puzzle on Ceres. The new findings offer the third: a long-lasting source of chemical energy in Ceres’ ancient past that could have made it possible for microorganisms to survive. This result does not mean that Ceres had life, but rather, that there likely was “food” available should life have ever arisen on Ceres.
This illustration depicts the interior of dwarf planet Ceres, including the transfer of water and gases from the rocky core to a reservoir of salty water. Carbon dioxide and methane are among the molecules carrying chemical energy beneath Ceres’ surface.NASA/JPL-Caltech In the study, published in Science Advances on Aug. 20, the authors built thermal and chemical models mimicking the temperature and composition of Ceres’ interior over time. They found that 2.5 billion years or so ago, Ceres’ subsurface ocean may have had a steady supply of hot water containing dissolved gases traveling up from metamorphosed rocks in the rocky core. The heat came from the decay of radioactive elements within the dwarf planet’s rocky interior that occurred when Ceres was young — an internal process thought to be common in our solar system.
“On Earth, when hot water from deep underground mixes with the ocean, the result is often a buffet for microbes — a feast of chemical energy. So it could have big implications if we could determine whether Ceres’ ocean had an influx of hydrothermal fluid in the past,” said Sam Courville, lead author of the study. Now based at Arizona State University in Tempe, he led the research while working as an intern at NASA’s Jet Propulsion Laboratory in Southern California, which also managed the Dawn mission.
Catching Chill
The Ceres we know today is unlikely to be habitable. It is cooler, with more ice and less water than in the past. There is currently insufficient heat from radioactive decay within Ceres to keep the water from freezing, and what liquid remains has become a concentrated brine.
The period when Ceres would most likely have been habitable was between a half-billion and 2 billion years after it formed (or about 2.5 billion to 4 billion years ago), when its rocky core reached its peak temperature. That’s when warm fluids would have been introduced into Ceres’ underground water.
The dwarf planet also doesn’t have the benefit of present-day internal heating generated by the push and pull of orbiting a large planet, like Saturn’s moon Enceladus and Jupiter’s moon Europa do. So Ceres’ greatest potential for habitability-fueling energy was in the past.
This result has implications for water-rich objects throughout the outer solar system, too. Many of the other icy moons and dwarf planets that are of similar size to Ceres (about 585 miles, or 940 kilometers, in diameter) and don’t have significant internal heating from the gravitational pull of planets could have also had a period of habitability in their past.
More About Dawn
A division of Caltech in Pasadena, JPL managed Dawn’s mission for NASA’s Science Mission Directorate in Washington. Dawn was a project of the directorate’s Discovery Program, managed by NASA’s Marshall Space Flight Center in Huntsville, Alabama. JPL was responsible for overall Dawn mission science. Northrop Grumman in Dulles, Virginia, designed and built the spacecraft. The German Aerospace Center, Max Planck Institute for Solar System Research, Italian Space Agency and Italian National Astrophysical Institute were international partners on the mission team.
For a complete list of mission participants, visit:
https://solarsystem.nasa.gov/missions/dawn/overview/
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Explore Hubble Science Hubble Space Telescope As NASA Missions Study… Hubble Home Overview About Hubble The History of Hubble Hubble Timeline Why Have a Telescope in Space? Hubble by the Numbers At the Museum FAQs Impact & Benefits Hubble’s Impact & Benefits Science Impacts Cultural Impact Technology Benefits Impact on Human Spaceflight Astro Community Impacts Science Hubble Science Science Themes Science Highlights Science Behind Discoveries Hubble’s Partners in Science Universe Uncovered AI and Hubble Science Explore the Night Sky Observatory Hubble Observatory Hubble Design Mission Operations Missions to Hubble Hubble vs Webb Team Hubble Team Career Aspirations Hubble Astronauts Multimedia Images Videos Sonifications Podcasts e-Books Online Activities 3D Hubble Models Lithographs Fact Sheets Posters Hubble on the NASA App Glossary News Hubble News Social Media Media Resources More 35th Anniversary Online Activities 4 min read
As NASA Missions Study Interstellar Comet, Hubble Makes Size Estimate
Hubble captured this image of the interstellar comet 3I/ATLAS on July 21, 2025, when the comet was 277 million miles from Earth. Hubble shows that the comet has a teardrop-shaped cocoon of dust coming off its solid, icy nucleus. Image: NASA, ESA, David Jewitt (UCLA); Image Processing: Joseph DePasquale (STScI) A team of astronomers has taken the sharpest-ever picture of the unexpected interstellar comet 3I/ATLAS using the crisp vision of NASA’s Hubble Space Telescope. Hubble is one of many missions across NASA’s fleet of space telescopes slated to observe this comet, together providing more information about its size and physical properties. While the comet poses no threat to Earth, NASA’s space telescopes help support the agency’s ongoing mission to find, track, and better understand near-Earth objects.
Hubble’s observations allow astronomers to more accurately estimate the size of the comet’s solid, icy nucleus. The upper limit on the diameter of the nucleus is 3.5 miles (5.6 kilometers), though it could be as small as 1,000 feet (320 meters) across, researchers report. Though the Hubble images put tighter constraints on the size of the nucleus compared to previous ground-based estimates, the solid heart of the comet presently cannot be directly seen, even by Hubble. Observations from other NASA missions including the James Webb Space Telescope, TESS (Transiting Exoplanet Survey Satellite), and the Neil Gehrels Swift Observatory, as well as NASA’s partnership with the W.M. Keck Observatory, will help further refine our knowledge about the comet, including its chemical makeup.
Hubble also captured a dust plume ejected from the Sun-warmed side of the comet, and the hint of a dust tail streaming away from the nucleus. Hubble’s data yields a dust-loss rate consistent with comets that are first detected around 300 million miles from the Sun. This behavior is much like the signature of previously seen Sun-bound comets originating within our solar system.
The big difference is that this interstellar visitor originated in some other solar system elsewhere in our Milky Way galaxy.
3I/ATLAS is traveling through our solar system at a staggering 130,000 miles (209,000 kilometers) per hour, the highest velocity ever recorded for a solar system visitor. This breathtaking sprint is evidence that the comet has been drifting through interstellar space for many billions of years. The gravitational slingshot effect from innumerable stars and nebulae the comet passed added momentum, ratcheting up its speed. The longer 3I/ATLAS was out in space, the higher its speed grew.
“No one knows where the comet came from. It’s like glimpsing a rifle bullet for a thousandth of a second. You can’t project that back with any accuracy to figure out where it started on its path,” said David Jewitt of the University of California, Los Angeles, science team leader for the Hubble observations.
The paper will be published in The Astrophysical Journal Letters. It is already available on Astro-ph.
New Evidence for Population of Wandering Space Relics
“This latest interstellar tourist is one of a previously undetected population of objects bursting onto the scene that will gradually emerge,” said Jewitt. “This is now possible because we have powerful sky survey capabilities that we didn’t have before. We’ve crossed a threshold.”
This comet was discovered by the NASA-funded Asteroid Terrestrial-impact Last Alert System (ATLAS) on July 1, 2025, at a distance of 420 million miles from the Sun. ATLAS is an asteroid impact early warning system developed by the University of Hawai’i.
In the meantime, other NASA missions will provide new insight into this third interstellar interloper, helping refine our understanding of these objects for the benefit of all. 3I/ATLAS should remain visible to ground-based telescopes through September, after which it will pass too close to the Sun to observe, and is expected to reappear on the other side of the Sun by early December.
The Hubble Space Telescope has been operating for more than three decades and continues to make ground-breaking discoveries that shape our fundamental understanding of the universe. Hubble is a project of international cooperation between NASA and ESA (European Space Agency). NASA’s Goddard Space Flight Center in Greenbelt, Maryland, manages the telescope and mission operations. Lockheed Martin Space, based in Denver, also supports mission operations at Goddard. The Space Telescope Science Institute in Baltimore, which is operated by the Association of Universities for Research in Astronomy, conducts Hubble science operations for NASA.
To learn more about Hubble, visit: https://science.nasa.gov/hubble
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Comet 3I/ATLAS
Hubble captured this image of the interstellar comet 3I/ATLAS on July 21, 2025, when the comet was 277 million miles from Earth. Hubble shows that the comet has a teardrop-shaped cocoon of dust coming off its solid, icy nucleus.
Comet 3I/ATLAS Compass Image
This image of interstellar comet 3I/ATLAS was captured by the Hubble Space Telescope’s Wide Field Camera on July 21, 2025. The scale bar is labeled in arcseconds, which is a measure of angular distance on the sky. One arcsecond is equal an angular measurement of 1/3600 of o…
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Last Updated Aug 07, 2025 Editor Andrea Gianopoulos Location NASA Goddard Space Flight Center Contact Media Claire Andreoli
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Image: A team of astronomers has taken the sharpest-ever picture of the unexpected interstellar comet 3I/ATLAS, using the crisp vision of the NASA/ESA Hubble Space Telescope.
ESA's Planetary Defence Office responded promptly to the discovery of the comet, and has been tracking it since the beginning of July.
Now, Hubble's observations from space are allowing astronomers to more accurately estimate the size of the comet’s solid icy nucleus. The upper limit on the diameter of the nucleus is 5.6 km, but it could be as small as 320 m across, researchers report.
Though the Hubble images put tighter constraints on the nucleus size compared to previous ground-based estimates, the solid heart of the comet presently cannot be directly seen, even by Hubble. Further observations, including by the NASA/ESA/CSA James Webb Space Telescope, will help refine our knowledge about the comet, including its chemical makeup.
Hubble also captured a dust plume ejected from the Sun-warmed side of the comet, and the hint of a dust tail streaming away from the nucleus. Hubble’s data show that the comet is losing dust in a similar manner to that from previously seen Sun-bound comets originating within our Solar System.
The big difference is that this interstellar visitor originated in some other stellar systems, elsewhere in our Milky Way galaxy.
3I/ATLAS is traveling through our Solar System at roughly 210 000 km per hour, the highest speed ever recorded for a Solar System visitor. This breathtaking sprint is evidence that the comet has been drifting through interstellar space for many billions of years. The gravitational slingshot effect from innumerable stars and nebulae the comet passed added momentum, ratcheting up its speed. The longer 3I/ATLAS was out in space, the higher its speed grew.
This comet was discovered by the Asteroid Terrestrial-impact Last Alert System (ATLAS) on 1 July 2025 at a distance of 675 million km from the Sun. 3I/ATLAS should remain visible to ground-based telescopes until September, after which it will pass too close to the Sun to observe. It is expected to reappear on the other side of the Sun by early December.
Icy wanderers such as 3I/ATLAS offer a rare, tangible connection to the broader galaxy. To actually visit one would connect humankind with the Universe on a far greater scale. To this end, ESA is preparing the Comet Interceptor mission. The spacecraft will be launched in 2029 into a parking orbit, lying in wait for a suitable target – a pristine comet from the distant Oort Cloud that surrounds our Solar System, or, unlikely but highly appealing, an interstellar object.
While it is improbable that we will discover an interstellar object that is reachable for Comet Interceptor, as a first demonstration of a rapid response mission that waits in space for its target, it will be a pathfinder for possible future missions to intercept these mysterious visitors.
The research paper based on Hubble observations will be published in The Astrophysical Journal Letters.
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