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Title: Dynamics of Planetary Rings Under Thermal Forces
Authors: Wen-Han Zhou et al.
First Author’s Institution: The University of Tokyo
Status: Published in ApJL

If you ask anyone what their favourite planet is, the answer you’ll most likely hear is Saturn. Why? Why else than the beautiful and intricate ring system surrounding the gas giant. The other gas and ice giants in our solar system — Jupiter, Uranus, and Neptune — have ring systems themselves but none quite as striking as Saturn’s. Would it surprise you to learn that astronomers’ best models have not yet totally explained why Saturn’s rings look the way they do?

In contrast, it may not surprise you to hear that people have been trying to explain the rings for as long as we have seen them with telescopes. We now know that planetary rings are collections of relatively small particles (think micrometre up to metre sized), most likely having once been the material of a larger body that was disrupted either by collisions or tidal forces. This material, due to the gravity of its local planet, is sculpted into a flat disc where more subtle interactions then lead to substructure forming within the disc such as gaps and ringlets. Many of these substructures are explained by well-understood physics — for example gaps being carved by embedded moonlets or resonances sculpting ring edges — though there remain some outstanding problems in our understanding.

The authors of today’s article set their sights on the problematic inner edge of Saturn’s A ring (Figure 1). They describe some mechanisms — namely the collisions of micrometeoroids within the rings — by which a sharp ring edge can be maintained, but there exists a gap in the understanding of how such an edge can form in the first place. All hope is not lost, though, as today’s authors reintroduce a physical process they call the “eclipse–Yarkovsky” effect, which seems to explain these phenomena.

Billions of Rocket-Powered Bumper Cars

The idea behind this process revolves entirely around light. When sunlight hits a particle within a planetary ring, non-absorbed sunlight imparts a little “bump” onto a particle, ever so slightly altering its trajectory. At the same time, some of the sunlight is absorbed into the particle, which heats it up; light is soon re-emitted via thermal radiation, which, again, can slightly change the trajectory of these tiny particles. From a point on the surface of each ring particle (see rightmost side of Figure 2), the photons from this thermal radiation are all emitted in random directions; however, across the whole surface of the particle there is a net force! These tiny particles are spinning, and so the side just near “sunset” is hottest and emitting the most thermal photons. In this way, the pressure from the sunlight plus the thermal radiation of each particle imparts a net torque on the ring itself which changes the angular momentum of the ring.

What we described just then is essentially solar radiation pressure plus the Yarkovsky effect. It turns out that the net force from this process typically averages out to zero as the ring particles orbit around the planet. This assumes, though, that the sunlight is constantly shining on the ring. Stunning imagery of Saturn tells us that this isn’t the case, so what happens when we take into account the shadow cast on the ring from the planet? Today’s authors find that the net effect induces a positive change in angular momentum of the ring particles, which they call the eclipse–Yarkovsky effect.

After today’s authors detailed all of the math involved in this process (and there is a lot), they put it into practice to try to help explain Saturn’s curious rings. Including the eclipse–Yarkovsky effect together with other known effects that drive ring evolution allowed them to reproduce the optical depth profile (how thick the ring looks) of Saturn’s A ring better than ever before (notably the sharp inner edge in Figure 3). On top of this, the effect provides another avenue for moonlet formation in the outer edges of ring systems as the positive torque from the effect drives material out toward and away from the Roche limit.

Undeniably useful for Saturn, the eclipse–Yarkovsky effect may also explain some other conundra in the solar system. Mars may have once had rings, which are thought to have eventually clumped together to form the inner moon Phobos. This idea is problematic, though, in that current models suggest there should still be some residual ring system around Mars even after Phobos formed. Enter the eclipse–Yarkovsky effect: being 100 times stronger for Mars than Saturn (due to its more intense incident sunlight), the effect may have driven out and dispersed that residual ring altogether. While the authors are currently looking into this possibility, the reintroduction of the eclipse–Yarkovsky effect has already shown great promise for our most beautiful ringed planetary neighbour.

Original astrobite edited by Wasi Naqvi.

About the author, Ryan White:

I am a first-year PhD student at Macquarie University in Australia, working mainly on binary/multiple systems with massive stars (Wolf–Rayets in particular!). Outside of study, I’m probably drinking coffee, baking, reading, or going for a run. You can also find me procrastinating on Bluesky @astroryan.bsky.social.

The post Shining a Light on the Shadowy Movements in Saturn’s Rings appeared first on AAS Nova.

"From orbit, volcanoes are some of the most beautiful natural sights."

Why does one side of the Moon have a lot of craters, while the other side does not? Stephen LogesBrooksville, Florida When the first photos of the Moon’s farside were obtained, people usually expressed the difference between the back and the front in terms of “more craters on the back.” It might be better toContinue reading "Why does one side of the Moon have a lot of craters, while the other does not?"

The post Why does one side of the Moon have a lot of craters, while the other does not? appeared first on Astronomy Magazine.

A meteorite discovered in Africa could be evidence of a lost protoplanet that once orbited our Sun, according to researchers at the University of Colorado at Boulder.

In a recent paper published in Earth and Planetary Science Letters, the team revealed evidence of an ancient protoplanet that may have been as large as Mars based on simulations of how the meteorite sample may have formed.

The four-and-a-half-billion-year-old world carried an unexpected geological makeup, which the researchers say casts doubt on common assumptions regarding planetary evolution.

Protoplanetary Demise

According to the UC Boulder team, the massive protoplanetary body collided with another object four and a half billion years ago, shattering it completely. This is the first definitive evidence of a lost protoplanet in our solar system, based on analysis of the angrite meteorite NWA 12774, a shard of that planetary embryo recovered from the Sahara Desert.

“It’s incredible to think there was once a world this large,” said lead author Aaron Bell, an assistant research professor in the Department of Earth Science at CU Boulder. “We only know it existed because a few fragments of it happened to land on Earth. These meteorites preserved evidence of a completely different pathway through which early planets developed.”

A Rare Meteorite Sample

Angrites, a rare type of volcanic rock, serve as a record of our solar system’s distant past. These rocks began forming only a few million years after the solar system’s birth, making them valuable evidence of this early era. However, they are extremely rare and difficult to find.

NWA 12774 is one of only 68 angrite samples identified among more than 80,000 meteorites cataloged by scientists. Given its rarity, the discovery could potentially reshape how researchers understand these ancient rocks.

Until now, scientists had assumed that angrites originated from relatively small asteroids less than 124 miles (200 kilometers) wide, based largely on their chemical composition. Large rocky planets such as Earth and Mars contain significant amounts of silicon dioxide, while angrites contain very little of the compound.

Unexpected Meteorite Discovery

Researchers began to reconsider those assumptions when they identified clinopyroxene in the meteorite sample. This mineral, commonly found in Earth’s crust and mantle, appeared unusually rich in aluminum, suggesting that it formed under significant pressure deep within a planetary body.

To investigate this unusual characteristic of NWA 12774, the University of Colorado Boulder team recreated the conditions under which the sample could have formed. Their analysis revealed that pressures of at least 17.5 kilobars were required to produce the aluminum-rich clinopyroxene found in the meteorite. For comparison, one kilobar is roughly equivalent to the pressure at the deepest part of Earth’s oceans, near the bottom of the Mariana Trench.

Rethinking Meteorite Origins

The researchers’ discovery proved that at least this particular angrite sample could not have formed inside a small meteorite, as a body with a radius of at least 621 miles would be required to generate the pressure needed to produce the crystals. 

Additional evidence suggested the parent body may have been even larger. The crystals’ sharp edges and delicate internal structures indicate they likely formed at relatively shallow depths beneath the surface. Reconciling both the high-pressure conditions and the shallow formation depth suggests that the parent body may have ranged in size from the Moon to Mars.

“There are many meteorites sitting in drawers that haven’t been thoroughly studied, so there were likely more of these protoplanets we don’t know about,” Bell said.

Exactly what happened to this ancient world remains uncertain, but researchers believe it was likely destroyed in a massive collision early in the solar system’s history. Fragments of that lost protoplanet may have later contributed material to other bodies, potentially including Earth itself.

“The materials that formed the angrite parent body are fundamentally different from the ingredients of Earth and Mars,” Bell concluded. “It points to a distinct and separate evolutionary path in planetary formation in the early history of our solar system.”

The paper, “High-Pressure Clinopyroxene in Northwest Africa 12774 and New Geobarometric Evidence for a Planetary Embryo-Sized Angrite Parent Body,” appeared in Earth and Planetary Science Letters on July 1, 2026.

Ryan Whalen covers science and technology for The Debrief. He holds an MA in History and a Master of Library and Information Science with a certificate in Data Science. He can be contacted at ryan@thedebrief.org, and follow him on Twitter @mdntwvlf.

When the third known object from the galactic space beyond our Sun barreled through the solar system last year, Earth was in a terrible spot to view its flyby. Thankfully, however, a spacecraft that was previously busy mapping Mars took advantage of much better positioning for a closer look.

Cheap Seats

Astronomers have now observed three interstellar objects as they’ve flown through the solar system: 1I/ʻOumuamua, which shocked astronomers in 2017; 2I/Borisov, which followed in 2019 and behaved almost identically to a solar system comet; and now 3I/ATLAS, which was found buzzing toward the Sun in July 2025. As soon as 3I/ATLAS was spotted, pretty much every telescope on the planet took a look. The data swiftly revealed much that intrigued astronomers: while 3I/ATLAS was behaving essentially like a standard comet, its chemistry was nothing like its solar system counterparts, and its coma and dust outflow were strangely shaped. Among other oddities, it seemed to counterintuitively have a dust tail that pointed toward the Sun.

Unfortunately for astronomers, 3I/ATLAS didn’t make it easy for them to study the shape of its coma. Thanks to a cosmic coincidence, the interstellar visitor was traveling almost perfectly within the plane of our solar system, and Earthbound observers were often limited to an edge-on view of its tail. Even worse, 3I/ATLAS looped around the back of the Sun from our perspective, meaning no one on the planet could observe the comet for a few weeks in the fall. This led a group of astronomers to consider their assets that are farther from home.

Better View from Mars

The Tianwen-1 spacecraft, which entered Martian orbit in early 2021 and has been diligently mapping the Red Planet ever since, has a high-resolution camera that’s normally pointed at the planet’s surface. By spinning the spacecraft around, a team of researchers led by Xin Ren (National Astronomical Observatories, Chinese Academy of Sciences) repurposed the camera to act as a small telescope when 3I/ATLAS flew by. In another cosmic coincidence, 3I/ATLAS happened to pass very near Mars last fall, and this close approach gave Tianwen-1 a great out-of-plane view of the coma. The orbiter managed to capture 57 images of 3I/ATLAS over three days last fall, representing China’s first-ever observations of an object from an asset in deep space.

The team took full advantage of the great view and leveraged the spacecraft’s unique perspective to extract some intriguing results. By tracking how the gentle pressure of sunlight nudged the escaping grains, the researchers found that the coma is dominated by surprisingly large dust. With an average size of hundreds of microns across, the dust is more like coarse sand than smoke, and they found that it ambles away from the comet at just 3–10 meters per second. All told, 3I/ATLAS was shedding dust at roughly 1,000 kilograms every second. The big grains may be a fingerprint of a cold, distant birthplace: models suggest such grains collect in the frigid outer reaches of planet-forming disks, hinting that 3I/ATLAS was forged far from its parent star before being flung into the dark.

As new surveys begin to turn up interstellar interlopers more often, this improvised observation makes a tidy point: the spacecraft already scattered across the solar system can double as a fleet of opportunistic comet-watchers, each offering a view we simply can’t get from home.

Citation

“Interstellar Object 3I/ATLAS Observed from Mars by China’s Tianwen-1 Spacecraft,” Xin Ren et al 2026 ApJL 1003 L10. doi:10.3847/2041-8213/ae61b3

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Discovered in December 2024, the roughly 60-meter-wide asteroid 2024 YR4 was initially thought to have a slim chance of striking Earth in 2032. Further observations ruled out an Earth impact but left open the possibility of a Moon impact. New JWST observations show that 2024 YR4 will speed past both Earth and the Moon without a collision.

Another Update on 2024 YR4

In April 2025, we featured a Research Note that described March 2025 JWST observations of 2024 YR4 and characterized the asteroid’s size and albedo. At the close of that article, the authors suggested that further JWST observations in early 2026 could help to refine our understanding of the asteroid’s trajectory and determine whether it would strike the Moon.

On 18 and 26 February 2026, JWST carried out those critical observations. In this dataset, the asteroid is bright enough to be detected confidently, and the background is peppered with a sufficient number of reference stars — two factors necessary to determine the precise track of the asteroid as it zipped through space.

Trajectory Refinement

Julien de Wit (Massachusetts Institute of Technology) and collaborators analyzed the new JWST data and determined the asteroid’s position. The team used multiple methods to reduce the data and showed that their results were consistent regardless of the reduction method, ultimately yielding a measurement with an uncertainty of just 50 milliarcseconds. This is a huge improvement over the previous trajectory estimate, which had an uncertainty of 700 milliarcseconds.

Combining the latest JWST observations with existing data stretching back to the asteroid’s discovery, de Wit and coauthors determined a new, highly precise orbit for the object — one that definitively shows that the asteroid will safely pass by the Moon at a distance of 22,900 ± 800 km in 2032. In addition to ruling out the upcoming lunar impact, the team also ruled out any collisions with Earth in the next 100 years. Phew!

High-Impact Science

This work highlights JWST’s potential as a tool for planetary defense. The February 2026 observations detailed here represent the faintest-ever detection of a near-Earth object, and JWST can detect objects far fainter than ground-based telescopes can. This ability allows JWST to observe potentially hazardous asteroids over a larger swath of their orbits, which translates to earlier trajectory estimation — JWST pinned down 2024 YR4’s orbit two years before the asteroid would have become bright enough for ground-based telescopes to do so.

JWST’s role may be even more important for smaller objects that rapidly become undetectable after discovery. De Wit’s team demonstrated this for a 10-meter-diameter 2024 YR4 clone on the same trajectory; for an object of this size, JWST would be able to rule out an Earth impact before the asteroid became undetectable, but ground-based telescopes could not. With surveys from facilities like Vera C. Rubin Observatory and Near-Earth Object Surveyor set to discover hundreds of thousands of new near-Earth objects, JWST’s role as a hazard assessor will likely be in high demand.

Citation

“JWST Observations of Asteroid 2024 YR4 Rule Out a 2032 Lunar Impact and Demonstrate a New Regime for Planetary Defense Follow-Up,” Julien de Wit et al 2026 ApJL 1003 L21. doi:10.3847/2041-8213/ae6a95

The post Asteroid 2024 YR4 Won’t Hit the Moon, New JWST Observations Show appeared first on AAS Nova.

The outer solar system is inhabited by swarms of small objects that are challenging to observe and characterize. When one of these objects travels in front of a star, from our perspective, the passage provides a brief chance to study these distant, icy denizens of our solar system. In a recent article, Estela Fernández-Valenzuela (University of Central Florida) and coauthors described how they predicted and observed stellar crossings by Weywot, the largest moon of the dwarf planet Quaoar, which lies roughly 44 au from the Sun. In the image above, the black dashed lines indicate the areas where Weywot was predicted to briefly blot out the light from a star, and the blue lines show the updated regions based on Hubble Space Telescope observations. In each panel, the green squares and red circles show where the occultation was and was not detected, respectively. There were five successful detections of Weywot’s passage across a star, allowing the team to constrain Weywot’s diameter to 116–172 km. The team also found that Weywot is much darker than the body it orbits, which has important implications for how the system formed. To learn more about the planning process for and results of these observations, be sure to check out the full research article linked below.

Citation

“Weywot, an Unusually Low-Albedo Satellite in the Trans-Neptunian Region,” Estela Fernández-Valenzuela et al 2026 ApJL 1002 L37. doi:10.3847/2041-8213/ae6076

The post Featured Image: Chasing Weywot’s Shadow appeared first on AAS Nova.

The Lucy spacecraft, en route to its primary mission targets, zipped past the main-belt asteroid Dinkinesh and revealed its tiny satellite, Selam. New research examines the surfaces and histories of these small rocky worlds.

A Stop Along the Way

In 2021, the Lucy spacecraft embarked on a 12-year mission to study several Jupiter trojan asteroids, which share Jupiter’s orbit. The spacecraft won’t have its first encounter with a Jupiter trojan until 2027, but it hasn’t been idle during its long journey. In November 2023, Lucy performed a dress rehearsal of its trojan-encounter maneuvers during a flyby of a 738-meter-wide main-belt asteroid called (152830) Dinkinesh.

During this flyby, Lucy flew within 430 km (267 mi) of the asteroid and made a surprise discovery: Dinkinesh has a tiny companion, which has been named Selam. (The name Dinkinesh comes from the Amharic name for the Lucy fossil discovered in 1974; Selam is similarly named after a hominid fossil that is sometimes called “Lucy’s baby.”) Remarkably, Selam is the first known asteroid satellite that is a contact binary, made up of two separate bodies that have gently merged into one.

Craters and Boulders

In a recent research article, Edward Bierhaus (Lockheed Martin Space) and collaborators analyzed Lucy flyby images to study the surfaces of Dinkinesh and Selam. The team analyzed global features like troughs and ridges and measured visible craters and boulders.

While the small numbers of craters detected — 29 for Dinkinesh and 3 for Selam — makes further analysis difficult, the team determined that Dinkinesh’s crater size–frequency distribution is shallower than expected, though similar to that of small near-Earth asteroids (e.g., Ryugu). The seemingly shallow distribution may be an effect of the phase angle and resolution of the observations, or it could be a sign of impact armoring or other surface processes.

The size–frequency distribution of Dinkinesh’s boulders, on the other hand, is somewhat steeper. This discovery may mean that S-type (stony) asteroids like Dinkinesh have different boulder size distributions than C-type (carbonaceous) asteroids.

Possible Histories

An analysis of the collisional timescales in the main asteroid belt suggests that Dinkinesh is a fragment of a larger asteroid that was split apart at least once, though it’s not yet possible to say which parent body it might have come from. After splitting off from its parent asteroid, Dinkinesh appears to have been subjected to the Yarkovsky–O’Keefe–Radzievskii–Paddack (YORP) effect. This effect arises when sunlight falls on a small asymmetric asteroid, creating a torque that can alter its spin rate. In extreme cases, the YORP effect can crank up an asteroid’s spin rate so much that it sheds some of its surface material or flies apart altogether.

Dinkinesh seems to show clear signs of YORP-driven structural failure. Sumak Fossa (a large trough) and Fab Dorsum (a ridge running along the asteroid’s equator) may have formed through this process. If Sumak Fossa was excavated by a YORP-induced mass-shedding event, both Fab Dorsum and Selam could have formed out of the cast-off material.

With Lucy en route to its primary objective, there’s still much for us to learn from this mission about the small bodies of our solar system. In the meantime, be sure to check out the full article linked below, as there are far more details about Dinkinesh and Selam than could be included in this short summary!

Citation

“The Geology of a Small Main-Belt S-Class Binary Asteroid System: Dinkinesh and Its Contact Binary Satellite Selam as Observed by the Lucy Mission,” E. B. Bierhaus et al 2025 Planet. Sci. J. 6 299. doi:10.3847/PSJ/ae1968

The post Details on Dinkinesh and Its Surprise Satellite from the Lucy Mission appeared first on AAS Nova.

Editor’s Note: After a short hiatus, the Monthly Roundup is back! This series of articles, which began in 2023, examines multiple perspectives or findings on a single topic.

The discovery of interstellar object 3I/ATLAS on 1 July 2025 was one of last year’s top astronomy stories. First identified by the Asteroid Terrestrial-impact Last Alert System (ATLAS), 3I/ATLAS is just the third interstellar object that astronomers have seen speeding through our solar system; it was preceded by 1I/ʻOumuamua in 2017 and 2I/Borisov in 2019.

Last summer, professional and amateur astronomers worldwide rolled out the red carpet in 3I/ATLAS’s honor, enlisting a pack of ground-based and spacefaring paparazzi to capture its every move. Observations in the first few months after 3I/ATLAS’s discovery revealed cometary features, including a fuzzy coma of gas and dust, a tail that trailed behind the object, and a plume of dust on the side facing the Sun.

With 3I/ATLAS having now made its closest approach to the Sun, venturing within 1.36 au of our star on 29 October 2025, the comet is wrapping up its tour of the solar system and heading back out to interstellar space — but the research continues. Today, we’re taking a look at five of the more than three dozen research articles published in the AAS journals that have examined 3I/ATLAS and its journey through our solar system. As always, this Monthly Roundup contains only a short summary of each article, so be sure to check out the full research articles linked at the bottom of this post!

Early Spectra of 3I/ATLAS

Bin Yang (Diego Portales University and the Planetary Science Institute) and collaborators obtained spectra of 3I/ATLAS less than two weeks after it was discovered, when it was 4.0–4.4 au from the Sun. Using the Gemini South telescope and the Infrared Telescope Facility (IRTF), Yang’s team sought to characterize its coma, the dusty envelope of gas that puffs out from the icy nucleus as the comet warms up.

These observations showed that 3I/ATLAS has a relatively featureless, red-sloped spectrum from 0.5 to 0.8 microns, similar to certain asteroids and active comets in our solar system. In the near-infrared, 3I/ATLAS’s spectrum was flatter, with a broad absorption feature around 2.0 microns.

Yang and coauthors found that the near-infrared spectrum was well fit by a model including a blend of amorphous carbon and water ice (63% carbon and 37% water ice by volume) at a temperature of 120K. 3I/ATLAS’s spectrum bears certain similarities to well-studied solar system comets like C/2006 W3 and 6P/d’Arrest, which suggests that the particles in these objects’ comae are similar in size or composition. Ultimately, the discovery of abundant water ice in 3I/ATLAS’s coma, along with the carbon dioxide spotted in other studies, suggests that the comet formed in the cold, volatile-rich outer regions of its home system.

Unique Polarization Properties

3I/ATLAS is the second interstellar object for which astronomers have obtained polarization information. The first, 2I/Borisov, showed a high degree of positive polarization, comparable to the exceptional solar system comet Hale–Bopp.

Using the Very Large Telescope, the Nordic Optical Telescope, and the 2m Ritchey-Chrétien-Coude telescope to study 3I/ATLAS’s polarization between 17 July and 28 August 2025, Zuri Gray (University of Helsinki) and coauthors showed that 3I/ATLAS is also exceptional — but in the opposite direction. In contrast to 2I/Borisov’s strong positive polarization, 3I/ATLAS is strongly negatively polarized, with an unusually deep and narrow polarization profile. The narrowness of 3I/ATLAS’s polarization profile is similar to that of certain rare asteroids and cometary nuclei, but 3I/ATLAS is more strongly negatively polarized than these objects.

Gray’s team suggested that 3I/ATLAS’s extreme polarization behavior could be evidence for a mixture of large icy and dark particles in its coma. It’s also possible that it’s the first identified member of a new class of comets, distinct from both solar system comets and interstellar comet 2I/Borisov.

Is 3I/ATLAS Truly a Pristine Relic of the Star System It Came From?

Interstellar objects like 3I/ATLAS have been hailed as pristine beacons that grant us a rare glimpse into the conditions of other star systems. But as new work by Romain Maggiolo (Royal Belgian Institute for Space Aeronomy) and collaborators shows, 3I/ATLAS was likely greatly altered by its journey through interstellar space.

Spectroscopic measurements from JWST suggest that 3I/ATLAS has extremely high abundance of carbon dioxide and carbon monoxide compared to water. A comet’s chemical abundance ratios can be either inherited from the material from which the comet formed, or they can be due to processing after its formation. The team finds that comet 3I/ATLAS’s extreme abundance ratios can be attributed to the comet being pummeled by galactic cosmic rays — high-energy charged particles — as it cruised through interstellar space.

This means that 3I/ATLAS’s current composition doesn’t match its initial composition at the time of its formation, and the cosmic-ray-altered layer of the comet’s nucleus may be 15–20 meters thick. Could volatile outgassing and dust ejection scratch away enough of the comet’s outer layers to expose its pristine interior? This depends on the level of activity the comet experienced as it passed close to the Sun in October 2025. If the comet outgassed strongly, it could have shed tens of meters from its irradiated shell, exposing the pristine core material. Under low to moderate outgassing scenarios, however, the pristine inner material remains hidden beneath the processed shell. Now past the comet’s closest approach to the Sun, we’ll soon know more about whether the composition of the outgassed material has changed as the comet has moved through the solar system.

3I/ATLAS as a Template for Future Encounters: Planning a Potential Rendezvous

It’s only a matter of time before the next interstellar object pays our solar system a visit, and researchers are already thinking about how they’ll study the next visitor. One of the best ways to learn about an interstellar interloper would be to send a spacecraft to rendezvous with it and collect data from up close.

To plan for possible future rendezvous, Atsuhiro Yaginuma (Michigan State University) and collaborators considered what it would have taken for an existing spacecraft to meet up with 3I/ATLAS shortly after it was discovered. The team considered ready-to-launch spacecraft on Earth as well as operational spacecraft currently orbiting Mars.

Their calculations showed that meeting up with 3I/ATLAS from Mars would have required less energy than launching a new spacecraft from Earth, with Mars-originating flybys potentially possible with existing technologies. For Earth-originating flybys launched on or after the discovery date of 1 July, linking up with 3I/ATLAS is likely beyond current capabilities — but if the comet had been discovered earlier, a rendezvous launched from Earth may have been possible.

This highlights the importance of detecting interstellar objects as early as possible, as well as the advantage of stationing well-fueled spacecraft at key locations around the solar system; these spacecraft could be deployed rapidly after an interstellar object is discovered, enabling the collection of valuable data. (This is similar to the premise of the European Space Agency’s Comet Interceptor mission, which will wait at one of the Sun–Earth Lagrange points for the arrival of a long-period comet; such a mission could be repurposed to track down an interstellar comet.)

So, About Those Aliens…

Like its predecessor 1I/ʻOumuamua, 3I/ATLAS prompted speculation that it’s not a natural object, though there’s no compelling evidence that it’s anything but a comet. If 3I/ATLAS were an interstellar probe, we might be able to unmask it as such by intercepting its radio communications. In a recent Research Note, Ben Jacobson-Bell (University of California, Berkeley) and coauthors described their search for narrow-band radio signals — the communication medium for all spacecraft in our solar system — from 3I/ATLAS.

The Breakthrough Listen project pointed the 100-meter Green Bank Telescope in 3I/ATLAS’s direction, just one day before the object made its closest approach to Earth at a distance of 1.8 au. The team identified nine possible “events” in their data, all of which were ruled to be radio-frequency interference. Based on this non-detection, Jacobson-Bell and collaborators ruled out the presence of isotropic, continuously outputting radio transmitters with power greater than 0.1 watt. (For comparison, a cellphone puts out approximately 1 watt, and spacecraft radios tend to put out a few dozen watts.) Other searches for radio transmissions from 3I/ATLAS have similarly detected no signals.

Citation

“Spectroscopic Characterization of Interstellar Object 3I/ATLAS: Water Ice in the Coma,” Bin Yang et al 2025 ApJL 992 L9. doi:10.3847/2041-8213/ae08a7

“Extreme Negative Polarization of New Interstellar Comet 3I/ATLAS,” Zuri Gray et al 2025 ApJL 992 L29. doi:10.3847/2041-8213/ae0c08

“Interstellar Comet 3I/ATLAS: Evidence for Galactic Cosmic-Ray Processing,” Romain Maggiolo et al 2026 ApJL 996 L34. doi:10.3847/2041-8213/ae2fff

“The Feasibility of a Spacecraft Flyby with the Third Interstellar Object 3I/ATLAS from Earth or Mars,” Atsuhiro Yaginuma et al 2025 ApJ 995 64. doi:10.3847/1538-4357/ae11b2

“Breakthrough Listen Observations of 3I/ATLAS with the Green Bank Telescope at 1–12 GHz,” Ben Jacobson-Bell et al 2025 Res. Notes AAS 9 351. doi:10.3847/2515-5172/ae3083

The post Monthly Roundup: Interstellar Visitor 3I/ATLAS appeared first on AAS Nova.

Editor’s Note: Astrobites is a graduate-student-run organization that digests astrophysical literature for undergraduate students. As part of the partnership between the AAS and astrobites, we occasionally repost astrobites content here at AAS Nova. We hope you enjoy this post from astrobites; the original can be viewed at astrobites.org.

Title: High-Speed Boulders and the Debris Field in DART Ejecta
Authors: Tony L. Farnham et al.
First Author’s Institution: University of Maryland
Status: Published in PSJ

The DART Mission: A First Step in Planetary Defense

In a groundbreaking experiment, NASA’s Double Asteroid Redirection Test (DART) became the first mission to intentionally crash a spacecraft into an asteroid to test whether such an impact could change the asteroid’s path. The target was Dimorphos, a small companion orbiting a larger asteroid called Didymos, located about 11 million kilometers from Earth.

Luckily, neither Dimorphos nor Didymos was ever on any sort of collision course with anything (and they’re still not). But by impacting an object orbiting another, the effect of the collision could more easily be measured and so Dimorphos was chosen as the target. You see, the goal wasn’t destruction, but deflection. The scientists wanted to see if a spacecraft could alter an asteroid’s orbit by striking it — and if so, by how much. When DART slammed into Dimorphos at over 22,500 kilometers per hour, it successfully shortened the asteroid’s roughly 12-hour orbit by about 33 minutes. This confirmed that hitting an asteroid with a spacecraft — in this case scientifically called a kinetic impactor — could be a viable method to redirect a potentially hazardous object in space.

But the change in momentum didn’t just come from the spacecraft itself. Much of the momentum transfer came from the plume of debris — called ejecta — that blasted out from the impact site. This debris, spreading out in multiple directions, added to the total push on the asteroid. Understanding how this ejecta moved exactly is key to calculating the full effect of the impact and was one of the primary goals for the DART mission.

With this exact purpose in mind, a small companion spacecraft called LICIACube (Light Italian Cubesat for Imaging of Asteroids), released by DART two weeks before the crash, flew past moments after the collision. It snapped several images of the debris cloud, as seen in Figure 1, as it raced past. It is with a reanalysis of these images that today’s authors have managed to track a number of boulders in the ejected material.

Boulders, Boulders Everywhere!

You can say that DART really made an impact — pun intended. It kicked up a lot of material as it struck Dimorphos. In some parts the ejecta plumes are dense enough to block sunlight and even cast shadows on Dimorphos. In the images, like the one seen in Figure 2, the authors were able to make out more than 100 boulders, some as big as 3.6 meters in radius. Tracking the boulders allowed them to calculate velocities and their contribution to the momentum budget. Some of the boulders were ejected at speeds up to nearly 200 kilometers per hour and carried almost as much momentum as the DART craft itself.

Using the assumption that the objects are somewhat spherical, the authors calculate that the total volume of all 104 boulders that they managed to identify and track amounts to 403 cubic meters of material, which is equivalent to a sphere 4.6 meters in radius. If you use the bulk density of Dimorphos, this suggests that the mass ejected in these objects is around 0.02% of Dimorphos’s total mass. And this is only for the boulders tracked — the study identified more boulder, but LICIACube was not able to track all of them and could only detect sizes down to 0.2 meter!

The authors also found that the boulders are clustered, suggesting that they were ejected in preferred directions. They conclude that this non-uniform distribution likely changed Dimorphos’s orbital plane. Additionally, the momentum imparted by boulder ejection also likely altered the rotational state of the asteroid, making it tumble around in its orbit.

So what happened? Although there are no constraints on their actual points of origin, the authors suggest that a likely scenario might be that the ejected rocks are the shattered pieces of two large boulders that were seen in some of the last images from the DART spacecraft itself. The two boulders on the surface — named Bodhran and Atabaque after their drum-like shapes — were likely struck by the solar panels as seen in Figure 3.

The shallow angles and high ejection speeds are consistent with this scenario. Regardless of how they were ejected, though, it is clear that a significant amount of momentum can be found in the debris and that this process plays an important part in understanding how a kinetic impactor can deflect asteroids.

The European Space Agency’s Hera mission, now en route and arriving in 2026, aims to carry out an in-depth post-impact analysis. It could determine if Dimorphos is tumbling in its slightly modified orbit and help assess the momentum transfer from the impact debris. All this will contribute to a better understanding of just how much the impact changed the asteroid’s orbit and how much more momentum came from the ejected material than was contributed by the DART spacecraft to Dimorphos. These data will be key to refining asteroid deflection strategies in the case that we might need them in the future. After all, the dinosaurs didn’t have any, and look where it got them!

Original astrobite edited by Chloe Klare.

About the author, Kasper Zoellner:

I have a Master of Science in astronomy and I am currently working towards a PhD in physics and educational science. My greatest passion is the search for exoplanets and how stellar variability may influence the possibility of life. I am also interested in science outreach, education and discussing what sci-fi novel to read next!

The post Shot by the DART and We’re to Blame! Now That Space Rock Won’t Be the Same appeared first on AAS Nova.

Editor’s Note: Astrobites is a graduate-student-run organization that digests astrophysical literature for undergraduate students. As part of the partnership between the AAS and astrobites, we occasionally repost astrobites content here at AAS Nova. We hope you enjoy this post from astrobites; the original can be viewed at astrobites.org.

Title: Impacts on Ocean Worlds Are Sufficiently Frequent and Energetic to Be of Astrobiological Importance
Authors: Shannon M. MacKenzie et al.
First Author’s Institution: Johns Hopkins University Applied Physics Laboratory
Status: Published in PSJ

Asteroids and meteorites are usually associated with doom and destruction (rest easy, dinosaurs), but they may have also been essential for the emergence of life on Earth. It is popularly theorized that some of the base building blocks of life, like volatiles and organics, were delivered here by meteorites and that the energy of these impacts synthesized even more, like HCN and amino acids. Expectedly, the same should be true for other planets. Today’s article explores this possibility using nearby analogies for potentially habitable exoplanets: our solar system’s ocean worlds.

Why Do Meteorites Carry Organics?

The solar system formed from one massive cloud of gas and dust, so the composition everywhere is approximately the same. However, early Earth was an extremely hot ball of magma that destroyed its organic matter. Luckily, organics were able to survive in objects like meteorites in the cold outskirts of the solar system.

Ocean Worlds in Our Neighborhood

In the search for extraterrestrial life, we start by looking for the basic necessities — and water is a big one. Though Earth is the only planet in our solar system with liquid water, several moons of Jupiter and Saturn have it as well. These moons are beyond the balmy habitable zone, so their surfaces are covered in icy crusts, but beneath those crusts are subsurface oceans of liquid water, making these moons “ocean worlds” (see Figure 1). On their own, the presence of water makes these moons astrobiologically interesting, and they will also elucidate ocean worlds that are further away.

Today’s authors studied typical impact events on Jupiter’s moon Europa and Saturn’s moons Enceladus and Titan to determine 1) if organics could survive the impacts, and 2) what processes could occur in the resulting melted material in the impact craters before it refreezes.

Surviving the Impact

To evaluate survivability, the authors modeled the maximum pressure of an impact on an ocean world’s ice crust for a range of impact velocities and angles. Around Jupiter and Saturn, most impactors are either icy or rocky objects that originate from the Kuiper Belt or Oort cloud, so the authors modeled both types of impactors. Rocky impactors create higher pressures (shown in gray in Figure 2) than icy impactors (shown in black in Figure 2). From the sizes of observed craters on the ocean world moons, previous works determined the velocities and pressures of impacts, which are shown by the colored boxes in Figure 2. Finally, a number of other works have estimated the ranges of survivable pressures for biota and biologically important molecules, which are shown by the green and black bars on the right of Figure 2. Impressively, the survivable pressure ranges are within the observed and modeled pressures of impacts! So these life building blocks can be, and likely have been, deposited on the ocean world moons.

Crater Melt Pools

When an impactor hits the icy crust, some of the ice will melt. The deposited organics will end up in a pool of liquid water in the crater, which is an ample environment for prebiotic chemistry until the pool freezes. From the observed crater sizes and modeled velocities, the authors estimated how much liquid water could remain in a crater and how long it would take to freeze. Freeze times ranged from a few Earth years for the smallest craters (<4 kilometers in diameter) to thousands of years for the largest craters (hundreds of kilometers). In labs on Earth mimicking the crater conditions, amino acids have been synthesized in as short as a few months to a few years, so synthesis is possible in the melt pools.

The pools eventually freeze, trapping any deposited or synthesized material on the icy surface. Other processes, like future impacts, are required to break through the icy crust and transport material to the subsurface oceans where theorized hydrothermal vents could allow more complex development.

Tangible Evidence

In summary, survivable impacts on the ocean world moons are common, and each provides an opportunity for prebiotic chemistry to arise. Unlike most objects astronomers study, the proximity of these ocean worlds means that we can thoroughly understand them through physical samples. NASA’s Cassini detected organic compounds in the plumes that burst off the surface of Enceladus, and the Dragonfly mission is set to head for Titan in 2028 to collect and analyze samples once it arrives in 2034. In the coming decades, we may witness the discovery of more precursors to life or microbial life itself in the subsurface oceans of moons in our solar system, and gain radical insight into the ocean worlds beyond.

Original astrobite edited by Sonja Panjkov.

About the author, Annelia Anderson:

I’m an Astrophysics PhD candidate at the University of Alabama, using simulations to study the circumgalactic medium. Beyond research, I’m interested in historical astronomy, and hope to someday write astronomy children’s books. Beyond astronomy, I enjoy making music, cooking, and my cat.

The post Seeding Life in the Oceans of Moons appeared first on AAS Nova.

There are more than 37,000 asteroids known to come within 1.3 au of the Sun. Of this near-Earth asteroid population, roughly 2,500 are classified as potentially hazardous — being more than about 140 meters across and coming within 0.05 au of Earth’s orbit (about 20 times the distance between Earth and the Moon). In the image above, Luisa Fernanda Zambrano-Marin (University of Granada and University of Central Florida) and collaborators present observations of 2020 BX₁₂, a potentially hazardous binary asteroid. The larger of the two asteroids in the system was discovered in January 2020 by the Asteroid Terrestrial-impact Last Alert System. About a week after the initial discovery, the 1,000-foot-wide Arecibo Telescope aimed its powerful planetary radar at 2020 BX₁₂ and revealed the asteroid’s small companion. 2020 BX₁₂ was the last of nearly 60 binary or triple near-Earth asteroids discovered with Arecibo before the telescope collapsed in December 2020. As Zambrano-Marin‘s team notes, the loss of Arecibo hampers scientists’ ability to find companions to near-Earth asteroids, which can be critical for determining the properties of these asteroids and guiding our planetary defense strategies. To learn more about this discovery, as well as what the team learned from follow-up spectroscopy, be sure to check out the full research article linked below.

Citation

“2020 BX₁₂—The Last Binary Asteroid Discovered at Arecibo,” Luisa Fernanda Zambrano-Marin et al 2025 Planet. Sci. J. 6 91. doi:10.3847/PSJ/adbe39

The post Featured Image: The Last Asteroid Pair Discovered by Arecibo appeared first on AAS Nova.

The giant planet’s bow shock isn’t just deflecting the solar wind, it’s acting as a powerful particle accelerator, firing electrons to relativistic energies of at least 1 MeV, according to a new analysis of data from NASA’s Juno spacecraft.

The post Jupiter Accelerates Electrons to Near-Light Speed, Offering Clues to Cosmic Ray Origins appeared first on Sci.News: Breaking Science News.

The James Webb Space Telescope observed a large amount of methane around 3I/ATLAS, revealing just how different it is from comets from our solar system.

NASA's MAVEN spacecraft was in excellent shape when it disappeared behind Mars on December 6 of last year. The routine passage, called an occultation, was supposed to last less than an hour, but ground teams didn't hear from the spacecraft when it was supposed to regain contact with Earth.

The loss of communication triggered contingency plans for engineers to try to restore a link with MAVEN, which orbits Mars more than 200 million miles from Earth. To no avail, they listened for faint signals and uplinked commands in the blind. Hopes of saving the mission faded over time, and NASA officials announced Wednesday that they're giving up on it.

"NASA has ceased efforts to search for the MAVEN spacecraft and are beginning activities to decommission the mission," said Mike Moreau, MAVEN's project manager at NASA's Goddard Space Flight Center in Maryland. 

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Comments

© NASA/University of Colorado/LASP

NASA's MAVEN spacecraft was in excellent shape when it disappeared behind Mars on December 6 of last year. The routine passage, called an occultation, was supposed to last less than an hour, but ground teams didn't hear from the spacecraft when it was supposed to regain contact with Earth.

The loss of communication triggered contingency plans for engineers to try to restore a link with MAVEN, which orbits Mars more than 200 million miles from Earth. To no avail, they listened for faint signals and uplinked commands in the blind. Hopes of saving the mission faded over time, and NASA officials announced Wednesday that they're giving up on it.

"NASA has ceased efforts to search for the MAVEN spacecraft and are beginning activities to decommission the mission," said Mike Moreau, MAVEN's project manager at NASA's Goddard Space Flight Center in Maryland. 

Read full article

Comments

© NASA/University of Colorado/LASP

A rainbow blanket of patchwork colors sprawls across South Africa in this new composite image created using data from NASA's latest Earth-observing mission.

A rare meteorite recovered from the Sahara Desert contains evidence of a long-lost moon-size world that existed just a few million years after the solar system formed.

Scientists propose that a moon base could act as an isolated first line of biological defense against extraterrestrial samples that might be harmful to Earth's biosphere.

The Northwest Africa (NWA) 12774, an angrite meteorite discovered in the Sahara Desert, likely in Mauritania, appears to be a fragment of a vanished protoplanet, offering the strongest evidence yet that a large planetary body formed and was later destroyed during the Solar System’s chaotic infancy.

The post Meteorite Found in Africa Preserves Evidence of Long-Lost Massive Protoplanet appeared first on Sci.News: Breaking Science News.