The Moon's surface is covered by impact craters, ranging from microscopic pits to massive basins over 1,000 kilometres across. These craters formed primarily during the Late Heavy Bombardment period about 4 billion years ago, when the inner Solar System experienced an intense period of asteroid and comet impacts. Unlike Earth, where weathering, erosion, and tectonic activity continually reshapes the surface, the Moon lacks an atmosphere and significant geological activity, allowing these impact features to remain preserved for billions of years. This remarkably preserved cratering record serves to capture crucial history of the formation and evolution of our Solar System.

Lunar craters over the South Pole

(Credit : NASA)

During the formation of craters a significant quantity of the ejected lunar material achieves the Moon’s escape velocity and reaches Earth. Studying these rocks helps us to understand how material moves between the two bodies. A team of researchers have turned their attention to this study and their paper has recently been published. The research, led by Jose Daniel Castro-Cisneros utilises better computer models than previous studies to track how Moon debris reaches Earth.

The study uses simulations to examine more starting conditions over longer time periods to better estimate how much lunar material reaches Earth and whether it contributes to near Earth objects. The team also hoped that by studying Moon debris trajectories, they would be able to piece together Earth's impact timeline and how it affected life and geology. They are also especially interested in objects like Kamo'oalewa, believed to be between 36-100 metres in diameter orbiting near Earth that might actually be a piece of the Moon.

Previous studies of lunar ejecta were improved upon by using the REBOUND simulation package to track particles from the Moon for 100,000 years. Unlike earlier work that used separate phases, the team simultaneously model Earth and the Moon using a more realistic ejection velocity distribution. They recorded data every five years and collision events defined as ejecta reaching 100 km above Earth's surface, providing a more comprehensive picture of how material transfers from the Moon to Earth.

Crater Tycho displaying its wonderful system of rays thought to be lunar ejecta.

The model employed, used simplified vertical impacts, though natural oblique impacts would direct more material toward Earth at lower angles, the approach simplified the process. Current environmental conditions were assumed but historically, when the Moon was closer and experiencing heavier bombardment (over 1.1 billion years ago), even more lunar material would have reached Earth. Future research should incorporate oblique impact models and ancient orbital configurations to better understand early Earth-Moon material exchange.

The team were able to conclude that, following lunar impacts, Earth collects about 22.6% of the ejected material over 100,000 years, with half of these collisions occurring within the first 10,000 years. The collision rate follows a power-law distribution over time (a relationship where a change in one quantity results in a proportional relative change in another) independent of the initial size of those quantities. Material launched from the Moon's trailing side has the highest Earth collision probability, while the leading side produces the lowest. When hitting Earth, lunar ejecta travel at 11.0-13.1 km/s and predominantly strike near the equator (with 24% fewer impacts at the poles). These impacts are nearly symmetrically distributed between morning and evening hours, peaking around 6 AM/PM.

This research significantly advances our understanding of lunar-Earth material exchange, showing that nearly a quarter of lunar impact ejecta reaches Earth—half within just 10,000 years. The findings about equatorial impact concentration and the importance of lunar launch location reveal previously unknown patterns in this process. These results enhance our understanding of the Earth-Moon system's shared impact history while supporting the lunar origin hypothesis for objects like Kamo’oalewa.

Source : 

• Lunar impact ejecta flux on the Earth

Near-Earth Objects (NEOs) are rocky bodies orbiting our Solar System that pass relatively close to Earth's orbit. Scientists have identified over 30,000 NEOs ranging from small boulders to massive rocks spanning several kilometres in diameter. These celestial bodies are of particular interest to astronomers not only for their scientific value in understanding the formation of our Solar System but also because they pose potential impact hazards to our planet. Space agencies like NASA continuously monitor these objects through programs such as the Near-Earth Object Surveillance Mission, calculating their trajectories to provide early warnings of possible collisions.

Near Earth Object Comet Hartley-2 captured by NASA's EPOXI mission

(Credit : NASA/JPL-Caltech/UMD)

Despite significant advances in asteroid detection technology in recent decades, important gaps remain. Ground-based survey programs like the Catalina Sky Survey and Pan-STARRS have collectively discovered over 90% of near-Earth asteroids larger than 1 kilometre, significantly reducing the risk from globally devastating impacts. However, detection rates drop dramatically for smaller objects, with less than 40% of potentially hazardous asteroids in the 140-meter range currently cataloged. Detection challenges include limitations of ground-based telescopes (affected by weather, daylight, and atmospheric interference), blind spots near the sun, and the inherently dark, low-albedo nature of many asteroids.

A Catalina Sky Survey Observatory at dusk at Mount Lemmon Observatory in the Santa Catalina Mountains near Tucson, Arizona

(Credit : Daniel Oberhaus)

International and U.S. defence protocols have identified the urgent need for rapid-response spacecraft reconnaissance capabilities, particularly for asteroids around 50 meters in diameter—objects large enough to cause significant regional damage yet small enough to evade detection until they're dangerously close. Even after the completion of advanced survey initiatives like NEO Surveyor and the Rubin Observatory, approximately half of these 50-meter objects will remain undiscovered until they're nearly upon us. This sobering reality means that for many potential impact scenarios, a quickly deployed flyby mission may represent our only chance to gather critical data before impact.

The Rubin Observatory against the Milky Way

(Credit : Rubin Observatory/NSF/AURA/B)

In a recent paper authored by Nancy L. Chabot and team from Johns Hopkins University, they assert that a planetary defence flyby reconnaissance mission must demonstrate capabilities to quickly reach a small ~50-meter NEO, determine its Earth impact probability, and gather essential physical data to inform decision makers. This presents significant technical challenges, including managing flyby speeds up to 25 km/s and high solar phase angles while collecting crucial data from such a small target.

The core principle of planetary defence is that we don't choose which asteroids threaten us—we must be prepared to respond to whatever object presents a danger. Therefore, the team argues that the mission's true purpose isn't simply demonstrating asteroid flyby technology, but developing robust capabilities specifically tailored for the small, short-warning-time objects most likely to require rapid space-based studies, an essential advancement in our planetary defence readiness.

Source : 

• A Mission to Demonstrate Rapid-Response Flyby Reconnaissance for Planetary Defense

This week brings the Hubble Space Telescope's 35th birthday — but instead of getting presents, the Hubble team is giving out presents in the form of four views of the cosmos, ranging from a glimpse of Mars to a glittering picture of a far-out galaxy.

It’s the latest observance of a tradition that goes back decades, in which NASA and the Space Telescope Science Institute release pictures to celebrate the anniversary of Hubble’s launch into Earth orbit aboard the space shuttle Discovery on April 24, 1990.

“Hubble opened a new window to the universe when it launched 35 years ago,” Shawn Domagal-Goldman, acting director of the Astrophysics Division at NASA Headquarters, said today in an image advisory marking the occasion.

“The fact that it is still operating today is a testament to the value of our flagship observatories, and provides critical lessons for the Habitable Worlds Observatory, which we plan to be serviceable in the spirit of Hubble.”

Hubble didn’t get off to a smooth start. After the 24,000-pound observatory was deployed, scientists discovered that its nearly 8-foot-wide mirror had a manufacturing flaw. In 1993, during the first of five servicing missions, astronauts installed hardware that greatly improved the sharpness of Hubble’s images.

Since then, Hubble’s observations have revolutionized astronomy, contributing to discoveries related to exoplanets, black holes, the nature of the early universe, the existence of dark energy and the accelerating expansion of the cosmos. NASA says Hubble has made nearly 1.7 million observations so far, focusing on about 55,000 astronomical targets and resulting in more than 22,000 research papers.

All those discoveries, and all those images, endeared Hubble to the general public. The loss of the shuttle Columbia and its crew in 2003 led NASA to suspend plans for much-needed repairs, but because of the resulting outcry over the telescope’s potential demise, the space agency agreed to a final servicing mission that took place in 2009.

At the time, NASA expected the telescope to provide dazzling views for an additional five or 10 years. Once again, Hubble exceeded expectations, racking up 16 years of operation without on-orbit repairs.

The images released today illustrate the breadth of Hubble’s range:

• Pictures of Mars were captured between last Dec. 28 and 30, near the time when Mars came closest to Earth in its orbit. The images show the planet’s bright orange Tharsis plateau and its dormant volcanoes, the north polar ice cap and wispy water-ice clouds.

• Another Hubble image from last December focuses on a small portion of the Rosette Nebula, a huge star-forming region 5,200 light-years from Earth. Dark clouds of gas, laced with dust, are silhouetted across the image. The Hubble team also released a wider-scale image of the nebula to add cosmic context.

• In January, Hubble snapped a picture of the planetary nebula NGC 2899, seemingly fluttering like a cosmic moth 4,500 light-years from Earth. The colorful clouds of dust and gas have been shaped by the radiation and stellar winds blasting out from the star at the image’s center.

• Hubble produced a new view of the spiral galaxy NGC 5335 in March. The picture reveals a bar-shaped structure that slices across the galaxy and channels gas inward toward the center, fueling the production of new stars. Patchy streamers of star formation swirl around the edges of the galaxy.

Mars near opposition. Image: NASA, ESA, STScI; Image Processing: Joseph DePasquale (STScI)

Planetary nebula NGC 2899.

Image: NASA, ESA,  STScI; Processing: Joseph DePasquale (STScI)

Spiral galaxy NGC 5335.

Image: NASA, ESA, STScI; Image Processing: Alyssa Pagan (STScI)

Clouds in the Rosette Nebula.

Image: NASA, ESA, STScI; Processing: Joseph DePasquale (STScI)

In recent years, Hubble has been experiencing periodic hiccups, and it's only a matter of time before a glitch puts it out of commission permanently. Meanwhile, the spotlight has been shifting to NASA's James Webb Space Telescope, which was launched in 2021 and has seven times as much light-gathering capability as Hubble does.

Unlike Hubble, JWST sees the universe primarily in infrared light. It doesn't have Hubble's capability to make observations in a wide spectrum ranging from infrared to ultraviolet. And because JWST is positioned at a gravitational balance point a million miles from Earth, it can't be serviced in space, as Hubble was.

In contrast, the Habitable Worlds Observatory would study the universe in visible and ultraviolet light, producing images that would be significantly sharper than Hubble's views. A major goal of that future mission would be to identify potentially habitable Earthlike planets orbiting distant stars. The HWO would also be designed with robotic servicing in mind.

NASA's current plans call for launching the Habitable Worlds Observatory by as early as the 2040s, but those plans — and more immediate plans to launch the Nancy Grace Roman Space Telescope next year — have been thrown into doubt by a proposal from the Trump administration to make deep cuts in NASA's science budget.

A recent analysis gives us new views of key deep-sky objects.

It’s a cosmic shame, that we tend to only see flat-looking, 2-dimensional views of deep-sky objects. And while we can’t just zoom out past the Andromeda galaxy for another perspective, or see the Crab Nebula from another vantage point in space, we can use existing data to simulate objects in 3D.

A recent collection released by Marshall Space Flight Center’s Chandra X-ray Center and the Harvard-Smithsonian Center for Astrophysics shows us familiar objects in a new way. These models combine information from space-borne observatories, including the Chandra X-ray observatory. Released from the payload bay of Space Shuttle Columbia on STS-93, Chandra has proven itself over the last two decades as NASA’s flagship X-ray observatory in space.

Chandra, shortly after deployment from shuttle Columbia's payload bay.

Credit: NASA

The 3D renderings were made using a combination of observational data and computer simulations. The technique not only allows armchair observers to see old objects in new ways, but it also gives astronomers a method to study these familiar targets from all sides.

“These 3D models allow people to explore—and print—examples of stars in the early and end stages of their lives,” states a recent Chandra X-ray Center (NASA) press release. “They also provide scientists with new avenues to investigate scientific questions and find insights about the objects they represent.”

NASA is even providing users with the files to 3D print these deep-sky objects, free to download. This gives a tactile dimension to the sky, something the user can hold and feel. This is an important factor when it comes to science outreach… after all, none of us can see the sky at x-ray wavelengths.

Here’s the highlighted object-by-object breakdown:

Cassiopeia A: Located about 11,000 light-years distant, Cassiopeia A or Cas A is a well-studied supernovae remnant. A prodigious x-ray and radio source, Cas A hosted the last known galactic supernovae about 340 years ago, although no definitive observations of the event exist.

Cas A, to include the 'Green Monster' loop.

Credit: INAF-Osservatorio Astronomico di Palermo/Salvatore Orlando.

More recently, the James Webb Space Telescope (JWST) has documented what’s become known as the ‘green monster’, a long oxygen-rich filament extending from Cas A. This may provide more insight into this young and evolving remnant.

A 3D printed rendition of Cas A.

Credit: NASA/CXC/SAO/A. Jubett & N. Wolk/Modeled by Sal Orlando.

BP Tauri: This is a young T Tauri star surrounded by a dust ring, just 10 million years old. T Tauri stars are crucial to our understanding of stellar and solar system formation, as they provide a snapshot of the early stages of the process. These are also very energetic and active stars, with flares that sculpt the surrounding cocoon of dust that the stars are embedded in. BP Tauri and the x-ray flares it produces are of primary interest to Chandra researchers.

The Cygnus Loop: This is a familiar target for deep-sky imagers located in the constellation of Cygnus, the Swan. Another, more ancient supernovae remnant, the Cygnus Loop has since undergone a complex interaction with the interstellar medium, allowing Chandra to probe this domain as the residual blast wave is heated to millions of degrees. The Cygnus Loop is an extended object visually extending over three degrees across, about six times the angular diameter of the Full Moon.

The location of the Cygnus Loop in the sky.

Credit: Stellarium.

G 292.0+1.8: The last selected object is an obscure but crucial one. G 292.0+1.8 is another supernovae remnant, located in the constellation Centaurus the Centaur. Astronomers are interested in this remnant for two main reasons: One, it is usually rich in molecular oxygen. Two, it exhibits a rare, reverse shock wave rebounding back towards the original explosion, giving the remnant an asymmetrical shape.

These 3D models were also highlighted in studies out of the Italian Institute for Astrophysics (INAF) in Palermo Italy by Salvatore Orlando and cited in papers from the Monthly Notices of the Royal Astronomical Society, The Astrophysical Journal and Astronomy & Astrophysics.

Who doesn’t want a 3D rendition of the Cygnus Loop on their desktop? For now, it’s the next best thing to going there in person.

The weather gets a little wild and weird on Jupiter. How wild? Spacecraft instruments have measured strong winds, tracked fierce lightning, and found huge methane plume storms rising from deep beneath the clouds. How weird? Think: mushballs raining down like hailstones. They're made of ammonia and water encased in a water ice shell. According to planetary scientists, these mushballs plunge through the Jovian atmosphere. What's more, they probably form on the other gas and ice giants, too.

According to planetary scientist Chris Moeckel and his former advisor Imke de Pater at UC Berkeley, the proof for these strange Jovian slushies came from 3D visualizations of the Jovian atmosphere. You can't tell they're there just by looking at the clouds, however. You have to find a way to peer into the atmosphere and measure the chemical fingerprints of the gases it contains. In 2020, data from the Juno mission and observations by radio telescopes on Earth uncovered strange "nonuniformities" in ammonia gas distribution around the planet. In other words, it isn't distributed evenly throughout the atmosphere. The Juno data in particular showed that ammonia isn't just poorly distributed - it's actually depleted to atmospheric depths of about 150 kilometers, according to de Pater.

“Juno really shows that ammonia is depleted at all latitudes down to about 150 km (93 miles), which is really odd,” said de Pater, who discovered 10 years ago that ammonia was depleted down to about 50 km (31 miles). “That’s what Chris is trying to explain with his storm systems going much deeper than we expected.”

A flattened map of Jupiter reveals the distribution of ammonia beneath the planet’s cloud tops, extending tens of kilometers below the visible cloud deck. Red regions indicate where ammonia is depleted, while black regions show where it is rising from deeper within the atmosphere. The depleted zones appear in bands flanking the equator (0° latitude on the map) and at the poles (not shown), while the upwelling of ammonia is most prominent just north of the equator. The striking absence of deep activity in the mid-latitudes suggests that most of Jupiter’s atmosphere is relatively shallow, with only a few storms punching deeper into the planet.

Credit Chris Moeckel and Imke de Pater, UC Berkeley

Follow the Ammonia Trail

To explain that missing ammonia, another scientist named Tristan Guillot proposed a wild idea: that strong updrafts during storms on Jupiter can lift ice particles high above the clouds. There, the ice mixes with ammonia vapor, which melts the ice into a slush. Just like on Earth, as the ice balls rise and fall, they grow. Eventually, these softball-sized mushballs fall back into the atmosphere, taking the ammonia with them. This helps explain why ammonia appears to be missing from the upper atmosphere: it’s being dragged down and hidden deep inside the planet, where it leaves faint signatures to be observed with radio telescopes.

To Moeckel and others, that idea seemed like an "out there" explanation. "Imke and I both were like, ‘There’s no way in the world this is true,’” said Moeckel. “So many things have to come together to actually explain this, it seems so exotic. I basically spent three years trying to prove this wrong. And I couldn’t prove it wrong.”

Jovian Conditions Conducive to Mushballs

It turns out that conditions in Jupiter's atmosphere could support the formation of mushballs. That atmosphere is mostly hydrogen and helium, inhabited by clouds in its upper layers. Beneath the clouds and upper atmosphere lies a deeper layer of fluid metallic hydrogen. A rocky inner core lives deep inside the planet. The atmosphere contains smaller amounts of ammonia molecules and water vapor, which rise and freeze into droplets. On Earth, droplets of water fall onto the surface as rain or hail. However, Jupiter has no surface until you get to the core. So, if those droplets do fall, how far down do they go? How big do they get?

An illustration depicting how violent storms on Jupiter — and likely other gas giants — generate mushballs and shallow lightning. The mushballs are created by thunderstorm clouds that form about 65 km (40 miles) beneath the cloud tops and fuel a strong updraft that carries water ice upward to extreme altitudes, occasionally above the visible cloud layer. Once they reach altitudes of about 22 km (14 miles) below the visible cloud layer, ammonia acts like an antifreeze, melting the ice and combining with it to form a slushy ammonia-water liquid that gets coated with water ice — a mushball. The mushballs keep rising until they become too heavy and fall back through the atmosphere, growing until they reach the water condensation layer, where they evaporate. This ends up redistributing ammonia and water from the upper atmosphere (green and blue layer) to layers deep below the clouds, creating areas of depleted ammonia visible in radio observations.

Credit NASA/JPL-Caltech/SwRI/CNRS

This is where the mushballs come in. First, scientists began trying to figure out the strange distribution of ammonia in particular. There were proposals that water and ammonia ice get locked up in hailstones. However, nobody could quite explain how to form them heavy enough to fall hundreds of kilometers through Jupiter's messy atmosphere. That's when Guillot made his proposal for the growth of slushy hailstones.

Making a 3D Model

To understand the weather conditions and the possible formation of those weird mushballs, Moeckel began working on a different approach based on the observational data. “I essentially developed a tomography method that takes the radio observations and turns them into a three-dimensional rendering of that part of the atmosphere that is seen by Juno,” Moeckel said.

Moeckel's 3D picture of Jupiter’s troposphere shows that the majority of the weather systems on Jupiter really are shallow. Most extend down perhaps only 10 to 20 kilometers below the visible clouds. Most of the colorful, swirling patterns in the bands encircling the planet are part of that shallow contingent of clouds.

Some weather, however, emerges much deeper in the troposphere, redistributing ammonia and water and essentially unmixing what was long thought to be a uniform atmosphere. The three types of weather events responsible are hurricane-like vortices, hotspots coupled to ammonia-rich plumes that wrap around the planet in a wave-like structure, and large storms that generate mushballs and lightning.

Tripping with a Mushball

“The mushball journey essentially starts about 50 to 60 kilometers below the cloud deck as water droplets. The water droplets get rapidly lofted all the way to the top of the cloud deck, where they freeze out and then fall over a hundred kilometers into the planet, where they start to evaporate and deposit material down there,” Moeckel said. “And so you have, essentially, this weird system that gets triggered far below the cloud deck, goes all the way to the top of the atmosphere, and then sinks deep into the planet.”

Unique signatures in the Juno radio data for one storm cloud provided an important clue to the mushball formation. “There was a small spot under a cloud that either looked like cooling, that is, melting ice, or an ammonia enhancement, that is, melting and release of ammonia,” Moeckel said. “It was the fact that either explanation was only possible with mushballs that eventually convinced me.”

What About Other Planets?

The 3D model and explanations of mushballs on Jupiter offer a more complete look at the complicated dynamics of the Jovian atmosphere. Interestingly, it's very likely that similar conditions for mushball creation could exist at the other gas and ice giants of the solar system. If so, that would give planetary scientists much more insight into the interiors of those worlds as well as the activities going on in their atmospheres.

In an age of exoplanet research, it's also likely that researchers can use Moeckel's tools to extrapolate what they've seen at Jupiter to similar-type worlds around other stars. Since they can see only the upper atmospheres of distant worlds, the ability to interpret chemical signatures in those atmospheres using radio and other observations is important.

For More Information

• On Jupiter, It's Mushballs All the Way Down
• Tempests in the Troposphere: Mapping the Impact of Giant Storms on Jupiter's Deep Atmosphere
• Jupiter's Tropical Atmosphere: Shallow Weather, Deep Plumes and Vortices

Ever since the Mariner probes and Viking missions travelled to Mars, scientists have known that liquid water once flowed on the surface. This is indicated by specific features that form in the presence of water here on Earth, including flow channels, delta fans, hydrated minerals, and sedimentary rocks. In recent decades, the many missions that have studied Mars' atmosphere, surface, and climate have revealed that Mars was a warmer, wetter place during the Noachian period (ca. 4.1 to 3.7 billion years ago).

This has stimulated questions about whether life could have emerged on Mars and where its once-abundant water (and maybe even life) could be found today. A new study by geologists at the University of Colorado Boulder (CU Boulder) provides a potential glimpse of what Mars may have looked like billions of years ago. Their findings suggest Mars experienced heavy precipitation that likely fed valleys and channels that carved the features we still see there today.

The research was led by Amanda Steckel, a postdoctoral geological scientist at Caltech (formerly at CU Boulder), and a member of the Perseverance science team. She was joined by Gregory E. Tucker, a geoscience professor at CU Boulder and a member of the Cooperative Institute for Research in Environmental Sciences (CIRES); Matthew Rossi and Brian Hynek were also co-authors on the study, a research scientist with CIRES and the Earth Lab and a geosciences professor with the Laboratory for Atmospheric and Space Physics (LASP) at CU Boulde, respectively.

While most scientists agree that Mars once had flowing water on its surface, where it came from remains a mystery. While most maintain that a global ocean once covered the entire Northern Lowlands of Mars, while large bodies spotted the southern hemisphere, many scientists assert that Mars was always cold and dry. In this scenario, water existed mainly as ice caps and glaciers that occupied the Northern Lowlands, which experienced occasional melting for short periods.

This is largely based on the fact that roughly 4 billion years ago, the young Sun was only 75% as bright as it is today. As a result, Mars must have had a significant greenhouse effect to maintain temperatures warm enough to support liquid water. Hence, there is an ongoing debate between proponents of the "warm-and-wet" versus the "cold-and-dry" models. To address this, Steckel and her colleagues ran a computer simulation originally developed for Earth studies by Professor Tucker. As Steckel explained in a CU Boulder press release:

"You could pull up Google Earth images of places like Utah, zoom out, and you’d see the similarities to Mars. It’s very hard to make any kind of conclusive statement. But we see these valleys beginning at a large range of elevations. It’s hard to explain that with just ice."

The researchers used the software to model the evolution of the Martian landscape on synthetic terrain similar to Mars' equatorial region. They added water from precipitation to some of their models and melting ice caps to others, and then simulated how this would shape the landscape over tens to hundreds of thousands of years. The team then compared the two models to data obtained by NASA's Mars Global Surveyor (MGS) and Mars Odyssey spacecraft. The precipitation model was consistent with what we see around Mars' equator today.

These include the vast network of channels in the Martian highlands that open onto the low-lying areas in the Northern Lowlands. The rock deposits and delta fans found in these areas further indicate that vast quantities of water once flowed across the landscape. "You'd need meters deep of flowing water to deposit those kinds of boulders," said Hynek. "Once the erosion from flowing water stopped, Mars almost got frozen in time and probably still looks a lot like Earth did 3.5 billion years ago."

While these results are convincing, there are still unanswered questions about Mars' ancient climate. For example, scientists are still unsure how Mars could maintain temperatures warm enough to support precipitation and flowing water, given how the Sun's output was less than it is today. However, this study still provides scientists with a glimpse at what Mars experienced in the past and could also provide new perspectives into the geological history of Earth.

Further Reading:

• University of Colorado

Planetary scientists have plenty of theories about Mars and its environmental past. Two of the most widely accepted are that there was a carbon dioxide atmosphere and, at one point, liquid water on Mars' surface. However, this theory has a glaring problem: Where should the rocks have formed from the interactions between carbon dioxide and water? According to a new paper by scientists at several NASA facilities using data collected by the rover Curiosity, the answer is right under the rover's metaphorical feet.

According to geology, carbon dioxide and water should react together to form "carbonates," a type of mineral that contains an ion made up of carbon and oxygen. This process is relatively common on Earth and even in some manufacturing processes, but the results have never before been seen on Mars, at least not in any quantity.

That is despite a significant amount of effort spent looking for them. Rovers have looked for them to no avail. Even satellites have done spectroscopy on most of the planet and haven't seen anything that could be a carbonate anywhere near the quantities to prove that Mars had an atmosphere of carbon dioxide and liquid water at one time. That was, until the little rover that could stepped in.

Curiosity has had a hand in plenty of important discoveries on the Red Planet. Here's a video from Fraser 7 years ago that discusses some of them.

Curiosity has dug holes throughout Mars' Gale Crater for almost 13 years. During that time, some significant discoveries were made, but this latest one has dramatically impacted our understanding of the evolution of the Martian climate. At three different drill sites around Mount Sharp, Curiosity found evidence for a mineral called siderite, a carbonate material formed with iron.

Siderite itself wasn't present on the surface, though. It was only found when Curiosity drilled down 3-4cm into the surface of a rock and analyzed the resulting drill powder in its CheMin instrument. After the instruments zapped it with X-rays, the researchers found the presence of the elusive mineral that could explain where Mars' atmosphere went, at least partially. 

The presence of carbonates under layers of other rock could also explain why they have been so hard to find up until now. Orbiting satellites wouldn't be able to see a few centimeters into existing rock, and most rover spectroscopy is done without drilling into a sample, so they wouldn't have been able to detect it either. But finding any does lend credence to the idea that Mars used to be habitable for basic microorganisms, at one point at least.

Here's a look back at Curiosity's first science target - Jake the Rock.

Scientists from several different NASA centers, including the Jet Propulsion Laboratory (Curiosity operation), Ames Research Center (CheMin Instrument operation), and John Space Center (data analysis) contributed to the work. According to Benjamin Tutolo, a professor at the University of Calgary, "the discovery of abundant siderite in Gale Crater represents both a surprising and important breakthrough in our understanding of the geologic and atmospheric evolution of Mars." 

It certainly does, though the estimated amount of siderite and other carbonates based on this newest data isn't enough to explain where all of Mars' atmosphere went. There could be other, more abundant hiding places, or the Red Planet could have lost its atmosphere slowly over time due to the solar wind, since it has lacked a magnetic field for so long. As rovers continue to explore its surface, a steady stream of new findings will continue to intrigue planetary scientists, and hopefully help them refine their theories on how Mars came to be what it is today.

Learn More:

• NASA / JPL - NASA’s Curiosity Rover May Have Solved Mars’ Missing Carbonate Mystery
• Tutolo et al - Carbonates identified by the Curiosity rover indicate a carbon cycle operated on ancient Mars
• UT - Could There Be Bacteria Living on Mars Today?
• UT - It's Not Just Rocks, Scientists Want Samples Mars's Atmosphere

RELATED VIDEOS

NASA’s Lucy spacecraft made a successful flyby of the second asteroid on its must-see list over the weekend, and sent back imagery documenting the elongated object’s bizarre double-lobed shape.

It turns out that asteroid Donaldjohanson — which was named after the anthropologist who discovered the fossils of a human ancestor called Lucy — is what’s known as a contact binary, with a couple of ridges in its narrow neck. In today’s image advisory, NASA compares the ridged structure to a pair of nested ice cream cones.

“Asteroid Donaldjohanson has strikingly complicated geology,” said Hal Levison, a planetary scientist at the Southwest Research Institute who serves as the Lucy mission’s principal investigator. “As we study the complex structures in detail, they will reveal important information about the building blocks and collisional processes that formed the planets in our solar system.”

Lucy came as close as 600 miles (960 kilometers) to Donaldjohanson on April 20, snapping images every two seconds or so as it zoomed past. The pictures confirmed the asteroid’s status as a contact binary — that is, a compound object formed by the sticky collision of two smaller celestial bodies. Donaldjohanson is somewhat larger than it was previously thought to be, with a length of about 5 miles (8 kilometers) and a width of 2 miles (3.5 kilometers) at the widest point.

The Easter encounter took place three and a half years after Lucy was launched, and 17 months after the 52-foot-wide probe flew past its first target asteroid, Dinkinesh, and a mini-moon called Selam. Like Donaldjohanson, Selam was found to be a contact binary.

Researchers consider both of Lucy’s encounters in the main asteroid belt, which lies between the orbits of Mars and Jupiter, to be mere warmups for the mission’s main event: a detailed study of so-called Jupiter Trojan asteroids. Such asteroids are trapped harmlessly at resonance points in Jupiter’s orbit due to the giant planet’s gravitational influence. No spacecraft has ever gotten close to a Jupiter Trojan.

Tom Statler, NASA program scientist for the $989 million Lucy mission, said the quality of the early imagery demonstrates the “tremendous capabilities” of Lucy’s instruments. “The potential to really open a new window into the history of our solar system when Lucy gets to the Trojan asteroids is immense,” he said.

Over the next few weeks, researchers will retrieve, process and analyze data from Lucy’s black-and-white imager as well as its color imager, infrared spectrometer and thermal infrared spectrometer. The spacecraft is scheduled to spend most of this year traveling through the main asteroid belt.

Lucy’s first encounter with a Jupiter Trojan asteroid, known as Eurybates, is due to take place in August 2027. Four additional Trojan encounters will follow between 2027 and 2033.

RELATED VIDEOS

Where did the water we believe is on the Moon come from? Most scientists think they know the answer - from the solar wind. They believed the hydrogen atoms that make up the solar wind bombarded the lunar surface, which is made up primarily of silica. When that hydrogen hits the oxygen atoms in that silica, the oxygen is sometimes released and freed to bond with the incoming hydrogen, which in some cases creates water. But no one has ever attempted to replicate that process to prove its feasibility. A new paper by Li Hsia Yeo and their colleagues at NASA's Goddard Space Flight Center describes the first experimental evidence of that reaction.

To perform this experiment on Earth, the authors needed two things: something equivalent to the solar wind and something comparable to lunar regolith. The solar wind is comprised of protons—basically hydrogen atoms with their electrons stripped off. Mimicking this on Earth proved tricky, as they had to build a custom miniaturized particle accelerator to simulate the solar wind.

While it might seem technically simpler, their next task was certainly more administratively challenging—obtaining a sample of actual Moon regolith from the Apollo missions. Dust collected during Apollo 17's final lunar trip had already been packed in an airtight storage container since the 1970s, but the authors went ahead and baked the sample again just to make sure there was no water present.

Fraser discusses the best use of the Moon.

Once the samples were obtained and the accelerator was set up, the final piece of the experimental puzzle was a spectrometer, which could show the presence of water. When ready, they blasted the sample with enough simulated "solar wind" to be the equivalent of about 80,000 years on the lunar surface. During that time, they watched for infrared dips around 3um, precisely what they saw, representing a tell-tale water sign.

However, it is also a tell-tale sign of hydroxyl (OH), which has the same spectral profile as water and is also one of the potential by-products of the solar wind hitting the lunar regolith. As a press release announcing the finding states, "they can't conclusively say if their experiment made water molecules." However, finding even hydroxyl molecules is a step in the right direction.

One other data point lends credence to the continual replenishment of water via the solar wind, instead of more sporadic replenishment from sources such as micrometeoroids - the spectrographic signal of water seems to vary with time. It is strong in the morning, decreases throughout the lunar "day", and then increases again over the lunar "night". The most obvious explanation for this cycle is that some water burns off during the day, being exposed to the Sun. Over the two-week-long lunar night, the amount of water starts to build back up again, as would be expected if it is created by an external force such as the solar wind, and not being stripped away right away.

New data from LADEE shows how water might show up on the Moon after a micrometeoroid impact.
Credit - NASA's Goddard Space Flight Center Conceptual Image Lab

Ultimately, this experiment lends more credibility to the idea that lunar water is created by the interaction between the lunar regolith and the solar wind and that the solar wind itself is always slightly replenishing the amount of water available on the Moon. Artemis astronauts, or whoever winds up back on the lunar surface, will undoubtedly be happy for that, no matter how that water got there.

Learn More:

• NASA - Can Solar Wind Make Water on Moon? NASA Experiment Shows Maybe
• L.H. Yeo et al - Hydroxylation and Hydrogen Diffusion in Lunar Samples: Spectral Measurements During Proton Irradiation
• UT - The Solar Wind is Creating Water on the Surface of the Moon
• UT - The Moon's Atmosphere Comes from Space Weathering

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Scientists have known for a while that Mars currently lacks a magnetic field, and many blame that for its paltry atmosphere - with no protective shield around the planet, the solar wind was able to strip away much of the gaseous atmosphere over the course of billions of years. But, evidence has been mounting that Mars once had a magnetic field. Results from Insight, one of the Red Planet's landers, lend credence to that idea, but they also point to a strange feature - the magnetic field seemed to cover only the southern hemisphere, but not the north. A team from the University of Texas Institute for Geophysics thinks they might know why - in a recent paper, they described how a fully liquid core in Mars could create a lopsided magnetic field like the one seen in Insight’s data.

The Earth's core isn't completely molten despite what you may have learned in elementary school. There are two distinct cores - a solid "Inner" core and a molten "Outer" core. The inner core remains solid due to the immense pressures on the iron and nickel found there. So, the magnetic field that covers our whole planet is, in fact, created only by the Outer Core.

Researchers have long thought that a similar dynamic, solid inner and molten outer core, was present on Mars when it maintained a magnetic field billions of years ago. After about 3.9 billion years, the rocks that formed some of the large impact basins from that time, such as Hellas and Isidis, would contain rocks that would have magnetized while they were cooling due to the presence of the field. Since they don't, there is little evidence for a strong global magnetic field past that point. The going theory was that, as the planet's core cooled, the entire core became solid, eliminating the spinning molten metal that creates the magnetic field in the first place.

Fraser discusses the question of when Mars' dynamo shut down.

However, there was a strange feature in Mars' magnetic field—a massive difference in strength between the field in the northern and southern hemispheres. This dichotomy was first noticed during the Mars Global Surveyor mission back in 1997, but data from the Insight lander also confirmed a stark difference between the two hemispheres.

Various explanations have been offered for why the dichotomy existed. These ranged from the effects of large asteroid impacts to very early localized tectonic activity. However, the scientific community has not widely accepted previous explanations.

Enter the new theory from Chi Yan of the University of Texas and their co-authors. Theirs is a two-fold explanation. First, the red planet could have had a wholly molten core, and second, a massive temperature difference between the northern and southern hemispheres led to the heat escaping only in the southern hemisphere.

Magnetic fields can be artificial - as Fraser discusses here.

In Mars' case, a molten core would be a primary mover of the process known as a "planetary dynamo," which creates planetary-scaled magnetic fields. With a solid inner core like the Earth's, the dynamo effect could have been disrupted by inefficiencies in the system's fluid dynamics.

It could also explain how the temperature gradients allow such uneven heat extraction. If the southern hemisphere had much higher thermal conductivity, heat would be more likely to flow through it, causing the churning that creates the planetary dynamo to happen primarily on the southern side of the planet. 

To prove their point, the authors created a model version of early Mars using a supercomputer at the Maryland Advanced Research Computing Center. They varied the fluid dynamics of Mars as well as the conductivity of its crust. They found that the conditions that most accurately matched the results from Insight and Global Surveyor occurred when Mars' core was wholly molten, and there was a significant difference in the thermal conductivity of the northern and southern hemispheres.

Keeping Mars' any artificial atmosphere Mars has would require a magnetic field - or something similar.

As with all research, there is plenty more left to do. The authors suggest further analysis of some of the seismic data from Insight to see if any additional data was already collected that could align with the molten core theory. Other potential paths forward could include improved modeling for a broader range of internal and external planetary conditions or a deeper understanding of Martian meteorites from various regions and times.

For now, this new theory seems to hold water—or molten iron, depending on who you ask. But there is a lot more work that needs to be done to prove this theory and its implications for the existence of life on Mars.

Learn More:

• UT Austin - Molten Martian Core Could Explain Red Planet’s Magnetic Quirks
• C. Yan et al - Mars' Hemispheric Magnetic Field From a Full-Sphere Dynamo
• UT - When Did Mars Lose its Global Magnetic Field?
• UT - Mars Lacks a Planet-Wide Magnetosphere, but it Does Have Pockets of Magnetism

The surface of Mars is extremely cold, irradiated, and desiccated. But at one time, the planet was much warmer and wetter, with flowing water, lakes, and even an ocean covering most of its northern hemisphere. Because of this, scientists speculate that life may have emerged on Mars billions of years ago and could still be there today. Ever since the Viking 1 and 2 missions landed on the surface in 1976, the search for evidence of past (and maybe present) life has been ongoing.

As missions like Curiosity and Perseverance continue to explore promising regions that were once lakebeds (the Gale and Jezero craters), there are still questions about where to look next. In a recent paper, researchers proposed searching for photosynthetic bacteria embedded in the snow and ice around Mars' mid-latitudes. Using "radiatively habitable zones" on Earth as a template, they argue that photosynthetically active bacteria could survive within exposed patches of ice.

The research was led by Dr. Aditya Khuller, a postdoctoral researcher at NASA's Jet Propulsion Laboratory (JPL) and the University of Washington's Polar Science Center (UW-PSC). He was joined by colleagues from the UW Applied Physics Laboratory, the School of Earth & Space Exploration at Arizona State University (SESE-ASU), and the Institute of Arctic and Alpine Research (InstAAR) at the University of Colorado Boulder (UC Boulder). The paper that detailed their findings was presented at the 56th Lunar Planetary Science Conference (2025 LPSC).

On Earth, bacteria can survive and thrive in ice, even at depths of several meters. Earth's protective ozone layer protects these organisms from harmful ultraviolet (UV) radiation, allowing them to safely absorb what is known as photosynthetically active radiation (PAR). On Mars, which has a thin atmosphere (less than 1% of Earth's) and no ozone layer, about 30% more damaging UV radiation reaches the surface. However, numerical modeling predicts ice and snow around the equator can melt below the surface.

The presence of this liquid water at these depths could make these subsurface environments the most easily accessible locations for future astrobiology missions. To investigate this possibility, the team developed a radiative transfer model (RTM) based on previous research that employs the Delta-Eddington method (a simplified means of calculating radiative fluxes). This model allowed them to simulate vertically-stacked layers of snow, ice, and Martian dust.

Since solar flux has not yet been measured within ice on Mars, the team employed glacier ice in Greenland as an analog. Their results showed that in all cases, most of the solar radiation is absorbed within the top few meters of the ice, but increases based on grain size. Overall, they found that solar radiation can reach a maximum depth of about 6.5 meters (21.3 ft) in clean ice. At the same time, biologically damaging UV penetrated to about 3 m (~10 ft) in clean granular, packed ice (firn). Their results also indicated that PAR penetration varied considerably based on the amount of dust in the ice.

For ice with 0.01% dust, PAR reached just 25 cm (~10 inches) below the surface, while the peak penetration depth of UV was reduced to about 7 cm (2.75 inches). For ice with 0.1% dust concentrations, this was reduced to only 5 cm (~2 inches), with a peak UV penetration of 1.5 cm (0.6 inches). Overall, they found that Mars may have radiatively habitable zones within exposed patches of mid-latitude ice at depths ranging from a few centimeters for dusty ice to several meters for cleaner ice.

On Earth, microbes require temperatures of more than -18 °C (-0.67 °F) for cell division to occur. Meanwhile, favorable solar radiative conditions and the presence of liquid water are required for photosynthesis. And while conditions within the Martian polar ice are too cold for melting to happen at these depths, numerical models suggest that small amounts of melt and runoff can occur in exposed patches of mid-latitude snowpack just beneath the surface. As the team indicates, this could have significant implications in the search for life on Mars:

"Under similar ephemeral near-freezing conditions, widespread microbial habitats containing cyanobacteria, chlorophytes, fungi, diatoms, and heterotrophic bacteria are found in the shallow subsurface (top few centimeters to meters) of ice sheets, glaciers, and lake ice containing dust and sediment on Earth.

"In the summer, ice in the shallow subsurface melts due to solar heating at these locations. Photosynthesis then occurs in the subsurface, below a translucent ice lid, with nutrients scavenged from the dust and sediment present in the subsurface liquid water. During winter, the subsurface liquid refreezes, and photosynthesis ceases until the next summer."

Therefore, if ice and snow in equatorial regions experience seasonal melting, microbes like cyanobacteria could combine this water with nutrients from Martian dust in the ice to conduct photosynthesis. If such habitats exist, they would constitute the most easily accessible locations for finding evidence of life on Mars.

Further Reading: 

• USRA