planetary science

Formation of oceans within icy moons could cause the waters to boil

astronomy, freezing, ice, moons, oceans, planetary science, Science / Kris Guyer / November 25, 2025

That can have significant consequences on the stresses experienced by the icy shells of these moons. Water is considerably more dense than ice. So, as a moon’s ocean freezes up, its interior will expand, creating outward forces that press against the gravity holding the moon together. The potential of this transition to shape the surface geology of a number of moons, including Europa and Enceladus, has already been explored. So, the researchers behind the new work decided to look at the opposite issue: what happens when the interior starts to melt?

Rather than focus on a specific moon, the team did a general model of an ice-covered ocean. This model treated the ice shell as an elastic surface, meaning it wouldn’t just snap, and placed viscous ice below that. Further down, there was a liquid ocean and eventually a rocky core. As the ice melted and the ocean expanded, the researchers tracked the stresses on the ice shell and the changes in pressure that occurred at the ice-ocean interface. They also tracked the spread of thermal energy through the ice shell.

Pressure drop

Obviously, there are limits to how much the outer shell can flex to accommodate the shrinking of the inner portions of the moon that are melting. This creates a low-pressure area under the shell. The consequences of this depend on the moon’s size. For larger moons—and this includes most of the moons the team looked at, including Europa—there were two options. For some, gravity is sufficiently strong to keep the pressure at a point where the water at the interface remains liquid. In others, the gravity was enough to cause even an elastic surface to fail, leading to surface collapse.

For smaller moons, however, this doesn’t work out; the pressure gets low enough that water will boil even at the ambient temperatures (just above the freezing point of water). In addition, the low pressure will likely cause any gases dissolved in the water to be released. The result is that gas bubbles should form at the ice-water interface. “Boiling is possible on these bodies—and not others—because they are small and have a relatively low gravitational acceleration,” the researchers conclude. “Consequently, less ocean underpressure is needed to counterbalance the [crustal] pressure.”

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NASA really wants you to know that 3I/ATLAS is an interstellar comet

3I/ATLAS, astronomy, comet, planetary science, Science / Kris Guyer / November 19, 2025

The HiRISE camera, meant to image Mars’ surface, was repurposed to capture 3I/ATLAS. Credit: NASA/JPL-Caltech/University of Arizona

As eccentricity continues to rise from there, the question shifts from “what shape is its trajectory?” to “how much does the Sun alter its path through the Solar System?” For 3I/Atlas, with an eccentricity of over six, the answer is “not very much at all.” The object has approached the inner Solar System along a reasonable approximation of a straight line, experienced a gentle bend around the Sun near Mars’ orbit, and now will be zipping straight out of the Solar System again.

So, the object clearly did not originate here, which means getting a better look at it is a high priority. Unfortunately, 3I/ATLAS’s closest approach to Earth’s orbit happened when it was on the far side of the Sun from Earth. We’ve been getting closer to it since, but the hardware that got the best views was all orbiting Mars and is designed largely to point down. NASA’s Nicky Fox, the associate administrator for Science, praised the operators for getting NASA’s hardware “pushed beyond their designed capabilities” when imaging the object.

That includes using the MAVEN mission (designed to study Mars’ atmosphere) to get spectral information, and the HiRISE camera, which captured the image below. Other images came from a solar observatory and two separate missions that are on their way to visit asteroids. Other hardware that can normally image objects like this, such as the Hubble and JWST, pivoted to image 3I/ATLAS as well.

What we now know

Hubble has gotten the best view of 3I/ATLAS; its data suggests that the comet is, at most, just a couple of kilometers across. It doesn’t show much variability over time, suggesting that, if it’s rotating, it’s doing so very slowly. It has shown some differences as it warmed up, first producing a jet of material on its side facing the Sun before radiation pressure pushed that behind it to form a tail. There is some indication that, as we saw during the Rosetta mission’s visit to one of our Solar System’s comets, most of the material may be jetting out of distinct “hotspots” on the comet’s surface.

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Tracking the winds that have turned Mars into a planet of dust

dust, dust devils, Mars dust storms, planetary science, Science / Kris Guyer / November 13, 2025

Where does all this dust come from? It’s thought to be the result of erosion caused by the winds. Because the Martian atmosphere is so thin, dust particles can be difficult to move, but larger particles can become more easily airborne if winds are turbulent enough, later taking smaller dust motes with them. Perseverance and previous Mars rovers have mostly witnessed wind vortices that were associated with either dust devils or convection, during which warm air rises.

CaSSIS and HRSC data showed that most dust devils occur in the northern hemisphere of Mars, mainly in the Amazonis and Elysium Planitiae, with Amazonis Planitia being a hotspot. They can be kicked up by winds on both rough and smooth terrain, but they tend to spread farther in the southern hemisphere, with some traveling across nearly that entire half of the planet. Seasonal occurrence of dust devils is highest during the southern summer, while they are almost nonexistent during the late northern fall.

Martian dust devils tend to peak between mid-morning and midafternoon, though they can occur from early morning through late afternoon. They also migrate toward the Martian north pole in the northern summer and toward the south pole during the southern summer. Southern dust devils tend to move faster than those in the northern hemisphere. Movement determined by winds can be as fast as 44 meters per second (about 98 mph), which is much faster than dust devils move on Earth.

Weathering the storm

Dust devils have also been found to accelerate extremely rapidly on the red planet. These fierce storms are associated with winds that travel along with them but do not form a vortex, known as nonvortical winds. It only takes a few seconds for these winds to accelerate to velocities high enough that they’re able to lift dust particles from the ground and transfer them to the atmosphere. It is not only dust devils that do this—the team found that even nonvortical winds lift large amounts of dust particles on their own, more than was previously thought, and create a dusty haze in the atmosphere.

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Here’s how orbital dynamics wizardry helped save NASA’s next Mars mission

blue origin, Commercial space, escapade, launch, Mars, NASA, new glenn, ng-2, planetary science, rocket lab, Science, solar system, Space, uc berkeley / Paul Patrick / November 9, 2025

Blue Origin is counting down to launch of its second New Glenn rocket Sunday.

The New Glenn rocket rolls to Launch Complex-36 in preparation for liftoff this weekend. Credit: Blue Origin

CAPE CANAVERAL, Florida—The field of astrodynamics isn’t a magical discipline, but sometimes it seems trajectory analysts can pull a solution out of a hat.

That’s what it took to save NASA’s ESCAPADE mission from a lengthy delay, and possible cancellation, after its rocket wasn’t ready to send it toward Mars during its appointed launch window last year. ESCAPADE, short for Escape and Plasma Acceleration and Dynamics Explorers, consists of two identical spacecraft setting off for the red planet as soon as Sunday with a launch aboard Blue Origin’s massive New Glenn rocket.

“ESCAPADE is pursuing a very unusual trajectory in getting to Mars,” said Rob Lillis, the mission’s principal investigator from the University of California, Berkeley. “We’re launching outside the typical Hohmann transfer windows, which occur every 25 or 26 months. We are using a very flexible mission design approach where we go into a loiter orbit around Earth in order to sort of wait until Earth and Mars are lined up correctly in November of next year to go to Mars.”

This wasn’t the original plan. When it was first designed, ESCAPADE was supposed to take a direct course from Earth to Mars, a transit that typically takes six to nine months. But ESCAPADE will now depart the Earth when Mars is more than 220 million miles away, on the opposite side of the Solar System.

The payload fairing of Blue Origin’s New Glenn rocket, containing NASA’s two Mars-bound science probes. Credit: Blue Origin

The most recent Mars launch window was last year, and the next one doesn’t come until the end of 2026. The planets are not currently in alignment, and the proverbial stars didn’t align to get the ESCAPADE satellites and their New Glenn rocket to the launch pad until this weekend.

This is fine

But there are several reasons this is perfectly OK to NASA. The New Glenn rocket is overkill for this mission. The two-stage launcher could send many tons of cargo to Mars, but NASA is only asking it to dispatch about a ton of payload, comprising a pair of identical science probes designed to study how the planet’s upper atmosphere interacts with the solar wind.

But NASA got a good deal from Blue Origin. The space agency is paying Jeff Bezos’ space company about $20 million for the launch, less than it would for a dedicated launch on any other rocket capable of sending the ESCAPADE mission to Mars. In exchange, NASA is accepting a greater than usual chance of a launch failure. This is, after all, just the second flight of the 321-foot-tall (98-meter) New Glenn rocket, which hasn’t yet been certified by NASA or the US Space Force.

The ESCAPADE mission, itself, was developed with a modest budget, at least by the standards of interplanetary exploration. The mission’s total cost amounts to less than $80 million, an order of magnitude lower than all of NASA’s recent Mars missions. NASA officials would not entrust the second flight of the New Glenn rocket to launch a billion-dollar spacecraft, but the risk calculation changes as costs go down.

NASA knew all of this in 2023 when it signed a launch contract with Blue Origin for the ESCAPADE mission. What officials didn’t know was that the New Glenn rocket wouldn’t be ready to fly when ESCAPADE needed to launch in late 2024. It turned out Blue Origin didn’t launch the first New Glenn test flight until January of this year. It was a success. It took another 10 months for engineers to get the second New Glenn vehicle to the launch pad.

The twin ESCAPADE spacecraft undergoing final preparations for launch. Each spacecraft is about a half-ton fully fueled. Credit: NASA/Kim Shiflett

Aiming high

That’s where the rocket sits this weekend at Cape Canaveral Space Force Station, Florida. If all goes according to plan, New Glenn will take off Sunday afternoon during an 88-minute launch window opening at 2: 45 pm EST (19: 45 UTC). There is a 65 percent chance of favorable weather, according to Blue Origin.

Blue Origin’s launch team, led by launch director Megan Lewis, will oversee the countdown Sunday. The rocket will be filled with super-cold liquid methane and liquid oxygen propellants beginning about four-and-a-half hours prior to liftoff. After some final technical and weather checks, the terminal countdown sequence will commence at T-minus 4 minutes, culminating in ignition of the rocket’s seven BE-4 main engines at T-minus 5.6 seconds.

The rocket’s flight computer will assess the health of each of the powerful engines, combining to generate more than 3.8 million pounds of thrust. If all looks good, hold-down restraints will release to allow the New Glenn rocket to begin its ascent from Florida’s Space Coast.

Heading east, the rocket will surpass the speed of sound in a little over a minute. After soaring through the stratosphere, New Glenn will shut down its seven booster engines and shed its first stage a little more than 3 minutes into the flight. Twin BE-3U engines, burning liquid hydrogen, will ignite to finish the job of sending the ESCAPADE satellites toward deep space. The rocket’s trajectory will send the satellites toward a gravitationally-stable location beyond the Moon, called the L2 Lagrange point, where it will swing into a loosely-bound loiter orbit to wait for the right time to head for Mars.

Meanwhile, the New Glenn booster, itself measuring nearly 20 stories tall, will begin maneuvers to head toward Blue Origin’s recovery ship floating a few hundred miles downrange in the Atlantic Ocean. The final part of the descent will include a landing burn using three of the BE-4 engines, then downshifting to a single engine to control the booster’s touchdown on the landing platform, dubbed “Jacklyn” in honor of Bezos’ late mother.

The launch timeline for New Glenn’s second mission. Credit: Blue Origin

New Glenn’s inaugural launch at the start of this year was a success, but the booster’s descent did not go well. The rocket was unable to restart its engines, and it crashed into the sea.

“We’ve incorporated a number of changes to our propellant management system, some minor hardware changes as well, to increase our likelihood of landing that booster on this mission,” said Laura Maginnis, Blue Origin’s vice president of New Glenn mission management. “That was the primary schedule driver that kind of took us from from January to where we are today.”

Blue Origin officials are hopeful they can land the booster this time. The company’s optimism is enough for officials to have penciled in a reflight of this particular booster on the very next New Glenn launch, slated for the early months of next year. That launch is due to send Blue Origin’s first Blue Moon cargo lander to the Moon.

“Our No. 1 objective is to deliver ESCAPADE safely and successfully on its way to L2, and then eventually on to Mars,” Maginnis said in a press conference Saturday. “We also are planning and wanting to land our booster. If we don’t land the booster, that’s OK. We have several more vehicles in production. We’re excited to see how the mission plays out tomorrow.”

Tracing a kidney bean

ESCAPADE’s path through space, relative to the Earth, has the peculiar shape of a kidney bean. In the world of astrodynamics, this is called a staging or libration orbit. It’s a way to keep the spacecraft on a stable trajectory to wait for the opportunity to go to Mars late next year.

“ESCAPADE has identified that this is the way that we want to fly, so we launch from Earth onto this kidney bean-shaped orbit,” said Jeff Parker, a mission designer from the Colorado-based company Advanced Space. “So, we can launch on virtually any day. What happens is that kidney bean just grows and shrinks based on how much time you need to spend in that orbit. So, we traverse that kidney bean and at the very end there’s a final little loop-the-loop that brings us down to Earth.”

That’s when the two ESCAPADE spacecraft, known as Blue and Gold, will pass a few hundred miles above our planet. At the right moment, on November 7 and 9 of next year, the satellites will fire their engines to set off for Mars.

An illustration of ESCAPADE’s trajectory to wait for the opportunity to go to Mars. Credit: UC-Berkeley

There are some tradeoffs with this unique staging orbit. It is riskier than the original plan of sending ESCAPADE straight to Mars. The satellites will be exposed to more radiation, and will consume more of their fuel just to get to the red planet, eating into reserves originally set aside for science observations.

The satellites were built by Rocket Lab, which designed them with extra propulsion capacity in order to accommodate launches on a variety of different rockets. In the end, NASA “judged that the risk for the mission was acceptable, but it certainly is higher risk,” said Richard French, Rocket Lab’s vice president of business development and strategy.

The upside of the tradeoff is it will demonstrate an “exciting and flexible way to get to Mars,” Lillis said. “In the future, if we’d like to send hundreds of spacecraft to Mars at once, it will be difficult to do that from just the launch pads we have on Earth within that month [of the interplanetary launch window]. We could potentially queue up spacecraft using the approach that ESCAPADE is pioneering.”

Stephen Clark is a space reporter at Ars Technica, covering private space companies and the world’s space agencies. Stephen writes about the nexus of technology, science, policy, and business on and off the planet.

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Scientists: It’s do or die time for America’s primacy exploring the Solar System

alan stern, congress, juno, NASA, nasa budget, New Horizons, planetary science, President Donald Trump, Science, scott bolton, solar system, Space, space policy, swri, White House / Rejus Almole / September 13, 2025

“When you turn off those spacecraft’s radio receivers, there’s no way to turn them back on.”

A life-size replica of the New Horizons spacecraft on display at the Smithsonian National Air and Space Museum’s Steven F. Udvar-Hazy Center near Washington Dulles International Airport in Northern Virginia. Credit: Johns Hopkins University Applied Physics Laboratory

Federal funding is about to run out for 19 active space missions studying Earth’s climate, exploring the Solar System, and probing mysteries of the Universe.

This year’s budget expires at the end of this month, and Congress must act before October 1 to avert a government shutdown. If Congress passes a budget before then, it will most likely be in the form of a continuing resolution, an extension of this year’s funding levels into the first few weeks or months of fiscal year 2026.

The White House’s budget request for fiscal year 2026 calls for a 25 percent cut to NASA’s overall budget, and a nearly 50 percent reduction in funding for the agency’s Science Mission Directorate. These cuts would cut off money for at least 41 missions, including 19 already in space and many more far along in development.

Normally, a president’s budget request isn’t the final say on matters. Lawmakers in the House and Senate have written their own budget bills in the last several months. There are differences between each appropriations bill, but they broadly reject most of the Trump administration’s proposed cuts.

Still, this hasn’t quelled the anxieties of anyone with a professional or layman’s interest in space science. The 19 active robotic missions chosen for cancellation are operating beyond their original design lifetime. However, in many cases, they are in pursuit of scientific data that no other mission has a chance of collecting for decades or longer.

A “tragic capitulation”

Some of the mission names are recognizable to anyone with a passing interest in NASA’s work. They include the agency’s two Orbiting Carbon Observatory missions monitoring data signatures related to climate change, the Chandra X-ray Observatory, which survived a budget scare last year, and two of NASA’s three active satellites orbiting Mars.

And there’s New Horizons, a spacecraft that made front-page headlines in 2015 when it beamed home the first up-close pictures of Pluto. Another mission on the chopping block is Juno, the world’s only spacecraft currently at Jupiter.

Both spacecraft have more to offer, according to the scientists leading the missions.

“New Horizons is perfectly healthy,” said Alan Stern, the mission’s principal investigator at Southwest Research Institute (SWRI). “Everything on the spacecraft is working. All the spacecraft subsystems are performing perfectly, as close to perfectly as one could ever hope. And all the instruments are, too. The spacecraft has the fuel and power to run into the late 2040s or maybe 2050.”

New Horizons is a decade and more than 2.5 billion miles (4.1 billion kilometers) beyond Pluto. The probe flew by a frozen object named Arrokoth on New Year’s Day 2019, returning images of the most distant world ever explored by a spacecraft. Since then, the mission has continued its speedy departure from the Solar System and could become the third spacecraft to return data from interstellar space.

Alan Stern, leader of NASA’s New Horizons mission, speaks during the Tencent WE Summit at Beijing Exhibition Theater on November 6, 2016, in China. Credit: Visual China Group via Getty Images

New Horizons cost taxpayers $780 million from the start of development through the end of its primary mission after exploring Pluto. The project received $9.7 million from NASA to cover operations costs in 2024, the most recent year with full budget data.

It’s unlikely New Horizons will be able to make another close flyby of an object like it did with Pluto and Arrokoth. But the science results keep rolling in. Just last year, scientists announced the news that New Horizons found the Kuiper Belt—a vast outer zone of hundreds of thousands of small, icy worlds beyond the orbit of Neptune—might extend much farther out than previously thought.

“We’re waiting for government, in the form of Congress, the administration, to come up with a funding bill for FY26, which will tell us if our mission is on the chopping block or not,” Stern said. “The administration’s proposal is to cancel essentially every extended mission … So, we’re not being singled out, but we would get caught in that.”

Stern, who served as head of NASA’s science division in 2007 and 2008, said the surest way to prevent the White House’s cuts is for Congress to pass a budget with specific instructions for the Trump administration.

“The administration ultimately will make some decision based on what Congress does,” Stern said. “If Congress passes a continuing resolution, then that opens a whole lot of other possibilities where the administration could do something without express direction from Congress. We’re just going to have to see where we end up at the end of September and then in the fall.”

Stern said shutting down so many of NASA’s science missions would be a “tragic capitulation of US leadership” and “fiscally irresponsible.”

“We’re pretty undeniably the frontrunner, and have been for decades, in space sciences,” Stern said. “There’s much more money in overruns than there is in what it costs to run these missions—I mean, dramatically. And yet, by cutting overruns, you don’t affect our leadership position. Turning off spacecraft would put us in third or fourth place, depending on who you talk to, behind the Chinese and the Europeans at least, and maybe behind others.”

Stern resigned his job as NASA’s science chief in 2008 after taking a similar stance arguing against cuts to healthy projects and research grants to cover overruns in other programs, according to a report in Science Magazine.

An unforeseen contribution from Juno

Juno, meanwhile, has been orbiting Jupiter since 2016, collecting information on the giant planet’s internal structure, magnetic field, and atmosphere.

“Everything is functional,” said Scott Bolton, the lead scientist on Juno, also from SWRI. “There’s been some degradation, things that we saw many years ago, but those haven’t changed. Actually, some of them improved, to be honest.”

The only caveat with Juno is some radiation damage to its camera, called JunoCam. Juno orbits Jupiter once every 33 days, and the trajectory brings the spacecraft through intense radiation belts trapped by the planet’s powerful magnetic field. Juno’s primary mission ended in 2021, and it’s now operating in an extended mission approved through the end of this month. The additional time exposed to harsh radiation is, not surprisingly, corrupting JunoCam’s images.

NASA’s Juno mission observed the glow from a bolt of lightning in this view from December 30, 2020, of a vortex near Jupiter’s north pole. Citizen scientist Kevin M. Gill processed the image from raw data from the JunoCam instrument aboard the spacecraft. Credit: NASA/JPL-Caltech/SwRI/MSSS Image processing by Kevin M. Gill © CC BY

In an interview with Ars, Bolton suggested the radiation issue creates another opportunity for NASA to learn from the Juno mission. Ground teams are attempting to repair the JunoCam imager through annealing, a self-healing process that involves heating the instrument’s electronics and then allowing them to cool. Engineers sparingly tried annealing hardware space, so Juno’s experience could be instructive for future missions.

“Even satellites at Earth experience this [radiation damage], but there’s very little done or known about it,” Bolton said. “In fact, what we’re learning with Juno has benefits for Earth satellites, both commercial and national security.”

Juno’s passages through Jupiter’s harsh radiation belts provide a real-world laboratory to experiment with annealing in space. “We can’t really produce the natural radiation environment at Earth or Jupiter in a lab,” Bolton said.

Lessons learned from Juno could soon be applied to NASA’s next probe traveling to Jupiter. Europa Clipper launched last year and is on course to enter orbit around Jupiter in 2030, when it will begin regular low-altitude flybys of the planet’s icy moon Europa. Before Clipper’s launch, engineers discovered a flaw that could make the spacecraft’s transistors more susceptible to radiation damage. NASA managers decided to proceed with the mission because they determined the damage could be repaired at Jupiter with annealing.

“So, we have rationale to hopefully continue Juno because of science, national security, and it sort of fits in the goals of exploration as well, because you have high radiation even in these translunar orbits [heading to the Moon],” Bolton said. “Learning about how to deal with that and how to build spacecraft better to survive that, and how to repair them, is really an interesting twist that we came by on accident, but nevertheless, turns out to be really important.”

It cost $28.4 million to operate Juno in 2024, compared to NASA’s $1.13 billion investment to build, launch, and fly the spacecraft to Jupiter.

On May 19, 2010, technicians oversee the installation of the large radiation vault onto NASA’s Juno spacecraft propulsion module. This protects the spacecraft’s vital flight and science computers from the harsh radiation at Jupiter. Credit: Lockheed Martin

“We’re hoping everything’s going to keep going,” Bolton said. “We put in a proposal for three years. The science is potentially very good. … But it’s sort of unknown. We just are waiting to hear and waiting for direction from NASA, and we’re watching all of the budget scenarios, just like everybody else, in the news.”

NASA headquarters earlier this year asked Stern and Bolton, along with teams leading other science missions coming under the ax, for an outline of what it would take and what it would cost to “close out” their projects. “We sent something that was that was a sketch of what it might look like,” Bolton said.

A “closeout” would be irreversible for at least some of the 19 missions at risk of termination.

“Termination doesn’t just mean shutting down the contract and sending everybody away, but it’s also turning the spacecraft off,” Stern said. “And when you turn off those spacecraft’s radio receivers, there’s no way to turn them back on because they’re off. They can never get a command in.

“So, if we change our mind, we’ve had another election, or had some congressional action, anything like that, it’s really terminating the spacecraft, and there’s no going back.”

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We saw the heart of Pluto 10 years ago—it’ll be a long wait to see the rest

Kuiper belt, NASA, New Horizons, planetary science, Pluto, Science, solar system, Space / Paul Patrick / July 15, 2025

A 50-year wait for a second mission wouldn’t be surprising. Just ask Uranus and Neptune.

Four images from New Horizons’ Long Range Reconnaissance Imager (LORRI) were combined with color data from the spacecraft’s Ralph instrument to create this enhanced color global view of Pluto. Credit: NASA/Johns Hopkins University/SWRI

NASA’s New Horizons spacecraft got a fleeting glimpse of Pluto 10 years ago, revealing a distant world with a picturesque landscape that, paradoxically, appears to be refreshing itself in the cold depths of our Solar System.

The mission answered numerous questions about Pluto that have lingered since its discovery by astronomer Clyde Tombaugh in 1930. As is often the case with planetary exploration, the results from New Horizons’ flyby of Pluto on July 14, 2015, posed countless more questions. First and foremost, how did such a dynamic world come to be so far from the Sun?

For at least the next few decades, the only resources available for scientists to try to answer these questions will be either the New Horizons mission’s archive of more than 50 gigabits of data recorded during the flyby, or observations from billions of miles away with powerful telescopes on the ground or space-based observatories like Hubble and James Webb.

That fact is becoming abundantly clear. Ten years after the New Horizons encounter, there are no missions on the books to go back to Pluto and no real prospects for one.

A mission spanning generations

In normal times, with a stable NASA budget, scientists might get a chance to start developing another Pluto mission in perhaps 10 or 20 years, after higher-priority missions like Mars Sample Return, a spacecraft to orbit Uranus, and a probe to orbit and land on Saturn’s icy moon Enceladus. In that scenario, perhaps a new mission could reach Pluto and enter orbit before the end of the 2050s.

But these aren’t normal times. The Trump administration has proposed cutting NASA’s science budget in half, jeopardizing not only future missions to explore the Solar System but also threatening to shut down numerous operating spacecraft, including New Horizons itself as it speeds through an uncharted section of the Kuiper Belt toward interstellar space.

The proposed cuts are sapping morale within NASA and the broader space science community. If implemented, the budget reductions would affect more than NASA’s actual missions. They would also slash NASA’s funding available for research, eliminating grants that could pay for scientists to analyze existing data stored in the New Horizons archive or telescopic observations to peer at Pluto from afar.

The White House maintains funding for newly launched missions like Europa Clipper and an exciting mission called Dragonfly to soar through the skies of Saturn’s moon Titan. Instead, the Trump administration’s proposed budget, which still must be approved by Congress, suggests a reluctance to fund new missions exploring anything beyond the Moon or Mars, where NASA would focus efforts on human exploration and bankroll an assortment of commercial projects.

NASA’s New Horizons spacecraft undergoing launch preparations at Kennedy Space Center, Florida, in September 2005. Credit: NASA

In this environment, it’s difficult to imagine the development of a new Pluto mission to begin any time in the next 20 years. Even if Congress or a future presidential administration restores NASA’s planetary science budget, a Pluto mission wouldn’t be near the top of the agency’s to-do list.

The National Academies’ most recent decadal survey prioritized Mars Sample Return, a Uranus orbiter, and an Enceladus “Orbilander” mission in their recommendations to NASA’s planetary science program through 2032. None of these missions has a realistic chance to launch by 2032, and it seems more likely than not that none of them will be in any kind of advanced stage of development by then.

The panel of scientists participating in the latest decadal survey—released in 2022—determined that a second mission to Pluto did not merit a technical risk and cost evaluation report, meaning it wasn’t even shortlisted for consideration as a science priority for NASA.

There’s a broad consensus in the scientific community that a follow-up mission to Pluto should be an orbiter, and not a second flyby. New Horizons zipped by Pluto at a relative velocity of nearly 31,000 mph (14 kilometers per second), flying as close as 7,750 miles (12,500 kilometers).

At that range and velocity, the spacecraft’s best camera was close enough to resolve something the size of a football field for less than an hour. Pluto was there, then it was gone. New Horizons only glimpsed half of Pluto at decent resolution, but what it saw revealed a heart-shaped sheet of frozen nitrogen and methane with scattered mountains of water ice, all floating on what scientists believe is likely a buried ocean of liquid water.

Pluto must harbor a wellspring of internal heat to keep from freezing solid, something researchers didn’t anticipate before the arrival of New Horizons.

New Horizons revealed Pluto as a mysterious world with icy mountains and very smooth plains. Credit: NASA

So, what is Pluto’s ocean like? How thick are Pluto’s ice sheets? Are any of Pluto’s suspected cryovolcanoes still active today? And, what secrets are hidden on the other half of Pluto?

These questions, and more, could be answered by an orbiter. Some of the scientists who worked on New Horizons have developed an outline for a conceptual mission to orbit Pluto. This mission, named Persephone for the wife of Pluto in classical mythology, hasn’t been submitted to NASA as a real proposal, but it’s worth illustrating the difficulties in not just reaching Pluto, but maneuvering into orbit around a dwarf planet so far from the Earth.

Nuclear is the answer

The initial outline for Persephone released in 2020 called for a launch in 2031 on NASA’s Space Launch System Block 2 rocket with an added Centaur kick stage. Again, this isn’t a realistic timeline for such an ambitious mission, and the rocket selected for this concept doesn’t exist. But if you assume Persephone could launch on a souped-up super heavy-lift SLS rocket in 2031, it would take more than 27 years for the spacecraft to reach Pluto before sliding into orbit in 2058.

Another concept study led by Alan Stern, also the principal investigator on the New Horizons mission, shows how a future Pluto orbiter could reach its destination by the late 2050s, assuming a launch on an SLS rocket around 2030. Stern’s concept, called the Gold Standard, would reserve enough propellant to leave Pluto and go on to fly by another more distant object.

Persephone and Gold Standard both assume a Pluto-bound spacecraft can get a gravitational boost from Jupiter. But Jupiter moves out of alignment from 2032 until the early 2040s, adding a decade or more to the travel time for any mission leaving Earth in those years.

It took nine years for New Horizons to make the trip from Earth to Pluto, but the spacecraft was significantly smaller than an orbiter would need to be. That’s because an orbiter has to carry enough power and fuel to slow down on approach to Pluto, allowing the dwarf planet’s weak gravity to capture it into orbit. A spacecraft traveling too fast, without enough fuel, would zoom past Pluto just like New Horizons.

The Persephone concept would use five nuclear radioisotope power generators and conventional electric thrusters, putting it within reach of existing technology. A 2020 white paper authored by John Casani, a longtime project manager at the Jet Propulsion Laboratory who died last month, showed the long-term promise of next-generation nuclear electric propulsion.

A relatively modest 10-kilowatt nuclear reactor to power electric thrusters would reduce the flight time to Pluto by 25 to 30 percent, while also providing enough electricity to power a radio transmitter to send science data back to Earth at a rate four times faster, according to the mission study report on the Persephone concept.

However, nuclear electric propulsion technologies are still early in the development phase, and Trump’s budget proposal also eliminates any funding for nuclear rocket research.

A concept for a nuclear electric propulsion system to power a spacecraft toward the outer Solar System. Credit: NASA/JPL-Caltech

A rocket like SpaceX’s Starship might eventually be capable of accelerating a probe into the outer Solar System, but detailed studies of Starship’s potential for a Pluto mission haven’t been published yet. A Starship-launched Pluto probe would have its own unique challenges, and it’s unclear whether it would have any advantages over nuclear electric propulsion.

How much would all of this cost? It’s anyone’s guess at this point. Scientists estimated the Persephone concept would cost $3 billion, excluding launch costs, which might cost $1 billion or more if a Pluto mission requires a bespoke launch solution. Development of a nuclear electric propulsion system would almost certainly cost billions of dollars, too.

All of this suggests 50 years or more might elapse between the first and second explorations of Pluto. That is in line with the span of time between the first flybys of Uranus and Neptune by NASA’s Voyager spacecraft in 1986 and 1989, and the earliest possible timeline for a mission to revisit those two ice giants.

So, it’s no surprise scientists are girding for a long wait—and perhaps taking a renewed interest in their own life expectancies—until they get a second look at one of the most seductive worlds in our Solar System.

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A new Martian climate model suggest a mostly cold, harsh environment

carbonates, climate model, Climate science, Curiosity rover, Mars, planetary science, rover, Science / Paul Patrick / July 13, 2025

“Very early in Mars’ history, maybe 4 billion years ago, the planet was warm enough to support lakes and river networks,” Kite told Ars. “There were seas, and some of those seas were as big as the Caspian Sea, maybe bigger. It was a wet place.” This wet period, though, didn’t last long—it was too short to make the landscape deeply weathered and deeply eroded.

Kite’s team used their model to focus on what happened as the planet got colder, when the era of salts started. “Big areas of snowmelts created huge salt flats, which eventually built up over time, accumulating into a thick sedimentary deposit Curiosity rover is currently exploring,” Kite said. But the era of salts did not mark the end of liquid water on the Martian surface.

Flickering habitability

The landscape turned arid, judging by Earth’s standards, roughly 3.5 billion years ago. “There were long periods when the planet was entirely dry,” Kite said. During these dry periods, Mars was almost as cold as it is today. But once in a while, small areas with liquid water appeared on the Martian surface like oases amidst an otherwise unwelcoming desert. It was a sterile planet with flickering, transient habitable spots with water coming from melted snow.

This rather bleak picture of the Martian landscape’s evolution makes questions about our chances for finding traces of life in there tricky.

“You can do a thought experiment where you take a cup of water from the Earth’s ocean and pour it into one of those transient lakes on Mars,” Kite said. “Some microbes in this cup of water would do fine in such conditions.” The bigger question, he thinks, is whether life could originate (rather than just survive) on ancient Mars. And, perhaps more critically, whether hypothetical life that originated even before the salts era, when the planet was warm and wet, could persist in the oases popping up in the Kite’s model.

The answer, sadly, is probably not.

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Testing a robot that could drill into Europa and Enceladus

astronomy, Enceladus, Europa, exobiology, icy moon, planetary science, Science, Space / Mike M. / May 31, 2025

We don’t currently have a mission to put it on, but NASA is making sure it’s ready.

Geysers on Saturn’s moon Enceladus Credit: NASA

Europa and Enceladus are two ocean moons that scientists have concluded have liquid water oceans underneath their outer icy shells. The Europa Clipper mission should reach Europa around April of 2030. If it collects data hinting at the moon’s potential habitability, robotic lander missions could be the only way to confirm if there’s really life in there or not.

To make these lander missions happen, NASA’s Jet Propulsion Laboratory team has been working on a robot that could handle the search for life and already tested it on the Matanuska Glacier in Alaska. “At this point this is a pretty mature concept,” says Kevin Hand, a planetary scientist at JPL who led this effort.

Into the unknown

There are only a few things we know for sure about conditions on the surface of Europa, and nearly all of them don’t bode well for lander missions. First, Europa is exposed to very harsh radiation, which is a problem for electronics. The window of visibility—when a potential robotic lander could contact Earth—lasts less than half of the 85 hours it takes for the moon to complete its day-night cycle due to the Europa-Jupiter orbit. So, for more than half the mission, the robot would need to fend for itself, with no human ground teams to get it out of trouble. The lander would also need to run on non-rechargeable batteries, because the vast distance to the Sun would make solar panels prohibitively massive.

And that’s just the beginning. Unlike on Mars, we don’t have any permanent orbiters around Europa that could provide a communication infrastructure, and we don’t have high-resolution imagery of the surface, which would make the landing particularly tricky. “We don’t know what Europa’s surface looks like at the centimeter to meter scale. Even with the Europa Clipper imagery, the highest resolution will be about half a meter per pixel across a few select regions,” Hand explains.

Because Europa has an extremely thin atmosphere that doesn’t provide any insulation, the temperatures on top of its ice shell are estimated to vary between minus-160° Celsius during the daytime maximum and minus-220° C during the night, which means the ice the lander would be there to sample is most likely hard as concrete. Hand’s team, building their robot, had to figure out a design that could deal with all these issues.

The work on the robotic system for the Europa lander mission began more than 10 years ago. Back then, the 2013–2022 decadal strategy for planetary science cited the Europa Clipper as the second-highest priority large-scale planetary mission, so a lander seemed like a natural follow-up.

Autonomy and ice drilling

The robot developed by Hand’s team has legs that enable it to stabilize itself on various types of surfaces, from rock-hard ice to loose, soft snow. To orient itself in the environment, it uses a stereoscopic camera with an LED light source for illumination hooked to computer-vision algorithms—a system similar to the one currently used by the Perseverance rover on Mars. “Stereoscopic cameras can triangulate points in an image and build a digital surface topography model,” explains Joseph Bowkett, a JPL researcher and engineer who worked on the robot’s design.

The team built an entirely new robotic arm with seven degrees of freedom. Force torque sensors installed in most of its joints act a bit like a nervous system, informing the robot when key components sustain excessive loads to prevent it from damaging the arm or the drill. “As we press down on the surface [and] conduct drilling and sampling, we can measure the forces and react accordingly,” Bowkett says. The finishing touch was the ICEPICK, a drilling and sampling tool the robot uses to excavate samples from the ice up to 20 centimeters deep.

Because of long periods the lander would need operate without any human supervision, the team also gave it a wide range of autonomous systems, which operate at two different levels. High-level autonomy is responsible for scheduling and prioritizing tasks within a limited energy budget. The robot can drill into a sampling site, analyze samples with onboard instruments, and decide whether it makes sense to keep drilling at the same spot or choose a different sampling site. The high-level system is also tasked with choosing the most important results for downlink back to Earth.

Low-level autonomy breaks all these high-level tasks down into step-by-step decisions on how to operate the drill and how to move the arm in the safest and most energy-efficient way.

The robot was tested in simulation software first, then indoors at JPL’s facilities, and finally at the Matanuska Glacier in Alaska, where it was lowered from a helicopter that acted as a proxy for a landing vehicle. It was tested at three different sites, ranked from the easiest to the most challenging. It completed all the baseline activities as well as all of the extras. The latter included a task like drilling 27 centimeters deep into ice at the most difficult site, where it was awkwardly positioned on an eight-to-12-degree slope. The robot passed all the tests with flying colors.

And then it got shelved.

Switching the ocean worlds

Hand’s team put their Europa landing robot through the Alaskan field test campaign between July and August 2022. But when the new decadal strategy for planetary science came out in 2023, it turned out that the Europa lander was not among the missions selected. The National Academies committee responsible for formulating these decadal strategies did not recommend giving it a go, mainly because they believed harsh radiation in the Jovian system would make detecting biosignatures “challenging” for a lander.

An Enceladus lander, on the other hand, remained firmly on the table. “I was also on the team developing EELS, a robot intended for a potential Enceladus mission, so thankfully I can speak about both. The radiation challenges are indeed far greater for Europa,” Bowkett says.

Another argument for changing our go-to ocean world is that water plumes containing salts along with carbon- and nitrogen-bearing molecules have already been observed on Enceladus, which means there is a slight chance biosignatures could be detected by a flyby mission. The surface of Enceladus, according to the decadal strategy document, should be capable of preserving biogenic evidence for a long time and seems more conducive to a lander mission. “Luckily, many of the lessons on how to conduct autonomous sampling on Europa, we believe, will transfer to Enceladus, with the benefit of a less damaging radiation environment,” Bowkett told Ars.

The dream of a Europa landing is not completely dead, though. “I would love to get into the Europa’s ocean with a submersible and further down to the seafloor. I would love for that to happen,” Hand says. “But technologically it’s quite a big leap, and you always have to balance your dream missions with the number of technological miracles that need to be solved to make these missions possible.”

Science Robotics, 2025. DOI: 10.1126/scirobotics.adi5582

Jacek Krywko is a freelance science and technology writer who covers space exploration, artificial intelligence research, computer science, and all sorts of engineering wizardry.

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NASA’s Psyche spacecraft hits a speed bump on the way to a metal asteroid

asteroid, electric propulsion, jet propulsion laboratory, Maxar, NASA, planetary science, psyche, Science, solar system, Space / Rejus Almole / May 1, 2025

An illustration depicts a NASA spacecraft approaching the metal-rich asteroid Psyche. Though there are no plans to mine Psyche, such asteroids are being eyed for their valuable resources. Credit: NASA/JPL-Caltech/ASU

Each electric thruster on Psyche generates just 250 milli-newtons of thrust, roughly equivalent to the weight of three quarters. But they can operate for months at a time, and over the course of a multi-year cruise, these thrusters provide a more efficient means of propulsion than conventional rockets.

The plasma thrusters are reshaping the Psyche spacecraft’s path toward its destination, a metal-rich asteroid also named Psyche. The spacecraft’s four electric engines, known as Hall effect thrusters, were supplied by a Russian company named Fakel. Most of the other components in Psyche’s propulsion system—controllers, xenon fuel tanks, propellant lines, and valves—come from other companies or the spacecraft’s primary manufacturer, Maxar Space Systems in California.

The Psyche mission is heading first for Mars, where the spacecraft will use the planet’s gravity next year to slingshot itself into the asteroid belt, setting up for arrival and orbit insertion around the asteroid Psyche in August 2029.

Psyche launched in October 2023 aboard a SpaceX Falcon Heavy rocket on the opening leg of a six-year sojourn through the Solar System. The mission’s total cost adds up to more than $1.4 billion, including development of the spacecraft and its instruments, the launch, operations, and an experimental laser communications package hitching a ride to deep space with Psyche.

Psyche, the asteroid, is the size of Massachusetts and circles the Sun in between the orbits of Mars and Jupiter. No spacecraft has visited Psyche before. Of the approximately 1 million asteroids discovered so far, scientists say only nine have a metal-rich signature like Psyche. The team of scientists who put together the Psyche mission have little idea of what to expect when the spacecraft gets there in 2029.

Metallic asteroids like Psyche are a mystery. Most of Psyche’s properties are unknown other than estimates of its density and composition. Predictions about the the look of Psyche’s craters, cliffs, and color have inspired artists to create a cacophony of illustrations, often showing sharp spikes and grooves alien to rocky worlds.

In a little more than five years, assuming NASA gets past Psyche’s propulsion problem, scientists will supplant speculation with solid data.

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Mars’ polar ice cap is slowly pushing its north pole inward

geology, Insight, Mars, mars quakes, planetary science, polar ice cap, Science / Rejus Almole / March 1, 2025

The orbiters that carried the radar hardware, along with one or two others, have been orbiting long enough that any major changes in Mars’ gravity caused by ice accumulation or crustal displacement would have shown up in their orbital behavior. The orbital changes they do see, “indicates that the increase in the gravitational potential associated with long-term ice accumulation is higher than the decrease in gravitational potential from downward deflection.” They calculate that the deformation has to be less than 0.13 millimeters per year to be consistent with the gravitational signal.

Finally, the model had to have realistic conditions at the polar ice cap, with a density consistent with a mixture of ice and dust.

Out of those 84 models, only three were consistent with all of these constraints. All three had a very viscous Martian interior, consistent with a relatively cold interior. That’s not a surprise, given what we’ve already inferred about Mars’ history. But it also suggests that most of the radioactive elements that provide heat to the red planet are in the crust, rather than deeper in the interior. That’s something we might have been able to check, had InSight’s temperature measurement experiment deployed correctly. But as it is, we’ll have to wait until some unidentified future mission to get a picture of Mars’ heat dynamics.

In any case, the models also suggest that Mars’ polar ice cap is less than 10 million years old, consistent with the orbitally driven climate models.

In a lot of ways, the new information is an update of earlier attempts to model the Martian interior, given a few more years of orbital data and the information gained from the InSight lander, which also determined the thickness of Mars’ crust and size of its core. But it’s also a good way of understanding how scientists can take bits and pieces of information from seemingly unrelated sources and build them into a coherent picture.

Nature, 2025. DOI: 10.1038/s41586-024-08565-9 (About DOIs).

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Don’t panic, but an asteroid has a 1.9% chance of hitting Earth in 2032

asteroids, NASA, near earth object, planetary science, Science, solar system, Space / Mike M. / February 6, 2025

More data will likely reduce the chance of an impact to zero. If not, we have options.

Discovery images of asteroid 2024 YR4. Credit: ATLAS

Something in the sky captured the attention of astronomers in the final days of 2024. A telescope in Chile scanning the night sky detected a faint point of light, and it didn’t correspond to any of the thousands of known stars, comets, and asteroids in astronomers’ all-sky catalog.

The detection on December 27 came from one of a network of telescopes managed by the Asteroid Terrestrial-impact Last Alert System (ATLAS), a NASA-funded project to provide warning of asteroids on a collision course with Earth.

Within a few days, scientists gathered enough information on the asteroid—officially designated 2024 YR4—to determine that its orbit will bring it quite close to Earth in 2028, and then again in 2032. Astronomers ruled out any chance of an impact with Earth in 2028, but there’s a small chance the asteroid might hit our planet on December 22, 2032.

How small? The probability has fluctuated in recent days, but as of Thursday, NASA’s Center for Near Earth Object Studies estimated a 1.9 percent chance of an impact with Earth in 2032. The European Space Agency (ESA) put the probability at 1.8 percent. So as of now, NASA believes there’s a 1-in-53 chance of 2024 YR4 striking Earth. That’s about twice as likely as the lifetime risk of dying in a motor vehicle crash, according to the National Safety Council.

These numbers are slightly higher than the probabilities published last month, when ESA estimated a 1.2 percent chance of an impact. In a matter of weeks or months, the number will likely drop to zero.

No surprise here, according to ESA.

“It is important to remember that an asteroid’s impact probability often rises at first before quickly dropping to zero after additional observations,” ESA said in a press release. The agency released a short explainer video, embedded below, showing how an asteroid’s cone of uncertainty shrinks as scientists get a better idea of its trajectory.

Refining the risk

Scientists estimate that 2024 YR4 is between 130 to 300 feet (40 and 90 meters) wide, large enough to cause localized devastation near the impact site. The asteroid responsible for the Tunguska event of 1908, which leveled some 500 square miles (1,287 square kilometers) of forest in remote Siberia, was probably about the same size. The meteor that broke apart in the sky over Chelyabinsk, Russia, in 2013 was about 20 meters wide.

Astronomers use the Torino scale for measuring the risk of potential asteroid impacts. Asteroid 2024 YR4 is now rated at Level 3 on this scale, meaning it merits close attention from astronomers, the public, and government officials. This is the second time an asteroid has reached this level since the scale’s adoption in 1999. The other case happened in 2004, when asteroid Apophis briefly reached a Level 4 rating until further observations of the asteroid eliminated any chance of an impact with the Earth in 2029.

In the unlikely event that it impacts the Earth, an asteroid the size of 2024 YR4 could cause blast damage as far as 30 miles (50 kilometers) from the location of the impact or airburst if the object breaks apart in the atmosphere, according to the International Asteroid Warning Network (IAWN), established in the aftermath of the Chelyabinsk event.

The asteroid warning network is affiliated with the United Nations. Officials activate the IAWN when an asteroid bigger than 10 meters has a greater than 1 percent chance of striking Earth within the next 20 years. The risk of 2024 YR4 meets this threshold.

The red points on this image show the possible locations of asteroid 2024 YR4 on December 22, 2032, as projected by a Monte Carlo simulation. As this image shows, most of the simulations project the asteroid missing the Earth. Credit: ESA/Planetary Defense Office

Determining the asteroid’s exact size will be difficult. Scientists would need deep space radar observations, thermal infrared observations, or imagery from a spacecraft that could closely approach the asteroid, according to the IAWN. The asteroid won’t come close enough to Earth for deep space radar observations until shortly before its closest approach in 2032.

Astronomers need numerous observations to precisely plot an asteroid’s motion through the Solar System. Over time, these observations will reduce uncertainty and narrow the corridor the asteroid will follow as it comes near Earth.

Scientists already know a little about asteroid 2024 YR4’s orbit, which follows an elliptical path around the Sun. The orbit brings the asteroid inside of Earth’s orbit at its closest point to the Sun and then into the outer part of the asteroid belt when it is farthest from the Sun.

But there’s a complication in astronomers’ attempts to nail down the asteroid’s path. The object is currently moving away from Earth in almost a straight line. This makes it difficult to accurately determine its orbit by studying how its trajectory curves over time, according to ESA.

It also means observers will need to use larger telescopes to see the asteroid before it becomes too distant to see it from Earth in April. By the end of this year’s observing window, the asteroid warning network says the impact probability could increase to a couple tens of percent, or it could more likely drop back below the notification threshold (1 percent impact probability).

“It is possible that asteroid 2024 YR4 will fade from view before we are able to entirely rule out any chance of impact in 2032,” ESA said. “In this case, the asteroid will likely remain on ESA’s risk list until it becomes observable again in 2028.”

Planetary defenders

This means that public officials might need to start planning what to do later this year.

For the first time, an international board called the Space Mission Planning Advisory Group met this week to discuss what we can do to respond to the risk of an asteroid impact. This group, known as SMPAG, coordinates planning among representatives from the world’s space agencies, including NASA, ESA, China, and Russia.

The group decided on Monday to give astronomers a few more months to refine their estimates of the asteroid’s orbit before taking action. They will meet again in late April or early May or earlier if the impact risk increases significantly. If there’s still a greater than 1 percent probability of 2024 YR4 hitting the Earth, the group will issue a recommendation for further action to the United Nations Office for Outer Space Affairs.

So what are the options? If the data in a few months still shows that the asteroid poses a hazard to Earth, it will be time for the world’s space agencies to consider a deflection mission. NASA demonstrated its ability to alter the orbit of an asteroid in 2022 with a first-of-its-kind experiment in space. The mission, called DART, put a small spacecraft on a collision course with an asteroid two to four times larger than 2024 YR4.

The kinetic energy from the spacecraft’s death dive into the asteroid was enough to slightly nudge the object off its natural orbit around a nearby larger asteroid. This proved that an asteroid deflection mission could work if scientists have enough time to design and build it, an undertaking that took about five years for DART.

Italy’s LICIACube spacecraft snapped this image of asteroids Didymos (lower left) and Dimorphos (upper right) a few minutes after the impact of DART on September 26, 2022. Credit: ASI/NASA

A deflection mission is most effective well ahead of an asteroid’s potential encounter with the Earth, so it’s important not to wait until the last minute.

Fans of Hollywood movies know there’s a nuclear option for dealing with an asteroid coming toward us. The drawback of using a nuclear warhead is that it could shatter one large asteroid into many smaller objects, although recent research suggests a more distant nuclear explosion could produce enough X-ray radiation to push an asteroid off a collision course.

Waiting for additional observations in 2028 would leave little time to develop a deflection mission. Therefore, in the unlikely event that the risk of an impact rises over the next few months, it will be time for officials to start seriously considering the possibility of an intervention.

Even without a deflection, there’s plenty of time for government officials to do something here on Earth. It should be possible for authorities to evacuate any populations that might be affected by the asteroid.

The asteroid could devastate an area the size of a large city, but any impact is most likely to happen in a remote region or in the ocean. The risk corridor for 2024 YR4 extends from the eastern Pacific Ocean to northern South America, the Atlantic Ocean, Africa, the Arabian Sea, and South Asia.

There’s an old joke that dinosaurs went extinct because they didn’t have a space program. Whatever happens in 2032, we’re not at risk of extinction. However, occasions like this are exactly why most Americans think we should have a space program. A 2019 poll showed that 68 percent of Americans considered it very or extremely important for the space program to monitor asteroids, comets, or other objects from space that could strike the planet.

In contrast, about a quarter of those polled placed such importance on returning astronauts to the Moon or sending people to Mars. The cost of monitoring and deflecting asteroids is modest compared to the expensive undertakings of human missions to the Moon and Mars.

From taxpayers’ point of view, it seems this part of NASA offers the greatest bang for their buck.

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Edge of Mars’ great dichotomy eroded back by hundreds of kilometers

erosion, geology, Mars, oceans, planetary science, Science / Paul Patrick / January 20, 2025

A shoreline transformed?

The huge area covered by these mounds gives a sense of just how significant this erosion was. “The dichotomy boundary has receded several hundred kilometres,” the researchers note. “Nearly all intervening material—approximately 57,000 cubic kilometers over an area of 284,000 square kilometers west of Ares Vallis alone—has been removed, leaving only remnant mounds.”

Based on the distribution of the different clays, the team argues that their water-driven formation took place before the erosion of the material. This would indicate that water-rock interactions were going on over a very wide region early in the history of Mars, which likely required an extensive hydrological cycle on the red planet. As the researchers note, a nearby ocean would have improved the chances of exposing this region to water, but the exposure could also have been due to processes like melting at the base of an ice cap.

Complicating matters further, many of the mounds top out below one proposed shoreline of the northern ocean and above a second. It’s possible that a receding ocean could have contributed to their erosion. But, at the same time, some of the features of a proposed shoreline now appear to have been caused by the general erosion of the original plateau, and may not be associated with an ocean at all.

Overall, the new results provide mixed evidence for the presence of a Martian ocean. They clearly show an active water cycle and erosion on a massive scale, which are both consistent with having a lot of water around. At the same time, however, the water exposure the mesas and buttes have experienced needn’t have come through their being submerged by said ocean and, given their elevation, might best be explained through some other process.

Nature Geoscience, 2019. DOI: 10.1038/s41561-024-01634-8 (About DOIs).

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