A truly all-terrain rover on the moon or Mars may need to put a little wiggle in its walk. Wheeled rovers have trouble crossing the soft soil that covers large swaths of lunar and Martian terrain. NASA’s Spirit rover, for example, met its end after getting stuck in a sand trap on Mars in 2009 […] More

The sun could come from a large, loose-knit clan or a small family that’s always fighting.
New computer simulations of young stars suggest two pathways to forming the solar system. The sun could have formed in a calm, large association of 10,000 stars or more, like NGC 2244 in the present-day Rosette Nebula, an idea that’s consistent with previous research. Or the sun could be from a violent, compact cluster with about 1,000 stars, like the Pleiades, researchers report July 2 in the Astrophysical Journal.Whether a star forms in a tight, rowdy cluster or a loose association can influence its future prospects. If a star is born surrounded by lots of massive siblings that explode as supernovas before a cluster spreads out, for example, that star will have more heavy elements to build planets with (SN: 8/9/19).
To nail down a stellar birthplace, astronomers have considered the solar system’s chemistry, its shape and many other factors. Most astronomers who study the sun’s birthplace think the gentle, large association scenario is most likely, says astrophysicist Fred Adams of the University of Michigan in Ann Arbor, who was not involved in the new work.
But most previous studies didn’t include stars’ motions over time. So astrophysicists Susanne Pfalzner and Kirsten Vincke, both of the Max Planck Institute for Radio Astronomy in Bonn, Germany, ran thousands of computer simulations to see how often different kinds of young stellar families produce solar systems like ours.

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The main solar system feature that the pair looked for was the distance to the farthest planet from the star. Planet-forming disks can extend to hundreds of astronomical units, or AU, the distance between the Earth and the sun (SN: 7/16/19). Theoretically, planets should be able to form all the way to the edge. But the sun’s planetary material is mostly packed within the orbit of Neptune.
“You have a steep drop at 30 AU, where Neptune is,” Pfalzner says. “And this is not what you expect from a disk.”
In 2018, Pfalzner and her colleagues showed that a passing star could have truncated and warped the solar system’s outer edge long ago. If that’s what happened, it could help point to the sun’s birth environment, Pfalzner reasoned. The key was to simulate groupings dense enough that stellar flybys happen regularly, but not so dense that the encounters happen too often and destroy disks before planets can grow up.
“We were hoping we’d get one answer,” Pfalzner says. “It turned out there are two possibilities.” And they are wildly different from each other.
Large associations have more stars, but the stars are more spread out and generally leave each other alone. Those associations can stay together for up to 100 million years. Compact clusters, on the other hand, see more violent encounters between young stars and don’t last as long. The stars shove each other away within a few million years.
“This paper opens up another channel for what the sun’s birth environment looked like,” Adams says, referring to the violent cluster notion.
The new study doesn’t cover every aspect of how a tight cluster could have affected the nascent solar system. The findings don’t account for how radiation from other stars in the cluster could erode planet-forming disks, for example, which could have shrunk the sun’s disk or even prevented the solar system from forming. The study also doesn’t explain certain heavy elements found in meteorites, which are thought to come from a nearby supernova and so could require the sun come from a long-lived stellar family.
“I think [the research] is an interesting addition to the debate,” Adams says. “It remains to be seen how the pieces of the puzzle fit together.”
Pfalzner thinks that the star cluster would break apart before radiation made a big difference, and there are other explanations for the heavy elements apart from a single supernova. She hopes future studies will be able to use that sort of cosmic chemistry to narrow the sun’s birthplace down even further.
“For us humans, this is an important question,” Pfalzner says. “It’s part of our history.” More

Mars’ water is being skimmed off the top. NASA’S MAVEN spacecraft found water lofted into Mars’ upper atmosphere, where its hydrogen and oxygen atoms are ripped apart, scientists report in the Nov. 13 Science.
“This completely changes how we thought hydrogen, in particular, was being lost to space,” says planetary chemist Shane Stone of the University of Arizona in Tucson.
Mars’ surface was shaped by flowing water, but today the planet is an arid desert (SN: 12/8/14). Previously, scientists thought that Mars’ water was lost in a “slow and steady trickle,” as sunlight split water in the lower atmosphere and hydrogen gradually diffused upward, Stone says.
But MAVEN, which has been orbiting Mars since 2014, scooped up water molecules in Mars’ ionosphere, at altitudes of about 150 kilometers. That was surprising — previously the highest water had been seen was about 80 kilometers (SN: 1/22/18).
That high-up water varied in concentration as the seasons changed on Mars, with the peak in the southern summer, when seasonal dust storms are most frequent (SN: 7/14/20). During a global dust storm in 2018, water levels jumped even higher, suggesting dust storms lift water in a “sudden splash,” Stone says.
The top of Mars’ atmosphere is full of charged molecules that are primed for rapid chemical reactions, especially with water. So water up there is split apart quickly, on average lasting only four hours, leaving hydrogen atoms to float away (SN: 11/27/15). That process is 10 times faster than previously known ways for Mars to lose water, Stone and his colleagues calculated.
This process could account for Mars losing the equivalent of a 44-centimeter-deep global ocean in the past billion years, plus another 17-centimeter-deep ocean during each global dust storm, the team found. That can’t explain all of Mars’ water loss, but it’s a start. More

This is what it looks like to land on Mars.
NASA’s Perseverance rover took this video on February 18 as a jetpack lowered it onto the Red Planet’s surface.
“It gives me goosebumps every time I see it,” said engineer David Gruel of NASA’s Jet Propulsion Laboratory in Pasadena, Calif., at a news briefing on February 22.
The movie begins with the rover’s parachute opening above it as the rover and its landing gear enter the Martian atmosphere. Seconds later, a camera on the rover’s underside shows the heat shield falling toward the ground. If you look carefully, you can see one of the springs that pushed the heat shield off the rover came loose, said NASA engineer Allen Chen, the rover’s entry, descent and landing lead.
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NASA’s Perseverance rover captured video of its own landing using a set of cameras on the back of the entry vehicle, the sky crane and the rover itself.
“There’s no danger to the spacecraft here, but it’s something we didn’t expect, and wouldn’t have seen” without the videos, he said.
The rover filmed the ground coming closer and closer, getting glimpses of a river delta, craters, ripples and fractured terrain. Cameras on the top and bottom of the rover captured clouds of dust billowing as the rover’s jetpack, the sky crane, lowered it down to the ground on three cables. A camera on the sky crane showed the rover swinging slightly as it descended. Finally, the sky crane disconnected the cables and flew away, leaving Perseverance to begin its mission.
“It’s hard to express how emotional it was and how exciting it was to everybody” to see the movie for the first time, said deputy project manager Matt Wallace. “Every time we got something, people were overjoyed, giddy. They were like kids in a candy store.”
The movie looks so much like animations of the sky crane landing technique that NASA had released in the past that it almost doesn’t look real, says imaging scientist Justin Maki. “I can attest to, it’s real,” he says. “It’s stunning and it’s real.”

The rover also captured audio from the surface of the Red Planet for the first time, including a gust of Martian wind.
Perseverance landed in an ancient lakebed called Jezero crater, about two kilometers from what looks like an ancient river delta feeding into the crater (SN: 2/18/21). The rover’s primary mission is to search for signs of past life and to cache rock samples for a future mission to return to Earth.
The first images Perseverance sent back from Mars showed its wheels on a flat expanse. The ground is strewn with rocks that are shot through with holes, said deputy project scientist Katie Stack Morgan in a news briefing on February 19.
“Depending on the origins of the rocks, these holes could mean different things,” she said. The science team thinks the holes could be from gases escaping volcanic rock as lava cooled, or from fluid moving through the rock and dissolving it away. “Both would be equally exciting for the team.”

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Past observations have suggested that there’s water on the moon. New telescope observations conclude that those findings hold water.
Spacecraft have seen evidence of water ice in permanently shadowed craters at the lunar poles (SN: 5/9/16), as well as hints of water molecules on the sunlit surface (SN: 9/23/09). But water sightings in sunlit regions have relied on detection of infrared light at a wavelength that could also be emitted by other hydroxyl compounds, which contain hydrogen and oxygen. 
Now, the Stratospheric Observatory for Infrared Astronomy, or SOFIA, has detected an infrared signal unique to water near the lunar south pole, researchers report online October 26 in Nature Astronomy. “This is the first unambiguous detection of molecular water on the sunlit moon,” says study coauthor Casey Honniball, a lunar scientist at NASA’s Goddard Space Flight Center in Greenbelt, Md. “This shows that water is not just in the permanently shadowed regions — that there are other places on the moon that we could potentially find it.”
These observations could inform future missions to the moon that will scout out lunar water as a potential resource for human visitors (SN: 12/16/19).

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SOFIA, operated by NASA and the German Aerospace Center, is a 2.5-meter telescope that rides aboard a jumbo jet to get clear views of the sky (SN: 2/17/16). During a flight in August 2018, the telescope detected 6-micrometer infrared light emanating from a region near the moon’s southern Clavius crater. This wavelength of light is generated by the vibrations of sunlight-heated water molecules, but not other compounds containing hydroxyl, which consists of an oxygen atom bound to a hydrogen atom.
“I thought it was really brilliant” to confirm the presence of water on the moon with observations at this wavelength, says Jessica Sunshine, a planetary scientist at the University of Maryland in College Park. Sunshine was involved in past observations that spotted hints of water on the moon, but was not involved in the new study.
Based on the brightness of the observed infrared light, Honniball’s team calculated a water concentration of about 100 to 400 parts per million around the Clavius crater. That’s less than half a liter of water per metric ton of lunar soil. This concentration was about what the researchers expected, based on past spacecraft observations.
These water molecules are not frozen in ice, like the water in permanently shadowed regions of the moon. Nor is it liquid, Sunshine says. “There’s no moon puddles.” Instead, the water molecules are thought to be bound inside some other material on the lunar surface.
“The only way for us to be seeing water on the [sunlit] moon is if it is sheltered from this harsh environment,” Honniball says. These water molecules could be encased in glass forged by micrometeorite impacts, or wedged between soil grains that shield the water from blistering solar radiation.
Water could have formed on the moon itself, from hydrogen ions in the continual outward flow of charged particles from the sun reacting with oxygen on the surface (SN: 10/6/14). Or, if the water is stored in impact glass, it could have been delivered to the moon by micrometeorites. More