Eliana Willis

NASA’s OSIRIS-REx spacecraft is a cosmic rock collector. Cheers erupted from mission control at 6:12 p.m. EDT on October 20 as scientists on Earth got word that the spacecraft had gently nudged a near-Earth asteroid called Bennu, and grabbed some of its rocks to return to Earth.
“The spacecraft did everything it was supposed to do,” said mission principal investigator Dante Lauretta of the University of Arizona in Tucson on a NASA TV webcast. “I can’t believe we actually pulled this off.”
OSIRIS-REx arrived at Bennu in December 2018, and spent almost two years making detailed maps of the 500-meter-wide asteroid’s surface features and composition (SN: 10/8/20). Observations from Earth suggested Bennu should be smooth and sandy, but when OSIRIS-REx arrived, it found a treacherous, rocky landscape.
The team selected a relatively smooth patch in a crater named Nightingale. The spot was not without hazards, though — the team was so worried about a particularly large rock nearby that they named it “Mount Doom” (SN: 12/12/19).

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Luckily, the spacecraft did not need to fully land in the crater to complete its mission. As it hovered just above the surface, OSIRIS-REx reached out a robotic arm with an instrument called TAGSAM at the end, for Touch-And-Go Sample Acquisition Mechanism. The instrument tapped the asteroid lightly for several seconds, and released a burst of nitrogen gas to disturb the surface dust and pebbles. Once those small rocks were lofted, some hopefully were blown into the sample collector.
Because signals from Earth took 18½ minutes to reach Bennu, the spacecraft performed the sampling sequence autonomously. When the mission team got the signal that the spacecraft had finished its job and retreated to a safe distance from Bennu, team members pumped their arms in the air, cheered and sent each other socially distant high-fives and hugs.
OSIRIS-REx is not the first spacecraft to grab samples from an asteroid. That distinction goes to Japan’s Hayabusa mission, which brought back grains of asteroid Itokawa in 2010 (SN: 6/14/10). An encore to that mission, Hayabusa2, collected samples of asteroid Ryugu last year, and is on track to land in Australia in December (SN: 2/22/19).
But OSIRIS-REx attempted to collect much more material than Hayabusa2 did. Hayabusa2 hoped to collect 100 milligrams; OSIRIS-REx is aiming for a minimum of 60 grams, or a little more than two ounces.
Hayabusa2’s scientists have no way to know how much material it actually collected until the spacecraft returns to Earth. But OSIRIS-REx’s team plans to find out using the spacecraft itself. On October 24, the spacecraft will extend its arm and spin its whole body. The difference in the way it spins before and after the sample collection will reveal the mass of the sample.
OSIRIS-REx will return to Earth in 2023, where scientists will analyze the rocks in hopes of unlocking details of the history of the solar system and the origins of water and life on Earth (SN: 1/15/19). More

Fresh intel from Mars is sure to stir debate about whether liquid water lurks beneath the planet’s polar ice.
New data from a probe orbiting Mars appear to bolster a claim from 2018 that a lake sits roughly 1.5 kilometers beneath ice near the south pole (SN: 8/18/18). An analysis of the additional data, by some of the same researchers who reported the lake’s discovery, also hint at several more pools encircling the main reservoir, a study released online September 28 in Nature Astronomy claims.
If it exists, the central lake spans roughly 600 square kilometers. To keep from freezing, the water would have to be extremely salty, possibly making it similar to subglacial lakes in Antarctica. “This area is the closest thing to ‘habitable’ on Mars that has been found so far,” says Roberto Orosei, a planetary scientist at the National Institute for Astrophysics in Bologna, Italy, who also led the 2018 report.
Ali Bramson, a planetary scientist at Purdue University in West Lafayette, Ind., agrees “something funky is going on at this location.” But, she says, “there are some limitations to the instrument and the data…. I don’t know if it’s totally a slam dunk yet.”

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Orosei and colleagues probed the ice using radar on board the European Space Agency’s Mars Express orbiter. Short bursts of radio waves reflect off the ice, but some penetrate deeper and bounce off the bottom of the ice, sending back a second echo. The brightness and sharpness of that second reflection can reveal details about the underlying terrain.
The possible lake was originally found using radar data collected from May 2012 to December 2015. Now, in data collected from 2010 to 2019, the team once again found regions beneath the ice that are highly reflective and very flat. They say their findings not only confirm earlier hints of a large buried lake but also unearth a handful of smaller ponds encircling the main body of water and separated by strips of dry land.
“On Earth, there would be no debate” that a bright, flat radar reflection would be liquid water, Orosei says. These same analysis techniques have been used closer to home to map subglacial lakes in Antarctica and Greenland.
While much about these putative ponds remains unknown, one thing is certain: This new report is bound to spark controversy. “The community is very polarized,” says Isaac Smith, a planetary scientist with the Planetary Science Institute who is based in Ontario, Canada. “I’m in the camp that leans towards believing it,” he adds. “They’ve done their homework.”
One question centers on how water could stay liquid. “There’s no way to get liquid water warm enough even with throwing in a bunch of salts,” says planetary scientist Michael Sori, also at Purdue.
In 2019, he and Bramson calculated that the ice temperature — about –70° Celsius — is too cold even for salts to melt. They argue some local source of geothermal heat is needed, such as a magma chamber beneath the surface, to maintain a lake. That in turn has led to other questions about whether contemporary Mars could supply the necessary heat.
Smith — as well as the paper’s authors — thinks this isn’t a problem. As recently as 50,000 years ago, Smith says, the Martian south pole was warmer because the planet’s tilt (and hence its seasons) is constantly changing. Warmer temperatures could have propagated through the ice to create pockets of salty liquid. Alternatively, the ponds may have been there before the ice cap formed. Either way, at very high salt concentrations, once water has melted, it’s hard to get it to freeze again. “The melting temperature is different than the freezing temperature,” he says.
Even so, such liquid may be unlike any that most earthlings are familiar with. “Some supercooled brines at these cold temperatures are still considered liquid but turn into some weird glass,” Bramson says.
Resolving these questions will probably require more than radar. Multiple factors, such as the composition and physical properties of the ice, can alter the fate of the second echo from the bottom of the ice, says Bramson. Seismology, gravity and topography data could go a long way to revealing what lurks beneath the ice.
Whether anything could survive in such water is an open question. “We don’t know exactly what is in this water,” Orosei says.  “We don’t know the concentration of salts, which could be deadly to life.” But if life did evolve on Mars, he speculates, “these lakes could have been providing a Noah’s Ark that could have allowed life to survive even in in present conditions.“ More

A two-month stint on the moon would expose astronauts to roughly the same amount of radiation as they would get living on the International Space Station for five months, according to new measurements from the lunar surface.
Detectors on China’s lunar lander Chang’e-4 measured radiation from galactic cosmic rays at the moon’s surface in 2019, from January 3 to 12 — just after landing on the farside of the moon — and again from January 31 to February 10. An astronaut would be exposed to an average daily dose of 1,369 microsieverts of radiation, researchers report online September 25 in Science Advances.
That’s about 2.6 times as high as the average daily radiation exposure of 523 microsieverts recorded inside the ISS, the scientists say. Being on the moon “for two months would be OK. That is about the same amount of radiation astronauts receive at the ISS [over five months] and wouldn’t be incredibly dangerous,” says coauthor Robert Wimmer-Schweingruber, a physicist at Christian Albrechts University in Kiel, Germany.
The new study is perhaps the first to measure cosmic radiation at the moon’s surface, says Jeffery Chancellor, a physicist at Louisiana State University in Baton Rouge. “This is [a] pretty cool bit of data.” He cautions that radiation levels on other parts of the space station could be higher, so the authors may have overprojected the exposure difference between the moon’s surface and the ISS.
Galactic cosmic rays, high-energy charged particles that zip through space, come from outside the solar system. Earth’s magnetic field protects humans from these rays, but in space, it’s a whole different story.
Long exposure to such radiation can cause cellular and DNA damage resulting in cancers, cataracts, cardiac problems, neurodegenerative diseases and behavioral impairments, animal studies have shown (SN: 7/15/20). So far, it’s unclear exactly what impact such exposure might have on human health. The effects of spending a large amount of time in space may show many years after someone has been exposed, says Marjan Boerma, a radiation biologist at the University of Arkansas for Medical Sciences in Little Rock. 
The findings come at a time when United States and other nations are making plans to land humans on moon for the first time in decades (SN: 12/16/19). NASA has announced its plans to land the first U.S. woman and a man on the moon’s surface by 2024. More

The NASA Artemis missions aim to send astronauts to the moon by 2024. But to succeed, they’ll need to solve big problems caused by some tiny particles: dust.
Impacts on the moon’s surface have crushed lunar rock into dust over billions of years (SN: 1/17/19). The resulting particles are like “broken shards of glass,” says Mihály Horányi, a physicist at the University of Colorado Boulder. This abrasive material can damage equipment and even harm astronauts’ health if inhaled (SN: 12/3/13). Making matters worse, the sun’s radiation gives moon dust an electric charge, so it sticks to everything.
Horányi and colleagues have discovered a new method for combatting lunar dust’s static cling, using a low-powered electron beam to make dust particles fly off surfaces. It complements existing approaches to the sticky problem, the researchers report online August 8 in Acta Astronautica.

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During the Apollo missions, astronauts relied on a low-tech system to clean lunar dust off their spacesuits: brushes. Such mechanical methods, however, are thwarted by the electrically charged nature of lunar dust, which clings to the nooks and crannies of woven spacesuit fabric.
The newly described method takes advantage of the dust’s electrical properties. An electron beam causes dust to release electrons into the tiny spaces between particles. Some of these negatively charged electrons are absorbed by surrounding dust specks. Because the charged particles repel each other, the resulting electric field “ejects dust off the surface,” says Xu Wang, a physicist also at the University of Colorado Boulder.
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Abrasive, electrically charged lunar dust clings to surfaces and could wreak havoc on equipment and astronaut well-being during missions to the moon. An electron beam may aid future cleaning efforts. As shown here, when a beam hits artificial lunar dust on a glass plate, particles leap off the surface.
“This is a very unique idea,” says mechanical engineer Hiroyuki Kawamoto of Waseda University in Tokyo, who was not involved in the new work. Kawamoto and colleagues have developed their own dust-busting technologies, including a layer of electrodes that can be built into materials. When embedded in a spacesuit or on the surface of equipment, the electrodes generate electrostatic forces and fling away charged dust particles. Such systems are more complex than shooting an electron beam at surfaces, Wang says. But a potential downside to the simpler electric beam idea, Kawamoto says, is that it would require a robot or some other external means to direct it.
Another limitation of the electron beam is that it left behind 15 to 25 percent of dust particles. The researchers aim to improve the cleaning power. The team also envisions the electron beam as one of multiple approaches that future space explorers will take to keep surfaces clean, Horányi says, in addition to suit design, other cleaning technologies and, one day, even lunar habitats with moon dust mudrooms. More

Venus’ clouds appear to contain a smelly, toxic gas that could be produced by bacteria, a new study suggests.
Chemical signs of the gas phosphine have been spotted in observations of the Venusian atmosphere, researchers report September 14 in Nature Astronomy. Examining the atmosphere in millimeter wavelengths of light showed that the planet’s clouds appear to contain up to 20 parts per billion of phosphine — enough that something must be actively producing it, the researchers say. 
If the discovery holds up, and if no other explanations for the gas are found, then the hellish planet next door could be the first to yield signs of extraterrestrial life — though those are very big ifs.
“We’re not saying it’s life,” says astronomer Jane Greaves of Cardiff University in Wales. “We’re saying it’s a possible sign of life.”

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Venus has roughly the same mass and size as Earth, so, from far away, the neighboring planet might look like a habitable world (SN: 10/4/19). But up close, Venus is a scorching hellscape with sulfuric acid rain and crushing atmospheric pressures.
Still, Venus might have been more hospitable in the recent past (SN: 8/26/16). And the current harsh conditions haven’t stopped astrobiologists from speculating about niches on Venus where present-day life could hang on, such as the temperate cloud decks.
“Fifty kilometers above the surface of Venus, the conditions are what you would find if you walk out of your door right now,” at least in terms of atmospheric pressure and temperature, says planetary scientist Sanjay Limaye of the University of Wisconsin–Madison, who was not involved in the new study. The chemistry is alien, but “that’s a hospitable environment for life.”
Previous work led by astrochemist Clara Sousa-Silva at MIT suggested that phosphine could be a promising biosignature, a chemical signature of life that can be detected in the atmospheres of other planets using Earth-based or space telescopes.
On Earth, phosphine is associated with microbes or industrial activity — although that doesn’t mean it’s pleasant. “It’s a horrific molecule. It’s terrifying,” Sousa-Silva says. For most Earthly life, phosphine is poisonous because “it interferes with oxygen metabolism in a variety of macabre ways.” For anaerobic life, which does not use oxygen, “phosphine is not so evil,” Sousa-Silva says. Anaerobic microbes living in such places as sewage, swamps and the intestinal tracts of animals from penguins to people are the only known life-forms on Earth that produce the molecule.  
Still, when Greaves and colleagues searched Venus’ skies for signs of phosphine, the researchers didn’t expect to actually find any. Greaves looked at Venus with the James Clerk Maxwell Telescope in Hawaii over five mornings in June 2017, aiming to set a detectability benchmark for future studies seeking the gas in the atmospheres of exoplanets (SN: 5/4/20), but was startled to find the hints of phosphine. “That’s a complete surprise,” Greaves says. When she was analyzing the observations, “I thought ‘Oh, I must have done it wrong.’”
Signs of phosphine first showed up in data taken with the James Clerk Maxwell Telescope in Hawaii.Will Montgomerie/JCMT/EAO
So the team checked again with a more powerful telescope, the Atacama Large Millimeter/submillimeter Array in Chile, in March 2019. But the signature of phosphine — seen as a dip in the spectrum of light at about 1.12 millimeters — was still there. The gas absorbs light in that wavelength. Some other molecules also absorb light near that wavelength, but those either couldn’t explain the whole signal or seemed improbable, Greaves says. “One of those is a plastic,” she says. “I think a floating plastic factory is a less plausible explanation than just saying there’s phosphine.”
Phosphine takes a fair amount of energy to create and is easily destroyed by sunlight or sulfuric acid, which is found in Venus’ atmosphere. So if the gas was produced a long time ago, it shouldn’t still be detectable. “There has to be a source,” Greaves says.
Greaves, Sousa-Silva and colleagues considered every explanation they could think of apart from life: atmospheric chemistry; ground and subsurface chemistry; volcanoes outgassing phosphine from the Venusian interior; meteorites peppering the atmosphere with phosphine from the outside; lightning; solar wind; tectonic plates sliding against each other. Some of those processes could produce trace amounts of phosphine, the team found, but orders of magnitude less than the team detected.
“We’re at the end of our rope,” Sousa-Silva says. She hopes other scientists will come up with other explanations. “I’m curious what kind of exotic geochemistry people will come up with to explain this abiotically.”
The idea of searching for life on Venus “has been regarded as a pretty out-there concept,” says Planetary Science Institute astrobiologist David Grinspoon, who is based in Washington, D.C. Grinspoon has been publishing about the prospects for life on Venus since 1997, but was not involved in the new discovery.
“So now I hear about this, and I’m delighted,” he says. “Not because I want to declare victory and say this is definite evidence of life on Venus. It’s not. But it’s an intriguing signature that could be a sign of life on Venus. And it obligates us to go investigate further.”
Because of the planet’s acidic atmosphere, extreme pressures and lead-melting temperatures, sending spacecraft to Venus is a challenge (SN: 2/13/18). But several space agencies are considering missions that could fly in the next few decades.
In the meantime, Greaves and colleagues want to confirm the new phosphine detection in other wavelengths of light. Observations they had planned for the spring were put on hold by the coronavirus pandemic. And now, Venus is in a part of its orbit where it’s on the other side of the sun.
“Maybe when Venus comes around on the other side of the sun again,” Greaves says, “things will be better for us here on Earth.” More