Space

Dark matter just got even more puzzling.
This unidentified stuff, which makes up most of the mass in the cosmos, is invisible but detectable by the way it gravitationally tugs on objects like stars. (SN: 11/25/19). Dark matter’s gravity can also bend light traveling from distant galaxies to Earth — but now some of this mysterious substance appears to be bending light more than it’s supposed to. A surprising number of dark matter clumps in distant clusters of galaxies severely warp background light from other objects, researchers report in the Sept. 11 Science.
This finding suggests that these clumps of dark matter, in which individual galaxies are embedded, are denser than expected. And that could mean one of two things: Either the computer simulations that researchers use to predict galaxy cluster behavior are wrong, or cosmologists’ understanding of dark matter is.
Very high concentrations of dark matter can act like a lens to bend light and drastically alter the appearance of background galaxies as seen from Earth — stretching them into arcs or splitting them into multiple images of the same object on the sky. “It’s totally cool. It’s like a fun house mirror,” says astrophysicist Priyamvada Natarajan of Yale University.

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Judging by computer simulations of galaxy clusters, clumps of dark matter around individual galaxies that are dense enough to cause such dramatic gravitational lensing effects should be rare (SN: 10/4/15). Based on cluster simulations run by Natarajan and colleagues, “we would expect to see 1 [strong lensing] event in every 10 clusters or so,” says study coauthor Massimo Meneghetti, an astrophysicist at the Astrophysics and Space Science Observatory of Bologna in Italy.
But telescope images told a different story. The researchers used observations from the Hubble Space Telescope and the Very Large Telescope in Chile to investigate 11 galaxy clusters from about 2.8 billion to 5.6 billion light-years away. In that set, the team identified 13 cases of severe gravitational lensing by dark matter clumps around individual galaxies. These observations indicate there are more high-density dark matter clumps in real galaxy clusters than in simulated ones, Meneghetti says.
The simulations could be missing some physics that leads dark matter in galaxy clusters to glom tightly together, Natarajan says. “Or … there’s something fundamentally off about our assumptions about the nature of dark matter,” she says, like the notion that gravity is the only attractive force that dark matter feels.
Richard Ellis, a cosmologist at the University College London who was not involved in the work, thinks the crux of the problem is more likely in the computer simulations than in the nature of dark matter. “A cluster of galaxies is a very dangerous place. It’s like the Manhattan of the universe,” he says — busy with galaxies whizzing past one another, colliding and getting torn up. “There’s awful physics that goes into predicting how many of these little lensed things they should find,” Ellis says, so the new result “is intriguing, but my suspicion is that there’s something in the simulations … that isn’t quite right.”
Future observations with the upcoming Euclid space telescope (SN: 11/14/17), the Nancy Grace Roman Space Telescope and Vera C. Rubin Observatory (SN: 1/10/20) could help clear matters up, says Bhuvnesh Jain, an astrophysicist at the University of Pennsylvania who was not involved in the work. “These three telescopes are going to produce extremely large samples of galaxy clusters,” he says. That may lead to a new understanding of the physics in these turbulent environments, and help determine whether unrealistic simulations are to blame for this dark matter mystery. More

In one of the most complex cosmic dances astronomers have yet spotted, three rings of gas and dust circle a trio of stars.
The star system GW Orionis, located about 1,300 light-years away in the constellation Orion, includes a pair of young stars locked in a close do-si-do with a third star making loops around both. Around all three stars is a broken-apart disk of dust and gas where planets could one day form. Unlike the flat disk that gave rise to the planets in our solar system, GW Orionis’ disk consists of three loops, with a warped middle ring and an inner ring even more twisted at a jaunty angle to the other two.
The bizarre geometry of this system, the first known of its kind, is reported in two recent studies by two groups of astronomers. But how GW Orionis formed is a mystery, with the two teams providing competing ideas for the triple-star-and-ring system’s birth.
In a Sept. 4 study in Science, astronomer Stefan Kraus of the University of Exeter in England and colleagues suggest that gravitational tugs and torques from the triple-star ballet tore apart and deformed the primordial disk. But in a May 20 study in the Astrophysical Journal Letters, Jiaqing Bi of the University of Victoria in Canada and colleagues think that a newborn planet is to blame.
“The question is how do you actually form such systems,” says theoretical physicist Giuseppe Lodato of the University of Milan, who was not on either team. “There could be different mechanisms that could do that.”

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Astronomers have seen tilted disks of gas and dust around binary star systems, but not systems of more than two stars (SN: 7/30/14). Around half of the stars in the galaxy have at least one stellar companion, and their planets often have tilted orbits with respect to their stars, going around more like a jump rope than a Hula-Hoop (SN: 11/1/13). That misalignment could originate with the disk in which the planets were born: If the disk was askew, the planets would be too.
About a decade ago, astronomers first realized that GW Orionis has three stars and a planet-forming disk, and the scientists scrambled to get a closer look. (At the time, it was impossible to tell if that disk was a single loop or not.) Bi’s team and Kraus’ team aimed the Atacama Large Millimeter/submillimeter Array in Chile at the triple-star system.
Both groups spotted the trio of stars: one about 2.5 times and another about 1.4 times the sun’s mass orbiting each other once every 242 days, and another 1.4 solar mass star orbiting the inner pair about every 11 years.
The observations also revealed three distinct rings of dust and gas encircling the stars. The closest ring to the star trio lies about 46 times the distance from Earth to the sun; the middle one about 185 times the Earth-sun distance; and the outermost ring about 340 times that distance. For perspective, Neptune is about 30 times the distance from Earth to the sun.
That innermost ring is strongly misaligned with respect to the other rings and the stars, the teams found. Kraus’ group added observations from the European Southern Observatory’s Very Large Telescope to show the shadow of the inner ring on the inside of the middle loop. That shadow revealed that the middle ring is warped, swooping up on one side and down on the other.
Astronomers looked at GW Orionis with the ALMA telescope array (left, blue) and the SPHERE instrument on the Very Large Telescope (right, red), both in Chile. The ALMA observations revealed the disk’s tri-ringed structure, while the SPHERE images showed the shadow cast by the innermost ring, allowing scientists to describe the rings’ deformed shapes in detail.Left image: ALMA/ESO, NAOJ, NRAO; Right image: ESO, S. Kraus et al, Univ. of Exeter
Next, both groups ran computer simulations to figure out how the system formed. This is where their conclusions begin to differ, Bi says. His team suggests that a newly formed, not-yet-discovered planet cleared its orbit of gas and dust, splitting the inner ring off from the rest of the disk (SN: 7/16/19). Once the disk was split, the inner ring was free to swing around the stars, settling into its skewed alignment.
Simulations from Kraus’s team, though, found that the chaotic gravity from the triple stars’ orbital dance alone was enough to break up the disk, a phenomenon called disk tearing. Each star tends to keep the disk aligned with itself, and the tug-of-war warped and sheared the disk, and twisted the inner ring even further. Theoretical studies had suggested disk tearing might happen in multiple star systems, but this is the first time it’s been seen in real life, Kraus contends.
“I think it’s plausible that there could be planets somewhere in the system, but they’re not needed to explain the misalignment,” he says. “We don’t need to invoke undiscovered planets to explain what we see.”
[embedded content]
A trio of stars in GW Orionis are surrounded by an enormous, warped disk of gas and dust, new observations reveal. This animation, which is based on computer simulations and observational data, shows the complex geometry of the deformed and broken-apart disk.
The difference may lie in the assumptions that the groups made about the disk’s properties, in particular its viscosity, says astrophysicist Nienke van der Marel, Bi’s colleague at the University of Victoria. A more viscous disk would tear like how Kraus and colleagues propose, but a less viscous disk needs a planet to break apart, she says. She thinks her team’s work is more realistic based on observations of other star systems. But with current technology, there’s no way to tell what the properties of GW Orionis’ disk are really like.
And neither group could explain what made the disk split into three. “We don’t really know what’s causing the outer ring,” Klaus says.
Lodato, who predicted the disk-tearing effect in 2013, thinks GW Orionis is proof that the phenomenon really exists. Back then, Lodato and colleagues were “very worried” that their simulations showed an effect that was introduced by the computations, not real physics, he says. “Now observations tell us that it does happen in reality.”
Future telescopes may also be able to spot the planet if it exists, van der Marel says. More

Observations of thousands of white dwarf stars have confirmed a decades-old theory about the relationship between their masses and sizes. More

Small, frequent lightning storms zip across Jupiter’s cloud tops. NASA’s Juno spacecraft spotted the flashes for the first time, scientists report August 5 in Nature.
“It’s a very exotic thing that doesn’t exist on Earth,” says physicist Heidi Becker of NASA’s Jet Propulsion Laboratory in Pasadena, Calif.
Previous spacecraft have revealed high-energy “superbolts” on Jupiter. That lightning originates 50 to 65 kilometers below Jupiter’s cloud tops, where liquid water droplets form. Scientists think superbolts form like lightning on Earth does: Colliding ice crystals and water droplets charge each other up, then stretch the charge between them when they separate (SN: 6/25/20).
Juno, which arrived at Jupiter in 2016, got much closer to the giant planet’s cloud tops than previous missions. Becker and her team turned the spacecraft’s navigation camera — which normally observes stars to track Juno’s position — on Jupiter’s nightside in February 2018. To the team’s surprise, the clouds crackled with electricity.
Newly observed lightning showed up as bright dots (indicated with arrows) on Jupiter’s nightside, seen in this composite image from two of Juno’s cameras. The insets are pixelated representations of the events’ brightness (yellow is more bright; blue is less bright).H.N. Becker et al/Nature 2020
Superbolts are up to 100,000 times as strong as these small flashes. But the cloud-top lightning is 10 times as frequent. Strangely, the smaller bolts appeared to come from just 18 kilometers below the cloud tops, where it’s too cold for liquid water to exist alone.
Shallow lightning must have a different origin than the deeper lightning, Becker says. Perhaps ammonia in the upper cloud decks acts as antifreeze, creating droplets of ammonia and water combined. Juno has also seen evidence that violent storms in deeper cloud layers sometimes toss ice crystals high above where they’re normally found. When those crystals collide with the ammonia-water droplets, they may charge up and create lightning, Becker and her colleagues reason.
Similar small lightning storms may happen on other planets, including exoplanets, Becker says (SN: 5/13/16). “Every time you have a new realization, it feeds into new theories that will be developed not only for our solar system but for other solar systems.” More

An observatory in the heart of Antarctica could have the world’s clearest views of the night sky.
If an optical telescope were built on a tower a few stories tall in the middle of the Antarctic Plateau, it could discern celestial features about half the size of those typically visible to other observatories, researchers report online July 29 in Nature. The observatory would achieve such sharp vision by peering above the atmosphere’s lowermost layer, known as the boundary layer, responsible for much of the undulating air that muddles telescope images (SN: 10/4/18).
The thickness of Earth’s boundary layer varies across the globe. Near the equator, it can be hundreds of meters thick, limiting the vision of premier optical telescopes in places like the Canary Islands and Hawaii (SN: 10/14/19). Those telescopes usually cannot pick out celestial features smaller than 0.6 to 0.8 arc seconds — the apparent width of a human hair from about 20 meters away.
“But in Antarctica, the boundary layer is really thin,” says Bin Ma, an astronomer at the Chinese Academy of Sciences in Beijing, “so it is possible to put a telescope above.”
Ma and colleagues took the first-ever measurements of nighttime atmospheric blur from the highest point in East Antarctica, called Dome A. From April to August 2019, instruments on an 8-meter-tall tower at China’s Kunlun research station tracked how Earth’s atmospheric turbulence distorted incoming starlight. A nearby weather station also monitored atmospheric conditions, such as temperature and wind speed. Using these observations, researchers characterized the boundary layer at Dome A and its effect on telescope observations.
From April to August 2019, instruments atop an 8-meter-tall tower at China’s Kunlun research station in East Antarctica observed how the local atmosphere distorted light from celestial objects.Zhaohui Shang
The boundary layer was, on average, about 14 meters thick; as a result, the light sensors at the top of the 8-meter tower were completely free of boundary layer blur only about one-third of the time. But when these instruments were above the layer, atmospheric interference was so low that a telescope could pick out details on the sky 0.31 arc seconds across, on average. The best recorded atmospheric conditions would let a telescope see features as small as 0.13 arc seconds.
“One-tenth of an arc second is extremely good,” says Marc Sarazin, an applied physicist at the European Southern Observatory in Munich who was not involved in the work. This is “really something you rarely achieve in Chile or on Mauna Kea” in Hawaii.
Researchers have found similarly excellent visibility above the boundary layer at another spot on the Antarctic Plateau, known as Dome C. But the boundary layer there is around 30 meters thick — making it more difficult to build an observatory above it. An optical telescope planned for construction on a 15-meter tower at Kunlun could take advantage of Dome A’s stellar views above the boundary layer, Ma says. Such crisp telescope images could help astronomers study a range of celestial objects, from solar system bodies to distant galaxies.

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Megan Barrington watched the sun rise over the rocky outcrop. When light struck at exactly the right angle, she mounted a gizmo that looked like eye exam equipment on a tripod and aimed it at the spot. The goal: gather evidence that this windswept wilderness once teemed with life, and then beam the information to her colleagues back home.
Soon, a version of that setup (minus Barrington) will be deployed on Mars. The state-of-the-art, zoomable, multispectral camera is part of the toolkit on NASA’s Perseverance rover (SN: 7/28/20). “That instrument is going to allow me to look at the mineralogy of Mars at Jezero crater,” the rover’s landing spot, says Barrington, a planetary scientist at Cornell University.
The rover is scheduled to launch to Mars on July 30. A February role-playing exercise in the Nevada desert by Barrington and six colleagues was a kind of dress rehearsal for the rover’s various instruments. Another 150 team members around the world played the “Earth” team during those two weeks, sending commands from remote mission control and receiving data as it would appear coming from the real rover.
“We’re not just simulating a Mars mission,” says engineer Raymond Francis of NASA’s Jet Propulsion Laboratory in Pasadena, Calif., who organized and led the trip. “We’re simulating a specific Mars mission by presenting data … to the people who designed the instrument that will take that data. So the standard is high not to look like clowns.”

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Perseverance has the most demanding and ambitious to-do list of any rover yet: seek signs of past Martian life, prepare the way for future human missions and collect at least 20 samples of Martian rock for eventual return to Earth. And that’s just in its first two years. For contrast, Curiosity rover has drilled a few dozen holes over eight years on Mars, and didn’t store any of those samples for later (SN: 7/7/18, p. 8).
The dress rehearsal in the desert will help ensure that when Perseverance lands on the Red Planet in February 2021, its handlers on Earth can get straight to the science.
“We don’t want to get there and learn how to explore Mars while on Mars,” Francis says. “We want [team members] to be ready when the rover hits the ground.”
Water marks the spot
The first order of business was to find the right spot for the dry run. “We had to pick a site that kind of looked like Mars,” Francis says. “The parking lot would not do.” The team wanted the site to look as Mars-like as possible, no factories, footprints or foliage to break the illusion.
An ideal site would have geology that echoed Jezero crater, which is thought to be the remnants of an ancient lakebed and river delta (SN: 11/19/18). It also had to be within a few hours’ drive of JPL, and not totally off the grid — the rover team slept in hotels, ate dinner in restaurants and had reliable Wi-Fi to send data to the Earth team every night.
The final requirement was that it be someplace the Earth team hadn’t seen before. If mission control members recognized the site, they could bias their findings with what they already knew.
Engineer and team leader Raymond Francis gets up close with the rocks to make a measurement.JPL-Caltech/NASA
“Most of the popular Mars analogs are already well known to the Mars community,” Francis says. “So we had to be a little sneaky.”
Previous exercises, in November 2017 and February 2019, were run in the Mojave Desert in California. For 2020, the rover team headed to Walker Lake in western Nevada. The lake’s water has been receding for a thousand years, so there are spots near the ancient shoreline where the present-day lake is invisible.
Walker Lake’s rocks preserved a cornucopia of biological signals for the ground team to discover: fossilized fish bones and shells of tiny shrimplike crustaceans called ostracods, which are not expected on Mars; and microbial fossils called stromatolites, which could plausibly be found in Jezero crater (SN: 10/17/18).
Toolkit
Francis and his team brought handheld versions of almost all the rover’s instruments to gather whatever data the Earth team requested. They had a drill, handheld spectrometers, lasers, a ground-penetrating radar that they transported in a jogging stroller, plus several elaborate camera setups to represent the rover’s navigation, hazard avoidance and zoomable 3-D science cameras.
Perhaps the most important piece of equipment was the broom used for sweeping away footprints. It became a running joke, Francis says: “We’ve got all this equipment, a multibillion-dollar mission, and it’s all hinging on this 99-cent broom.”
Almost everything went smoothly. But a few days into the mission, Barrington’s zoomable camera had “a major malfunction,” she says. She framed her shot, and…. nothing happened. The camera wasn’t getting any power, she realized. “I took it apart and rewired many pieces, to no avail,” she says.
She and her teammates finally realized one of the power adapters had completely blown. She had to drive two hours to the nearest city to get a new one.
Of course, driving into town to get a new part won’t be an option on Mars. The real camera, called Mastcam-Z, has been through weeks of rigorous testing and calibration, and is probably up to the task. But “we all go into missions knowing that sometimes irreversible mistakes occur,” Barrington admits. “All we can do at that point is use the instruments to the fullest capacity of which they are capable of operating.”
Planetary scientist Megan Barrington adjusts her instrument, a multispectral, zoomable camera standing in for Perseverance’s Mastcam-Z.JPL-Caltech/NASA
Signs of life, big and small
There was one major giveaway that the team was actually on Earth. “This is very much middle-of-nowhere desert, which is good,” Francis says. But the rover site was mere steps from a U.S. Department of Defense munitions facility, one of the largest in the world.
“It was really something to behold,” Barrington says. “They had hundreds of bunkers lined up in rows as far as you could see…. All of that was one very crooked metal fence away from us.”
More than once, military police showed up to check the team’s credentials. “I had to approach them and say, hello, people with the guns, I need you to stop walking now,” Francis says. “We’re running a Mars rover simulation and we don’t want you to put your footprints in this sand.”
Despite Francis and colleagues’ best efforts, the bunkers showed up in a few photos. The ground team gamely ignored them, apart from a few jokes about SpaceX founder Elon Musk building a Martian city.
By the end of the two-week exercise, the remote science team reviewing the data had noticed the ostracods and fishbones, and started exploring the stromatolites. “They were doing a good job of finding the biomarkers,” Francis says, who now has hope that “if Mars is hiding stromatolites, maybe we’ll see them.”
Coming home to quarantine
The field trip ended on February 27, just as awareness of the novel coronavirus SARS-CoV-2 was rising in the United States. By March 15, JPL told employees to work from home. “We only had a few days together before we were all on remote work,” Francis says.
The pandemic has already contributed to the delay of the launch of the European and Russian ExoMars rover, which was also supposed to launch in July (SN: 3/12/20).  If Perseverance misses the late July to early August launch window, the rover can’t head to Mars until 2022.
If the pandemic is still an issue by the time the rover lands in February, Francis doesn’t know what the team will do. “But,” he says, “the good news is the mission is designed for remote operations.” More

Science writer Kate Greene couldn’t have known that her memoir about her time on a make-believe Mars mission would be published as millions of people on Earth isolated themselves in their homes for months amid a pandemic.

But her book is one of two about Mars published this month that are oddly well-suited to the present moment. Once Upon a Time I Lived on Mars and Sarah Stewart Johnson’s The Sirens of Mars are both about exploration. Yet they’re also about many different types of isolation and the human yearning to not be alone.
Greene participated in a mock Mars mission, called HI-SEAS, for Hawaii Space Exploration Analog and Simulation, in 2013. She and five others lived in a dome on a rocky, barren patch atop Mauna Loa volcano for four months with no fresh food, no fresh air (all excursions were conducted in clunky “spacesuits”) and no instantaneous contact with the outside world.
NASA and other space agencies run such missions to figure out best practices for keeping astronauts sane and productive in isolated and stressful environments. It’s well-documented that boredom can lead to mistakes or inattention. Other simulated Mars missions suggest that astronauts isolated together could develop an us-versus-them mentality that would lead the crew to stop listening to mission control, which could be dangerous on a long mission.

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With humor and sensitivity, Greene relates how her crew got along (or didn’t), what she read, what she ate and the time-delayed e-mails she exchanged with loved ones back on “Earth.” Through the book’s series of essays, she uses the mission as a lens to examine everything from the ethics and economics of space travel to the nature of time, love and home.
Her descriptions of boredom and seclusion feel especially apt in a time of social distancing: “the way certain aspects of your environment, daily schedule and conversations smooth over, lose their texture.” Greene relates her experience to astronaut Michael Collins’ time orbiting in the Apollo 11 capsule alone while his crewmates walked on the moon. She connects both of those experiences to that of her brother, who spent the last year and a half of his life confined to a hospital room.
“On this oasis of a planet,” she writes, “there are so many ways to feel isolated, each of us with the potential to sit with the terror of being alive and possibly alone in the cosmos.”

The Sirens of Mars starts with a much broader view of Mars exploration. In lyrical, engaging writing, Stewart Johnson, a planetary scientist, chronicles how our perception of Mars has swung from a world teeming with life, to definitely dead and boring, and back again over and over since the invention of telescopes.
Stewart Johnson brings together a cast of characters to tell this history, from Galileo to the present-day team working on the Curiosity rover. Those characters include astronomer Carl Sagan, whose Cosmos TV series Stewart Johnson watched as a child. Sagan was almost ridiculed out of science for his obsession with “exobiology.”
She also introduces less famous but equally important people, like Sagan’s colleague Wolf Vishniac, whose “Wolf Trap” life-detection experiment was cut from NASA’s life-hunting Viking landers in the 1970s. To get over his disappointment, Vishniac went searching for microbes in Antarctica and died in an accident there before the Viking missions launched (SN: 12/22/73).
In this sweeping history of human fascination with the Red Planet, Stewart Johnson also tells a personal story of finding her place in the world, from an inquisitive child to an unrooted adventurer to a wife and mother and member of a scientific team.
She makes a clear case that the search for life on Mars is an effort to not be alone. In one of the most poignant scenes in her book, she is hiking on Mauna Kea — the next volcano over from Greene’s Mars habitat — and finds a fern growing amid the volcanic desolation.
“It was then, on that trip, that the idea of looking for life in the universe began to make sense to me,” she writes. “I suddenly saw something I might haunt the stratosphere for, something for which I’d fall into the sea…. a chance to discover the smallest breath in the deepest night and, in so doing, vanquish the void that lurked between human existence and all else in the cosmos.”
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A new map of the entire sky, as seen in X-rays, looks deeper into space than any other of its kind. The map, released June 19, is based on data from the first full scan of the sky made by the eROSITA X-ray telescope onboard the Russian-German SRG spacecraft, which launched in July 2019. The […] More