planetary science

Sprinkles of helium rain may fall on Jupiter.

At pressures and temperatures present within the gas giant, the hydrogen and helium that make up the bulk of its atmosphere don’t mix, according to laboratory experiments reported in the May 27 Nature. That suggests that deep within Jupiter’s atmosphere, hydrogen and helium separate, with the helium forming droplets that are denser than the hydrogen, causing them to rain down (SN: 4/19/21).

Jupiter’s marbled exterior is pretty familiar territory, but it’s still not clear what happens far below the cloud tops. So researchers designed an experiment to compress hydrogen and helium, reaching pressures nearly 2 million times Earth’s atmospheric pressure and temperatures of thousands of degrees Celsius, akin to inner layers of gas giants.

“We are reproducing the conditions inside the planets,” says physicist Marius Millot of Lawrence Livermore National Laboratory in California.

Millot and colleagues squeezed a mixture of hydrogen and helium between two diamonds and hit the concoction with a powerful laser to compress it even further. As the pressure and temperature increased, the researchers saw an abrupt increase in how reflective the material was. That suggests that helium was separating from the hydrogen, which becomes a liquid metal under these conditions (SN: 8/10/16). At even higher pressures and temperatures, the reflectivity decreased, suggesting that hydrogen and helium began mixing again.

The researchers calculated that hydrogen and helium would separate about 11,000 kilometers below the cloud tops of Jupiter, down to a depth of about 22,000 kilometers.

The results could help scientists explain observations made by spacecraft Galileo (SN: 2/18/02) and Juno (SN: 3/7/18), such as the fact that Jupiter’s outer layers of atmosphere have less helium than expected. More

The Ingenuity helicopter proved it could fly on Mars. Now it has loftier goals. Having passed all its original engineering tests, the tiny spacecraft will now begin a new job, supporting the Perseverance rover in its science mission.

“It’s like Ingenuity is graduating,” said Ingenuity project manager MiMi Aung of NASA’s Jet Propulsion Laboratory in Pasadena, Calif., in a news briefing on April 30.

The helicopter arrived at Mars with two main goals: demonstrate that flight was possible on the Red Planet and show that it could return critical flight data to Earth. Those were both achieved in Ingenuity’s first flight on April 19 and then surpassed as the helicopter flew farther, higher and faster on April 22 and April 25 (SN: 4/19/21).

The original plan was for Ingenuity to take up to six flights total, then ground itself forever as Perseverance drove away to do science. That was partly because the Perseverance team expected to drive far from the rover’s landing site in search of rocks that might preserve signs of past Martian life (SN: 2/22/21).

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“We thought we would be doing an intensive drive campaign in which the helicopter would not be able to keep up,” said Perseverance project scientist Ken Farley of Caltech in the briefing. “But based on the rocks we have seen in the area, we really wish to spend a considerable amount of time where we are.”

Ingenuity has also been performing surprisingly well, Aung said. The rover and the helicopter might be able to communicate from more than a kilometer apart, giving them both more flexibility.

Ingenuity took its fourth flight on April 30 to scout for a new launch pad. The fifth flight, to be scheduled after the team has examined the data, will be a one-way journey to that new home.

After that, Ingenuity will switch into support mode. Up until now, the Perseverance team has generously supported the helicopter, Aung said. “The rover is primary going forward,” she said.

The helicopter will have future flights in support mode. The team says Ingenuity will scout potential scientific observations and rover routes from the sky, make 3-D digital elevation maps and take a look at places a rover can’t go. “The lessons learned from that exercise will benefit future missions with aerial platforms tremendously,” Aung said.

The team isn’t sure how the helicopter’s mission will end. Ingenuity was designed to last just 30 Martian days. The new support phase will extend its mission by another 30 days, unless something goes wrong before then. “We don’t know how many freeze and thaw cycles it can go through before something breaks,” said Ingenuity chief engineer Bob Balaram. More

NASA’s Perseverance rover just created a breath of fresh air on Mars. An experimental device on the rover split carbon dioxide molecules into their component parts, creating about 10 minutes’ worth of breathable oxygen. It was also enough oxygen to make tiny amounts of rocket fuel.

The instrument, called MOXIE (Mars Oxygen In-Situ Resource Utilization Experiment), is about the size of a toaster (SN: 7/28/20). Its job is to break oxygen atoms off carbon dioxide, the primary component of Mars’ atmosphere. It’s like “an electrical tree,” says principal investigator Michael Hecht of MIT. “We breathe in CO2 and breathe out oxygen.”

MOXIE flew to Mars with Perseverance, which arrived on the Red Planet on February 18 (SN: 2/22/21). On April 20, the instrument warmed up to about 800° Celsius and ran for long enough to produce five grams of oxygen. That’s not enough to breathe for very long. But the main reason to make oxygen on Mars isn’t for breathing, Hecht says. It’s for making fuel for the return journey to Earth.

“When we burn anything, gas in the car or a log in the fireplace, most of what we’re burning is oxygen,” Hecht says. On Earth, we take all that oxygen for granted. “It’s free here. We don’t think about it.”

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Future astronauts will have to either bring oxygen with them or make it on Mars. A rocket powerful enough to lift a few astronauts off the Red Planet’s surface would need about 25 metric tons of oxygen — too much to pack for the journey.

MOXIE is a prototype for the device astronauts could use to make rocket fuel in the future. When running at full power, the instrument can create about 10 grams of oxygen per hour. The instrument, powered by Perseverance, will run for about one Martian day at a time. A scaled-up version could run continuously for 26 months before astronauts arrive, Hecht says.

MOXIE can’t run continuously because Perseverance needs to divert its power back to its other instruments to continue its science mission of searching for signs of past life on Mars (SN: 1/10/18). MOXIE will get a chance to run at least nine more times over the next Martian year (about two Earth years).

The success of the technology could set the stage for a permanent research station on Mars, like the McMurdo station in Antarctica, something Hecht would like to someday see. “That’s not something I expect to see in my lifetime, but something I expect to see progress towards in my lifetime,” he says. “MOXIE brings it closer by a decade.” More

Editor’s note: This story will be updated periodically.

A helicopter just flew on Mars. NASA’s Ingenuity hovered for about 40 seconds above the Red Planet’s surface, marking the first flight of a spacecraft on another planet.

In the wee hours on April 19, the helicopter spun its carbon fiber rotor blades and lifted itself into the thin Martian air. It rose about three meters above the ground, pivoted to look at NASA’s Perseverance rover, took a picture, and settled back down to the ground.

“Goosebumps. It looks just the way we had tested it in our test chambers,” Ingenuity project manager MiMi Aung said in a news briefing after the flight. “Absolutely beautiful flight. I don’t think I can ever stop watching it over and over again.”

As data from the flight started coming in to Ingenuity’s mission control room at NASA’s Jet Propulsion Lab in Pasadena, Calif., at about 6:35 a.m. EDT, a hush fell. And then cheers erupted as Håvard Grip, Ingenuity’s guidance, navigation and control lead, announced: “Confirmed that Ingenuity has performed its first flight, the first flight of a powered aircraft on another planet.”

NASA’s Ingenuity helicopter took this photo of its own shadow while hovering about three meters in the Martian air on April 19.JPL-Caltech/NASA

“It’s amazing, brilliant. Everyone is super excited,” said mechanical engineer and team member Taryn Bailey. “I would say it’s a success.”

The flight, originally scheduled for April 11, was delayed to update the helicopter’s software after a test of the rotor blades showed problems switching from preflight to flight mode. After the reboot, a high-speed spin test April 16 suggested the shift was likely to work, setting the stage for the April 19 flight.

“I never let you celebrate fully. Every time we hit a major milestone I’m like, not yet, not yet,” Aung told the team moments after the flight was confirmed. Now is the moment to celebrate, she said. “Take that moment and after that, let’s get back to work and more flights. Congratulations.”

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Ingenuity lifted into the thin Martian atmosphere for the first time on April 19, proving that flight is possible on another planet. This video was taken by the Perseverance rover, which watched from a safe distance away.

This first-ever flight was a test of the technology; Ingenuity won’t do any science during its mission, set to last 30 Martian days from the moment it separated from the rover, the equivalent of 31 days on Earth. But its success proves that powered flight is possible in Mars’ thin atmosphere. Future aerial vehicles on Mars could help rovers or human astronauts scout safe paths through unfamiliar landscapes, or reach tricky terrain that a rover can’t traverse.

“Technology demonstrations are really important for all of us,” said Thomas Zurbuchen, associate administrator for NASA’s Science Mission Directorate. “It’s taking a tool we haven’t been able to use and putting it in the box of tools we have available for all of our missions at Mars.”

Ingenuity’s flight was the culmination of more than seven years of imagining, building, testing and hoping for the flight team.

“That is what building first-of-a-kind systems and flight experiments are all about: design, test, learn from the design, adjust the design, test, repeat until success,” Aung said in a news briefing on April 9.

Aung and her team began testing early prototypes of a Mars helicopter in a 7.62-meter-wide test chamber at JPL in 2014. It wasn’t a given that flying on Mars would even be possible, Aung said. “It’s challenging for many different reasons.”

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Before it hitched a ride to Mars on the rover Perseverance, Ingenuity underwent extensive testing in a Mars simulator on Earth. Its engineers experimented with early prototypes and later with Ingenuity itself. These tests convinced the team that the craft could fly in Mars’ thin atmosphere.

Even though Mars’ gravity is only about one-third of Earth’s, the air’s density is about 1 percent that at sea level on Earth. It’s difficult for the helicopter’s blades to push against that thin air hard enough to get off the ground.

Another way to think about it is that the air is thinner on Mars than it is at three times the height of Mount Everest, Ingenuity engineer Amelia Quon of JPL said in the news briefing. “We don’t generally fly things that high,” Quon said. “There were some people who doubted we could generate enough lift to fly in that thin Martian atmosphere.”

So Quon and her team put the helicopter through a battery of tests over the course of five years. “My job … was to make Mars on Earth, and enough of it that we could actually fly our helicopter in it,” Quon said. The Mars simulation chamber could be emptied of Earth air and pumped full of carbon dioxide at Mars-like densities. Some versions of the helicopter were suspended from the ceiling to simulate Mars’ lower gravity. And wind speeds up to 30 meters per second were simulated by a bank of about 900 computer fans blowing at the helicopter.

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The final version of Ingenuity is light, about 1.8 kilograms. Its blades are longer (about 1.2 meters wingspan) and rotate faster (about 2,400 rotations per minute) than a similar vehicle would need to be able to fly on Earth. By the time the helicopter hitched a ride to Mars with the Perseverance rover in July 2020, the engineers were confident the helicopter could fly and remain in control at Mars (SN: 7/30/20).

Perseverance landed in a region called Jezero crater on February 18 (SN: 2/22/21). The helicopter was folded up beneath Perseverance’s belly under a protective shield until March 21.

Over  the next few weeks, Perseverance drove around to find a flat spot for Ingenuity to launch. Then Ingenuity slowly unfolded itself and was finally lowered gently to the ground beneath Perseverance on April 3. The rover drove away quickly to get Ingenuity out of its shadow and allow the helicopter to charge its batteries with its solar panel, giving it enough power to survive the freezing Martian night. 

Ingenuity arrived on Mars folded up under the Perseverance rover in a protective shield the size of a pizza box. After landing, Perseverance dropped the shield and slowly lowered Ingenuity to the ground, then drove away.JPL-Caltech/NASA

On April 8 and 9, Ingenuity unfolded its rotor blades and tested their ability to spin in preparation to take to the air. After trouble-shooting the software problem and retesting the rotor blades April 16, the flight got a green light for April 19. It was scheduled for roughly 3:30 a.m. Eastern Daylight Time on April 19, which corresponds to 12:30 p.m. Mars time, in the early afternoon. That gave the craft’s solar panel enough time to charge up its batteries for the flight. It was also a time when Perseverance’s weather sensors, called MEDA, suggested the average wind speed would be about six meters per second.

NASA’s Ingenuity helicopter tested its spinning rotor blades on April 8, a week and a half before taking flight in the thin Martian air for the first time.JPL-Caltech/NASA

Ingenuity had to pilot itself through the flight. That’s partly because of the communication delay — Mars is far enough from Earth that light signals take about 15 minutes to travel between the two planets. But it’s also because Mars’ thin air makes the helicopter difficult to steer. “Things happen too quickly for a human pilot to react to it,” Quon said.

Perseverance filmed the flight from about 65 meters away, at a spot named Van Zyl Overlook. Ingenuity also filmed the flight from its own perspective, with two sets of cameras: Its downward facing navigation cameras capturing the view below it in black and white, and its color cameras scanning the horizon.

Over several days, NASA’s Perseverance rover gently lowered the Ingenuity helicopter to the ground and then took this selfie with it on April 6 from about four meters away. The rover then drove off to a safe distance of 65 meters to get ready to watch Ingenuity’s first flight.MSSS/JPL-Caltech/NASA

Now that this first flight went well, the team hopes to take up to four more flights over the course of Ingenuity’s mission, possibly starting as soon as April 22. Each will be a little bit more daring and riskier, Aung said. “We are going to continually push all the way to the limit of this rotorcraft.” And each one will be a nail-biter: Just one bad landing could end things immediately. Ingenuity has no way to right itself after a fall.

That may be the way the mission ends, Aung admitted in the April 19 news briefing. “Ultimately, we expect the helicopter will meet its limit,” she said. Even if it eventually  wipes out in a crash, the engineering team will learn valuable information from how the helicopter eventually fails.

At the end of Ingenuity’s mission, Perseverance will drive off, leaving the little helicopter that could behind, and continue its own mission: to search for signs of past life in Jezero crater, and to store rocks for a future mission to return to Earth. More

Whether they’re made of methane on Saturn’s moon Titan or iron on the exoplanet WASP 76b, alien raindrops behave similarly across the Milky Way. They are always close to the same size, regardless of the liquid they’re made of or the atmosphere they fall in, according to the first generalized physical model of alien rain.

“You can get raindrops out of lots of things,” says planetary scientist Kaitlyn Loftus of Harvard University, who published new equations for what happens to a falling raindrop after it has left a cloud in the April Journal of Geophysical Research: Planets. Previous studies have looked at rain in specific cases, like the water cycle on Earth or methane rain on Saturn’s moon Titan (SN: 3/12/15). But this is the first study to consider rain made from any liquid.

“They are proposing something that can be applied to any planet,” says astronomer Tristan Guillot of the Observatory of the Côte d’Azur in Nice, France. “That’s really cool, because this is something that’s needed, really, to understand what’s going on” in the atmospheres of other worlds.

Comprehending how clouds and precipitation form are important for grasping another world’s climate. Cloud cover can either heat or cool a planet’s surface, and raindrops help transport chemical elements and energy around the atmosphere.

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Clouds are complicated (SN: 3/5/21). Despite lots of data on earthly clouds, scientists don’t really understand how they grow and evolve.

Raindrops, though, are governed by a few simple physical laws. Falling droplets of liquid tend to default to similar shapes, regardless of the properties of the liquid. The rate at which that droplet evaporates is set by its surface area.

“This is basically fluid mechanics and thermodynamics, which we understand very well,” Loftus says.

She and Harvard planetary scientist Robin Wordsworth considered rain in a variety of different forms, including water on early Earth, ancient Mars and a gaseous exoplanet called K2 18b that may host clouds of water vapor (SN: 9/11/19). The pair also considered Titan’s methane rain, ammonia “mushballs” on Jupiter and iron rain on the ultrahot gas giant exoplanet WASP 76b (SN: 3/11/20). “All these different condensables behave similarly, [because] they’re governed by similar equations,” she says.

The team found that worlds with higher gravity tend to produce smaller raindrops. Still, all the raindrops studied fall within a fairly narrow size range, from about a tenth of a millimeter to a few millimeters in radius. Much bigger than that, and raindrops break apart as they fall, Loftus and Wordsworth found. Much smaller, and they’ll evaporate before hitting the ground (for planets that have a solid surface), keeping their moisture in the atmosphere.

Eventually the researchers would like to extend the study to solid precipitation like snowflakes and hail, although the math there will be more complicated. “That adage that every snowflake is unique is true,” Loftus says.

The work is a first step toward understanding precipitation in general, says astronomer Björn Benneke of the University of Montreal, who discovered water vapor in the atmosphere of K2 18b but was not involved in the new study. “That’s what we are all striving for,” he says. “To develop a kind of global understanding of how atmospheres and planets work, and not just be completely Earth-centric.” More

As our planet orbits the sun, it swoops through clouds of extraterrestrial dust — and several thousand metric tons of that material actually reaches Earth’s surface every year, new research suggests.

During three summers in Antarctica over the past two decades, researchers collected more than 2,000 micrometeorites from three snow pits that they’d dug. Extrapolating from this meager sample to the rest of the world, tiny pebbles from space account for a whopping 5,200 metric tons of weight gain each year, researchers report in the April 15 Earth and Planetary Science Letters.

Much of Antarctica is the perfect repository for micrometeorites because there’s no liquid water to dissolve or otherwise destroy them, says Jean Duprat, a cosmochemist at Sorbonne University in Paris (SN: 5/29/20). Nevertheless, collecting the samples was no easy chore.

First, Duprat and colleagues had to dig down two meters or more to reach layers of snow deposited before 1995, the year when researchers set up a field station at an inland site dubbed Dome C. Then they used ultraclean tools to collect hundreds of kilograms of snow, melt it and sieve the tiny treasures from the frigid water.

To hunt for micrometeorites that have fallen to Antarctica in recent decades, researchers dig trenches (pictured) to collect snow that is later melted and then sieved for the space dust.J. Duprat, C. Engrand, CNRS Photothèque

In all, the team found 808 spherules that had partially melted as they blazed through Earth’s atmosphere and another 1,280 micrometeorites that showed no such damage. The particles ranged in size from 30 to 350 micrometers across and all together weigh mere fractions of a gram. But the micrometeorites were all found within three areas totaling just a few square meters, the merest fraction of Earth’s surface. Assuming that particles of space dust are just as likely to fall in Antarctica as anywhere else let the team estimate how much dust fell over the entire planet.

The team’s findings “are a wonderful complement to previous studies,” says Susan Taylor, a geologist at the Cold Regions Research and Engineering Laboratory in Hanover, N.H., who was not involved in the new study. That’s because Duprat and colleagues found a lot of the small stuff that would have dissolved elsewhere, she notes.

About 80 percent of the micrometeorites originate from comets that spend much of their orbits closer to the sun than Jupiter, the researchers estimate. Much of the rest probably derive from collisions of objects in the asteroid belt. All together, these tiny particles deliver somewhere between 20 and 100 metric tons of carbon to Earth each year, Duprat and colleagues suggest, and could have been an important source of carbon-rich compounds such as amino acids early in Earth’s history (SN: 12/4/20). More

Seventeen tiny particles recovered from a flat-topped mountain in eastern Antarctica suggest that a space rock shattered low in the atmosphere over the ice-smothered continent about 430,000 years ago.

The nickel- and magnesium-rich bits were sifted from more than 6 kilograms of loose sediments collected atop the 2,500-meter-tall summit of Walnumfjellet, says Matthias van Ginneken, a cosmochemist at the University of Kent in England. Their exotic chemistry doesn’t match Earth rocks, but it does match the proportions of elements seen in a type of meteorite called a carbonaceous chondrite, van Ginneken and his colleagues report March 31 in Science Advances.

Most of the particles range in size from 0.1 to 0.3 millimeters across, and more than half consist of spherules that are fused together into odd-shaped globs. The elemental mix in the spherules closely matches that of particles found at two other far-flung sites in Antarctica— one more than 2,750 kilometers away — which suggests that all of the materials originated in the same event. Because the other particles were found in ice cores and dated to about 430,000 years ago, the team presumes that the newly found particles from Walnumfjellet fell then too.  

The chemistry of nickel- and magnesium-rich spherules (pictured) found on a mountaintop in Antarctica match that of a certain type of stony meteorites.Scott Peterson/micro-meteorites.com

The chemistry of nickel- and magnesium-rich spherules (pictured) found on a mountaintop in Antarctica match that of a certain type of stony meteorites.Scott Peterson/micro-meteorites.com

The meteor that broke up over Antarctica was between 100 to 150 meters across, the team’s simulations suggest, and probably burst at low altitude. Blast waves may have pummeled a 100,000-square-kilometer area of the ice sheet, the team estimates. The explosion left no crater, but peak temperatures where the plume of hot gases reached Earth’s surface would have hit 5,000° Celsius and may have melted up to a few centimeters of ice. A similar airburst over a densely populated area today would result in millions of casualties and severely damage an area hundreds of kilometers across (SN: 5/2/17). 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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