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Tuesday, May 21, 2024

NASA Lands the Perseverance Rover on Mars

In the Mission Support Area at Lockheed Martin’s campus in Littleton, Colorado, masked people sat close to computers, flying three spacecraft in orbit around Mars. These three—the Mars Reconnaissance Orbiter, Maven, and Odyssey—were all tasked, in one way or another, with downloading data from another spacecraft: the Mars Perseverance rover, which was attempting to land on the Red Planet. Information from these orbiters would help engineers learn about Perseverance’s status as it made its way through the atmosphere, and determine whether it survived. “Space is not a place to go,” read the words painted on one wall. “Space is a place to do.”

Scattered among the usual notes about unauthorized visitors and classified meetings, signs about social distancing, masks, and symptoms were plastered around the building. “No masks with exhaust valves” warned one, aerospacily. One was posted behind the head of Lockheed’s David Scholz, who about an hour before landing had been standing in a conference room 6 feet from everything, sporting a blue surgical mask above his double-pocketed tan shirt. NASA’s video feed played in the background. Scholz had just described himself as a “confident nervous wreck.” That’s because he is the principal engineer for a device called an “aeroshell,” which cocoons the rover against the most extreme conditions of its downward trip toward the surface of Mars.

The Lockheed engineers had been working on this project for years, and today, Scholz and his team could finally watch it be put to use. But that’s all they could do: watch. Their system was automated, and would do its job without them.

And so they watched as a human-made object fell from the sky, aiming to touch down in a crater called Jezero. The landing, scheduled for 12:55 pm Pacific Time, would mark the end of the Perseverance rover’s journey through space and the beginning of its stay at this desolate destination: a depression that was—billions of years ago—home to a lake and a river delta. It’s a place where life could, theoretically, have once survived.

Looking for spots that seem like they might have been amenable to ancient life, and evidence of potential past habitation, are among the Mars 2020 mission’s goals. The rover will also collect and store geological samples for a future mission to retrieve, and try producing oxygen from the planet’s plentiful carbon dioxide, in anticipation of future human astronauts’ needs.

But to get there, the spacecraft had to survive a harrowing process that engineers call “entry, descent, and landing,” or EDL, which is what the Lockheed Martin team was now nervously awaiting. These final stages happen during what’s been called (to the point of cliché) the “seven minutes of terror”—the time when the spacecraft must autonomously orchestrate its own E, D, and L without smashing into the ground. During its wild ride, the rover would experience speeds of around 12,100 mph and feel the equivalent of 12 times Earth’s gravity during deceleration. Its protective sheath would heat up to about 2,370 degrees Fahrenheit. Much could go awry: The craft could get too hot; its bits might not separate when they were supposed to; even if they did separate correctly, they could “recontact” (read: hit) each other; Perseverance could land in the wrong location; it could end up making its own impact crater. Choose your own nightmare.

“The key thing about EDL is that everything has to go right,” Allen Chen of NASA’s Jet Propulsion Laboratory, who leads the EDL team, had told me a couple of weeks before the landing. “There’s no partial credit.”

That 100 percent, A+ performance is what fires up nerves for even the confident engineers here at Lockheed Martin who worked on the aeroshell. The aeroshell has two parts: the heat shield, which looks like a steampunk space frisbee, and the backshell, a classic space capsule. The heat shield faces down toward the planet when the spacecraft smacks into the atmosphere, taking the business end of the pressure and heat. It’s made from tiles of a material called PICA, or phenolic-impregnated carbon ablator. “As it gets hot, it starts to decompose, and that decomposition absorbs a lot of energy and also creates gas that forms a boundary layer that protects the heat shield from the environment,” Scholz had explained ahead of the landing. The protected shield, in turn, protects its cargo. The device burns through the atmosphere at a tilt, which Scholz calls “an angle of attack,” and steers itself with thrusters.

The backshell houses, among other things, a parachute and the last leg of the landing system. Its key protective ingredient is called, catchily, SLA-561V, which Lockheed Martin developed for the Viking missions in the 1970s. The company has actually made every single one—10, in total—of the aeroshells NASA has shot to Mars. Both sections of the shell carry instruments that measure conditions during the drop, to better inform future missions because there’s nothing like ground—or, in this case, atmosphere—truth.

“Being a part of it is humbling,” Scholz told me the week before landing. Today, he bounced between two boardroom-type tables; on one of them, a 3D-printed model of the aeroshell sat on a pedestal near an industrial-sized container of “multi-task wipes.” A home-theater-sized screen displayed the scene at NASA, and a set of “Lockheed Martian” (get it?) stickers adorned the top of a cabinet nearby. Scholz shook his head occasionally as he stared at the feed from NASA TV and another screen showing downlinked data, tapping his foot.

Chen, who was at JPL in Pasadena watching the descent with much of the “EDL family,” had already filled me in on what the aeroshell was supposed to do next. “Landing on Mars is all about finding a way to stop, and stopping in the right place,” he had said. The first step is the extreme sport of using the atmosphere to slow spacecraft down. Then, 7 miles above the Red Planet, new technology called a “range trigger” would deploy a parachute based on where the spacecraft was relative to where it needed to end up—rather than when it reaches a specific velocity, as previous missions have done. Twenty seconds later, the heat shield would fly off, as pyrotechnics snapped off nine separate mechanisms and separated it from the rover and backshell. That snap would lay bare the radar and cameras that make up a new system called terrain-relative navigation. This system compares onboard maps to what the lander’s sensors see in real time, to show the spacecraft its location and help it avoid hazardous geology during its autonomous landing.

Then the skycrane, a sort of hovercraft hooked to the top of the rover, would fire up its eight downward-pointed rockets, which would guide Perseverance to the right spot, while continuing to slow it. The skycrane would gently lower the rover, attached to it by bridle cords, to solid ground, like a stork depositing a baby. Explosives would snap the stork from its delivery.

Perseverance would be, finally, alone.

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But it would take a while for that message to get to mission control, because signals can’t travel instantaneously between Earth and Mars. (“Whatever is happening has already happened,” Chen had told me, “and there’s nothing you can do.”)

As Perseverance entered the atmosphere, the Lockheed Martin conference room fell silent. No one spoke or picked up any of the Krispy Kreme doughnuts on the table. Every piece of information about the rover’s progress came an agonizing 11 or so minutes after it had actually occurred, a fact never far from anyone’s mind.

“The heat shield has been separated,” came the word from NASA TV, and the room erupted in whoops and applause for a few seconds—that being, of course, this team’s big moment—before falling quiet once again.

A few minutes later, NASA gave confirmation that the backshell had separated. More applause burst out.

“Excellent!” yelled someone.

“I’m here hugging,” said someone else, hugging, in fact, the air.

Then these words from NASA: “Touchdown confirmed.”

Several people in the Lockheed Martin room stood, clapping. “We landed on Mars!” one person said in amazement. “Holy cow,” responded their coworker.

“It feels,” Scholz said, “fantastic.”

Once Perseverance was safely on the ground, a team led by Jessica Samuels, surface mission manager for the mission at JPL, took over for the EDL family, checking in on and commissioning the instruments and the rover. “At that point, we start round-the-clock operations,” she had told me a couple weeks before landing. Perseverance will undergo this commissioning and check-out for about a month, and later this spring will test fly a small helicopter called Ingenuity, the first thing to make a powered flight on another planet, before science operations really start in a few months.

During that time, scientists have designed the rover to drive an average of 650 feet every martian day, often hitting up places of interest they identified ahead of time, and using the more-detailed data gathered from the ground to inform future movements and data collection. Perseverance will take photos, keep track of the weather, scan the surface with ground-penetrating radar, collect and analyze samples of rock and regolith to learn about their composition, and sock some away for potential future return to Earth.

Two instruments on Perseverance’s robotic arm will lend a hand in searching for signs of biology. PIXL shines an X-ray beam at rocks, glowing them up, with the specifics of the glow dependent on the rocks’ chemistry. Based on the resulting map of chemicals, textures, and structures, scientists can learn about how the rocks came to be how they are—including, perhaps, if life made them that way. Another instrument, called Sherloc, focuses on organic compounds and minerals. It’s both a microscope that takes pictures and a spectrometer that reveals composition of surface material. Combine those two sets of information, and “you end up producing a chemical map of what you’re looking at,” says Luther Beegle, Sherloc’s principal investigator. Minerals can reveal the long-ago conditions at a given spot—like the saltiness of the disappeared water—and whether they may have been habitable. And organics could be (though are not necessarily) signs of past life, especially if they show up in weird formations, like clumps. They speak to the planet’s past hospitality, whether or not any organisms took advantage of that.

Studying the origins of life is hard on Earth; the planet’s dynamic surface has erased evidence of the past, as plate tectonics recycle material. But Mars is a kind of time capsule, a tableau of the way the planet used to be. “Most of the geological processes turned off,” says Beegle.

If Sherloc shows scientists something especially promising, Perseverance will drill a sample to stash in a sealed tube for a future mission to find and return to Earth. Beegle says the current plan is to bring them back on a sample return mission slated to launch in 2026. But mission planning is rarely certain in the long term, subject as it is to political and budgetary winds. NASA’s webpage detailing Mars 2020’s science objectives is more circumspect, couching the samples’ homecoming in “if and when” terms.

Whatever Sherloc’s detective work finds, Beegle will be excited. It is, he says, “just as fascinating if Mars had life as if it didn’t have life.” If the Red Planet didn’t produce any organisms, it could mean that life has a hard time getting started; the coefficient of static friction for abiogenesis may be higher than many hoped.

But regardless, Sherloc will help find out. Readying such an instrument for a run on another planet is always cortisol-producing for the scientists who build it: They have to worry about whether the sensitive equipment will survive the shakedown of launch and landing, and that their moving parts and electronics will work exactly like they did in the terrestrial clean room. Beegle was a surface sampling system scientist for the Curiosity rover, which landed in 2012, when NASA’s team came up with the expression “seven minutes of terror.” Beegle recalls a colleague responding wryly to the catchphrase with “I’ve just lived seven years of terror”—the time he spent designing and testing new technology.

The terror also continues after touchdown, because if things go wrong, there may be no easy fix. Or any fix. “Everything stresses you out,” Beegle says. “Every time we turn the instrument on, there will be a worry in the back of your head that something is broken.” But sending a rover out to explore Mars is like sending your teenage kid out to drive, he says. He’ll worry every time he hands her the keys. But he also trusts that she’ll do a good job.

Another instrument aboard will be focused on a more familiar kind of life: humans. An experimental device called Moxie is designed to produce 99.6 percent pure oxygen from martian carbon dioxide, starting sometime in early March. From the outside, Moxie looks like a golden milk crate, stashed inside Perseverance’s main body. It takes in the CO~2~, then electrochemically prises it into oxygen and carbon monoxide. The amount it will make will be much smaller than what even a lone human explorer would need, producing oxygen that could “maybe to keep a small dog alive, something like a Boston terrier, maybe,” says Asad Aboobaker, a JPL engineer who works on Moxie.

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But this test project isn’t only about respiration. It’s also about rocket propellant, of which oxygen is usually a major component. “NASA wants to send people to Mars, but it also wants to get them back,” says Aboobaker. It’s borderline unreasonable to launch and land astronauts with the propellant they need to return, so one approach is to have the astronauts produce their own wherever they land. “That’s the real thrust—if I may make a pun—of this project,” says Aboobaker. Ideally, this small system will help them learn about how to scale the technology up for future missions.

We don’t know when humans might need that oxygen, or whether those rock-filled sample tubes will for sure come home, or whether we’ll indeed see signs of martian life in them or Perseverance’s analysis. But all of these experiments point toward an uncertain future: When we’ll learn more about whether we’re alone, and mount even more ambitious missions—for future robots and humans. Today, Perseverance moved in that direction, as it landed softly on this dusty otherworld.

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