Scientists look ahead to the search for past Martian life with Perseverance


WASHINGTON — On the eve of the landing of the rover Perseverance on Mars, scientists are looking ahead to the work it will do searching for evidence of past life on the planet and collecting samples for return to Earth.

At a Feb. 17 briefing a little more than 24 hours before Mars 2020 arrives at Mars, project officials confirmed that the spacecraft is operating well and on course for a landing at 3:55 p.m. Feb. 18 at Jezero Crater.

“Perseverance could land itself already without any more help from us on the ground,” Matt Wallace, deputy project manager, said at the briefing, based on its current status and the procedures on board to perform the various steps of entry, descent and landing (EDL). “So, the spacecraft is ready and, I think, the team is also ready.”

Mars 2020 is headed toward one corner of its targeted landing area, highlighted in maps of Jezero Crater as a green box. “Anywhere in that area, the entry, descent and landing system can finish the job of getting it down to Jezero Crater,” Allen Chen, EDL lead for the mission, said. “We think that the landing system can finish the job from here.”

Controllers had the option of one final trajectory correction maneuver late Feb. 17, but Chen said that would not be necessary. “We’re very comfortable pretty much anywhere in that green box, even here on the edge.”

The focus on the mission has been on the landing, including the famous “seven minutes of terror” during EDL, but others on Mars 2020 are looking ahead to what happens should Perseverance land as designed. “It turns out, after landing, it’s not over. In fact, it’s just beginning. The science mission is just beginning,” said Jennifer Trosper, deputy project manager.

If all goes well, initial images from the rover could come immediately after landing from hazard cameras, or hazcams, mounted on the front and rear of the rover. More data, including higher quality images, would come after a pass over the landing site by the European Space Agency’s ExoMars Trace Gas Orbiter around 9:30 p.m. Eastern.

Deployments of the rover’s mast, which has additional cameras other instruments mounted on it, will follow over a few days, along with a high-gain antenna and tests of other systems. “We hope to be driving in a few weeks,” she said, moving to a location where it will release Ingenuity, the small helicopter mounted underneath it, for flight tests.

The mission’s team of scientists will be getting ready for full-scale science activities. The landing “marks a fundamental transition from the getting-there phase of the mission to the doing phase, to actually exploring Jezero Crater,” said Ken Farley, project scientist for the mission.

Those scientists will be eagerly awaiting to use Perseverance’s instruments to study the landing site, including looking for evidence that the planet was once inhabitable and potentially inhabited by microbial life.

“Perseverance is the first real astrobiology mission since Viking,” said Lori Glaze, director of NASA’s planetary science division. The twin Viking landers, which touched down on Mars in 1976, carried instruments to look for evidence of present-day life. “We know that the experiments that we designed probably weren’t quite the right way to go about that.”

The instruments on Perseverance will look for biosignatures, like organic materials or structures left behind by past life. Ken Williford, deputy project scientist, used as one example stromatolites, sedimentary formations created by microbial life on the early Earth, showing off an example of one found in Australia.

“We may get so lucky as to find something so beautifully preserved as this stromatolite,” he said. “But far more likely is that anything we find will be much more ambiguous.”

Mary Voytek, director of NASA’s astrobiology program, agreed. “This particular mission is finding itself in more of a gray area,” able to find features that could be explained by both biological and abiological processes. “We’re going to have instruments, particularly when we bring the samples back, that will be able to distinguish that.”

A key role for Perseverance will be to cache dozens of samples, each about the size of a piece of chalk, that will be returned by later missions. That will allow scientists to study them in far greater detail in terrestrial laboratories than would be possible with instruments that could be flown on spacecraft to Mars and eliminate that ambiguity.

Sample collection will begin in the summer, and drive the pace of the mission. “This is a very fast-paced, high-stakes operation. It’s kind of a race to get it done,” Farley said of the daily cycle of analyzing data returned by Perseverance, deciding on next steps and uploading commands to the rover. That’s required significant training for the hundreds on the science team. “Scientists do not usually perform under these kinds of circumstances.”

The missions that will collect those samples and return them to Earth — a lander led by NASA with a European rover, and an orbiter led by ESA with a NASA collection system — are still in early phases of their design. NASA approved last December moving the Mars Sample Return program into Phase A of development, working on initial designs and key technologies.

That Phase A work also includes incorporating recommendations made by an independent review board, whose report last November broadly endorsed the program but raised a number of concerns about the design of the missions, their cost and schedule. In particular, it recommended that the launch of the lander and orbiter missions, currently scheduled for 2026, be pushed back to as late as 2028 based on NASA experience on other missions.

“We’re taking the findings and recommendations from that report very seriously,” Bobby Braun, Mars Sample Return program manager at the Jet Propulsion Laboratory, said. The program is analyzing various trades in the design of the missions based on that report and other work, an effort that he said will be completed by the end of Phase A this October.

That work, though, depends on Perseverance sticking the landing in Jezero Crater. Wallace, asked at the briefing for the odds of a successful landing, said it was “very, very hard” to provide a numerical estimate. “There’s no go-backs, there’s no retries. It’s a difficult and dangerous part of the mission, and I think you always have to respect that,” he said. “I think we’ve done everything we can to make it successful, and we’ll see how it goes tomorrow.”