After months of spaceflight, an 8-minute planetary plunge, and weeks of Mars exploration, NASA’s Perseverance rover is beginning its primary scientific task: drilling out a finger-size core of martian rock from a former lakebed for return to Earth. If all goes well, the first drilling sample will be collected by early August, the agency announced today.
Perseverance has operated well since its February landing, and during its recent drive, the rover has turned on its autonomous navigation, allowing it to cover more terrain than when under pure human operation. The rover has also tested its rock-storage system, feeding a sampling tube that it kept in the drill bit since landing, to capture ambient contamination, back into the robotic arm in its guts. There the tube was first imaged and then sealed for storage. “The great news is that it all worked perfectly,” says Jennifer Trosper, Perseverance’s project manager at NASA’s Jet Propulsion Laboratory. “We are ready to sample.”
Now, 1 kilometer south of its landing site, Perseverance has reached the spot where it will drill what its operating team calls paver stones—flat, white, dust-coated rocks found throughout much of the floor of Jezero crater. This terrain is believed to be the oldest in the crater. But it remains unclear whether this landscape was deposited by the lake or instead formed by volcanic flows, the latter of which could capture, with radioactive elements, an accurate date of the lake’s existence. Recent close-up images taken of the paver stones fail to resolve the scenarios: The rocks are covered with sand grains and pebbles, along with some sort of purplish coating, confounding remote measurements, says Ken Farley, the mission’s project scientist and a geologist at the California Institute of Technology.
In the next week or so, the rover will unleash one instrument that could help answer this puzzle: an abrasion bit mounted at the end of its 2-meter-long arm. After grinding into the rock, the arm will blow compressed gas to clear away the grit, giving a clear glimpse of the underlying rock. The rover can then use its arm-mounted camera and laser and x-ray probes to expose its structure and mineralogy. “I’m pretty confident we will be able to answer this question,” Farley says.
Whether the rocks are volcanic or sedimentary, after Perseverance performs the abrasion procedure, the team will direct the rover to drill and collect a core sample of the pavers, targeting a rock that is average in chemistry, mineralogy, and texture. The chalk-size core will be stored in an ultraclean metallic tube, one of 38 samples that the rover eventually collects, with about 30 of those likely to be returned to Earth by later missions. For now, it will reside in the rover’s belly until later in the mission, when it will likely be deposited in a cache on the surface near the crater’s rim a year and a half from now.
Perseverance has already spotted some surprises about Jezero crater, including the billions-of-years-old fossilized delta to its west that is the rover’s destination next year. Midway up the delta front, there are distinctive layered deposits that show the lake was quite high, quiet, and stable for a long time, Farley says. But even higher up, from a time later in the lake’s history, there are 1-meter-wide smooth boulders that could only have been carried by floodwaters. This suggests the lake could have seen distinct phases in its life. This fits into a larger picture of the planet’s history, from when lakes were common on the surface to a colder time when there were only periodic floods, Farley says.
Some tests of this hypothesis could come from the paver stones or Perseverance’s next target, Séítah, a region of sand dunes and ridges to its west that the car-size rover has skirted past. Seen from orbit to be rich in olivine, a volcanic mineral, and carbonates, which can form when olivine is exposed to water and carbon dioxide, Séítah is a barrier and an opportunity—the rover can’t drive through it to reach the delta without getting stuck, but it has unexpectedly complex geology, including terrain that might preserve signs of past life. After the paver stones, the Perseverance team has devised an incursion from above and behind to access its secrets.
First, the Ingenuity helicopter, in its ninth flight earlier this month, scouted across Séítah in a 625-meter journey, breaking records for flight duration and speed before landing on the other side of its dunes. The helicopter photographed the intersection of Séítah with the paver unit that Perseverance is currently exploring—important to confirming whether the pavers are, in fact, older. And it also scouted fractures that could hold evidence of whether ancient subsurface habitats existed in Jezero.
Meanwhile, from afar, Perseverance has spied fine layering in Séítah’s ridges, including a prominent 40-meter-tall plateau dubbed Kodiak that is, in all likelihood, a remnant of the delta’s further reach into the lakebed. Such layering could be caused by mudstones, which smother and preserve life on Earth. But the layers could have a volcanic origin, as well—and so the rover will loop south around Séítah later this year, nudging into a flat space where it can safely sample.
Once the Séítah campaign is done, Perseverance will backtrack all the way north to its landing site, “putting the pedal to the metal,” Trosper says. And from the landing site, the rover will head north then west on a safe route to the looming cliff of the main delta—and the life-trapping muds entombed within it.