Perseverance's mission is to search for signs of ancient microbial life on Mars. Jezero Crater was selected as the landing site because it held a lake some 3.5 billion years ago. Scientists suspect Jezero could provide the geological context needed to hunt for fossils of microbes that may once have lived on Mars.
As part of its ongoing mission in the crater, Perseverance set out to extract a sample from a rock called "Brac." Before the mission even set foot on Martian soil, scientists were excited about Brac based on data gathered by instruments from the Mars orbiters.
"There was a lot of buzz about this rock before Perseverance left Earth, and now we have a sample of it," said Ken Farley, project scientist for Perseverance, based at the California Institute of Technology in Pasadena. "Brac lived up to the hype."
The rock sample arrived at NASA's Perseverance Sample Caching Facility at Johnson Space Center in Houston on July 31, 2023, following an 11-month journey back to Earth. It's one of the 10 samples the Perseverance team expects the mission to return from Jezero Crater in future missions.
When the Brac sample arrived, mission team members gathered around the tube like eager schoolchildren on the first day of school.
"It was such an exciting day in the clean room," said Farley. "Everybody has been looking forward to analyzing our first rock from the Jezero Crater floor. These rocks hold important clues to the geologic history of the crater, including when it was filled with water, and why that water disappeared."
The Brac sample is a dark, fine-grained sandstone. It contains grains of olivine, a mineral rich in iron and magnesium. This mineral typically precipitates out of molten magma, indicating the rock was once molten and, as such, is consistent with the team's prediction that the Jezero Crater floor used to be covered by lava flows.
"The mineral composition is consistent with volcanic rocks in the region, but we're going to do more analyses now that the sample is in our lab," Farley said. "We want to know not just what the rock is made of, but what processes contributed to its formation, why it's here in Jezero Crater, and whether those conditions could have supported microbial life."
With the Brac sample safely stowed away in the lab, the mission team will conduct a similar, detailed examination of the nine remaining tubes and then select the most promising samples for return to Earth.
By the end of this decade, three sample-return missions are planned: ESA (European Space Agency) will send a spacecraft to retrieve the samples, transfer them to a NASA lander, and then launch them into Mars' orbit. NASA's Mars Sample Return Orbiter will capture, contain, and return the samples to Earth. Once back in Earthly labs, a large scientific team will conduct a wide-ranging suite of analyses to determine if Brac and other Jezero samples once held signs of life.
