Mars images reveal where Perseverance should look for ancient life
“This is what we came to search for.”
Shortly after the Perseverance rover landed on Mars on February 18, the car-sized robot captured its first images of Jezero Crater.
Sanjeev Gupta, a member of the Perseverance science team, recalls the first batch of images. The lighting was bad — and the ground control team couldn’t see the site’s details.
The next day, the team captured images during Mars’ early morning light. That’s when the mood shifted.
“You could see these large inclined beds that are dipping,” Gupta tells Inverse. “Then we started analysis and we thought, well this is actually very exciting because this is exactly what one would expect.”
Back on Earth, Gupta is a terrestrial geologist. He worked at the Gulf of Suez in the Sinai Peninsula — an experience that helped him make a critical connection: the same signs that signal a delta in Egypt were showing up on Mars.
According to a study co-authored by Gupta and published Thursday in the journal Science, Perseverance’s initial images are the first ground-based evidence that Mars may have once housed a delta branching out into a lake in Jezero Crater.
These images are clues: a way to help the rover narrow down and select the type of rock it should choose as a mission sample. In the best-case scenario, these rocks will contain evidence of ancient life.
What you need to know first — If you look at a photo of Mars, you’ll see a dry, desert-like terrain. But mounting evidence suggests the Red Planet was once a warm, wet world with lakes and rivers. It may have even been habitable.
We mostly know this from data collected by orbiting satellites. This is why the new Science study marks a change in direction.
“It completely changes once you land on the ground and you can actually see the rocks in detail,” Gupta says. “For Jezero Crater, it was inferred that there was a delta from orbital data.”
But the recent analysis of the images of Jezero Crater shows clear signatures of an ancient delta on Mars through long-distance observations.
What’s new — The study team used images captured by Perseverance during the rover’s first three months on Mars.
“When we bring those rocks back, we'll be able to analyze them for the chemical signatures of life.”
The images are of the western fan-shaped deposit of sediments — the delta. A delta is a landform that emerges as river flow deposits sediment.
After zooming in on the images and analyzing them, the images revealed a delta building out into a lake.
“What's exciting is that we already have this inkling from zoomed-in images and we'll be driving there the next couple of years so we'll be able to analyze them in really great detail,” Gupta says. “But it is amazing to say, ‘we've actually now got what we were looking for — this is what we came to search for.’”
Perseverance will make its way to the location identified in the images, and collect rock samples that could reveal clues of ancient life on Mars. The mission is designed to stow away those samples in a location on Mars where they will later be retrieved by another rover and taken to Earth.
“When we bring those rocks back, we'll be able to analyze them for the chemical signatures of life,” Gupta says.
The images also revealed large boulders about a meter wide at the uppermost part of a cliff. This may indicate that Mars may have also experienced high-energy, flash flooding.
“I certainly wasn’t expecting that.”
The scientists behind the recent analysis aren’t sure exactly what may have caused the flooding, but it could indicate intense rainfall on Mars.
“I certainly wasn’t expecting that,” Gupta says. “It’s quite dramatic.”
These results suggest the downstream of the delta may be the best place to search for signs of ancient life. This is the area where the delta likely built out toward a lake — and where preserved organic matter may linger.
“This data allows us to target those areas,” Gupta says. “We know where to go to look for evidence and collect samples that might contain evidence for ancient life.”
What’s next — Perseverance is currently driving toward the delta, and targeting similar rocks at the base while en route.
These rocks date back to about 3.9 billion years ago, early on in Mars’ history when the planet may have been habitable. Ultimately, the rover will collect around 40 rock samples from Mars.
“We’re going to be collecting a lot of samples and building up a picture of the overall environment,” Gupta says. “But it’s really exciting to have some initial results from the mission already.”
Abstract: Observations from orbital spacecraft have shown that Jezero crater, Mars, contains a prominent fanshaped body of sedimentary rock deposited at its western margin. The Perseverance rover landed in Jezero crater in February 2021. We analyze images taken by the rover in the three months after landing. The fan has outcrop faces that were invisible from orbit, which record the hydrological evolution of Jezero crater. We interpret the presence of inclined strata in these outcrops as evidence of deltas that advanced into a lake. In contrast, the uppermost fan strata are composed of boulder conglomerates, which imply deposition by episodic high-energy floods. This sedimentary succession indicates a transition, from a sustained hydrologic activity in a persistent lake environment, to highly energetic short-duration fluvial flows.