Perseverance carries hope of finding signs of ancient life on Mars

As the Perseverance rover cruises to Mars, hundreds of scientists anxiously await the moment when the planet’s newest robot explorer will land and start searching for signs of ancient life. The results of that search, says Katie Stack Morgan, could “reframe our place as humans in the solar system.”

Morgan, deputy project scientist for the Mars 2020 mission, made the remark in an interview during the ScienceWriters2020 virtual conference, where she outlined the Perseverance mission and its unique capabilities in a recorded presentation released Oct. 14 as part of the Council for the Advancement of Science Writing’s New Horizons in Science briefings. She has been with the project since its beginning in 2013.

Although Mars is uninhabitable now, findings from previous rover missions led scientists to believe that life, of the microbial variety, could have formed on Mars billions of years ago. Perseverance is the first rover specifically equipped to answer the question of whether there was life on Mars, or Earth remains the only planet that has ever supported life.

The rover will be at the right place with the right set of tools to find the answer, Morgan said.

As part of the National Aeronautics and Space Administration’s Mars Exploration Program, Perseverance has four scientific objectives: to search for environments where life could have thrived long ago, identify signs of this life, collect and cache samples on Mars for future recovery, and, finally, prepare for future human missions on Mars by testing new technologies.

To ensure these objectives are met, Morgan coordinates the efforts of more than 350 scientists around the world. In the interview, she described this role as both “a challenge and a blessing.”

Location, location, location

It took five years to pick the best landing site for the rover: Jezero Crater. With an estimated age of 3.8 billion Earth years, this crater was formed around the time of the earliest known signs of life on Earth. Jezero Crater also has an outlet valley, something usually formed when water accumulating in a lake spills over the rim. The presence of the outlet valley implies that water must have been in the crater for a significant period of time, increasing the odds of life forming. This location also has a well-preserved delta, an ideal deposit to search for evidence for life.

“If this same environment that we have on Jezero would be found here on Earth, it would absolutely be habitable,” Morgan said in her presentation.

If microbes ever formed in Jezero Crater, they probably would have had to compete for light with sediment brought in by rivers flowing into the lake. Over time, these “gooey layers of microbial life,” as Morgan calls them, would have become fossilized in various shapes. Perseverance will look for these shapes within rocks and try to answer the question: did this promising shape form in a biological way (“microbes try[ing] to save their community”), or simply through physics (gravity)? The rover is the best equipped to answer this question, said Morgan.

The payload on Perseverance includes tools never before sent to the surface of Mars, including SHERLOC, an ultraviolet spectrometer that can analyze the structure of elements within rocks, and SuperCam, which vaporizes rocks and uses two laser technologies to analyze the elements in the vaporized rocks as well as how they’re arranged. With this equipment, geologists can identify whether the rocks contain biosignatures — signs of ancient life—that only microbes could leave behind.

Even if Perseverance finds signs of life, determining whether life existed on Mars will have to wait until samples cached by the rover are brought back to Earth for further analysis by a later mission. For now, Perseverance is still in cruise mode, traveling 1,000 miles a minute. Already 146 million miles away from Earth, the rover is expected to touch down in February 2021.