When the agency's newest rover mission searches for fossilized microscopic life on the Red Planet, how will scientists know whether they've found it?

NASA's Mars 2020 Perseverance rover will be the agency's ninth mission to land on the Red Planet. Along with characterizing the planet's geology and climate, and paving the way for human exploration beyond the Moon, the rover is focused on astrobiology, or the study of life throughout the universe. Perseverance is tasked with searching for telltale signs that microbial life may have lived on Mars billions of years ago. It will collect rock core samples in metal tubes, and future missions would return these samples to Earth for deeper study.

"To quote Carl Sagan," said Gentry Lee, chief engineer for the Planetary Science Directorate at NASA's Jet Propulsion Laboratory, "'If we see a hedgehog staring in the camera, we would know there's current and certainly ancient life on Mars, but based on our past experiences, such an event is extremely unlikely. Extraordinary claims require extraordinary evidence, and the discovery that life existed elsewhere in the universe would certainly be extraordinary.'"

Mars 2020 mission scientists believe that Jezero Crater, the landing site for Perseverance, could be home to such evidence. They know that 3.5 billion years ago, Jezero was the site of a large lake, complete with its own river delta. They believe that while the water may be long gone, somewhere within the 28-mile-wide (45-kilometer-wide) crater, or perhaps along its 2,000-foot-tall (610-meter-tall) rim, biosignatures (evidence that life once existed there) could be waiting.

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