If the agency’s latest rover mission searches for fossilized microscopic life on the red planet, how will scientists know if they found it?
NASA’s Mars 2020 Perseverance rover will be the agency’s ninth mission to land on the Red Planet. In addition to 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 has been charged with looking for telltale signs that billions of years ago microbial life lived on Mars. It will collect rock core samples in metal pipes, and future missions would return these samples to Earth for deeper study.
To quote Carl Sagan, said Gentry Lee, chief engineer of the Planetary Science Directorate of NASA’s Jet Propulsion Laboratory, “If we saw a hedgehog staring into the camera, we would know there is a current and certain old life on Mars. but based on our past experience, 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. ”
Scientists on the Mars 2020 mission believe that Jezero Crater, the landing site for Perseverance, could be home to such evidence. They know that Jezero was the site of a large lake 3.5 billion years ago, complete with its own river delta. They believe that, although the water has long since disappeared, somewhere in the 28-mile-wide (45-kilometer) crater, or perhaps along the 2,000-foot-high (610-meter) rim, biosignatures (evidence that life once existed there) could be to wait.
“We expect the best places to look for biosignatures are in Jezero’s lake bottom or in coastal sediments that can be covered with carbonate minerals, which are especially good at preserving certain types of fossilized life on Earth,” said Ken Williford, deputy project scientist for the Mars 2020 Perseverance rover mission at JPL. “But as we look for evidence of ancient microbes in an ancient alien world, it’s important to be open to us.”
NASA’s fifth rover to fourth planet from the sun carries a new set of scientific instruments to build on the discoveries of NASA’s Curiosity rover, which found parts of Mars could support microbial life billions of years ago.
On the hunt for biosignatures
Any biosignature hunt includes the rover’s array of cameras, especially Mastcam-Z (on the rover’s mast), which can zoom in to inspect scientifically interesting targets. The mission’s science team can order Perseverance’s SuperCam instrument – also on the mast – to fire a laser at a promising target, generating a small plasma cloud that can be analyzed to help determine its chemical composition. If that data is intriguing enough, the team can order the rover’s robotic arm to go inside for a closer look.
To do that, Perseverance will rely on one of two tools on the turret at the end of its arm. PIXL, the planetary X-ray lithochemistry instrument) will use its small but powerful X-ray beam to search for potential chemical fingerprints from past lives. The SHERLOC instrument (the Scanning Habitable Environments with Raman & Luminescence for Organics & Chemicals) has its own laser and can detect concentrations of organic molecules and minerals formed in aqueous environments. Together, SHERLOC and PIXL will provide high-resolution maps of elements, minerals and molecules in rocks and sediments from Mars, allowing astrobiologists to assess their composition and determine the most promising cores.
One enduring hope of the science team is to find a surface feature that cannot be attributed to anything but ancient microbial life. One of those features could be something like a stromatolite. On Earth, stromatolites are undulating, rocky hills long ago formed by microbial life along ancient coasts and in other environments where metabolic energy and water were abundant. Such a striking feature would be difficult to describe in geological processes.
“Yes, there are certain shapes that form in rocks, where it’s extremely difficult to imagine an environment with no life that could cause that shape to form,” Williford said. “But that said, there are chemical or geological mechanisms that can produce domed stratified rocks, as we typically think of as a stromatolite.”
Enter the Perseverance sample caching system. The steamer-sized collection of engines, planetary gearboxes and sensors is among the most complex, capable, and cleanest mechanisms ever sent into space. With this, the science team collects the most intriguing samples they can find, stores them in sample tubes, and then deposits them later so that future missions can collect the sample tubes and fly them back to Earth for analysis.
“The tools needed to definitively prove that microbial life once existed on Mars is too large and complex to bring to Mars,” said Bobby Braun, Mars Sample Return program manager at JPL. “That’s why NASA is working with the European Space Agency on a multi-mission called Mars Sample Return to retrieve the samples that Perseverance collects and return them to Earth for study in laboratories around the world.”
And when that happens, samples from Mars’ Perseverance rover could tell us that billions of years ago life existed elsewhere in the universe. But they can also indicate the opposite. So what?
“We have strong evidence that Jezero Crater once had the ingredients for life. Even if we conclude after returned sample analysis that the lake was uninhabited, we will have learned something important about the range of life in the cosmos, ”said Williford. “Whether Mars was once a living planet or not, it is essential to understand how rocky planets like ours form and evolve. Why did our own planet remain hospitable while Mars became a desolate wasteland? “
Perseverance may not be the final word on whether the Red Planet ever contained life, but the data it gathers and the discoveries it makes will play a key role when that result is achieved.
Humanity has focused on Mars since Galileo became the first human to see it through a telescope in 1609. Has it ever had life? The answer may be waiting for us somewhere in Jezero Crater. NASA’s Perseverance rover will begin the process of finding out tomorrow.
More about the mission
A primary objective of Perseverance’s mission on Mars is astrobiology, including the search for signs of ancient microbial life. The rover will characterize past geology and climate, pave the way for human exploration of the Red Planet, and be the first mission to collect and store Martian rock and regolith.
Subsequent missions from NASA in conjunction with ESA (European Space Agency) would send spacecraft to Mars to collect these sealed samples from the surface and return them to Earth for in-depth analysis.
The Mars 2020 mission is part of a larger program that includes missions to the moon as a way to prepare for human exploration of the red planet. With a mission to bring astronauts to the moon by 2024, NASA will establish a sustainable human presence on and around the moon by 2028 through NASA’s Artemis lunar exploration plans.
JPL, which is operated for NASA by Caltech in Pasadena, California, built and operated the Perseverance rover.
For more on perseverance:
mars.nasa.gov/mars2020/
nasa.gov/perseverance
For more information about NASA’s Mars missions, visit:
https://www.nasa.gov/mars
News Media Contacts
DC Agle
Jet Propulsion Laboratory, Pasadena, California.
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Alana Johnson / Gray Tombstone
NASA Headquarters, Washington
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