Billions of years ago, the Martian surface could have supported microbial life as we know it. But did such life ever actually exist there?
Scientists have sought answers to astrobiological questions on Earth, studying regions similar enough to Mars to understand what the Red Planet's microscopic fossil record might look like.
One research trip late last year involved fossilised microbes in the Australian outback. Earlier this year, seven mission scientists headed to a dry lakebed in Nevada as 150 worked with them remotely for the Rover Operations Activities for Science Team Training, aka the ROASTT.
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Rather than bringing a car-sized rover, the seven field team members stood in for it.
Wielding cameras and portable spectrometers during simulated operations spread out over a two-week period, they received instructions from the scientists located elsewhere, just as the rover will after it lands on 18 February 2021.
Like all Mars rovers, Perseverance will be run by a distributed team of scientists and engineers – some located in the operations centre at NASA's Jet Propulsion Laboratory, which leads the new mission, and some located at research institutions around the world.
They will discuss where to go, which samples to study, and – for the first time – which rocks to collect in metal tubes for eventual return to Earth for deeper study.
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The Nevada exercise not only helped team members practice what to look for with Perseverance; it helped them get used to working with one another and with the rover.
The field site was also an opportunity for research: Besides simulating a rover, the field team members were studying the field site, providing insights that could help shape the search for past life on Mars.
The field team also had an important low-tech tool: a cheap broom used to sweep away their footprints, both to preserve the Martian feel of the landscape and to avoid providing the remote scientist a sense of scale in the rock images they were providing.
Walker Lake is an ideal training ground for spotting ancient microscopic life. The lake once extended much farther than it does today; the parts of it that dried up tens of thousands of years ago are now studded with stromatolites – collections of fossilised microbes and sediment that have hardened into what often look like bulbous, moundlike growths.
It remains to be seen whether Jezero Crater, Perseverance's landing site, has anything akin to stromatolites, but it, too, is an ancient lakebed.
JPL scientist Raymond Francis, who led the field team, explained, “It's especially important for scientists who are new to Mars rovers. It's a team effort, and everyone has to learn how their roles fit into the whole mission.”
Lisa Mayhew, a geochemist and geomicrobiologist at the University of Colorado Boulder, is one of those newcomers.
To study the relationship between water, rocks and microbial life in extreme environments, she's worked with deep-sea remotely operated vehicles, like the Woods Hole Oceanographic Institution's Jason.
In places such as the Lost City, located at the bottom of the Atlantic Ocean, she's watched Jason explore craggy mineral towers.
Microbes in and on these towers thrive by metabolising energy-rich gases, like hydrogen and methane, produced from reactions between water and rock. Some scientists think life on Earth may have originated in such places.
"While it's similar in many ways to operating and directing Jason, it's happening on a much larger scale and you're pretty clueless until you're actually planning a rover drive. You have to learn all the different software tools and understand the distinction between different roles,” Mayhew added.
Perseverance is a robotic scientist weighing about 1,025 kilograms. The rover's mission will search for signs of past microbial life.
It will characterise the planet's climate and geology, collect samples for future return to Earth, and pave the way for human exploration of the Red Planet. No matter what day Perseverance launches during its 17 July-5 August launch period, it will land at Mars' Jezero Crater on 18 February 2021.
The Mars 2020 Perseverance rover 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.
Charged with returning astronauts to the moon by 2024, NASA will establish a sustained human presence on and around the moon by 2028 through NASA's Artemis lunar exploration plans.
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