Published: Fri, June 08, 2018
Science | By Joan Schultz

Life on Mars? Rover’s Latest Discovery Puts It ‘On the Table’


But now new results from NASA's Curiosity rover, including the discovery of ancient organic material, have revived the hope of doing just that.

While we know that Mars was habitable in the past, the case demonstrates just how hard it will be to ever prove the existence of past life on its surface.

NASA's Jennifer Eigenbrode said in an interview this year, 'I look at organic molecules in rocks, ice and sediments and try to figure out where they came from and what happened to them over time. Organic matter can be one of several things: a record detailing ancient life, a food source for life or something that exists in the place of life. That's not to say there are no non-biological sources, but on our world they're swamped by cow farts and belching bacteria.

Since it landed at the Gale Crater in 2012, the Curiosity Rover has been sniffing out methane in the area. What the study has done, though, is to propel the search for life on Mars higher up the list of global space exploration priorities - giving space agencies ammunition to argue for a coordinated programme of missions to explore the Red Planet. The rover has returned a lot of fascinating science, but its latest discovery offers the best evidence yet for life on Mars.

At this point, we simply don't know whether the origin is biological or geological.

The two studies appear in the journal Science.

NASA now operates three orbiters and two surface rovers at Mars with a new lander - InSight - on the way.

Auckland University astrobiologist Kathleen Campbell, who formerly worked at Nasa, said it was the first time the building blocks of life had been shown "for sure" to be on the planet.

These chemicals might not mean a great deal to most of us, but to areologists (that's Martian geologists) it's an indication that the organic chemistry in Martian mudstone is extremely similar to our own.

The nuclear-powered rover has detected a variety of organic compounds, a requirement for life as it's known on Earth, in three-billion-year-old rocks deposited on the floor of Gale Crater. "If you explore both of those paths forward, it's astounding", Eigenbrode said. That leaves open the possibility that microorganisms once populated the red planet - and still might. And if life does exist elsewhere, it may be very different or even form differently from how we understand life on Earth. The 2020 rover will include an advanced spectrometer to scan for organic molecules.

Over five years, Curiosity has used its Tunable Laser Spectrometer to measure methane in the atmosphere at the Gale crater.

Over the years, scientists have amassed a number of clues that can help answer the question of Mars' habitability, including evidence of liquid water. The rover spotted the chemical signature in samples take from sedimentary rocks the formed some 3 billion years ago.

Even though the TGO mission can't get as close to the source as the Curiosity Rover, Dr Webster said it could locate potential areas where methane is concentrated or coming from. She said the discoveries break down some of the strongest arguments put forward by life-on-Mars skeptics, herself included.

This work was funded by NASA's Mars Exploration Program for the agency's Science Mission Directorate (SMD) in Washington.

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