NASA's Perseverance to throw light on geological evolution of the Red Planet

There has been enormous enthusiasm in the space science community since NASA chose Jezero crater as the landing site for its upcoming Mars 2020 rover mission after a five year search.

NASA's Perseverance rover to Mars, expected to launch in July, will look for signs of past microbial life in river delta deposits formed over billions of years that might have enhanced preservation of evidence of life.

The delta, speculated to have formed due to sediment deposits at the mouth of Hypanis Valles, a river system on ancient Mars, separates the southern highlands from the northern lowlands.

Scientists believe that Mars once had an ancient ocean and a water cycle similar to Earth's and large seas or an ocean ever existed in the northern lowlands.

A new Stanford study, published online in AGU Advances on April 23, offers guidance for sample recovery in order to better understand the ancient Martian climate, duration of this delta formation and whether wet Mars was habitable.

"There probably was water for a significant duration on Mars and that environment was most certainly habitable, even if it may have been arid," according to lead author Mathieu Lapotre, an assistant professor of geological sciences at Stanford's School of Earth, Energy & Environmental Sciences (Stanford Earth). "We showed that sediments were deposited rapidly and that if there were organics, they would have been buried rapidly, which means that they would likely have been preserved and protected."

Jezero crater was selected for NASA's next rover mission partly because the site contains a river delta, which on Earth are known to effectively preserve organic molecules associated with life. But without an understanding of the rates and durations of delta-building events, the analogy remained speculative.

The study incorporates a recent discovery the researchers made about Earth: Single-threaded sinuous rivers that don't have plants growing over their banks move sideways about ten times faster than those with vegetation. Based on the strength of Mars' gravity, and assuming the Red Planet did not have plants, the scientists estimate that the delta in Jezero crater took at least 20 to 40 years to form, but that formation was likely discontinuous and spread out across about 400,000 years.

Findings from Jezero crater could aid our understanding of how life evolved on Earth. If life once existed there, it likely didn't evolve beyond the single-cell stage, scientists say. That's because Jezero crater formed over 3.5 billion years ago, long before organisms on Earth became multicellular. If life once existed at the surface, its evolution was stalled by some unknown event that sterilized the planet. That means the Martian crater could serve as a kind of time capsule preserving signs of life as it might once have existed on Earth.

"Being able to use another planet as a lab experiment for how life could have started somewhere else or where there's a better record of how life started in the first place—that could actually teach us a lot about what life is," Lapotre said. "These will be the first samples that we've seen as a rock on Mars and then brought back to Earth, so it's pretty exciting."