NASA’s Perseverance Rover will go to Jezero Crater, which is increasingly seen as a place to search for evidence of past lives on Mars

In 2018, NASA decided that the landing site for its Mars 2020 Perseverance rover would be the Jezero crater. At the time, NASA said the Jezero crater was one of the “oldest and most scientifically interesting landscapes that Mars has to offer.” That assessment has not changed; in fact it has become stronger.

New research paper says the Jezero crater was formed over long enough periods of time to promote both habitability and preservation of evidence.

Jezero Crater is a dry paleo-lake bed, with a preserved river delta and sediment. It contains at least five different types of rocks that can be sampled. The crater also has geological features that are approximately 3.6 billion years old. It is an excellent feature to study and hopefully collect samples for your eventual return to Earth. Scientists hope the Rover Perseverance can find fossilized evidence of a single-celled early life.

“Being able to use another planet as a laboratory experiment on how life might have started elsewhere or where there is a better record of how life started in the first place, that could really teach us a lot about what life is.”

Mathieu Lapôtre, lead author, Stanford University

A new study based on the analysis of satellite images reinforces the scientific convenience of Jezero.

The study is titled “The Rhythm of River Meandering on Mars and the Implications for Deposits in the Western Delta of Jezero Crater”. It is published in the AGU Advances magazine. The lead author is Mathieu Lapôtre, assistant professor of geological science at the Stanford School of Earth, Energy and Environmental Sciences. The other author is Alessandro Ielpi from Laurentian University.

One of science’s main obstacles to understanding the history of Mars is timing. With telescopes, orbiters, landers, and rovers, we have learned a lot about Mars. Especially in the past two decades, scientists have uncovered compelling evidence showing that Mars was once warm, humid, and habitable. But questions of time remain.

There is ample evidence of ancient riverbeds on Mars, and some of the weather questions revolve around those rivers. How long did the rivers flow on Mars and how often? How long ago How long did it take deltas like that of Jezero crater? Mars was likely habitable at the same time as life evolved on Earth, and understanding the age of the ancient rivers of Mars and how long they lasted is a key to understanding habitability.

In their article, the authors write: “Here we develop a new model for calculating the rate of displacement of Martian rivers, which, when applied to orbital observations of the Jezero delta, allows us to determine a minimum duration for the formation of the delta ” Combined with other models and the work of other scientists, the pair of authors says that “… our results suggest that it took the delta a few decades to form over a total time period of probably hundreds of thousands of years.”

During those hundreds of thousands of years, there were many dry and arid periods. They say that the river that flows into the Jezero crater probably flowed for only one day every 15 to 30 years; maybe a little more often. On Earth, sediments preserve organic molecules, and the same is probably true on Mars. So if the sediments in Jezero were quickly buried, there is a good chance that the organic molecules will also be preserved there.

“There was probably water for a significant period on Mars and that environment was certainly habitable, even if it had been arid,” lead author Mathieu Lapôtre said in a press release. “We showed that the sediments were deposited quickly and that if there were organic compounds, they would have been quickly buried, which means they probably would have been preserved and protected.”

Rivers on Earth, Rivers on Mars

This study is related to another recent study of 2019 carried out by the same authors in rivers of our planet, specifically a type of river called “winding rivers of a single thread”.

That document showed that winding single-thread rivers without plants that stabilize their banks move laterally ten times faster than the same type of rivers with plant-stabilized banks. This lateral movement of river channels is called meander migration.

The tendency of rivers to meander has been studied for a long time. The authors say in their 2019 article that the river meander is “among the most unequivocal indicators of hydrologically mature planets.”

Based on the probable fact that the Martian rivers had no plants to stabilize their banks, and considering the gravity on Mars, the pair of researchers says that the Jezero Delta took at least 20 to 40 years to form, but that period of time was intermittent, and spanned some 400,000 years.

And that brings us back to the problem of time.

“This is useful because one of the great unknowns on Mars is time,” said Lapôtre. “By finding a way to calculate the speed of the process, we can start to gain that dimension of time.”

On Earth, meandering single-thread rivers are most often found with vegetation on their banks. Only recently were these types of plantless rivers detected, and before that, scientists thought that before plants appeared on Earth, there were only twisted, multi-strand rivers. But now scientists have found many single-threaded rivers without banks of vegetation.

“This specifically has not been done before because single-threaded rivers without plants were not really on anyone’s radar,” Lapôtre said. “It also has interesting implications for how rivers on Earth could have worked before there were plants.”

All rivers can go through drier spells, and it’s wet spells that create sediment buildup in deltas. The researchers think that on Mars, dry periods were 20 times more frequent than on Earth today. “People have been thinking more and more about the fact that the flows on Mars were probably not continuous and that there were times when they had flows and others when they had dry periods,” Lapôtre said. “This is a novel way to establish quantitative restrictions on the frequency with which the fluxes probably occurred on Mars.”

If there was life in the Jezero crater, most scientists seem to think that it never evolved much and was restricted to single-celled organisms. With this new understanding of how sediment deposits formed in Jezero Crater, and how it probably preserved evidence of life, it makes the Perseverance Rover mission even more exciting.

Life on Earth began about 3.5 billion years ago, around the same time as the Jezero crater was formed. Any life on Earth would have been single-celled when the crater formed. If single-celled life was present in Jezero long before multicellular life evolved on Earth, then something stopped Martian life, depleting the atmosphere and sterilizing the planet.

Since Earth is such a geologically active planet compared to Mars, many ancient proofs of life have been erased. But that never happened on Mars. In that sense, the Jezero crater may be a kind of time capsule, waiting to be opened by NASA’s Perseverance Rover.

We may finally, unequivocally, have evidence of past lives on Mars.

“Being able to use another planet as a laboratory experiment of how life could have started elsewhere or where there is a better record of how life started in the first place, that could actually teach us a lot about what life is.” Lapôtre said. “These will be the first samples we’ve seen as a rock on Mars and then brought back to Earth, so it’s quite exciting.”

Plus: