Life on Mars? NASA’s Perseverance probe begins unprecedented search for signals | Science

A probea NASA, has reached an important moment in its mission to Mars. This Tuesday (5/17), the six-wheeled robot will start climbing an ancient delta in the crater where it landed.

It will drive uphill, stopping occasionally to examine the rocks that seem most likely to have signs of past life on the planet.

On the way back, Perseverance will collect some of these rocks, placing the samples at the base of the delta to be picked up by later missions. The goal is to bring this material back to Earth in the 2030s for further analysis.

“The Jezero Crater delta is Perseverance’s main astrobiological target,” the project’s assistant scientist, Katie Stack Morgan, told the BBC.

“These are the rocks that we think have the most potential to hold signs of ancient life, and they can also tell us about the climate of Mars and how it changes over time,” she said.

Since then, the spacecraft has been testing tools and instruments, piloting an experimental mini-helicopter and collecting an overall impression of the site.

But the robot’s main purpose in traveling to the site of the Red Planet has always been to study the massive mound of sediment west of Jezero.

Based on satellite images, scientists suspect it is a delta. The first observations of Perseverance in the field now confirm this diagnosis.

The delta contains fine-grained rocks deposited in layers — Photo: NASA/JPL-CALTECH/ASU/MSSS

A delta is a structure that forms from silt and sand dumped by a river as it enters a larger body of water. The sudden deceleration that occurs in the flow of the river allows anything carried in suspension to fall.

In the case of Jezero, the largest body of water was most likely a crater-scale lake that existed billions of years ago.

“Rivers that flow into a delta bring nutrients, which are obviously useful for life; and therefore the fine-grained sediments that are brought and deposited at a high rate in a delta are good for conservation”, explains the scientist of the mission, Sanjeev. Gupta, from Imperial College London, UK.

“Also, if there was life inside, it could have been taken downstream and concentrated in a delta.”

In recent days, Perseverance has been moving up a “ramp” in the delta dubbed the Hawksbill Gap. This is a gentle slope that will bring the robot to an altitude of a few tens of meters above the crater floor.

The spacecraft has a powerful set of tools and instruments on its robotic arm — Photo: NASA/JPL-CALTECH

The ascension is a reconnaissance mission. Perseverance will “walk” in search of the most interesting rocks.

“The spacecraft has an incredible array of instruments that can tell us about the chemistry, mineralogy and structure of the delta by examining the sediments down to the scale of a grain of salt,” explains the scientist from Briony Horgan mission of Purdue University in the US state of Indiana.

“We will learn about the chemistry of this ancient lake, whether its waters were acidic or neutral, whether it was a habitable environment, and what kind of life it might have supported.”

Let’s be clear: no one knows if there was life on Mars, but these three or four rocks that Perseverance will collect from the bottom of the crater could perhaps find clues – if they exist.

An illustration shows Jezero Crater as it would have looked billions of years ago if it had been a lake — Photo: NASA/JPL-CALTECH

The robot itself is unlikely to be able to draw definitive conclusions, no matter how clever its instruments. Even on Earth, where we know microbial life has existed for billions of years, evidence for its earliest fossilized forms is difficult to interpret and still controversial.

To establish whether there was life on Mars, it will be necessary to wait for the arrival of the rocks on Earth for a detailed analysis that only the largest laboratories are equipped to carry out.

“The claim that there is microscopic life on another planet in our solar system is a huge claim. And so the evidence must also be huge,” says Jennifer Trosper, Perseverance Project Manager at NASA.

“I don’t think the instruments we have on their own can provide that level of evidence. They can provide something like, ‘We think this might be it,’ and then later when we get the samples back to Earth and use more sophisticated instruments, we can be sure of that,” she told BBC News.

Illustration of samples leaving Mars for Earth on a rocket launched from Jezero Crater — Photo: NASA

At the end of the year, Perseverance should deposit a first set of rocks during its return to the bottom of the crater. This will include not only the rocks collected during Hawksbill’s descent, but four samples collected over the previous months from the bottom of the crater.

A NASA, in collaboration with the European Space Agency, is in an advanced stage of planning the missions needed to retrieve these deposited rocks and send them to Earth. Those projects – which involve another probe, a Mars rocket and a carrier spacecraft – are expected to launch later this decade.

Perseverance still has years of work ahead of it. After depositing its first stockpile of rocks, the spacecraft will return to Hawksbill Gap at the top of the delta and beyond, to visit rocks that appear to be remnants of the shoreline of ancient Lake Jezero.

These deposits are made up of carbonate minerals and, again, appear to have formed in an environment conducive to recording past life on Mars – if it ever existed.

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