“We are definitely in the right place.”
There is a sense of relief in the scientific team in charge of the discovery vehicle Perseverance (Persist in Portuguese) made by the US space agency NASA on Mars.
Researchers are now confident that they have sent the vehicle to a location that offers the best possible chance of finding traces of life on the Red Planet.
“Percy”, as the robot is affectionately called, landed in Jezero Crater in February 2021 and has since taken thousands of photos of the surrounding area.
The interpretation of these images is the basis for the first scientific article based on these findings, published this week in the journal Science.
The analysis confirmed that the persistence is where it was once the bottom of a large lake on the surface of Mars, fed by a meandering river that reached a depression to the west. We are talking about a time that happened 3.5 billion years ago, when the climate of Mars was more like that of Earth.
From observations of persistence, it was possible to find that at the point where the river joins the lake, the flow abruptly decreases and the suspended sediments eventually precipitate, forming a delta. It is a wedge-shaped formation that you can see at many places on Earth.
It was in this environment that some microorganisms may have proliferated and perhaps traces remain that will be preserved today.
Professor Sanjeev Gupta from Imperial College London, a co-author of the Science paper, comments: “Some people said to me, ‘What’s new in this? Didn’t we already know that Jezero Crater had a delta?’ Well, actually, we didn’t know. We recognized from orbital images that Jezero had a delta, but you can’t be completely sure until you’re on the ground.
An alluvial fan or ejection cone is a geological formation in which, in general, a fan of material is deposited in a very high-energy environment, such as an ocean or river.
Martian microbes, if they were present, would have preferred the calmer, more stable waters of the delta.
Persistence descended about 2 km from the main delta, but the images captured by its telescope are more interesting, especially since it is located on an isolated mound, scientists have dubbed the Kodiak.
“It is possible to see some stratification in these remnants that would normally produce a developing delta.”
There are horizontal beds formed by fine-grained sediments that the river has thrown into the pit from its entrance to the lake. Above them are visible sediments that descend down the slope through the most advanced lobes of the delta. And higher still are sediments that were deposited by the river after the expansion of the delta’s banks.
In addition to the Kodiak and the main delta formation, Jezero has several large rocks. This indicates the existence of a flood at a later time in the crater’s history.
“Something has changed in hydrology. We don’t know if it was a climate-related phenomenon, we don’t know”, says Professor Gupta. “For rocks to move so big, you need something like a flood. Maybe there were glacial lakes in the local basin that sent these streams of water toward Jezero.”
Gupta told BBC News, “We see lakes overflowing on Earth in places like the Himalayas. In the Ganges basin, you have these big rocks mixed with normal river sand and that’s where a glacial lake flooded. “
Persistence’s science team will send you to the base of the main delta formation to drill through the ground in search of tiny boulders of clay they hope to find. They will also focus on a ring of limestone cliffs around the edge of Jezero, which probably represents the edge of Crater Lake at its deepest.
The robot has a mission to collect and store more than two dozen rock samples from different locations. These samples will be brought back to Earth in the early 2030s to be tested in laboratories capable of determining whether microbial life forms exist on the surface of Mars.
Plans for this are well underway and include sending another robot from NASA and its European Space Agency partners to retrieve samples from the crater spot where Perseverance stores them.
It will be a British made vehicle. He will collect the rocks and transfer them to a rocket that will propel them to a point in Mars orbit, where a satellite will be waiting to finally take them to Earth.
“We are about to enter the most exciting moment in the exploration of Mars,” says Sue Horn, head of space exploration at the UK Space Agency.
“With the propulsion system of the sample vehicle being tested next month, the dream of examining samples of the Red Planet will soon become a reality.”