The researchers are sure they have now sent the robot to a location that offers the best possible opportunity to find signs of ancient life.
There is an air of relief in the science team leading the US Space Agency (NASA) Perseverance rover on Mars. The researchers are sure they have now sent the robot to a location that offers the best possible opportunity to find signs of ancient life. “Percy” landed in Jezero Crater in February and has since taken thousands of images of its surroundings.
The interpretation of these images forms the basis of the first scientific article to be printed, in this week’s edition of Science Magazine.
Analysis confirms that the rover sits on the floor of a former large lake that was fed by a meandering river entering the deep basin from the west. We are talking about events over 3.5 billion years ago, when the climate on the Red Planet was much milder.
From the observations of Perseverance, it is now certain that where the river system met the lake water, flows suddenly slowed down and the suspended sediment fell to form a delta – the kind of “landform” in wedge shape that you will see everywhere on Earth. .
It was in such an environment that the microorganisms could have thrived and their chemical traces could have been preserved.
“People said to me, ‘So what’s up here? Didn’t we know there was a delta in the Jezero crater? ‘. Well, we actually didn’t. We had deduced from the orbital imagery that Jezero contained a delta, but until you’re on the ground, you can’t be absolutely sure. We could have looked at an alluvial fan, ”said Professor Sanjeev Gupta of Imperial College London, UK, who is co-lead author of the new scientific paper.
An alluvial cone is a related landform in which, generally speaking, the cone of deposits is deposited in a much higher energy environment, such as during a flash flood. It is not such a favorable environment for biology. Martian microbes, assuming they existed, would have preferred the calmer, more persistent waters associated with a delta.
Perseverance has landed a few miles from the main delta formation, but the telescoping views from the rover are appealing, especially when it comes to an isolated mound, or mound, nicknamed Kodiak.
It is possible to see in this vestige part of the classical stratification produced by a developing delta.
There are horizontal “bottoms” made up of fine-grained sediments dumped by the river furthest from its entry into the crater lake. Above these are sloping “forests” which were the sediments that tumbled down the slopes of the advancing lobes of the delta. And higher still are the “topsets,” which were the sediment deposited by the river after the edges of the delta had extended away. Again, these are horizontal.
At the top of Kodiak and the main Jezero Delta formation are many large boulders. These speak of flood events late in the history of water in the crater.
“Something has changed in hydrology. We don’t know if it was climate related, ”said Prof Gupta. “But to move these big rocks, you need something like a flood. Maybe there were glacial lakes in the local watershed that sent this floodwaters into Jezero.
“We are seeing lake explosions on Earth in places like the Himalayas. In the Ganges basin these large boulders are mixed with normal river sands and that’s where there was an episode of sudden flooding from a glacial lake, ”he told BBC News .
The Perseverance science team will send the rover to the base of the main delta formation to drill what should be fine-grained mudstones. They will also target a ring of carbonate rocks around the edge of Jezero which likely represents the shores of the crater lake when it was deepest.
The robot is responsible for collecting and packaging more than two dozen rock samples from various locations. These samples will be brought back to Earth in the early 2030s for examination in laboratories that have the expertise to determine if microscopic life forms have ever touched the surface of Mars.
Plans for this recovery exercise are well advanced. This will mean that NASA and its partners at the European Space Agency send another rover to “fetch” the samples wherever Perseverance stores them in the crater.
It will be a British-built vehicle. It will pick up the samples and transfer them to a rocket which will then propel them into orbit of Mars where a satellite freighter will wait for them to take them home. “We are about to enter the most exciting time in the exploration of Mars,” said Sue Horne, head of space exploration at the British Space Agency.
“Soon the dream of examining specimens from the Red Planet will come true as the Sample Fetch Rover’s locomotion system is tested next month.”
(Excerpts from BBC / Jonathan Amos, science correspondent @BBCAmoson Twitter)