Thunderbolt on Mars! On July 25, 2024, NASA’s Jet Propulsion Laboratory (JPL) released a statement that could shed light on our conception of extraterrestrial life on the Red Planet. Indeed, the institution in charge, among other things, of Mars rovers declared that Perseverance “has found a fascinating rock that some evidence suggests may have supported microbial life billions of years ago.”
A rock found in a river valley
The “six-wheeled geologist”, that’s what JPL calls Perseverance, collected a rock in the shape of an arrowhead on July 21. The latter, nicknamed “Chevaya Falls” has not been found anywhere.
Indeed, it was in the Neretva Vallis, an ancient river valley approximately 400 meters wide, that the rover made its discovery. Several billion years ago, this place, now a desert, like the rest of Mars, had been hollowed out by running water.
“We designed Perseverance’s route to visit areas likely to contain interesting samples. This trip paid off as we found something we had never seen before.” explains Nicola Fox, associate administrator of NASA’s science mission directorate, in comments reported by the JPL press release.
The supposed signs of ancient life on Mars…
The “Chevaya Falls” rock therefore shows signs of potential ancient life on Mars. But what are they?
To reach their conclusion, the JPL scientists relied on the particular instrument that lends itself perfectly to an in-depth investigation of a mystery deemed insoluble: SHERLOC or Scanning Habitable Environments with Raman & Luminescence for Organics & Chemicals (Analysis of habitable environments using Raman [ndr, un spectromètre présent sur le rover] and luminescence for organic and chemical substances.
This instrument therefore made it possible to identify that the rock collected on July 21 contained organic compounds, carbon-based molecules which would be considered as constituent elements of life. On the other hand, “Chevaya Falls” also presents another characteristic that could betray the presence, billions of years ago, of life on Mars: white spots surrounded by a black halo.
According to analyses, the latter contain iron and phosphate. “These spots are a big surprise. On Earth, these types of features in rocks are often associated with fossilized traces of microbes living underground.” says David Flannery, an Australian astrobiologist and member of the Perseverance science team.
…Or something else entirely
It is very important to pay attention to the meaning of the words NASA uses. The US space agency does not say that Mars once harbored life. No, she specifies that according to the first analyzes of the “Chevaya Falls” rock, the Red Planet “could have harbored life”.
Indeed, analyzes compared to what we know on Earth could indicate that life was indeed present on Mars. However, still in this same press release, JPL is cautious and specifies that the observations made on “Chevaya Falls” do not allow us to be 100% sure that life was ever established there.
The carbon-based molecules mentioned above could have been formed by non-biological processes which therefore do not involve life. But even more, in their analyses, JPL scientists also highlighted the presence of olivine, a mineral that forms thanks to magma.
This latest find is all the more important because the presence of such an element in the rock could not indicate signs of ancient life on Mars, but rather the total absence of it on the planet. Because if olivine is the origin of the white spots on “Chevaya Falls”, this would indicate that the element was introduced into the rock while it was subjected to very high temperatures.
This could have resulted in an abiotic chemical reaction, a characteristic of an environment where it is impossible for life to develop.
On Mars, when one mystery seems to be solved, another hatches in the second. Future analyzes of “Chevaya Falls” will be carried out, if possible on Earth, in order to refine the conclusions regarding the presence or not of ancient life on Mars. “Chevaya Falls is the most puzzling, complex, and potentially important rock studied to date by Perseverance.” declared Ken Farley, Perseverance project scientist at Caltech, which perfectly summarizes the situation in which JPL scientists currently find themselves.
Source : Jet Propulsion Laboratory
This article was originally published on July 26, 2024
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