When an article comes out on Nature Astronomy that speaks of “potential biosignures” on Mars, NASA sends the press releases, the newspapers are excited, Twitter (X, as the hell that cute bird has been renowned) explodes with “we found life on Mars”, and I always think the same thing: ok, we go to read, to bring the martian enthusiasts with their feet. It is true, we found interesting chemical traces: organic carbon signals sufficiently preserved to be detected, minerals that on earth we associate with microbial metabolic reactions, but between this and having a microbus fossil in hand there is an abyss.
The Rover Perseverance, in the Bright Angel formation of the Jezero crater (who seems to be a lake), has identified nodules and reaction fronts rich in Vivianite (reduced iron phosphate) and gigite (iron sulphide), as well as iron, phosphorus, sulfur and raman signals of aromatic organic matter (not in the sense that you can season the pasta). All these elements are organized in millimeter structures that tell of redox processes that occurred at low temperature in an environment saturated with water, conditions that on earth we find in areas where microbes reduce iron or sulphates. For this reason, the sample Sapphire Canyon, taken in that area, is considered by the authors the best candidate to seek potential biosignures when (and if) will be analyzed in the terrestrial workshops. Because the problem is that Perseverance analyzes up to a certain point, we must wait for a mission, technically not trivial, to send a rover that you take champions and bring them back here.
Scientists who have signed the paper are very cautious: they explain that Vivianite and Greigite can form even in the absence of life, only thanks to geological chemistry if there are iron, sulfur, phosphorus and the right conditions. Furthermore, they clarify that organic matter could have habitual origin, arriving from meteorites or being the product of non -biological chemical reactions. Without isotopic analysis and laboratory studies it cannot be said if these traces are truly biological. In paper, prudence is explicit, only that the NASA press releases, animated graphics, newspapers of the newspapers arrive, and it seems almost that we are already establishing the champagne for the discovery of life, which also serves (let’s face it) to remind everyone because it is worth financing the return of the champions, a project that at the moment has budget problems, and among other things it is not very popular in the global economic moment that Here of the stones from Mars.
It has been said that it is the first time that we are so close to having found traces of life in our sun system: it is true, because the sum of the clues is more coherent than in the past. Amedeo Balbi, to give a number, spoke of a “three out of ten” on the scale of probability of having found something organic. Indeed it is so: we are really a little closer. However, as Balbi declares, it is a bit as if one started making tennis lessons and said that it is the first time that it is closer to becoming the number one in the world as Sinner. Makes the idea. (By the way, if you are interested in the birth of life, I would like to point out the book from the stars to the cell, the biologist and the extraordinary popularizer Francesco Cacciante, a next release for apogee).
The scientifically interesting part is that these results indicate where to search: the sulphates work from ideal custodians to preserve organic molecules, and the sedimentary context of Bright Angel is perfect for finding intact material. But precisely until the champions are analyzed on earth, he remains fascinating chemical, not Martian paleontology.
In any case, it is preferable that scientists remain rigorous instead of launching into too optimistic ads. The risk otherwise is that when we find an unequivocal biosignure, nobody notices it because we will have become accustomed to hear “we found life on Mars” every two years. Mars remains our best laboratory to understand if life can emerge elsewhere, for now only tells us that there were water, nutrients, chemical gradients, and a perfect scene for life (billions of years ago, although some microorganism could still be there, I want to fish though).
We will see the rest: it would be fascinating to discover traces of Martian microbial life, although the wing and the various Apollo missions were an American success because there was competition with the USSR,
At this moment we are so geopolitically messed up that traces of microbes on Mars are not a very popular topic for us human multicellular organisms that try to avoid world war on earth.