By remotely analyzing a Martian surface sample collected by the Curiosity rover in 2017, a NASA team recently identified new organic molecules. The latter had never been detected until now on the surface of Mars. Details of the study are reported in the journal Nature.
Wet chemistry experiments on the Curiosity rover's Sample Analysis Instrument were designed to facilitate gas chromatography-mass spectrometry analyzes of polar molecules such as amino acids and carboxylic acids .
As part of a new study, a team focused on the analysis of several samples taken from the dunes of "Bagnold" in 2017. Placed in a cup previously filled with chemical reagents, these samples revealed no amino acid derivatives. In contrast, the researchers isolated benzoic acid and ammonia , two possible indicators of ancient life. On Mars, this is a first.
Although this is an exciting discovery, it cannot demonstrate with certainty that carbon-based life forms once lived on the surface of the red planet. The team indeed underlines in its article that these molecules could also be the result of geological processes. However, it's still taken.
"This experiment is definitely a success “, enthuses Maëva Millan, of NASA’s Goddard Spaceflight Center and main author of this work. "Although we didn't find what we were looking for, biosignatures, we showed this technique to be really promising “.
This isn't the first time Curiosity has detected organic molecules in Martian soil. This new discovery expands this list.
In March 2020, Curiosity also distinguished itself by isolating an intriguing group of organic compounds:thiophenes. On Earth, the latter typically occur in kerogen, coal, crude oil, stromatolites, microfossils and, oddly enough, in white truffles.
Consisting of four carbon atoms and one sulfur atom, thiophenes can form as part of a sulfate reduction process that can be triggered in two ways .
The first does not imply the presence of life. In this specific case, to obtain thiophenes, the precursor compounds must be heated to 120°C. On Mars, these conditions can occur when meteorites hit the surface (which often happens).
However, bacteria could also initiate this sulphate reduction process. To do this, the environmental conditions must be milder than they are today on the red planet. Just over three billion years ago, Mars looked much friendlier . Its atmosphere was indeed thicker, allowing warmer temperatures and the presence of liquid water on the surface.
Like benzoic acid and ammonia, these thiophenes could therefore have a biological or abiotic origin. Hoping that the Perseverance rover, equipped differently from its counterpart, will one day be able to shed light on these molecules.
