NASA today held a press conference announcing two important discoveries made by the rover Curiosity, a tireless worker who has been operating on the surface of Mars since 2012.
These two discoveries, in reality, are related: Curiosity has found organic molecules in the soil and in the atmosphere of the red planet. Did it discover life? Not necessarily. But from today we know something more: the red planet, 3 billion years ago, most likely had the right conditions for it to develop.
Methane in the atmosphere of Mars
When it comes to methane, an organic molecule made up of a carbon atom and four of hydrogen, the eyes always shine on the exobiologists. The reason is soon said: on Earth, this gas, which we use as fossil fuel, is of biological origin.
That in the atmosphere of Mars there were traces of methane was well known, thanks to the findings of the European Mars Express probe. The news is that now Curiosity has also found them on the ground. Christopher Webster, of NASA’s Jet Propulsion Laboratory (JPL), has been studying methane on Mars for years. According to the latest data obtained by Curiosity, collected in the Gale crater over a period of three years, the methane concentration would follow a seasonal trend, ranging from 0.24 to 0.65 ppb (parts per billion). The theory proposed by Webster foresees that methane is enclosed in ice crystals called clathrates, similar to what happens in the terrestrial ocean slopes. The clathrates are like “cages” of ice that inside them trapping gaseous molecules. Once the gases escape, these structures collapse into conventional ice crystals.
The seasonal variations in temperature would be responsible for the escaping of methane from the clathrates. This does not answer with precision, however, to the main question: what methane does it have? Biological or not? We do not know yet, but the mere presence of this gas opens up new and fascinating prospects for the search for life on the red planet.
Organic compounds in the soil of Mars
The second discovery derives from a study by Jennifer Eigenbrode, from the NASA Goddard Space Flight Center. By analyzing the samples collected by Curiosity from 2012 to 2016, it was possible to isolate several organic molecules, for example thiophene, 2-3-methylthiophenes, methanethiol and dimethyl sulfide. These organic molecules have been preserved in the lacustrine origin of clay at the base of the Murray formation, 3.5 billion years old. Again, these molecules are of biological origin or not? Also in this case, unfortunately, we do not know the answer with absolute certainty.
The existence of these organic molecules, however, throw new light on the red planet, considered by many scientists a substantially dead world. Let’s recap briefly. We know that in the past the Martian atmosphere was thicker than now and that the water flowed liquid on its surface, digging canals and geological formations still visible today. We also know that on Mars there are organic molecules and that it possesses characteristics potentially compatible with life, at least that extremophilous. Furthermore, we know that the chemical elements necessary for life are all there: carbon, hydrogen, oxygen, sulfur, phosphorus, nitrogen. Certainly, if we want to have hope of finding life on the red planet, we must dig deeper, away from cosmic rays, in an environment where liquid water can exist and where delicate biological reactions can occur without interference.
But the most plausible answer, perhaps, is that life on Mars does not have life today, but that in the past it existed, at least in primordial form, and what we observe today is what remains of that short spark, that was lost a long time ago.