The Curiosity rover has carried out a chemical experiment on Mars that has never been done on another planet. Thanks to it, it has detected organic molecules that until now had gone unnoticed by us. Does that mean that there is or was life on the red planet? It could be, but it could also be due to many other things. Although we always read this type of news with joy and it gives a lot of sensational headlines, we must analyze the results with the optimism of what they mean for science, but the caution of what they imply in the search for extraterrestrial life.
Chemical advances millions of kilometers away. Curiosity’s SAM instrument has carried out an experiment known as thermochymolysis. In it, a reagent called tetramethylammonium hydroxide (TMAH) is used. to break large molecules into small fragments. Thanks to this, organic molecules can be detected that are invisible with other methods. Among other organic molecules, some rich in nitrogen have been found, which could be related to DNA synthesis. The discovery of benzothiophene, present in some biological processes, also stands out.
Let’s not go up. The authors of the study that has just been published thanks to the Curiosity rover they call for caution with its results. They insist that all the molecules found could come from abiotic processes or have reached Mars from other points in space. For example, benzothiophene could be formed by geological or hydrothermal processes. In addition, its presence has been found in meteorites and asteroids on Earth. It could also have reached Mars like this.
Only two tries. Regardless of whether the findings have to do with life or not, this study is very relevant for two reasons. On the one hand, because it was the first time that this experiment could be carried out outside of Earth. And, secondly, because Curiosity I only had two tries to do it, but he made good use of them. This is because TMAH was in the exact dose needed, inside two sealed capsules. If the first failed, the second could be tried. If this one did it too, goodbye experiment. That it was done without problems has been a great achievement.
This is an annotated close-up of three holes that NASA’s Curiosity drilled into Martian rock at a location nicknamed “Mary Anning” in October 2020. The sample where the rover found a large number of organic molecules came from “Mary Anning 3.” (A nearby site nicknamed “Mary Anning 2” was left unused.) NASA/JPL-Caltech/MSSS
A very old search. Science has been obsessed with the search for life on Mars since in the 17th century some scientists detected with their telescopes what appeared to be the presence of water ice. Already in the 21st century, advances in space exploration allowed orbiters and rovers to be sent to Mars in order to analyze possible signs of life. Some were found.
For example, in 2018 methane was detected in its atmosphere. This could be the result of microbial activity, but also geological processes. In 2020 Curiosity found carbon isotopes and later, in 2025, the longest carbon chain found to date. It is true that carbon is necessary for life, but it can also be related to many abiotic processes. In none of these cases has it been possible to demonstrate that there is life behind it, so we still cannot prove that there is life on Mars.
Maybe we lack tools. In 2023 a study was carried out in the Atacama Desert to analyze the tools normally used to search for life on Mars. This desert is one of the largest Martian analogues we have on Earth. It has many similar characteristics to those of the red planet; but, of course, it also has more than proven life. However, when analyzed with Mars exploration tools, many of the traces of life that should have appeared were not detected.
This shows that perhaps we haven’t found life on Mars yet because we don’t have the right tools. Although there may also simply not be any.
The future. Curiosity has carried out this experiment directly on Mars. However, the ideal would be to send rock samples to Earth, to use other more complex analysis technologies there. Another rover, Perseverance, is prepared to collect samples and send them to Earth. In fact, it was scheduled to do so. However, the mission was canceled by the United States Congress last January.
Meanwhile, other space agencies aim to replicate the TMAH experiments. This is the case of the ExoMars mission of the European Space Agencywhose Rosalind Franklin rover will also travel with this reagent to carry out thermochemolysis. We’ll have to wait to see what he discovers. Whatever it is, as always, we will read it with caution.
Image | POT
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