Since the Viking missions in the 1970s, there have been several attempts to look for signs of life on Mars. Now, half a century later, even the latest and most sophisticated instruments on NASA’s Curiosity and Perseverance rover have identified only low levels of simple organic molecules.
These results raise questions about whether our ability to detect signs of life is hampered by the device’s current limitations or the nature of the materials present in Martian rocks.
Potential evidence of life on Mars may be difficult, if not impossible, to detect with the current generation of instruments that probe Mars.
In this context, researcher Armando Azua-Bustos from the Astrobiology Center (CSIC and INTA joint centre), together with an international group of scientists, have been testing instruments that are being sent, or could be sent, to Mars, as well as as a laboratory state-of-the-art equipment.
With them, they analyzed samples in Piedra Roja, a place in the Atacama Desert (Chile) where the fossil sedimentary remains of an ancient river delta are found.
These deposits formed in extremely arid conditions between 160 and 100 million years ago and are geologically similar to the Martian crater Jezero, currently studied by the Perseverance rover.
The results of the study, published in the journal Nature Communicationssuggest that potential evidence of life on Mars may be difficult, if not impossible, to detect with the current generation of instruments that probe Mars.
The authors verified that Piedra Roja is formed by a variety of sediments interspersed with sandstone and clay typical of a riverbed, and determined the abundant presence of hematite, an iron oxide that gives Mars its characteristic red color.
a dark microbiome
In addition, in this terrestrial analogue of the red planet, “a variety of microorganisms that are very difficult to classify were found, which is why we propose the term ‘dark microbiome’ which, similar to the dark matter that is estimated to constitute an important part of the universe, we know is there, but which still resists being identified”, says Azua-Bustos.
Several “biosignatures” (substances that can indicate the presence of life in a place) were also found in Piedra Roja, at the limit of detection of instruments that can be found in a research laboratory.
“What was remarkable was that, using a variety of instruments that are on Mars or about to be sent to Mars,” says Azua-Bustos, “and depending on the biosignature you were looking for, several of them could barely detect it, or simply were not able to detect it. machete”.
Using a variety of Mars-designed instruments here, and depending on the biosignature looked for, several were barely able to detect them.
Armando Azua-Bustos (CAB, CSIC-INTA)
These findings underscore the importance of bringing Mars samples back to Earth in order to use the most powerful detection techniques available in laboratories.
These findings underscore the importance of bringing Mars samples back to Earth, such as those being collected by Perseverance.
In fact, NASA, along with the European Space Agency (ESA) and other institutions are currently collecting Martian samples with the Perseverance rover to send them to Earth in the future.
“It is very important to have terrestrial models as similar as possible to Mars in order to understand how the different biosignatures were preserved and to adjust the procedures and technology to find them”, says Professor Victor Parro, co-author of the work. .
“We know that there are traces of microbial life, but the challenge is to be able to detect them when they represent less than 1 part in 1,000,000,000 of mineral material”, he concludes.
Reference:
Armando Azua-Bustos et al. “Dark microbiome and extremely low organic compounds in fossil Atacama delta reveal detection limits of life on Mars”. Nature Communications, 2023.