In a major step toward confirming the presence of ancient life on Mars, NASA has detected large concentrations of organic carbon in samples taken by the Curiosity rover in the Gale Crater area. The measurement of organic carbon is one of the strongest indicators in the processes that give rise to life.
Scientists at NASA’s Goddard Space Flight Center identified at least 200 to 273 parts per million organic carbon in the material collected on Mars by the US space agency’s rover. This is comparable to or even more than the amount found in rocks from places with very little life on Earth, such as parts of the Atacama Desert in South America, and more than has been detected in Martian meteorites.
We know that our planet is inhabited by carbon based life forms. That means that the base of the chemical compounds that make life possible on Earth is the element carbon. Its function is crucial, because it joins other elements such as hydrogen and oxygen to create the complex molecules that allow life to develop. This explains why we look for carbon when trying to find evidence of life elsewhere in the Solar System, including on Mars.
The necessary conditions for life
According to a press release, the total organic carbon it is one of the most important measures to understand how much material is available in a given space as raw material for prebiotic chemistry and potentially for the development of life. The conclusions regarding the analysis of the samples obtained by the Curiosity rover are developed in a new study, led by the scientist Jennifer Stern.
According to this scientific work, recently published in the journal Proceedings of the National Academy of Sciences (PNAS), it is the first quantification of bulk organic carbon in sedimentary rocks on the surface of Mars, achieved thanks to a stepped combustion experiment made by the Curiosity rover in Gale Crater. The mudstone sample analyzed by the rover represents a previously habitable lacustrine environment: Life is believed to have been possible in aquatic environments on the Red Planet at some point in its history.
The analyzed region is a favorable space for the preservation of organic compounds formed in situ or transported from a wide catchment area, according to the researchers. Although the abundance of bulk organic carbon in these shale samples does not completely confirm the existence of past life on Mars, it is a key new clue to that effect. According to an article published in Universe Today, it is now necessary to confirm whether Curiosity’s measurement indicates the presence of compounds that create life or if the carbon comes from other sources.
3.5 billion year old samples
To make its measurement, Curiosity delivered powdered rock to its Sample Analysis at Mars (SAM) instrument for further study. An onboard oven heated the sample to progressively higher temperatures, simultaneously using oxygen and heat to convert the element into carbon dioxide (CO2). Although the experiment took place in 2014, it took several years of analysis for the science team to understand the results and put them in context with other mission findings.
It is worth noting, however, that the discovery of organic carbon on Mars is not new, but previous findings had important limitations. To find this compound in Gale Crater, Curiosity took a soil sample from an area of 3.5 billion year old shale rocks. The samples were taken from the Yellowknife Bay Formation, which contained a lake several billion years ago. According to scientists, the organic carbon was part of the material that settled at the bottom of the ancient lake.
Organic carbon concentrations in 3.5-billion-year-old lacustrine mudstones of Mars. Jennifer C. Stern et al. PNAS (2022). DOI:https://doi.org/10.1073/pnas.2201139119
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