NASA’s Curiosity rover has discovered a diverse mix of organic molecules on Mars, including chemicals widely considered to be the “building blocks” for the origin of life on Earth.
The discovery of more than 20 organic compounds in Martian soil occurred after carrying out an unprecedented chemical experiment and provides crucial clues about the planet’s past habitability.
The findings show that the Martian surface can preserve the types of molecules that could serve as evidence of ancient life, especially because some of them (nitrogen heterocycles) are the basis that form nucleic acids (DNA and RNA). Thus, finding these pieces in rocks on Mars suggests that the “ingredients” necessary for life were present and preserved.
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These molecules were found in clay-rich sandstones in Gale Crater, which scientists believe to be approximately 3.5 billion years old. This suggests that chemical diversity has been preserved despite radiation and geological processes over billions of years.
The experiment, however, cannot distinguish between organic compounds originating from possible past life on Mars and those formed by geological processes or brought by meteorites.
According to the researchers, even if the molecules were produced on the planet itself, they may have been created by geological and chemical processes without the intervention of living beings (abiotic production). To check whether they were signs of past life, it would be necessary to send rock samples to Earth.
Nicknamed Curiosity, the rover that made the discovery was launched in 2011 and landed in Gale Crater in 2012, as part of the Mars Science Laboratory mission. It is the largest exploring robot ever sent to Mars and aims to answer the following question: “Has Mars ever had the right environmental conditions to support small forms of life?”
To date, the rover has found chemical and mineral evidence of habitable environments in Mars’ past with its tools. He continues to explore the rock record from a time when the planet could have supported microbial life.
Was there life on Mars?
The characterization of organic matter is described by NASA scientists as a pillar for exploring both habitability and the search for signs of life. However, the confirmation of complex organic molecules, in itself, only indicates that Mars had the “necessary ingredients” to sustain life as we know it – that is, it does not confirm the existence of past life, but rather that Mars was habitable.
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The samples were collected from sediments from ancient lakes and rivers in Gale Crater. This type of environment, rich in clay, is considered ideal for concentrating and preserving organic matter for billions of years, which reinforces that the planet once had favorable environmental conditions, according to the article with the discoveries published by scientists this Wednesday, 21, in the journal Nature Communications.
“It’s really useful to have evidence that ancient organic matter is preserved, as this is a way to assess the habitability of an environment. And if we want to look for evidence of life in the form of preserved organic carbon, this shows that it is possible,” explains Amy Williams, professor of Geological Sciences at the University of Florida and scientist on the Curiosity and Perseverance rover missions to Mars.
Led by NASA’s Jet Propulsion Laboratory, Curiosity conducted the experiment in 2020 in the Glen Torridon region of the crater.
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Among the more than 20 chemicals identified by the experiment, the rover detected a nitrogen-containing molecule with a structure similar to DNA precursors – a chemical never before identified on Mars. Curiosity also identified benzothiophene, a sulfurous chemical with two rings often brought to planets by meteorites.
“The same material that rained on Mars from meteorites is what rained on Earth, and probably provided the building blocks for life as we know it on our planet,” says the scientist in the note released by the University of Florida.
