NASA's Curiosity rover has discovered organic molecules on Mars that had never been detected before, continuing to show that complex chemistry took place on the Red Planet. Organic molecules can be related to life, but they are not evidence of life, as other processes can form them.
As reported in Nature Astronomy, the team used the rover’s wet chemistry experiments, part of the Sample Analysis at Mars (SAM) instrument, to study the composition of and collected by the rover. The goal of the instrument is to discover organic compounds such as amino acids, the building blocks of life.
This work has not discovered amino acids – but has discovered ammonia and benzoic acid. Benzoic acid occurs naturally in many plants and berries and it was first described by Nostradamus (of the prophecies fame) in 1556. Now we have found evidence that it’s also found on Mars.
The experiment was conducted in December 2017 based on a sample collected months earlier from the Bagnold Dunes. The SAM analysis was originally planned to use drilled samples. The experiment has only nine cups of solvent to do the wet chemistry experiments, so they are an extremely precious commodity. Unfortunately, Curiosity was having drill problems for a while, so the team made the decision to use sand samples instead.
“The Bagnold Dunes had been studied for several months with the full complement of instruments aboard Curiosity," the team wrote in the paper. "The weathered dune sample had been exposed to ionizing radiation and was not expected to be rich in well preserved ancient organic molecules. However, it enabled not only a test of the derivatization protocol on the surface of Mars, but also a search for organic molecules present in the sample and a survey of those that might have been produced from reactions within the instrument.”
The sand was not expected to be rich in organic molecules, as it has been exposed to the elements for millions of years – so finding some is still quite exciting. The work creates an important baseline for future work with SAM on sample analysis that has already taken place, or on wet chemistry experiments that are yet to be conducted as Curiosity explored Mount Sharp inside Gale Crater.
The work is also important for a future non-NASA rover. The European Space Agency and Russian Roscomsos' Rosalind Franklin rover, launching next year, will carry the Mars Organic Molecule Analyzer (MOMA) instrument that will allow even more sophisticated wet chemistry on Mars.