NASA rover adds to the list of organic compounds detected on Mars

By Will Dunham

WASHINGTON, April 21 (Reuters) – Performing a type of experiment never before attempted beyond Earth, NASA’s Curiosity rover has identified more organic compounds on Mars as scientists work to learn whether the Red Planet once harbored life.

Five of the seven diverse organic compounds confirmed by the six-wheeled rover in rock that formed in a dry lake bed near the planet’s equator had never been identified before on Mars, the researchers said. “The experiment also hinted at the presence of another organic compound that has a structure similar to the precursors of DNA, the molecule that carries genetic information in living organisms on our planet.

Organic compounds, molecules primarily composed of carbon atoms bonded to other elements, provide the structural basis of all life on Earth. The total identified on Mars is now in the dozens. The scientists noted, however, that all of these compounds could have formed through non-biological processes.

Like Earth and the other planets in the solar system, Mars was formed about 4.5 billion years ago. Early in its history, Mars was warmer and wetter than the cold, arid place it is today. The researchers estimated that the rock sampled by the rover – sediments deposited by “running water” – was at least 3.5 billion years old.

“We cannot yet say that Mars ever supported life, but our findings further support the evidence that Mars was a habitable world around the time life on Earth appeared,” said astrobiologist and planetary scientist Amy Williams of the University of Florida, a member of the Curiosity science team and lead author of the study published Tuesday in the journal Nature Communications.

Definitively identifying evidence of past life would currently require bringing rock samples back to Earth for testing.

“To be clear, we did not find any evidence of life with this study, but we are further refining the basic molecules that were present on Mars,” Williams said.

Curiosity landed in Gale Crater, formed by an ancient impact on the Martian surface, in 2012. The experiment currently described in 2020 was conducted in a region of the crater called Glen Torridon, where an abundance of clay minerals shows that water was once present. If microbial life had appeared on Mars, bodies of water would likely have provided habitat.

Clay minerals can preserve organic molecules better than other minerals, making them a good target for finding such compounds, Williams said.

The experiment was conducted by the rover’s Sample Analysis at Mars, or SAM, instrument. The rover drilled into the bedrock at a location called “Mary Anning” in honor of a 19th-century English paleontologist. The powdered rock sample was then dropped into a small cup containing a chemical that breaks down the complex organic material into smaller pieces that can be detected by the SAM instrument.

“This study confirms that larger, more complex organic matter, called macromolecular carbon, is present and preserved near the bedrock surface of Mars despite the planet’s harsh radiation conditions. The experiment also produced smaller organic molecules from this degradation process that have never been observed on Mars before,” Williams said.

“The Curiosity rover was built to search for habitable environments, places where life would want to live if it ever appeared on Mars. This study contributes to that story, that Martian environments were habitable in the ancient past and contained the ingredients for life as we know it,” Williams said.

Last year, scientists announced that a rock sample obtained by another NASA rover, Perseverance, from another crater contained features that could have been produced when the rock was formed by chemical reactions involving microbes.

NASA rovers have been at the forefront of understanding Martian habitability, including the discovery of organic materials.

“Although we cannot say whether this organic matter comes from geological processes, meteorite falls or life, our work suggests that if complex organic matter from life were preserved on Mars, we should be able to detect it with instruments on current and future rover,” Williams said.

(Reporting by Will Dunham; editing by Daniel Wallis)