Newly detected organic molecules support the idea that Mars was once ‘amazingly habitable’ - CNN

The Curiosity rover has uncovered the most diverse array of organic molecules ever found on Mars, including seven that had never been detected before on the red planet.

These carbon-containing compounds are the same building blocks that enabled life to emerge on Earth.

The results, published Tuesday in the journal Nature Communications, came from a first-of-its-kind experiment on Mars: The rover collected a rock sample and dissolved it in a chemical solution to unlock the secrets of its composition.

The research team believes the organic molecules identified in the rock have been preserved on Mars for 3.5 billion years, said lead study author Dr. Amy Williams, associate professor of geological sciences at the University of Florida and a scientist on the Curiosity mission.

“These findings are important because they confirm that larger complex organic matter is preserved on Mars over geologic time periods, despite the harsh radiation environment,” Williams said. “This supports the search for habitable environments on Mars, which is defined as a place where life would have wanted to live if it was present.”

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The outcome complements Curiosity’s previous detections of organic compounds and adds support to the idea that Mars was likely once a habitable planet billions of years ago, as opposed to the frozen desert it is today.

“The revelation of the mission to me has been not just that Mars was habitable,” said study coauthor Ashwin Vasavada, Curiosity’s project scientist at NASA’s Jet Propulsion Laboratory in Pasadena, California. “It’s just how amazingly habitable it was.”

The milestone wet chemistry experiment was not designed to distinguish whether the molecules act as signs of ancient life on Mars, whether the molecules were delivered to the red planet by meteorite impacts or if the organic material was simply the result of geologic processes.

But the findings highlight a rallying point for many planetary scientists. To determine definitively whether life ever existed on Mars, rock samples need to be returned to Earth.

Seeking the perfect target

The Curiosity rover landed in Gale Crater on Mars in 2012 with the goal of determining whether the planet were ever habitable. For years, the rover ascended a feature called Mount Sharp within the crater, aiming to reach clay-rich layers that orbiters circling the planet had spied.

The clay layers, which can preserve organic molecules, suggested that water was not only present on Mars in the distant past, but that it disappeared and reappeared at the site over time.

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Curiosity took six or seven years after landing to reach the clay layer in the Glen Torridon region of Mount Sharp, but the wait was worth it, Vasavada said. The rover came across evidence of mudstones from ancient lakes as well as sandstone where moving water once trickled into the lakes.

Members of the rover’s vast team came together to decide the best possible spot for Curiosity to drill a sample to test for organic material. The rover only has two wet chemistry cups on board, so the team members wanted to make the experiment count. They decided on a site they named Mary Anning, after the pioneering 19th century British paleontologist.

Curiosity drilled the clay mineral-containing sandstone sample in 2020, pulverized it and placed it within the SAM, or Sample Analysis at Mars, instrument, located in the rover’s belly.

SAM can heat samples in a small oven and use other apparatuses within it to detect the gases released by minerals as they break down due to heat. The instrument has been used to make other key organic chemistry findings on Mars.

The rover dropped samples into a small cup of tetramethylammonium hydroxide, or TMAH. The corrosive solution can break apart large molecules that would be hard to identify and reveal otherwise invisible molecules, the University of Florida’s Williams said.

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The team was able to identify 21 carbon-containing molecules, including the newly detected nitrogen heterocycle, or a ring of carbon atoms that includes nitrogen — a structure that serves as a predecessor to RNA and DNA, or nucleic acids coded with genetic information.