Preserved for billions of years, organic compounds found on Mars

(CN) — NASA's Curiosity rover has found a new set of organic molecules on Mars, including compounds scientists say are linked to the building blocks of life.

The discovery comes from a chemical experiment carried out for the first time on another planet and suggests Mars can preserve complex organic material for billions of years.

Scientists say the rover identified more than 20 organic compounds in rock samples collected from Gale Crater, a former lake bed where water once existed.

Among them was a nitrogen-bearing molecule with a structure similar to chemicals that help form DNA, something never before detected on Mars.

The findings, published Tuesday in the journal Nature Communications, show Mars can preserve organic material, supporting the idea that the planet may once have had conditions suitable for life.

However, the compounds alone are not proof that life ever existed there.

"We think we're looking at organic matter that's been preserved on Mars for 3.5 billion years," said Amy Williams, a professor of geological sciences at the University of Florida who led the study, in a press release. "It's really useful to have evidence that ancient organic matter is preserved, because that is a way to assess the habitability of an environment. And if we want to search for evidence of life in the form of preserved organic carbon, this demonstrates it's possible."

Organic molecules are considered key ingredients for life, but they can also form through non-biological processes or arrive on planets via meteorites.

One of the compounds identified, benzothiophene, is commonly associated with material delivered from space.

"The same stuff that rained down on Mars from meteorites is what rained down on Earth, and it probably provided the building blocks for life as we know it on our planet," Williams said.

Curiosity landed on Mars in 2012 to investigate whether the planet once had environments capable of supporting life.

The rover conducted this latest experiment in 2020 in the Glen Torridon region of Gale Crater, an area rich in clay minerals that can preserve organic material.

To analyze the samples, scientists used an instrument aboard the rover called Sample Analysis at Mars, or SAM. The experiment relied on a chemical known as TMAH, which breaks apart larger organic molecules so they can be studied more easily.

Since the rover carries only a limited amount of the chemical, researchers had to carefully choose where to use it. The results suggest the technique can reveal complex organic chemistry that might otherwise remain hidden.

The findings could also shape future missions, including efforts to search for organic compounds on Mars and on Saturn's moon Titan.

While the new results do not confirm that life once existed on Mars, scientists say they show the planet can preserve the kinds of molecules that could point to it.

"We now know that there are big complex organics preserved in the shallow subsurface of Mars, and that holds a lot of promise for preserving large complex organics that might be diagnostic of life," Williams said.