NEW ROCHELLE, NEW YORK — In a study published in Astrobiology, astrobiologists at Washington State University and Technische Universitat in Berlin, say NASA's Curiosity rover found organic compounds called thiophenes in soil samples that may have been produced by bacteria.

The rover's instruments break down larger molecules and scientists can only examine chemical fragments. This means they cannot rule out a non-biological origin for the thiophenes, according to a press release from Washington State University.

On Earth, thiophenes are found in coal, crude oil and white truffles.

A thiophene molecule has four carbon atoms and a sulfur atom that make up a ring. Carbon and sulfur are essential elements to living organisms. The thiophene could be non-biological or bacterial in origin, but the evidence is not conclusive for either case.

The study's authors say that bacteria may have existed when Mars was hotter and wetter three billion years ago. Some of those bacteria may have played a role in the sulfate reduction that transforms sulfur to thiophenes.