“We identified several biological pathways for thiophenes that seem more likely than chemical ones, but we still need proof,” the study's co-author, Dirk Schulze‑Makuch, said in a statement. “If you find thiophenes on Earth, then you would think they are biological, but on Mars, of course, the bar to prove that has to be quite a bit higher.”
The research suggests that a biological process "most likely involving bacteria rather than a truffle though, may have played a role in the organic compound’s existence." However, it's also possible that it could come from non-biological sources, such as meteor impacts.
If indeed the thiophenes were formed from a biological process, it may have stemmed from bacteria that "could have facilitated a sulfate reduction process," as Mars was warm and wet 3 billion years ago.
More will be learned about the organic molecules from the European Space Agency's Rosalind Franklin rover, slated to launch in July 2020.
The researchers said that even if the next rover gets isotopic evidence of carbon and sulfur isotopes, which Schulze‑Makuch calls “a telltale signal for life," it may not be a guarantee there was or is life on Mars.
“As Carl Sagan said ‘extraordinary claims require extraordinary evidence,’” Schulze‑Makuch explained. “I think the proof will really require that we actually send people there, and an astronaut looks through a microscope and sees a moving microbe.”
NASA is slated to launch a new rover to Mars, known as Perseverance, on July 17, 2020. This rover will attempt to detect if there is any fossilized evidence of extraterrestrial beings, in addition to other tasks.
Upon its expected arrival on the Martian surface on Feb. 18, 2021, it will join the still functioning Curiosity rover and the now-deceased Opportunity rover on the Red Planet. Unlike Curiosity or Opportunity, this rover will carry the "first helicopter that will fly on another planet," NASA added.
NASA’s long-term goal is to send a manned mission to Mars in the 2030s.