Researchers poring over imagery and data from the Perseverance rover on Mars have found evidence of organic molecules in the planet’s Jezero Crater, potentially providing evidence of the planet’s carbon cycles and its ability to host life.
The discovery is by no means a confirmation that life once existed on Mars, but it is a sign that the conditions necessary for life as we know it once did. Perseverance is investigating many aspects of the fourth planet from the Sun, but chief among them is whether or not Mars hosted life in its ancient past.
The researchers found signals of organic molecules in all ten of the targets Perseverance scrutinised with its SHERLOC instrument (that’s short for the Scanning Habitable Environments with Raman and Luminescence for Organics and Chemicals instrument). The team’s recent research describing the organic-mineral associations around Jezero was published today in Nature.
Perseverance has been roaming the western end of Jezero Crater since it landed on Mars in February 2021. Since then, the rover has collected a cache of rock samples that should, if all goes well, be brought to Earth in the early 2030s.
But Perseverance isn’t just rock collecting. Scientists are using cameras aboard the rover to study the Martian terrain. Sweeping views of the rover’s environs offer evidence of where turbulent rivers once flowed on the now-arid planet, while close-up shots by Perseverance’s SHERLOC camera offers new insights into the chemistry of Martian rock.
“Our results support observations by previous robotic missions to Mars that the Red Planet was once rich in organic material, compounds made primarily of carbon and hydrogen, and that some of that organic material can still be detected billions of years later,” said study co-author Joseph Razzell Hollis, an astrobiologist at NASA’s Jet Propulsion Laboratory and the Natural History Museum in London, in an email to Gizmodo. “Each detection, each observation, gives us a little bit more information that brings us closer to understanding the history of Mars and whether it could have supported life in the past.”
Besides taking images, Perseverance’s SHERLOC instrument employs Raman and fluorescence spectroscopy, two ways of revealing the molecular composition of Martian rock, and the way those molecules and minerals are distributed across the rock surface. In addition to providing scientific data, these analyses do not damage the rock during the scanning process. That’s particularly useful for a rover that is trying to ship its rock samples to Earth in the next decade.
If life did exist in Jezero Crater, scientists think there’s a good chance it populated a river delta on the crater’s western rim. That’s because the oldest signs of life on Earth, 3.5-billion-year-old fossilized microbial mats called stromatolites, appear in similar shallows. With water flowing into Jezero for at least a million years and organic molecules sitting on the crater’s subaquatic floor, there was a pretty suitable environment for life as we know it.
The recent targets scrutinized by SHERLOC were observed in Máaz and Séítah, two formations on the floor of Jezero.
The team wasn’t able to exactly date the molecules they found, but Hollis said that “some of the signatures we detect consistent with organics are associated with minerals that were formed by alteration by water 3-4 billion years ago.” The results suggest that a more complex geochemical process may have been at work on Mars than previous data suggested, and at least some building blocks for life were present.
We’re still a long way from finding that which Bowie once ruminated on, but there likely won’t ever be a smoking gun.
As Abigail Allwood, an astrobiologist, geologist, and the principal investigator of Perseverance’s PIXL instrument, told Gizmodo in 2021: “You need to have several scales of observation that all have to sort of piece together to form sort of a complex tapestry, out of which forms the interpretation of ‘these things must have been biological, in a sense.’”
Ergo, the recent confirmation of organic molecules in Jezero Crater is just another line of evidence adding fuel to the fire of the possible. But the fact that they were there does make that possibility…more possible, if not plausible.
“As planetary scientists and astrobiologists, we are very careful with laying out claims—claiming that life is the source of organics or possible biosignatures is a ‘last resort hypothesis’,” Hollis said, “meaning we would need to rule out any non-biological sources first.”
“We are intrigued by these signals, since they could be organic, and would point to the possibility that building blocks of life could have been present for a long time on the surface of Mars, in more than one place,” he added. “We will need to bring these samples back to Earth to conclusively confirm the presence, type, and mineral associations of organic molecules before we can consider whether they are specific evidence of past life.”
So yes, the bad news is that we may have to wait for the Mars Sample Return (MSR) mission to get both off the ground and back to Earth before we have any more definitive idea of what may-or-may-not have eked out existence in Jezero Crater. But the good news is that there’s a chance.