Curiosity, the silver-haired veteran of the Red Planet rover corps, has proven once again there’s still life in its batteries and surface samples driller – but has it proven that there’s life on Mars? Many recent headlines seem to be blaring this, but David Bowie wouldn’t be adding a verse just yet, and NASA agrees … although what Curiosity dug up is definitely an unusual carbon signature that is one of the signs of life. But … is it THE sign of life on Mars?
“After analyzing powdered rock samples collected from the surface of Mars by NASA’s Curiosity rover, scientists today announced that several of the samples are rich in a type of carbon that on Earth is associated with biological processes.”
That’s a pretty strong opening sentence in NASA’s press release on the discovery, which highlights findings soon to be published in the journal the Proceedings of the National Academy of Sciences (PNAS). Before we dig into what Curiosity dug up, a shout-out is in order for SAM – the Sample Analysis at Mars (SAM) chemistry lab aboard Curiosity whose Tunable Laser Spectrometer (TLS) instrument inside it heated 24 samples from geologically diverse locations in the Gale crater (Curiosity’s Daytona International Speedway) to about 1,500 degrees Fahrenheit (850 degrees Celsius), releasing their gases and then measuring the isotopes. They surprisingly showed that nearly half of their samples containing high amounts of carbon 12 compared to the Martian atmosphere or Martian meteorites found on Earth. Drop the mic time?
“The hardest thing is letting go of Earth and letting go of that bias that we have and really trying to get into the fundamentals of the chemistry, physics and environmental processes on Mars.”
Not yet, says Goddard Space Flight Center astrobiologist and study participant Jennifer L. Eigenbrode. One explanation for the carbon signatures is that the Solar System once passed through a giant, molecular cloud of dust that left the carbon deposits behind. Another is that ultraviolet light converted CO2 to organic compounds through abiotic (non-biological) processes – this can happen on Earth as well. Finally, there's the biggie – Mars may have once had methane-producing microbes living on its surface.
“All three possibilities point to an unusual carbon cycle unlike anything on Earth today. But we need more data to figure out which of these is the correct explanation."
In a separate press release, Penn State geoscientist and study leader Christopher House points out that not only is Mars not like Earth today, it may have never been much like its close neighbor. The same could be said of Curiosity – it may not have its own helicopter like Perseverance, but its discoveries keep revealing more details about the freakiest show that may one day answer David Bowie’s most famous question -- is there life on Mars?