Mars Curiosity Rover Finds “Tantalizing” Signs of Life

NASA’s Mars Curiosity Rover has found signs of a type of carbon that is associated with biological processes when found on Earth. A recent announcement that organics found in a Martian meteorite are likely not from a biological process had briefly tempered the search for life on Mars, but if it holds up, this latest find may point to a biologically active past after all.


Researchers have been searching for signs of life on Mars since the 1970’s when the Viking lander missions found evidence that seemed to indicate there was currently active life on the red planet, a result that remains controversial to this day. Since then, a number of missions have made the case for Mars’ watery past, a case that seems to support a prolonged period of habitability.

Now, the Curiosity Rover team has added to that case with their latest announcement, one that may even help the Perseverance rover refine its own search for Martian life, while also attracting the attention of high profile SETI researcher Professor Able Mendez.

curiosity rover
Tweet by Professor Abel Mendez (Image Source: Twitter)



According to a press release from NASA announcing the latest finding: “Carbon is particularly important since this element is found in all life on Earth; it flows continuously through the air, water, and ground in a cycle that’s well understood thanks to isotope measurements. For instance, living creatures on Earth use the smaller, lighter carbon 12 atom to metabolize food or for photosynthesis versus the heavier carbon 13 atom. Thus, significantly more carbon 12 than carbon 13 in ancient rocks, along with other evidence, suggests to scientists they’re looking at signatures of life-related chemistry.”

“Looking at the ratio of these two carbon isotopes helps Earth scientists tell what type of life they’re looking at and the environment it lived in,” the same release adds.

Of course, these findings occurred on Mars not Earth, and the researchers behind the announcement say that there is still a lot we don’t know about the carbon cycle on Mars.

“We’re finding things on Mars that are tantalizingly interesting, but we would really need more evidence to say we’ve identified life,” said Paul Mahaffy, the principal investigator of the Sample Analysis at Mars (SAM) chemistry lab aboard Curiosity until his retirement in December 2021. “So we’re looking at what else could have caused the carbon signature we’re seeing, if not life.”

The team’s published results actually propose three different scenarios that could account for the excess carbon 12 found by Curiosity. One natural process involves the interaction of carbon dioxide gas in the Martian atmosphere with ultraviolet light, resulting in carbon-containing molecules settling on the planet’s surface.

The second, non-biological option, says the carbon found by Curiosity could have been left on Mars hundreds of millions of years earlier when the solar system passed through a giant molecular cloud rich in that particular type of carbon, an event the researchers describe as “rare.”

Of course, the third, and most tantalizing process for the carbon 12 proposed by the researchers involves the activity of biological life. And as noted, when carbon 12 is found at these levels on Earth, biology is the cause.

“On Earth, processes that would produce the carbon signal we’re detecting on Mars are biological,” said Christopher House, a scientist from Penn State who led the rover’s carbon study. “We have to understand whether the same explanation works for Mars, or if there are other explanations, because Mars is very different.”

“All three explanations fit the data,” added House. “We simply need more data to rule them in or out.”


Future missions hope to fill in more of these blanks in Mars’ history, particularly its carbon cycle, including a proposed sample return mission that would bring samples already collected by Perseverance back to Earth for closer study.

“Defining the carbon cycle on Mars is absolutely key to trying to understand how life could fit into that cycle,” said Andrew Steele, a Curiosity scientist based at the Carnegie Institution for Science. “We have done that really successfully on Earth, but we are just beginning to define that cycle for Mars.”

“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,” added Goddard astrobiologist Jennifer L. Eigenbrode, who participated in the carbon study. ““We need to open our minds and think outside the box, and that’s what this paper does.”

Follow and connect with author Christopher Plain on Twitter: @plain_fiction