NASA recently announced that its Perseverance Mars rover discovered rock material containing potential biosignatures, with NASA Administrator Sean Duffy characterizing the finding as “the closest we have ever come to discovering life on Mars.” 

A rock sample analyzed by the rover was found to be mudstone composed of clay and silt, materials that NASA calls “excellent preservers of past microbial life” here on Earth. The rover also found telltale signs of certain chemical reactions which often accompany microbial life, although the researchers caution non-biological processes could have given rise to those signals as well. The findings were published in the journal Nature.

Karyn Rogers, Ph.D., director of the Rensselaer Astrobiology Research and Education (RARE) Center at RPI, studies the relationships between microbial communities and environmental conditions in extreme ecosystems, with an eye toward understanding the nature of the origin of life on Earth, the potential for life throughout the solar system, and the extent of life in modern extreme environments. She says that the new findings are intriguing, but not slam-dunk proof of prior life on the red planet. In a recent Q&A she discussed the latest evidence for life on Mars as well as the broader search for the origins of life on our own planet. 

Q: How convincing are the new Perseverance findings for the presence of past life on Mars?   

Rogers: It’s critical that we are clear that this is not definitive evidence for past life on Mars. What they have observed could have been made by life, but until we can prove that it only could have been made by life, and no other processes, we can’t say this is definitive evidence for life.   

Nevertheless, this is a very interesting discovery that opens up new possibilities for exploration about the chemistry that can happen on different planets.  

Q: If we could bring this sample back to Earth to analyze it, would we have a better sense of whether it’s truly the result of a biological process? 

Rogers: There are two critical components that can move this discovery forward: one is observational, and one is experimental.  

On the observational side, we need to return these samples from Mars so we can do a robust analysis with all of the best techniques we have. Alongside this, it is critical to return all of the Mars samples, so we can put the planetary context around this sample in particular.  

But we also need to “do our homework,” and that gets back to what I talked about before. Are there other ways in Mars-like conditions to produce this chemistry, these minerals with these compositions, in the presence of organic matter that might not come from biology? Depending on the results of both of these, we could get to something definitive, or we might not.  

The marvelous part of science is that we don’t know the answer ahead of time.  

Q: Is there anything a rover could conceivably find that would provide slam dunk 10/10 evidence of past life? 

Rogers: The hardest part of being definitive about signs of life is that you have to prove the null hypothesis, which is that there is no other way than life to produce our observations. So, incontrovertible evidence from a rover is a big ask. If you think about what we can currently do with rovers, we don’t have the payload space to include every instrument we need, not yet.  

But, searching for life is not a one-and-done mission. What will really get us closer to being definitive is to continue what we have been doing, which is a serious, methodical, and robust exploration of the planet. The more we understand about Mars, the better we will be at differentiating what life can do, and what Mars can do without life. That’s the argument for more rover missions, and sample return. Sustained exploration with broad planetary context is going to be the key to our search for life elsewhere. 

Q: Is there anything else you'd want people to know about this finding or the search for the origins of life in general? 

There is cross-over space between the origin of life and the search for life, and one of the key parts of that is that every planet is different: if life started elsewhere on another planet, it is also going to be different than what we find on Earth. There will be some similarities, but there will be differences as well. And the differences between planets will mean differences in life or the signs of life from one planet to the next. 

About the RARE Center 

The mission of the RARE Center is to advance our understanding of life's potential on Earth, and beyond, by combining research across biology, chemistry, geology, and planetary science. The center is committed to fostering a collaborative environment that brings together researchers, students, and educators to explore the profound questions about life's beginnings and its place in the cosmos.