In a comment published this week in Nature Astronomy, Dr. Nathalie Cabrol from the SETI Institute hypothesized that life on Mars may not be as extinct as we currently claim. Instead, it may be abundant but underground.

As I noted earlier, Mars’ water disappeared early on in the red planet’s history, leaving behind a dry world, at least on the surface. But water isn’t the only factor important to life. There are other factors like the thin atmosphere, UV radiation, salt content, moisture levels, and temperature fluctuations that can affect the potential for life. As Dr. Cabrol explains: You can walk on the same landscape for miles and find nothing. Then, maybe because the slope changes by a fraction of a degree, the texture or the mineralogy of the soil is different because there is more protection from UV, all of a sudden, life is here. What matters in extreme worlds to find life is to understand the patterns resulting from these interactions.

So instead of following the water, she suggests following the patterns. We need to examine Mars as an entire biosphere, questioning where life could be now but also how it would have gotten there. Back when Mars was wet, it had rivers and oceans as well as the wind and dust storms we observe now. All of these mechanisms could have helped distribute microbial life forms around the planet. And now that life could be thriving below the surface.

Remember, however, that we said a few episodes ago that Percy is not going to look in places where life could still be. We want to be careful not to contaminate those places, but we’re planning to send humans to Mars, so we need to figure out how to sample those places before that happens. Quite the conundrum. We’ll keep you updated as decisions are made and missions are planned.

More Information

SETI Institute press release

“Tracing a modern biosphere on Mars,” Nathalie A. Cabrol, 2021 March 16, Nature Astronomy