Last week NASA convened a visionary meeting in New Mexico to consider a topic critical to astrobiology—whether life currently exists on Mars, and if so, how to detect it. The site of the conference was near the world-renowned Carlsbad Caverns, which attendees got to visit during a mid-conference workshop.
Caves, along with ice and salt deposits, are likely places to search for possible near-surface life on Mars, and Diana Northup from the University of New Mexico provided an overview of the many diverse shapes and forms microbes can take in caves. She suggested looking for similar mineral deposits on Mars. In another talk, Brady O’Connor from McGill University in Montreal reported on cold-adapted and metabolically active microbial communities found within ice in lava tube caves on Earth—again with intriguing implications for similar structures on Mars.
Water ice is believed to be important for locating extant life near the Martian surface, especially at higher latitudes. Carol Stoker from NASA’s Ames Research Center made the case for focusing on this possible microhabitat, and presented information on the proposed Icebreaker Life mission, which would search for biomarkers in Martian ice deposits.
Not all the water on Mars may be frozen, however. Andrew Schuerger’s lab at the University of Florida recently made a startling, albeit preliminary, discovery. He tested the effect of frost (first discovered on Mars by the Viking mission) on rocks under Martian conditions, and found that liquid water flowed on the rocks for about 15 minutes, before all the water turned into the gas phase. Would this short time be sufficient to support Martian life if frost occurred on a daily basis at some locations? We don’t know. But it’s an extremely interesting finding, and I’m very interested to hear about his further results.
The search for life in Martian salts was discussed by Shil DasSarma from the University of Maryland and myself. Both our talks made clear that salts may allow microbes to thrive very close to the surface of Mars—perhaps even just a few millimeters deep, which would allow for photosynthesis. If so, they should be easily retrievable on a future landing mission. I also pointed out that because Martian life would be exposed to extremely dry conditions for long periods of time, it may have novel biochemical adaptations that Earth microbes do not have. Penny Boston from the NASA Astrobiology Institute reported on her recovery of viable microorganisms within fluid inclusions in gypsum and quartz. Life may have been preserved in the same type of minerals as the Martian surface became too hostile for life.
A fourth potential habitat discussed at the meeting was the deep Martian subsurface. Although extensive drilling would be needed to explore these regions, future missions could reach depths as low as 100 meters below ground. One astonishing result, related to both the deep subsurface and salty microhabitats, was presented by Vlada Stamenkovic from the Jet Propulsion Lab. His computer modeling showed that there is enough oxygen on Mars to support microbes in brines, and perhaps even simple sponges, in some locations. Near the surface the oxygen would be supplied by the Martian atmosphere, whereas farther below it would come from radioactive decay. No one is claiming that there are sponges on Mars, but this finding challenges many scientists’ assumption that there is no available oxygen beneath the Martian surface.
I could go on listing the many intriguing findings presented at last week’s workshop. The scientists who presented in New Mexico will continue to work on their research, which should help NASA determine where to send a Life Detection Mission (or perhaps a precursor).
And if you ever wondered about the legal status of would-be Martian microbes—whether, for example, they might have certain rights—check out this abstract of a talk by William Kramer from Outer Space Consulting.