From “Limits of Microbial Life in an Undersea Volcano: Third of Earth’s Organisms Live in Rock and Sediments” (Science Daily, August 6, 2012), we learn about microbes living inside a black smoker:
At the low-hydrogen Endeavour site, they found that a few hyperthermophilic methanogens can eke out a living by feeding on the hydrogen waste produced by other hyperthermophiles.
“This was extremely exciting,” says Holden. “We hypothesized that the methanogens grow syntrophically with the hydrogen producing microbes, and it worked out that way in the lab with a strain from the site. So we have described a methanogen ecosystem that includes a symbiotic relationship between microbes, …
Mars is, of course, a bit more extreme than a black smoker.
See also: Origin of life: Researchers claim life could have existed 4.4 billion years ago,.before Earth cooled
Photo: Research submarine Alvin/Bruce Strickett, WHOIS