As unbelievable as it sounds, it's thought that up to a third of all the Earth's organisms by mass live in rocks and sediments. Suffice to say, we know excruciatingly little about the lives and ecology of these highly inaccessible creatures. But a new study from the University of Massachusetts Amherst is offering an unprecedented glimpse into these extremophiles — including a methane-exhaling microbe that dwells deep inside the cracks of active undersea volcanoes.
Given how hard it is to discover and study microorganisms that live deep inside of rocks, a number of biologists have focused their efforts on exploring hydrothermal vents at undersea volcanoes. And this makes good sense: Warm water flows bring nutrients and energy sources directly to the microbes, allowing them to live near the rock-ocean barrier. Biologists are thus able to observe these microbes in their actual habitat, offering an unprecedented opportunity to better understand the biogeochemical cycles of the deep ocean.
The study, which was led by microbiologist James Holden, also addressed the question of what metabolic processes might have looked like on Earth about three billion years ago — and what microbial life might look like on other planets.
And indeed, the timing of the paper is actually quite interesting given the recent landing of the Curiosity rover on Mars. Holden's study describes a kind of microbe called a "methanogen" — an organism that inhales hydrogen and carbon dioxide to produce methane as waste. It just so happens that Curiosity will be measuring Mars for its methane content — a possible indicator of habitability. Should the presence of methane be confirmed, NASA scientists will undoubtedly be interested in Holden's study.