Extremophiles on and beyond Earth

Professor Rick Cavicchioli (left) and Torsten Thomas, both from UNSW, process microbial samples collected at Ace Lake  a source of cold-loving methanogens.
Professor Rick Cavicchioli (left) and Torsten Thomas, both from UNSW, process microbial samples collected at Ace Lake a source of cold-loving methanogens. (Photo: Jeff Hoffman)

From a human perspective, the Antarctic environment is rather extreme. Because we view life on Earth and life beyond Earth through human eyes, gaining a perspective about what environments sustain life on Earth also enhances our view of where we might want to look for extraterrestrial life.

For example, methanogens are microbes that produce methane, and all biological methane on Earth is produced by these ‘archaea’. They live in surprising places like rice fields, wetlands, and also in cows’ stomachs and are responsible for all the methane ruminant animals belch out and release to the atmosphere as a powerful greenhouse gas. But some methanogens also grow deep in the ocean in hydrothermal vents and will grow in the laboratory in an autoclave at 122°C. Yet again, other methanogens grow in Antarctica (see main story) – they have been so active in the bottom of Ace Lake that the waters are saturated in methane!

Interestingly, some methanogens don’t need organic (biological) matter for growth. They can grow using totally inorganic compounds like hydrogen and carbon dioxide for generating energy and for carbon (needed for cell growth), and using ammonia for nitrogen (also needed for cell growth). In the process, they produce biological matter themselves. Because they grow without oxygen, they are perfect examples of the types of microbes that could be growing right now on Mars, or on the Jupiter moon, Europa.

Because there is evidence that water exists on Mars (a requirement for life as we know it), plus methane is produced and exists now in the Martian ‘atmosphere’, it could be that Earth-like methanogens grow there and produce Martian methane. Similarly, Jupiter’s moon Europa has subsurface water, so cold-adapted methanogens, similar to those we find in Antarctic lakes, could be growing there.

This is just one example of how studies of ‘extremophiles’, and particularly Antarctic extremophiles, provide us with clues about possible forms of extraterrestrial life and where to look for such life.

Rick Cavicchioli
School of Biotechnology and Biomolecular Sciences, UNSW