You may have heard about all the mysteries of life in space and even in the deep oceans. But there is also much yet unknown about life within the bowels of our planet — and scientists suspect that understanding the extreme adaptations of subterranean organisms could lead to greater understanding of potential life in space.
Many organisms found in the deep biosphere are microbes — single-cellular organisms from the Bacteria or Archaea kingdoms of life — but researchers have also discovered multicellular organisms, including animals, as well.
The diversity of subterranean organisms rivals even that of organisms on the surface, according to Oregon State University oceanographer and geomicrobiologist Rick Colwell. That variation has led scientists to discover some pretty shocking extremes, including organisms which can “hibernate” for millions of years before “coming back to life” again.
“It’s hard to describe some of this life in terms that we can even understand, because [the organisms] appear to be able to survive for such long periods of time with virtually no energy available,” said Colwell at the 2018 American Geophysical Union annual meeting. The organisms are sometimes referred to as “zombies” because they appear so near to death, but it appears that some can be brought “back to life.”
According to Colwell, it’s about the organisms’ extreme metabolisms. Although the precise mechanism is not understood, this factor of the microbes’ biology allows life to survive under the “extremely impoverished and forbidding conditions in deep Earth.”
The other interesting extremes of underground microbes are the intense temperatures, pressures and even pH of environments they can live in. Because new record-breaking discoveries are not uncommon, scientists don’t fully understand the range of environmental factors that organisms can live in, so it’s hard to rule out any environments as being “uninhabitable.”
It is precisely these sorts of discoveries which could help scientists better understand where, how and when life might exist in space, and how it could alter its environment. The environments in which life can thrive look so drastically different for different organisms, and environments are also themselves altered by the life that lives in them.
There is much that is not known about the development of the atmosphere and environments of earth, though in many ways subterranean organisms can give us clues. For example, a rich underground system of organisms likely contributed to carbon and carbon dioxide sequestration, making it possible for humans and other larger organisms to breathe the air on the surface.
Currently, it is difficult to rule out where life might exist in space, and the more we know about subterranean life, the more hope we might have to someday discover organisms on Mars, or the ocean moon of Saturn.
“What we learn here,” says Colwell, “will help us understand what to look for on other planets or [in] other systems where life could exist.”