The paper considered a community of bacteria called Candidatus Desulforudis audaxviator found at the bottom of a gold mine in South Africa. Discovered in 2009, these critters are incredibly weird. This species creates primitive ecosystems all by itself, the only one known to do so. And it likely evolved tucked deep underground for millions of years, learning how to survive without the sunlight that powers most other terrestrial ecosystems.
"This is the first time an ecosystem has been found to survive directly on the basis of nuclear energy," lead author Douglas Galante, an astronomer at the Brazilian Synchrotron Light Laboratory and the Brazilian Center for Research in Energy and Materials, told research funding agency FAPESP's press service.
So he and his colleagues wanted to consider whether the same sort of creature could make itself at home hidden away on one of the solar system's most intriguing moons. Europa, which orbits Jupiter, is coated in a crust of ice, but astronomers believe that underneath it, there's a giant ocean that could be harboring the conditions life needs.
The team can't be sure precisely what sort of nuclear fuel microbes on Europa might be able to access. But thanks to measurements taken on Earth and from meteorites that have landed here, they could make some educated guesses about how much uranium, thorium, and potassium might be decaying and releasing energy.
Based on those numbers, they found there could really be enough energy under Europa's ice shell to keep colonies of Candidatus Desulforudis audaxviator going. That means these deep-mine communities could be a helpful model for scientists trying to study the most primitive life.
"The ocean bed on Europa appears to offer very similar conditions to those that existed on primitive Earth during its first billion years," Galante told Agencia FAPESP. "Studying Europa today is to some extent like looking back at our own planet in the past."