When we talk about an asteroid hitting earth and wiping out all life, it’s generally presumed that we don’t really mean ALL life. There are some species that live far below ground that could survive. And one bacterium could potentially survive far longer than the rest of us because unlike the overwhelming majority of creatures on our planet, it uses radiation to survive instead of deriving power from the sun.
Desulforudis audaxviator lives in total darkness, just under two miles beneath the surface. There it manages to cling to life in a place that has no sunlight, no oxygen, and no organic compounds (like methane or ethane) to break apart for energy. Instead, it lives off the small trickle of radiation from the decaying uranium in the rocks around it.
According to researchers from the University of Sao Paulo, this could give us a great model for extraterrestrial life. Specifically life on Europa, the frozen ocean moon of Jupiter.
“We studied the possible effects of a biologically usable energy source on Europa based on information obtained from an analogous environment on Earth,” study lead, Douglas Galante told Brazilian news organization FAPESP.
Current hypotheses suggest that life on Europa may resemble that found in the depths of Earth’s oceans, piggybacking off of the chemical and thermal energy found in seafloor vents. But having another, totally separate mechanism for life to make energy dramatically increases the chances that life could adapt and survive under conditions found beyond our world.
“The uranium breaks down the water molecules to produce free radicals. The free radicals attack the surrounding rocks, especially pyrite, producing sulfate. The bacteria use the sulfate to synthesize ATP [adenosine triphosphate], the nucleotide responsible for energy storage in cells,” Galante said. “This is the first time an ecosystem has been found to survive directly on the basis of nuclear energy.”
In their paper, Galante and his team also posit that these conditions may well be found on Europa, meaning it’s feasible that yet another form of life could exist there.
“In our study, we worked with three radioactive elements: uranium, thorium and potassium, the most abundant in the terrestrial context. Based on the percentages found on Earth, in meteorites and on Mars, we can predict the amounts that probably exist on Europa,” Galante said.
Whether Europa could sustain life will ultimately come down to its chemistry. We know that, through the regular movement of Jupiter and Europa through the system of Jovian moons, could generate enough stretching and pulling of Europa’s core to keep it warm. In fact, we know this is the case. So, as long as the conditions were favorable for life there, and provided the chemical make-up of the moon itself favors it, life could very well exist in its depths.
Adding more fuel to these hypotheses are the fact that life on Earth started very shortly after the planet formed. Essentially, as soon as things weren’t totally molten, life sprang up — almost immediately in geological terms.
“The ocean bed on Europa appears to offer very similar conditions to those that existed on primitive Earth during its first billion years,” Galante added. So studying Europa today is to some extent like looking back at our own planet in the past.”
I dunno about you, but this has me very excited. Not just the fact that there are bacteria that can live on nuclear energy, but that it seems the more we look, the more we seem to find that life really will find a way.