In 2008, a bacterium called Candidatus Desulforudis audaxviator was discovered 2.8 kilometers (1.7 miles) underground in a gold mine in South Africa. Though the curious creatures were living well below the reach of the Sun, they were, well, alive, which was surprising, to say the least.
Life on Earth largely depends on the Sun. Plants are dependent on it for photosynthesis, and the rest of us consume those plants either directly or by eating the creatures that eat the plants. These small mine bugs, however, were our first encounter with a being that could survive through a process called radiolysis. They get all of their energy from nutrients that react to radiation or radioactive substances, and they may be key to our search for habitable planets and alien lifeforms.
In a paper published in the Journal of the Royal Society Interface, Dimitra Atri, a scientist at the Blue Marble Space Institute of Science (BMSIS), proposes an idea that changes the way we look for extraterrestrial life: If the deep-mine bacterium could live off of radioactive substances, then maybe radiolysis is possible in space.
Using models and computations, Atri studied if cosmic rays (charged particles that are abundant in space) could reach below the surface of planets, far from the reaches of solar or stellar energy. In Mars, for example, his models showed how it’s possible for cosmic rays to reach several feet below the surface where they could react to bits of nutrients and water.
“Generally, when we talk about looking for life elsewhere, we are looking for life exactly like ours. But this is a completely different type of energy,” Atri explained. “For radiolysis to happen, the planet needs lots of cosmic rays [and little protection]. It’s actually the opposite of what we think of finding life in other places.”
The search for extraterrestrial life exactly like ours has not, so far, yielded positive results. Some believe it never will. So maybe Atri is onto something, and we’re just looking for the wrong signs.
To confirm his theory, Atri would need a particle accelerator, and it could take several years before he could get a shot at using one. If he’s right, these bugs could be the key to finding life on other planets. Perhaps one day we could even develop technology that would allow humans to live by radiolysis, which would open up many doors in our search for a habitable planet.
It’s a moonshot, but one worth aiming for.