It's a radical explanation for Comet 67P's features.
There could be extraterrestrial life on Comet 67P/Churyumov-Gerasimenko, the target of the European Space Agency's Rosetta orbiter. That's according to a couple of UK-based scientists who claim that features on the comet's surface could be explained by microorganisms beneath the crust.
It's a radical view, and a controversial one, but astrobiologists Max Wallis from the University of Cardiff and Chandra Wickramasinghe, director of the Buckingham Center for Astrobiology, claim data from the Rosetta mission backs up their theory that the comet could harbour some form of life. "That's the conclusion that we've come to," said Wickramasinghe in a phone call.
He argues that comets could transport life through the galaxy, a theory that would have great implications for our origins and the nature of biology. "The implications would be that life is a truly cosmic phenomenon, not restricted to the Earth," Wickramasinghe said.
The European Space Agency's Rosetta spacecraft has been chasing Comet 67P for years, and made headlines last year when it began to orbit the comet and successfully sent a lander, Philae, onto the surface.
Data from the orbiter and lander's instruments is starting to be published and we're getting to know more about the rubber ducky-shaped comet. We've found organic compounds, and know that the dark surface of 67P is peppered with craters and fissures.
Wickramasinghe and Wallis' model proposes that biology under the icy surface of the comet could produce gases that push through cracks in the surface and replenish organic materials. In a phone call, Wickramasinghe compared the process to "rotting food in a can that pops out when the microbiology gets going and produces a lot of methane or other gases."
"The whole of the geometry of the comet, we have argued, is due to the processes of this kind," he said. The researchers published a paper relating to their theory in the Journal of Astrobiology and Outreach, and Wallis presented it today at the Royal Astonomical Society's National Astronomy Meeting in Wales.
They posit that the life in question would be a kind of extremophile—a tough organism that can survive extreme conditions. In the paper they write that, "While microorganisms probably require liquid water bodies for their early colonising of a comet, they can inhabit cracks in ice and sub-crustal snow, especially if they contain anti-freeze salts and biopolymers."
But it's not a widely accepted theory.
"I am unaware of it having much, if any support in the Rosetta community."
Matt Taylor, project scientist of ESA's Rosetta mission, said in an email that, "Given the radiation conditions and the very very low temperatures, well below -70 on sunlit surface, I don't see this as a possibility and it's not clear to me how much evidence there is backing up this claim."
He added that, "I am unaware of it having much, if any support in the Rosetta community," and that he "[takes] more credence from the plethora of papers coming from the mission from the hundreds of cometary scientists who have gone through the process of peer review of their results."
There are no instruments on Rosetta or Philae to expressly search for life, only organic materials.
Wickramasinghe has worked on the idea that comets could harbour life for a long time. He collaborated with the late British astronomer Sir Fred Hoyle on a hypothesis of "panspermia," whereby life on Earth would have originated in space.
Wickramasinghe's previous attempts to provide evidence for panspermia of this kind haven't yet swayed scientific opinion.
A less controversial theory—one that's acknowledged as by ESA as something Rosetta could help uncover—is that comets like 67P could have brought molecules to Earth that acted as the "building blocks of life," rather than life itself: complex organic molecules that could have been precursors to amino acids and "seeded" life as we know it.
Wickramasinghe conceded that the proposal of life on 67P would be disputed by critics, but blamed what he called "a relic of pre-Copernican times" that favours the idea that life is centred on Earth.