Saturn's moon Enceladus is one of the most promising places in the Solar System to look for life. It's wet, has plenty of resources and is quite warm in parts, which are all high on the microbial real estate wish list. In a new study, scientists subjected earthly bacteria to the kind of conditions found on Enceladus, and saw that the bugs were able to not only survive, but reproduce. The find adds weight to the idea that the icy moon might just be able to support life.
Most of our knowledge of Enceladus comes from the now-defunct Cassini probe, which spent over a decade imaging Saturn and its many moons. Data gathered during that time revealed a vast underground ocean, with hot deep vents on the seabed and geysers spewing ice and vapor into space. Cassini later dived through those plumes and analyzed their chemical composition, finding a rich cocktail of ingredients necessary for life as well as potential biosignatures like methane.
Now, as a more direct test for whether these conditions are suitable for life, researchers on the new study set out to recreate the oceans of Enceladus in the lab, drop bacteria in there and watch how they fared.
The bugs in question were Methanothermococcus okinawensis, a strain of methane-producing bacteria found deep in the seas around Japan. These microbes were chosen because they seem particularly well-suited to the conditions on Enceladus. They can survive in environments with very high pressure and temperature, and they metabolize carbon dioxide and molecular hydrogen – both of which were detected in large quantities in the moon's plumes. Sure enough, the bacteria were able to survive, reproducing and emitting methane.
"We have shown that methanogens are capable of multiplying under Enceladus-like conditions and some of the methane detected in the water ice fountains therefore could in principle be of biological origin," says Simon Rittmann, director of the study.
Exciting as it may be, there are huge asterisks hovering over this find. The recipe for the pseudo-Enceladus soup was extrapolated from Cassini data, so it might not be completely accurate. And, of course, there's the risk of making too strong a link – just because something may have the potential to live there, doesn't mean anything actually does.
That said, if nothing else the new study highlights how interesting Enceladus is and the icy moon will no doubt remain a place of interest in the hunt for extraterrestrial life.
The research was published in the journal Nature Communications.
Source: University of Vienna
We clearly need a better understanding of the chemistry of how life originates before we can make any claims about how likely it is that life exists anywhere else in our solar system.