The core of Saturn's icy moon Enceladus appears to have the conditions necessary for alien life to form beneath the surface, scientists have said. Researchers conducting laboratory experiments mimicking reactions known to take place on Enceladus have said the moon's core is similar to a primitive meteorite.
Yasuhito Sekine and colleagues from the University of Tokyo simulated the generation of tiny silica-rich particles that are known to originate from inside Enceladus's crust. These particles were detected in plumes of ice and suggested water-rock interactions are taking place deep inside the moon.
Publishing their findings in the journal Nature Communications, the authors note it has long been suggested Enceladus has a subsurface ocean. The discovery of silica nanoparticles show there are hydrothermal reactions taking place at the interior of the moon.
To find out more about these reactions, the team carried out laboratory experiments to reconstruct the conditions of the reactions. Their findings showed that to form silica particles, the moon's core had to be similar to that of carbonaceous chondrites - some of the most primitive known meteorites.
The team experimented with gasses similar to those seen in plumes coming from Enceladus. They were able to create liquids at the conditions found on the moon and say they are consistent with the formation of the minerals serpentine and sapnite – both of which are found on primitive meteorites.
If Enceladus' core does have this predicted composition, it would mean the moon formed very shortly after the formation of the solar system, or that this activity was triggered by a recent heating event. Furthermore, the scientists say that the reaction conditions would suggest hydrogen production is taking place – a finding that would mean there is energy for life to form beneath the icy surface.
"Under the required conditions, hydrogen production would proceed efficiently, which could provide chemical energy for chemoautotrophic life," they wrote.
Cassini's 'Plume Dive'
The study comes as Nasa prepares to sample the ocean of Enceladus when Cassini flies through the moon's plume of icy spray. The spacecraft, which launched in 1997, will run out of fuel in 2017 and late next year it will start its Grand Finale phase, where it will carry out some of its most daring manoeuvres. These flybys will include diving through the plumes of active geysers to learn more about the moon's interior.
The 28 October 'plume dive' will be the spacecraft's deepest ever dive through the moon's plume. While this flyby is not intended to detect life, it will provide new insights into how habitable the ocean environment lurking beneath the surface is. This will include how much hydrothermal activity is taking place. Researchers will also gain a better understanding of the chemistry of the plume, with the low altitude providing a greater sensitivity to more massive molecules.