The plumes of water vapour erupting from the surface of Enceladus seem to contain hydrogen cyanide, which – perhaps counter-intuitively – is a sign that the the ocean that lies beneath the surface of this icy moon of Saturn could be capable of hosting life.
The Cassini spacecraft flew through Enceladus’s plumes several times in the early 2000s, catching samples as it hurtled by. Preliminary analysis of those samples revealed several elements and compounds that could be important for life, but it was difficult to identify many specific compounds because the molecules tended to smash up after slamming into Cassini’s sampling chamber at high speeds.
Jonah Peter at Harvard University and his colleagues performed a reanalysis of the Cassini data using a new statistical method, and they were able to pick out more compounds that are present in the plumes. They found evidence for several compounds that had not been detected before, including hydrogen cyanide, acetylene, ethane and even traces of the alcohol methanol.
All of these compounds could be part of chemical reactions that are crucial for life, but hydrogen cyanide is particularly promising.
“We don’t yet have a complete picture of the molecules that are there and that would be necessary for the origin of life – we don’t even know how the origin of life happened on Earth,” says Peter. “But we do have a good idea of some of the building blocks that are required for the beginnings of life, and hydrogen cyanide is one of those extremely versatile building blocks.”
We know that it can be a building block for amino acids, RNA and other large biological molecules, so its presence in the plumes is a good sign for the possibility of life in Enceladus’s underground sea.