Bad Astronomy

Life’s cauldron may be bubbling underneath Enceladus

A few days ago I wrote about how the Cassini Saturn probe dove through water ice plumes erupting from the surface of the icy moon Enceladus. The pictures were incredible, but it may very well be that the other detectors got the big payoff.

They detected organic compounds in the plumes.

Now remember, organic molecules don’t necessarily mean life. What Cassini detected were heavy carbon-based molecules, including many that are the building blocks for making things like amino acids and other compounds necessary for life as we know it.

Edited to add: Carolyn Porco, imaging team leader for Cassini, says:

[…] it is now unambiguous that the jets emerging from the south polar fractures contain organic materials heavier than simple methane – acetylene, hydrogen cyanide, formaldehyde, propane, etc. – making the sub-surface sources of Enceladus’ dramatic geological activity beyond doubt rich in astrobiologically interesting materials.

It’s been supposed for some time that Enceladus, like Jupiter’s moon Europa, has a subsurface ocean. The surface itself is mostly water ice, implying strongly that any ocean would have water as well. The plumes erupt out from cracks in the surface, and when Cassini dove through them it got to directly sample the interior of Enceladus. And it tasted organic compounds, 20 times as dense as previously thought.

There was a second discovery as well: the cracks were much warmer than expected. They were at an admittedly chilly -93 Celsius, but that’s 17 Celsius higher than thought. Two plumes come from the warmest of these regions as well.

Coupled together, these two items indicate that if there is an ocean beneath the frozen crust of the moon, then it’s reasonably warm, and rich in organic compounds. We don’t know how life started on Earth, but it’s a good guess that an ocean thick with organic compounds was involved at some point.

This is a fantastically provocative and interesting development! The ingredients for life exist on a tiny moon orbiting a ringed giant, and better yet they sit in a mixing bowl that has been churning away for billions of years. What lies beneath that hidden face?