Why Cassini’s Close Flyby of Saturn’s Moon Is Exciting for Alien Hunters

On Wednesday, NASA's Cassini spacecraft will plunge into a plume of icy water vapour jetting out of Saturn's moon Enceladus. It'll take a little taste of the spray to find out more about conditions on Enceladus—and particularly in its subsurface ocean, which is one of the most promising targets for extraterrestrial life.

Cassini's October 28 flyby will see it dive into the vapour to a very close distance of just 48km from the surface of the moon's south polar region. The point of the mission is to collect information on the composition of that icy plume using the spacecraft's Ion and Neutral Mass Spectrometer (INMS) instrument.

It's been timed to coincide with when the plumes are most active.

The NASA mission overview explains that Cassini will be looking to sniff out a few things in particular: hydrogen, complex organic molecules, and more evidence of where the plumes come from. This information could all add to our knowledge of the icy ocean's potential habitability—for instance, NASA explains that the amount of hydrogen detected "has implications for the amount of energy available for creating a habitable environment in the ocean."

Alien enthusiasts shouldn't get too excited just yet, however, as the space agency emphasises in all of its communications that Cassini is not actually equipped to look for life. For one thing, the INMS instrument won't be able to detect complex organic molecules with enough resolution to tell if they're biological in nature.

But scientists hope to study the next closest thing to actual life and find out more about the habitability of Enceladus and the promising liquid ocean beneath its icy crust—which is conveniently heated, likely at least in part due to tides from Saturn's gravitational pull. We won't see results for several months after the flyby, owing to the time it takes to analyse and peer review the data.

Cassini will continue on its mission around Saturn, which it arrived at in 2004. It's next notable stop is in November, when it'll check out Saturn's largest moon Titan, before returning for its last targeted flyby of Enceladus in December.

We'll be eagerly waiting to see if there's any more evidence of little alien Enceladus fish.