Drink up. We’re about to get our best taste yet of the salty sea under Saturn’s moon Enceladus.

Tomorrow, NASA’s Cassini spacecraft is due to descend to within 49 kilometres of the surface – just a few kilometres higher than recent record-breaking skydives made by Alan Eustace and Felix Baumgartner on Earth. That will make it Cassini’s lowest pass ever through the plume of ice and vapour erupting from the moon.

During the mere tenths of a second the probe spends within the plume, an on-board detector will count the patter of ice particles hitting the spacecraft. That will show whether the plumes are tight sprays, or rise in sheets from fractures on the surface.


Another instrument will fingerprint simple organic molecules from the underground ocean. “We might have new organics that we haven’t seen previously,” said Linda Spilker of the Jet Propulsion Lab in Pasadena, California during a NASA press conference on Monday.

Cassini’s instruments can’t detect life directly, but can measure levels of hydrogen in the plumes. That in turn gives us hints to what conditions exist at potentially habitable vents on the seafloor.

On Earth, simple microbial ecosystems thrive in the warmth of hydrothermal vents, where they can produce energy by metabolising hydrogen. Something similar may be occurring on Enceladus. “You could perhaps have very diverse kinds of life there,” Spilker said.

(Image credit: NASA/JPL-Caltech/Space Science Institute)