Scientists have used data from the Cassini spacecraft to confirm the existence of a subsurface ocean on Saturn's moon, Enceladus. This discovery is a significant step in the search for extraterrestrial life.
Subsequent observations of the jets showed them to be relatively warm compared with other regions of the moon and to be salty, strongly suggesting the presence of liquid water below the surface. Planetary scientists have now directly investigated the interior of the enigmatic moon using Cassini's radio science experiment.
During three flybys in 2010 and 2012, Cassini passed within 100 km of Enceladus, twice over the southern hemisphere and once over the northern hemisphere. The spacecraft's velocity changed by a mere 0.2-0.3 millimeters per second due to the moon's gravity.
These tiny deviations were detectable in the spacecraft's radio signals, providing a measurement of how the gravity of Enceladus varied along the spacecraft's orbit. These measurements were then used to infer the distribution of mass inside the moon. This data confirms the presence of a global ocean beneath the icy shell.
This finding is crucial because liquid water is a key ingredient for life as we know it. The subsurface ocean on Enceladus, combined with the presence of organic molecules detected in the plumes, makes it a prime candidate for future exploration and the search for life beyond Earth.