Since geysers of water vapor and ice were spotted on Saturn’s moon Enceladus by the Cassini spacecraft in 2005, an undersurface reservoir of water has been theorized. On April 4, results of gravity measurements were released in the journal Science, which help characterize the size of the reservoir. Below an ice shell that is 30 to 40 km (19-25 miles) thick, there is an ocean 10 km (6 miles) deep. Enceladus itself is 504 km (313 miles) in diameter.
The jets of water from the south pole of Enceladus contain salty water and organic molecules. Thus, Enceladus is potentially favorable to microbial lift. Linda Spilker, Cassini’s project scientist at JPL, noted that the jets’ discovery “expanded our view of the ‘habitable zone’ within our solar system and in planetary systems of other stars. This new validation that an ocean of water underlies the jets furthers understanding about this intriguing environment.”
The water ice covering Enceladus makes it one of the brightest objects in the solar system. But because it reflects almost 100 percent of the sunlight striking it, it is also one of the coldest (-201° C or -330° F). At least, on the surface. [ More info from JPL ]