Scientists had long thought that Saturn’s moon Enceladus had an ocean of liquid water underneath its thick, icy surface (in 2004, NASA scientists saw water vapor and ice spewing from vents near the moon’s south pole). Today. NASA’s Cassini spacecraft revealed actual evidence that their theory was correct – an ocean lies hidden inside the moon.
NASA scientists discovered the evidence by deducing gravity variations using the Doppler Effect (the same principle used in our earthly radar systems). NASA’s Jet Propulsion Laboratory explained:
“As the spacecraft flies by Enceladus, its velocity is perturbed by an amount that depends on variations in the gravity field that we’re trying to measure. We see the change in velocity as a change in radio frequency, received at our ground stations here all the way across the solar system.”
The researchers believe the ocean, which could cover the entire planet or maybe just parts of it, is about 6 miles deep. The ice covering the ocean is believed to be 19-25 miles thick. Given the probability that liquid worlds can more easily host life, researchers now put Enceladus at the top of the list of the most likely places in our solar system to host microbial organisms.
Cassini was launched in 1997 and entered orbit around Saturn on July 1, 2004. Cassini’s primary mission ended on July 30, 2008 but was extended to June 2010. When that mission ended, NASA announced another extension, putting Cassini to work until at least 2017. This last extension allows 155 revolutions around the planet, 54 flybys of Saturn’s moon Titan, and 11 flybys of Enceladus. It has flown near Enceladus 19 times now. Cassini’s lifetime will end in 2017 when Cassini drops below one of Saturn’s rings (the D ring) and drops into Saturn’s atmosphere.
Check out some of the photos taken by Cassini below.