A liquid environment where alien life could exist
Space news (September 29, 2015) – 30 miles above the icy surface of Saturn’s moon Enceladus –
NASA planetary scientists and astrophysicists studying seven years of Cassini images and gravitational data provided by the Cassini Solstice Mission believe they have proof positive of the existence of a global liquid ocean of water beneath the icy shell of Saturn’s moon Enceladus.
By carefully mapping craters and other surface features planetary scientists were able to precisely measure changes in the rotation of Enceladus, which indicated a slight wobble in its orbit. A slight wobble they believe is caused by Enceladus not being perfectly round and traveling faster and slower at different times and positions of its orbit around Saturn. This difference in velocity as it orbits the sixth planet from Sol, causes Saturn to gently rock the moon as it rotates on its axis, producing the slight wobble.
Planetary scientists found the only way they can account for the magnitude of the very small wobble – called a libration- of Enceladus in computer simulations, is if a global ocean of liquid water exists beneath its outer ice shell.
“This was a hard problem that required years of observations, and calculations involving a diverse collection of disciplines, but we are confident we finally got it right,” said Peter Thomas, a Cassini imaging team member at Cornell University, Ithaca, New York, and lead author of the paper.
This is in line with previous data obtained by Cassini and interpreted by planetary scientists as a fine spray of water vapor containing icy particles and basic organic molecules erupting from surface fractures near Enceladus’s southern pole region. Astrophysicists believe the global ocean their analysis indicates exists beneath the ice shell of Enceladus is the source of the fine spray and a possible habitat life could develop and survive in.
“If the surface and core were rigidly connected, the core would provide so much dead weight the wobble would be far smaller than we observe it to be,” said Matthew Tiscareno, a Cassini participating scientist at the SETI Institute, Mountain View, California, and a co-author of the paper. “This proves that there must be a global layer of liquid separating the surface from the core,” he said.
Planetary scientists are currently trying to figure out where the energy keeping the global ocean from completely freezing is coming from. At this point, they think tidal forces due to the gravity of Saturn could be producing a lot more energy than previously calculated.
“This is a major step beyond what we understood about this moon before, and it demonstrates the kind of deep-dive discoveries we can make with long-lived orbiter missions to other planets,” said co-author Carolyn Porco, Cassini imaging team lead at Space Science Institute (SSI), Boulder, Colorado, and visiting scholar at the University of California, Berkeley. “Cassini has been exemplary in this regard.”
Where’s the heat coming from?
The heat energy keeping the global ocean of Enceladus from freezing could be partly coming from geothermal sources on the bottom of the ocean. Cassini is scheduled to pass over Enceladus again on October 28, 2015, at which time it will only be about 30 miles (49 kilometers) above the surface of the moon, which is the closest the spacecraft will come to the surface. Planetary scientists want to pass through the icy spray, again, to collect more data, and hopefully, determine the reasons the global ocean isn’t frozen.
You can read and learn more about Cassini’s mission to Saturn here.
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You can learn more about Saturn’s moon Enceladus here.
Learn about NASA’s search for the ‘Crucible of Life’.