Enceladus, a small moon orbiting the planet Saturn, is likely filled with liquid water under an icy crust. Giant oceans of salty water mean the moon could contain alien microbial life.
We know Mars was once flowing with water and there’s currently frozen water in the shadowed craters on Mercury. Two other moons in the outer solar system, Titan and Europa, also seem to contain liquid water.
Enceladus — which is about 300 miles across and maintains a temperature of minus 292 degrees Fahrenheit on its surface — is unusually active.
Scientists have suspected that Enceladus has liquid water since 2005, when NASA’s Cassini spacecraft observed huge plumes of it escaping the moon’s icy crust, like in the image below.
Until now, though, we haven’t had clear evidence of this liquid water. The discovery was published in the April 4 issue of the journal Science.
New gravity measurements were obtained by monitoring the tiny motions of NASA’s spacecraft Cassini, which has spent the last 10 years photographing and measuring Saturn and its moons.
The measurements indicated that there was a significant difference in the local gravity fields that would have been created by an ice-only pole and the one detected by Cassini’s instruments. The gravity from the southern pole tugged at the spacecraft harder than would have been expected if it was just made of ice.
Specifically, a dimple in the ice crust at the south pole didn’t decrease the local gravity as much as it should have. There had to be something denser between the ice crust and the solid silicate rock core to make up for this discrepancy: an ocean of water.
The measurement doesn’t specifically indicate this is a water ocean, but it’s the most likely explanation. Especially since we know the crust of the moon is water ice, and we know there are water plumes emanating from the southern pole.
The newly-discovered ocean is up to 6 miles deep and lies under up to 24 miles of ice.
“This water ocean…may extend halfway or more towards the equator in every direction,” study researcher David Stevenson, of Caltech, said in a statement.”This means that it is as large — or larger — than Lake Superior.”
“This then provides one possible story to explain why water is gushing out of these fractures we see at the south pole,” said Stevenson.
The researchers say this environment may be ripe for complex chemical reactions which might create conditions like those on the early Earth.
“Material from Enceladus’ south polar jets contains salty water and organic molecules, the basic chemical ingredients for life,” according to Cassini project scientist Linda Spilker of NASA’s Jet Propulsion Laboratory. “Their 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.”
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