Gravity measurements made with the Saturn-orbiting Cassini spacecraft indicate the small moon Enceladus has an ocean sandwiched between its rocky core and icy shell, a finding that raises the prospects of a niche for life beyond Earth.
The Cassini data shows the body of water, which is in the moon's southern hemisphere, must be as large or larger than Lake Superior and sitting on top of the moon's rocky core at a depth of about 31 miles.
"The ocean may extend halfway or more toward the equator in every direction," said planetary scientist David Stevenson, with the California Institute of Technology in Pasadena.
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Scientists infer the ocean is salty because water plumes shooting out of cracks in Enceladus' southern pole and sampled by Cassini contain salts, as well as organic molecules. That would happen if minerals from underlying rock were leaching into water, a chemistry that bodes well for the development and evolution of life.
"It was not a surprise to find a water reservoir certainly, because we knew that there are plumes, there is liquid water," said planetary scientist Luciano Iess with the Sapienza University of Rome.