Inside a moon of Saturn, beneath its icy veneer and above its rocky core, is a sea of water the size of Lake Superior, scientists announced Thursday.
The findings, published in the journal Science, confirm what planetary scientists have suspected about the moon, Enceladus, ever since they were astonished in 2005 by photographs showing geysers of ice crystals shooting out of its south pole.
“What we’ve done is put forth a strong case for an ocean,” said David J. Stevenson, a professor of planetary science at the California Institute of Technology and an author of the Science paper.
For many researchers, this tiny, shiny cueball of a moon, just over 300 miles wide, is now the most promising place to look for life elsewhere in the solar system, even more than Mars.
“Definitely Enceladus,” said Larry W. Esposito, a professor of astrophysical and planetary sciences at the University of Colorado, who was not involved in the research. “Because there’s warm water right there now.”
Enceladus is caught in a gravitational tug of war between Saturn and another moon, Dione, which bends its icy outer layer, creating friction and heat. In the years since discovering the geysers, NASA’s Cassini spacecraft has made repeated flybys of Enceladus, photographing the fissures (nicknamed tiger stripes) where the geysers originate, measuring temperatures and identifying carbon-based organic molecules that could serve as building blocks for life.
The underground sea is up to six miles thick, much deeper than a lake.
“It’s a lot more water than Lake Superior,” Stevenson said. “It may even be bigger. The ocean could extend all the way to the north pole.”
The conclusion was not a surprise, said Christopher P. McKay, a planetary scientist at NASA Ames Research Center in Mountain View, who studies the possibility of life on other worlds, but “it confirms in a really robust way what has been sort of the standard model.”
It also makes Enceladus a more attractive destination for a future mission, especially one that would collect samples from the plumes and return them to Earth to see if they contain any microbes.
The discussion on the possibility of extraterrestrial life in the solar system centers on four bodies: Mars; Enceladus; Europa, a moon of Jupiter; and Titan, another moon of Saturn.
McKay, who was not involved with gravity measurements, noted that only Enceladus was known to possess the four essential ingredients for life, at least as it exists on Earth: liquid water, energy, carbon and nitrogen.
“I would say it’s our best bet,” he said.
By Kenneth Chang