A new study suggests that Saturn’s moon Enceladus contains a vast, underground ocean. This new information could explain the geysers of water erupting from cracks in the planet’s surface, as seen by NASA’s Cassini spacecraft in 2005, and reinforces the claim that Enceladus could support life.
Enceladus, one of Saturn’s 53 moons, is tiny–about 500 km in diameter–and coated in ice. The ocean is about 30 to 40 km deep, and calculated to be under the moon’s southern pole.
“It’s even possible that it’s global,” said Dave Stevenson, a planetary scientist who co-authored the paper published in Science magazine. “All that we can say for certain is this layer of water is thickest at the south pole.”
The gravity measurements taken by the spacecraft Cassini show that Enceladus has an outer shell of ice and a rocky core, with an ocean of water in between these two layers, which is most likely located near the south pole.
Enceladus is not a perfect sphere–in fact, the southern part of it has a slight indent. As the spacecraft passed this part of the moon, its speed did not change as much as scientists had expected, indicating that there was something denser underneath the surface that continued the constant gravitational pull on the spacecraft.
Luciano Iess of Sapienza University in Rome, also a planetary scientist, was able to detect the underground ocean using this data. Iess collaborated with Stevenson and co-authored the paper with him, which will be published in Science magazine.
Enceladus first drew scientist’s attentions due to its unusual orbit around Saturn, which is more elliptical, rather than circular.
“This causes the ice to be squeezed and squished, and as a consequence there’s heating, and from that heating water is being produced,” Stevenson said.
This heating could have been the reason as to why geysers of water were seen in the first flyby performed by the Cassini spacecraft. Additionally, analysis of the area near these geysers indicates that water vapor and organic molecules are present.
“[Enceladus] provides potentially some of the materials necessary for life,” said Jonathan Lunine, a Cornell University planetary scientist on the team. “So it makes, in fact, the interior of Enceladus a very attractive potential place to look for life.”
Enceladus is hardly the first moon to have an underground ocean beneath its surface. Europa, one of Jupiter’s moons, is larger than Enceladus, and also contains an ocean.
“It might be both. It could be neither,” Lunine said in regard to whether Enceladus or Europa could contain life. “I think what this discovery tells us is that we just need to be more aggressive in getting the next generation of spacecraft both to Europa and to the Saturn system once the Cassini mission is over.”
Only further analysis of the present chemicals can tell whether there is life present on Enceladus. According to Lunine, finding these chemicals could be “the smoking gun for whether in fact there is life down there or not.”