Could icy moons like Saturn’s Enceladus in the outer solar system be home to microbes or other forms of alien life?
Intriguing new findings from data collected by NASA’s Cassini spacecraft suggest the possibility.
Plumes of gas erupting out of Enceladus — a small moon with an ocean of liquid water beneath its icy crust — contain hydrogen. Scientists infer a lot from that: that there are hydrothermal chemical reactions similar to those that occur at hot fissures at the ocean bottoms on Earth.
On Earth at least, hydrothermal vents thrive with microbial life, offering up the potential that icy moons far from Earth — called “ocean worlds” by NASA — could be habitable.
“That’s just going to be a tremendous opportunity to test our theories and see if there’s life there,” said James L. Green, director of planetary science at NASA.
This is the latest discovery by Cassini, which is heading into its final months after 13 years of exploring Saturn, its moons and rings. On April 22, Cassini begins a journey that will take it between the planet and its rings for 22 orbits before its mission finally ends with a crash into Saturn’s atmosphere in September.
Cassini’s findings also show that levels of carbon dioxide, hydrogen and methane measured in the Enceladus plume were out of equilibrium, an imbalance that could provide an energy source that organisms could tap into for food, according to a paper published Thursday in the journal Science.
“It indicates there is chemical potential to support microbial systems,” said J. Hunter Waite Jr., program director for the space science and engineering division at the Southwest Research Institute in San Antonio and lead author of the Science paper.
In a separate paper published Thursday in The Astrophysical Journal Letters, another team of researchers, using the Hubble Space Telescope, once again spotted what appears to be a similar plume rising from Europa, one of Jupiter’s big moons that also possesses an ocean beneath an icy exterior.
Cassini had earlier found that there are seas of methane on Saturn’s largest moon, Titan, a discovery that has inspired some scientists to suggest sending a boat there.
At a mere 310 miles wide, Enceladus was considered too small to be geologically interesting; scientists suspected that its interior had frozen solid long ago. But 11 years ago, Cassini spotted plumes rising from the south pole region, one of the biggest, most surprising discoveries of the mission.
The tidal forces of Saturn pulling and squeezing Enceladus appear to generate enough heat to melt the ice. From additional Cassini observations, scientists concluded that not only is there a pool of water near the south pole of Enceladus to generate the plumes, but a global ocean that lies beneath the moon’s ice
