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A Saturn moon may host life

Icy home:Scientists theorise that water interacts with rock at the bottom of the ocean of Enceladus, producing hydrogen gas that could feed microbes.NASA  

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 the earth.

Habitable conditions

On the earth at least, hydrothermal vents thrive with microbial life, offering up the potential that icy moons far away from Earth 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, a spacecraft that 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 .

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.

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.

Surprising find

In October 2015, Cassini swooped to within 30 miles of the surface of Enceladus, and one of the instruments collected and identified particles in the plume spray. It was mostly water molecules, but scientists also found hydrogen molecules.

“Just finding hydrogen was a surprise,” said Christopher R. Glein, a geochemist at the Southwest Research Institute and one of the authors of the Science paper.

After considering a variety of ways that could continually generate hydrogen, the scientists concluded that hydrothermal reactions offered the most likely explanation for producing that much of the gas.

Each water molecule consists of two hydrogen atoms and one oxygen atom. Geophysical models indicated that as hot water flows past the rocks, minerals in the rocks were grabbing the oxygen atoms and releasing hydrogen, the scientists reported.

There appeared to be enough energy to support microbes. “This is the first time we’ve been able to make a calorie count of an alien ocean,” Mr. Glein said.

New York Times News Service