Published: Thu, April 20, 2017
Science | By Boyd Webster

Here are 5 of our solar system's most important moons

Here are 5 of our solar system's most important moons

WASHINGTON-Two veteran NASA missions are providing new details about icy, ocean-bearing moons of Jupiter and Saturn, further heightening the scientific interest of these and other "ocean worlds" in our solar system and beyond.

The paper from researchers with the Cassini mission was published Thursday in the journal Science.

Scientists from Southwest Research Institute (SwRI) have discovered hydrogen gas in the plume of material erupting from Saturn's moon Enceladus.

"This is the closest we've come, so far, to identifying a place with some of the ingredients needed for a habitable environment", said Thomas Zurbuchen, an associate administrator with NASA. Molecular hydrogen with the plumes could serve as a marker for hydrothermal processes, which may provide the chemical energy required to support life as we know it. Scientists determined the gas in the plume almost 98 percent water, about 1 percent of which is hydrogen, with the rest being a mixture of carbon dioxide, methane and ammonia. The name comes from the byproduct - methane.

The hydrogen, liquid water and evidence of geothermal warming now makes Enceladus the most likely candidate for harboring alien life in the solar system, according to scientists.

Running low on fuel, Cassini is in the final months of its mission, heading for a crushing September 15 dive into Saturn's atmosphere to avoid an inadvertent collision with one of the planet's potentially habitable moons.

While Cassini has not spotted phosphorus or sulfur in Enceladus' ocean, scientists believe both are present because Enceladus' rocky core is chemically similar to meteorites known to contain both elements.

FILE - This image provided by NASA is a Hubble Space Telescope close-up of Saturn's disk, and it captures the transit of several moons across the planet's face.

During Cassini's close flyby of Enceladus on October 28, 2015, INMS detected molecular hydrogen as the spacecraft flew through the plume of gas and ice grains spewing from cracks on the surface. Cassini also sampled the plume's composition during flybys earlier in the mission.

Enceladus has an ocean surface and nearly all that is necessary for life that exists on Earth: ammonia, carbon dioxide and hydrogen, as well as some organic materials.

The presence of life-supporting hydrogen was detected by the Ion Neutral Mass Spectrometer onboard the Cassini spacecraft. Also, past warm estimations by the Galileo shuttle demonstrated that the current Europa tufts showed up straightforwardly over a problem area in the moon's sea.

But it made arguably it's most goundbreaking discovery this year, when it found the ocean on Enceladus, one of Saturn's moons, was releasing large amounts of pure hydrogen gas.

"The next time we go back ... you're going to take something that not only picks up on the habitability story, but it starts looking for evidence for life". "It would be like a candy store for microbes", said Hunter Waite, lead author of the Cassini study.

The new findings are an independent line of evidence that hydrothermal activity is taking place in the Enceladus ocean.

During its Enceladus dives, Cassini determined that the plumes consist mostly of water. Another idea is that water ejected by the plume falls onto the surface as a fine mist, changing the structure of the surface grains and allowing them to retain heat longer than the surrounding landscape. The focus then shifted for a while to Jupiter's moon Europa.

NASA just made another historic finding of ocean worlds. A spacecraft under development called the Europa Clipper, to launch sometime in the 2020s, could shed more light on the matter.

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