Maybe Enceladus Got Its Geysers Because Something Else Smashed Into It

A giant collision, and some tidal science.

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Ever since NASA's Cassini spacecraft discovered the water of Enceladus in 2005, the moon has intrigued scientists. The moon's underground ocean appears to have geysers which shoot out an "organic brew" of carbonated water with an essence of natural gas. Scientists at Johns Hopkins have developed a idea as to how they formed in the first place: something big hit Enceladus.

Led by researcher Kate Craft, the study looks closely at the fractures along the moon's south pole, colloquially referred to as "tiger stripes." Enceladus is small—it's Saturn's sixth largest moon, with a radius of 157 miles. It wouldn't take much for an asteroid to shatter the planet's exterior, which would then subsequently refreeze in the vacuum of space. "During and post-impact fracturing would occur," Craft and her team say in their presentation of their theory, "the crater would collapse, water would begin to refreeze and subsequent fluid exchange would occur."

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"The impact could have happened anywhere and then Enceladus would have rolled over until the impact point ended up at whichever pole happened to be nearest," co-author Francis Nimmo from the University of California Santa Cruz tells New Scientist, meaning that the impact could have knocked enough mass off the moon to change it permanently by causing a gravitational anomaly.

Enceladus doesn't operate alone, however. The moon is strongly affected by Saturn's gravitational pull, and once that water appeared, it began to feel tidal pulls, much like the Earth's moon creates waves here. If Craft is right then those tidal stresses have been pushing at the surface of Enceladus for a long, long time, possibly 100 million years. Long enough for the stresses to make themselves visible on the surface, at least.

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Cassini's information is useful, but a landing on the moon could give a fuller understanding of its underground ocean, including the tantalizing possibility that the geysers, which might share similarities with Earth's deep sea hydrothermal vents, have brought forth life. That's the question that surrounds not just Enceladus, but another moon of Saturn as well: Europa.

Cassini is scheduled to destroy itself by spiraling into Saturn in September. Whenever humanity's next trip out there is, it will certainly have its hands, robotic or human, full.

Source: Gizmodo

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