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There's Warm Water on One of Saturn's Moons

Scientists believe underwater hydrothermal vents are where life first formed on Earth.
​Image: NASA

​Saturn's moon Enceladus has long lived in the figurative shadow of its much larger fellow-moon Titan. The largest moon orbiting Saturn has an atmosphere, methane oceans, and NASA said it's the place to go for outer solar system emergency landings. But Enceladus, the sixth-largest moon orbiting the sixth-planet-from-the Sun can now boast that it is the first place in the solar system where hydrothermal activity has been observed—after Earth, obviously.

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In a new study â€‹published in Nature, a team of University of Colorado Boulder finally explained a decade-old mystery of where sodium-salt-rich ice grains detected on Enceladus were coming from.

In 2005, NASA's Cassini spacecraft discovered eruptions of water vapor and ice shooting from cracks near the moon's south pole, and the researchers determined that the grains Cassini was picking up as it approached Saturn were actually silica, which most commonly forms on Earth thanks to hydrothermal activity.

"Hydrothermal vents might have been the birthplace of the first living organisms on the early Earth"

This is notable, because hydrothermal vents on the floors of Earth's oceans have helped sprout some of our planet's weirdest life forms and liquid water is of course the major indicator of life. In fact, researchers say there's an analog to Enceladus's vents here on Earth.

"Enceladus's water–rock system[s] are similar to those found on Earth in an atypical hydrothermal field called Lost City, which was discovered in the early 2000s in the mid-Atlantic Ocean," Gabriel Tobie, a geodynamics researcher at France's University of Nantes, wrote in an accompanying news and views article.

"Because it is relatively cold, Lost City has been posited as a potential analogue of hydrothermal systems in active icy moons," he added. "What is more, alkaline hydrothermal vents might have been the birthplace of the first living organisms on the early Earth, and so the discovery of similar environments on Enceladus opens fresh perspectives on the search for life elsewhere in the Solar System."

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The size of the silica grains indicated to researchers that it could only be forming on Enceladus much the same way it does near hydrothermal vents deep on the Earth's ocean floor. A region of the moon's rock core must have a temperature of at least 90 degrees Celsius and be in contact with slightly more alkaline water to dissolve silica in sufficient amounts. Then the warm water contacts the cool and shoots upward, rather quickly, and ultimately into space.

"We methodically searched for alternate explanations for the nano-silca grains, but every new result pointed to a single, most likely origin," Frank Postberg, a co-author on the paper, said in a press release.

Silica grains in your tub usually only indicate that you've been at the beach and when they show up in an erupting plume on Enceladus it sort of means the same thing. There is, or was, an ocean environment below the moon's icy crust. Gravitational field measurements indicate that the 6-mile-deep ocean is near the moon's south pole, under 19 to 25 kilometers of ice.

So sure, researchers already think that Titan has salty oceans under its own icy exterior, and NASA has already been talking about dropping drones and robosubs on Saturn's biggest moon.

But if there's an ocean and hydrothermal activity on Enceladus, there's potential for exploration here as well.

It can be hard to be noticed when you're only the sixth largest of anything—just ask the city of Phoenix, Arizona, sixth largest in America. Still, sometimes all that sand means something exciting is going on beneath the surface. While this also works as ad for Phoenix, Enceladus boasts an ocean, so plan your travel accordingly.