Move over, Europa. It looks as though the most life-friendly habitat ever discovered outside of Earth is Enceladus—Saturn's sixth-largest moon.

Astrophysicists working with NASA's Saturn sweeping Cassini spacecraft have just announced that Enceladus has a warm ocean at its southern pole with ongoing hydrothermal activity—the first ever discovered outside of Earth. This new research, published in the journal Nature, builds upon last year's discovery of the moon's 6-mile-deep ocean, which is also believed to contain many of the chemicals commonly associated with life.

"We now have very strong evidence that there is a hot hydrothermal environment at the base of Enceladus's ocean, perhaps like those where we believe life began on Earth," says Jonathan Lunine, a planetary scientist at Cornell University who works with the Cassini spacecraft but was not involved in the new research. "This is yet another discovery in a series of really remarkable findings that have come one by one, to tell us that this may be the place to go look for life in the outer solar system."

The clues in the rings

Sean Hsu, an astrophysicist at the University of Colorado, Boulder who helped to lead the team behind this new discovery, says the discovery happened in what was perhaps a counterintuitive way. He and his colleagues estimated the temperature, salinity, and approximate pH of Enceladus's ocean by studying the dust in Saturn's outermost ring. Really.

"We've known from quite early on that Enceladus was the source of the material in Saturn's [outermost] ring… based on the ring's composition" Hsu says, "although we didn't know the exact mechanism for the material transfer." But the 2005 discovery of 125-mile-high icy geysers shouted out to scientists how Enceladus flung material skyward.

Enceladus's heat is created by gravitational friction from the pull of Saturn and its other moons

Hsu and his team analyzed a class of dust nanoparticles in this outermost ring. Using Cassini's mass spectrometer tool, they showed that these dust particles were made mostly of silica, and that they were the skeletons of evaporated geyser-flung saltwater. These particles point toward warm waters on Enceladus.

How? It turns out that the exact size range and makeup of the silicate particles gives the researchers a stunningly accurate blueprint of the conditions that forged them. For example, if Enceladus's ocean were really salty (say, over 4 percent, which is a bit more than Earth's oceans) then the silicate particles would have chemically clumped together, former bigger lumps than were found.

Here's what these particles revealed about Enceladus's deep ocean: The water is less than 4 percent salinity, has a pH between 8.5 and 10.5 (Earth's ranged between 8.0 to 8.3 before the industrial revolution), and is at least 200 degrees Fahrenheit at hot springs at the bottom of the ocean where the particles are forged. Outside of hydrothermal activity, no other known process could make these uniformly small silica particles, the scientists say.

Life on Enceladus?

With temperate, vent-warmed waters that contain nitrogen, methane, carbon dioxide, and various other chemicals required for Earth-like life, Enceladus could very much look like the Lost City hydrothermal field under the Atlantic Ocean—an environment where many scientists believe life first originated on Earth. That's a far cry from the scientific state of affairs 15 years ago, when scientists were sure Enceladus was a lump of boring, uneventful rock. This idea would have been laughable.

But while Hsu says Enceladus looks tantalizingly habitable, it's not clear whether life could (or does) exist on the moon. "An important consideration is the timescale of the Enceladus's ocean's hydrothermal activities," Hsu says. That is, we just don't know how long Enceladus's hydrothermal activity has gone on. Unlike thermal activity on Earth, which is powered by our hot, churning core, Enceladus's heat is created by gravitational friction from the pull of Saturn and its other moons.

But Cornell's Lunine says the question as to whether Enceladus's ocean does or doesn't contain life is one we could answer, and soon. All of the new information we're gleaning about Enceladus (and all of Saturn's moons) comes from the Cassini spacecraft, which was developed in the late '80s and early '90s. Despite carrying outdated tech and instruments, it's revolutionizing the way we think about the possibility of life in other parts of the solar system. Lunine is currently working on a proposal for an update to the Cassini mission, using a new spacecraft with both modern day technology and specialized machinery designed to seek out the bio-signs of life.

"If we go back to Enceladus and build upon the Cassini results with the instruments of today, the short answer is, we know that we'll be able to look for life frozen in the [geyser] particles, and really nail this habitability question," Lunine says.

Read next: Inside the epic 8-year journey to Ceres

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