By Enceladus’ famous plume dwarfs the moon itself.
Geysers on Saturn’s icy moon spew water vapor nearly 10,000 kilometers into space, a distance about 19 times the diameter of Enceladus, researchers report in a paper accepted in Nature Astronomy. If the geysers were on Earth, the plume would touch the edge of our planet’s atmosphere.
NASA’s now-defunct Cassini spacecraft discovered almost two decades ago that Enceladus ejects salty water from a subsurface reservoir (SN: 5/2/06). But the spacecraft’s orbit around Saturn meant it was too close to the moon to see the plume’s true extent.
In November, the James Webb Space Telescope turned its powerful infrared camera on Enceladus for the first time, gazing at the moon for about four minutes. JWST’s vantage point from across our solar system let it see the plume extending at least 9,600 kilometers from the south pole.
“Seeing it so big, water being everywhere, it was kind of a surprise,” says planetary scientist Geronimo Villanueva of NASA’s Goddard Space Flight Center in Greenbelt, Md.
JWST’s observations also shed light on how much water the plume pumps out and where those molecules end up.
Enceladus has been spewing the same amount of water since Cassini arrived at Saturn’s system 19 years ago: about 10 million billion trillion molecules per second (that’s a 10 followed by 28 zeros).
Roughly 30 percent of the molecules feed into a donut-shaped ring — called a torus — that encircles the entire Saturnian system. The remaining water either helps create one of Saturn’s iconic icy rings, or gets blown across the system, where the water may affect the atmospheric chemistry of Saturn and its other moons (SN: 10/8/19).
The plume’s consistency gives Villanueva hope that whenever scientists send another mission to Enceladus, the geysers will still be active. In the meantime, JWST will keep checking up on the moon. “The beauty with James Webb is we can point to it very often and see if that thing remains active all the time,” he says.
