NASA’s James Webb Space Telescope has detected a water vapor plume from Saturn’s moon, Enceladus that spans over 6,000 miles, which is approximately the distance from Los Angeles, California to Buenos Aires, Argentina. This discovery marks the first time a water emission has been observed over such a vast distance. Additionally, Webb provides scientists with a direct look at how this emission feeds the water supply for the entire system of Saturn and its rings.
Enceladus is a small ocean world, only about four percent the size of Earth and measuring just 313 miles across. Between the moon’s icy outer crust and rocky core is a global reservoir of salty water. Geysers on the moon’s surface, informally called “tiger stripes,” shoot out jets of ice particles, water vapor, and organic chemicals.
Previously, observatories have mapped jets hundreds of miles from the moon’s surface, but Webb’s exquisite sensitivity reveals a new story.
Geronimo Villanueva of NASA’s Goddard Space Flight Center, said:
“When I was looking at the data, at first, I was thinking I had to be wrong. It was just so shocking to detect a water plume more than 20 times the size of the moon. The water plume extends far beyond its release region at the southern pole.”
The plume’s length wasn’t the only characteristic that interested researchers. The rate of water vapor gushing out, approximately 79 gallons per second, was also noteworthy. At this rate, an Olympic-sized swimming pool could be filled in a few hours. In comparison, filling the same pool with a garden hose on Earth would take over two weeks.
The Cassini orbiter spent more than 10 years studying the Saturnian system. But while Cassini’s position within the Saturnian system provided valuable insights into this distant moon, Webb’s unique view from the Sun-Earth Lagrange Point 2, which is one million miles from Earth, along with the remarkable sensitivity of its Integral Field Unit aboard the NIRSpec Instrument, is providing new context.
“The orbit of Enceladus around Saturn is relatively quick, just 33 hours. As it whips around Saturn, the moon and its jets are basically spitting off water, leaving a halo, almost like a donut, in its wake. In the Webb observations, not only was the plume huge, but there was just water absolutely everywhere.”
This fuzzy donut of water that appeared ‘everywhere,’ described as a torus, is co-located with Saturn’s outermost and widest ring – the dense “E-ring.” The observations from Webb clearly show how the torus is fed by water vapor plumes from the moon. Astronomers have analyzed the Webb data and found that around 30% of the water remains within the torus, while the other 70% escapes and supplies the remaining water in the Saturnian system.
Webb will be the primary observation device for the ocean moon Enceladus in the future, and the discoveries made by Webb will aid in future solar system satellite missions that aim to explore the depths of the subsurface ocean, as well as determine the thickness of the ice crust, among other things.
“Right now, Webb provides a unique way to directly measure how water evolves and changes over time across Enceladus’ immense plume, and as we see here, we will even make new discoveries and learn more about the composition of the underlying ocean. Because of Webb’s wavelength coverage and sensitivity, and what we’ve learned from previous missions, we have an entire new window of opportunity in front of us.”
