The NASA/ESA/ASI Cassini mission spent over a decade exploring the Saturnian system, and not only imaged the plumes of Enceladus for the first time but flew directly through them and sampled what they were made of. While Cassini’s position within the Saturnian system provided invaluable insights into this distant moon, Webb’s unique view from the Sun-Earth Lagrange Point 2, 1.5 million kilometres from Earth, along with the remarkable sensitivity of its Integral Field Unit aboard the NIRSpec (Near-Infrared Spectrograph) Instrument, is offering new context.

The Webb observations directly demonstrate how the moon’s water vapour plumes feed the torus, a fuzzy doughnut of water that is co-located with Saturn’s E-ring. By analysing the Webb data, astronomers have determined that roughly 30 percent of the water stays within this torus, and the other 70 percent escapes to supply the rest of the Saturnian system with water.

In the coming years Webb will serve as the primary tool for observing the ocean moon Enceladus, and discoveries from Webb will help inform future Solar System satellite missions that will look to explore the depth of the subsurface ocean, how thick the ice crust is, and more.

Building on discoveries made by Webb, as well as those made by ESA's Jupiter Icy Moons Explorer (Juice) mission, ESA is planning to get even closer to the icy moons of Jupiter and Saturn with future missions, to search for possible biosignatures.

Webb’s observations of Enceladus were completed under Guaranteed Time Observation (GTO) programme 1250. The initial goal of this programme is to demonstrate the capabilities of Webb in a particular area of science and set the stage for future studies.

The team’s results were recently accepted for publication on 17 May in Nature Astronomy. A pre-print is available here.

More information

Webb is the largest, most powerful telescope ever launched into space. Under an international collaboration agreement, ESA provided the telescope’s launch service, using the Ariane 5 launch vehicle. Working with partners, ESA was responsible for the development and qualification of Ariane 5 adaptations for the Webb mission and for the procurement of the launch service by Arianespace. ESA also provided the workhorse spectrograph NIRSpec and 50% of the mid-infrared instrument MIRI, which was designed and built by a consortium of nationally funded European Institutes (The MIRI European Consortium) in partnership with JPL and the University of Arizona.

Webb is an international partnership between NASA, ESA and the Canadian Space Agency (CSA).

Contact:
ESA Media relations