Enceladus (NIRCam and NIRSpec IFU)

NASA’s James Webb Space Telescope’s exquisite sensitivity and highly specialised instruments are revealing details into how one of Saturn’s moon’s feeds the water supply for the entire system of the ringed planet. Enceladus, a prime candidate in the search for life elsewhere in our Solar System, is a small moon about four percent the size of Earth. New images from Webb’s NIRCam (Near-Infrared Camera) have revealed a water vapour plume jetting from the south pole of Enceladus, extending out 40 times the size of the moon itself. The Integral Field Unit (IFU) aboard the NIRSpec (Near-Infrared Spectrograph) instrument also provided insights into how the water from Enceladus feeds the rest of its surrounding environment.

Enceladus orbits around Saturn in just 33 hours, and as it does it sprays water and leaves behind a torus — or ‘doughnut’ — of material in its wake. This torus is depicted in the top diagram in light blue.

Webb’s IFU is a combination of camera and spectrograph. During an IFU observation, the instrument captures an image of the field of view along with individual spectra of each pixel in the field of view. IFU observations allow astronomers to investigate how properties — composition in this case — vary from place to place over a region of space.

The unique sensitivity of Webb’s IFU allowed researchers to detect many spectral features characteristic of water originating from the embedding torus around Enceladus and the plume itself. This simultaneous collection of spectra from the plume and the torus has allowed researchers to better understand their strong relationship. In this spectrum, the white lines are the data from Webb, and the best-fit models for water emission are overlaid in different colours –purple for the plume, green for the area central to the moon itself, and red for the surrounding torus.

Webb’s NIRCam was built by a team at the University of Arizona and Lockheed Martin’s Advanced Technology Center.

NIRSpec was built for the European Space Agency (ESA) by a consortium of European companies led by Airbus Defence and Space (ADS) with NASA’s Goddard Space Flight Center providing its detector and micro-shutter subsystems.

[Image description: The infographic shows a diagram of Saturn, Enceladus, and its torus at the top, the NIRCam image of Enceladus at the bottom left, and the spectra from the NIRSpec instrument at the bottom right.]