The James Webb and Hubble space telescopes have delivered complementary views of Saturn that allow scientists to effectively 'slice' through the planet's atmosphere at multiple altitudes, each telescope telling a different part of Saturn's story. Together, the observations help researchers understand how Saturn's atmosphere works as a connected three-dimensional system.
The Hubble image, captured on August 22, 2024, reveals the planet's softly banded atmosphere and iconic rings as visible light. Hubble has historically been used to track storms on Saturn, and the new photo clearly shows bands of atmospheric clouds. By contrast, the James Webb image, captured on November 29, 2024, shows Saturn's glowing icy rings and layered atmosphere in infrared light.
Where Hubble reveals subtle colour variations across the planet, Webb's infrared view senses clouds and chemicals at many different depths in the atmosphere, from the deep clouds to the tenuous upper atmosphere. The infrared sensors on Webb highlight details such as the highly-reflective ice of Saturn's rings, which appears practically white in the photo, and grey-green shading on the planet's poles.
The different colouring in Webb's image could be caused by a layer of high-altitude aerosols scattering light across latitudes, or charged molecules interacting with the planet's magnetic field and causing auroral activity. In the Webb image, a long-lived jet stream known as the 'ribbon wave' meanders across the northern mid-latitudes, influenced by otherwise undetectable atmospheric waves. There are also subtle ring features such as spokes and structure in the B ring that appear differently between the two observatories.
The Hubble image was captured as part of a more than a decade long monitoring programme called OPAL (Outer Planet Atmospheres Legacy) in August 2024, while the Webb image was captured a few months later using Director's Discretionary Time. OPAL has been studying the outer planets from 2014 to 2024 to obtain long-time baseline observations of Jupiter, Saturn, Uranus, and Neptune in order to understand their atmospheric dynamics and evolution.
These 2024 observations, taken 14 weeks apart, show the planet moving from northern summer toward the 2025 equinox. As Saturn transitions into southern spring, and later southern summer in the 2030s, Hubble and Webb will have progressively better views of that hemisphere. Hubble's observations of Saturn for decades have built a record of its evolving atmosphere, and programmes like OPAL, with its annual monitoring, are allowing scientists to track storms, banding patterns, and seasonal shifts over time.
Both sets of observations complement previous observations done by NASA's Cassini orbiter during its time studying the Saturnian system from 1997 to 2017. The capacity to combine multiple observatories' data into a coherent picture of planetary systems represents a significant return on decades of investment in space exploration, allowing scientists to extract far more knowledge from each mission dollar spent.