Webb telescope spies clouds beneath the thick haze of Saturn’s moon Titan

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The James Webb Space Telescope has spied clouds on one of the solar system’s most intriguing moons.

In November, the space observatory turned its infrared gaze on Saturn’s largest moon, Titan. It’s the only moon in our solar system that has a dense atmosphere — four times denser than Earth’s.

Titan’s atmosphere is made of nitrogen and methane, which gives it a fuzzy, orange appearance. This thick haze obscures visible light from reflecting off the moon’s surface, making it difficult to discern features.

A merging galaxy pair cavort in this image captured by the NASA/ESA/CSA James Webb Space Telescope. This pair of galaxies, known to astronomers as II ZW 96, is roughly 500 million light-years from Earth and lies in the constellation Delphinus, close to the celestial equator. As well as the wild swirl of the merging galaxies, a menagerie of background galaxies are dotted throughout the image.The two galaxies are in the process of merging and as a result have a chaotic, disturbed shape. The bright cores of the two galaxies are connected by bright tendrils of star-forming regions, and the spiral arms of the lower galaxy have been twisted out of shape by the gravitational perturbation of the galaxy merger. It is these star-forming regions that made II ZW 96 such a tempting target for Webb; the galaxy pair is particularly bright at infrared wavelengths thanks to the presence of the star formation. This observation is from a collection of Webb measurements delving into the details of galactic evolution, in particular in nearby Luminous Infrared Galaxies such as II ZW 96. These galaxies, as the name suggests, are particularly bright at infrared wavelengths, with luminosities more than 100 billion times that of the Sun. An international team of astronomers proposed a study of complex galactic ecosystems — including the merging galaxies in II ZW 96 — to put Webb through its paces soon after the telescope was commissioned. Their chosen targets have already been observed with ground-based telescopes and the NASA/ESA Hubble Space Telescope, which will provide astronomers with insights into Webb's ability to unravel the details of complex galactic environments. Webb captured this merging galaxy pair with a pair of its cutting-edge instruments; NIRCam — the Near-InfraRed Camera — and MIRI, the Mid-InfraRed Instrument. If you are interested in exploring the differences between Hubble and Webb's observations of II ZW 96, you can do so here.MIRI was contributed by ESA an

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The Webb telescope observes the universe in infrared light, which is invisible to the human eye — on November 5, the telescope spotted a bright cloud in Titan’s northern hemisphere and, soon after, detected a second cloud in the atmosphere.

The larger cloud was located over Titan’s northern polar region near Kraken Mare, the largest known liquid sea of methane on the moon’s surface.

Titan has Earth-like liquid bodies on its surface, but its rivers, lakes and seas are made of liquid ethane and methane, which form clouds and cause rain from the sky. Researchers also believe Titan has an internal liquid water ocean.

The Webb telescope's instruments captured these views of Titan. Clouds and other features are labeled, including a methane sea called Kraken Mare, the sand dunes of Belet and a bright spot called Adiri.

“Detecting clouds is exciting because it validates long-held predictions from computer models about Titan’s climate, that clouds would form readily in the mid-northern hemisphere during its late summertime when the surface is warmed by the Sun,” cowrote Conor Nixon, a planetary scientist at the NASA Goddard Space Flight Center in Greenbelt, Maryland, on NASA’s Webb blog.

Nixon is also the principal investigator on the Webb observation program for Titan.

The team of astronomers studying the Webb observations reached out to colleagues at the W. M. Keck Observatory in Hawaii to see if follow-up observations could reveal if the clouds were moving or changing shape.

“We were concerned that the clouds would be gone when we looked at Titan two days later with Keck, but to our delight there were clouds at the same positions, looking like they had changed in shape,” said Imke de Pater, emeritus professor of astronomy at the University of California, Berkeley, and lead of the Keck Titan Observing Team, in a statement.

Astronomers compared Webb (left) and Keck images of Titan to see how clouds evolved. Cloud A seems to be rotating, while Cloud B seems to be dissipating.

Atmospheric modeling experts helped the team determine that the two telescopes had captured observations of seasonal weather patterns on Titan.

Webb’s Near-Infrared Spectrograph instrument was also able to collect data on Titan’s lower atmosphere, which can’t be seen by ground-based observatories such as Keck due to interference from Earth’s atmosphere, in different wavelengths of infrared light.

These six infrared images of Saturn's moon Titan represent some of the clearest, most seamless-looking global views of the icy moon's surface produced so far. The views were created using 13 years of data acquired by the Visual and Infrared Mapping Spectrometer (VIMS) instrument on board NASA's Cassini spacecraft. The images are the result of a focused effort to smoothly combine data from the multitude of different observations VIMS made under a wide variety of lighting and viewing conditions over the course of Cassini's mission. Any full color image is comprised of three color channels: red, green and blue. Each of the three color channels combined to create these views was produced using a ratio between the brightness of Titan's surface at two different wavelengths (1.59/1.27 microns [red], 2.03/1.27 microns [green] and 1.27/1.08 microns [blue]). This technique (called a "band-ratio" technique) reduces the prominence of seams, as well as emphasizing subtle spectral variations in the materials on Titan's surface. For example, the moon's equatorial dune fields appear a consistent brown color here. There are also bluish and purplish areas that may have different compositions from the other bright areas, and may be enriched in water ice. (NASA/JPL-Caltech/University of Nantes/University of Arizona_

Unusual molecule found in atmosphere on Saturn's moon Titan

The data, which is still being analyzed, was able to see deeper into Titan’s atmosphere and surface than the Cassini spacecraft, which orbited Saturn and its moons for 13 years. Webb’s observations could also reveal the cause of a bright feature over Titan’s south pole.

The cloud observations were a long time coming.

“We had waited for years to use Webb’s infrared vision to study Titan’s atmosphere, including its fascinating weather patterns and gaseous composition, and also see through the haze to study albedo features on the surface,” Nixon said, referring to the bright and dark patches.

“Titan’s atmosphere is incredibly interesting, not only due to its methane clouds and storms, but also because of what it can tell us about Titan’s past and future — including whether it always had an atmosphere. We were absolutely delighted with the initial results.”

The team is planning more observations of Titan in June that may provide additional information about the gases in its atmosphere.