Weird clouds linger on Saturn's moon Titan

NASA's Cassini spacecraft captured these two images using its Imaging Science Subsystem (ISS) and Visual and Infrared Mapping Spectrometer (VIMS). The upper ISS image shows relatively cloud-free skies, while the VIMS image captures widespread cloud cover.
(Photo/NASA/JPL-Caltech/SSI/Univ. Arizona/Univ. Idaho)

Mysterious, thin, wispy clouds hide under the hazy upper atmosphere of Saturn's largest moon, Titan.

NASA's Cassini spacecraft flew over Titan on June 7 and July 25 and captured strikingly different photos of the moon's high northern latitude using the probe's Imaging Science Subsystem (ISS) and Visual and Infrared Mapping Spectrometer (VIMS). Only the VIMS (the bottom, color image) was able to peer through the moon's hazy atmosphere to capture an infrared view of the elusive clouds. The VIMS image shows widespread cloud cover during both flybys.

The different views captured by Cassini's two onboard imaging cameras raise the question of why clouds would be visible in some images but not others, according to a NASA image description. That's especially puzzling because the two images were taken fairly close together in time.

ISS consists of a wide-angle and a narrow-angle digital camera, which are sensitive to visible wavelengths of light and to some infrared and ultraviolet wavelengths. The monochrome image at the top was captured by ISS from a distance of about 398,000 miles (640,000 kilometers) and is almost cloud-free. However, the bottom image was captured from about 28,000 miles (45,000 km) by the VIMS at the longer, infrared wavelength, and bright clouds are visible in Titan's northern skies.