Saturn’s largest moon Titan boasts the distinction of being the only moon in the solar system to have a thick atmosphere…so thick, in fact, that its surface is perpetually hidden from our view—but not from the view of the Cassini spacecraft’s infrared cameras!
Cassini, now over ten months gone after its Sept. 2017 plunge into Saturn, spent thirteen years in orbit around Saturn and during that time used its VIMS (Visual and Infrared Mapping Spectrometer, run by the University of Arizona) instrument during over 100 close passes by Titan, penetrating its optically-opaque cloud cover and gathering data on its surface features.
Researchers have now taken that data and created an all new, near-seamless global map of Titan, making the best-yet “naked” view of the cloud-shrouded moon. (Don’t worry, it’s still SFW.)
Previous IR and synthetic-aperture radar maps of Titan were made from data acquired in relatively small sections at a time over the course of multiple flyby events. This resulted in a monochromatic patchwork-like result with hard seams between the observation sets. These new images have removed the seams and blended the areas together across the entirety of Titan’s 5,150-kilometer-wide globe, and the results are truly beautiful.
Regions of dark dune fields around Titan’s equator and mid-latitudes appear a rusty orange color, and regions of exposed water ice (which is like solid rock in the frigid temperatures found on Titan) are in light blue and purple.
While not “true color” the variations do help highlight the variations in surface types across the moon. Because of Titan’s thick hydrocarbon atmosphere, visible wavelengths of light just can’t make it down to the surface and back to a spacecraft’s camera so a workaround had to be devised using wavelengths that can.
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. (Source: NASA)
Work like this just shows how data from Cassini will continue to lead the way for new discoveries about Saturn and its family of moons, even after the spacecraft itself has long since become a part of the ringed planet itself.