NASA’s Cassini orbiter has provided us with new and amazing images of Titan, Saturn’s largest moon. Titan is the only other cosmic object in the Milky Way besides Earth known to harbor stable bodies of liquid on its surface, but the difference is that Titan’s lakes contain liquid methane and ethane. Now, Cassini has discovered salt flats — or, more accurately, whatever the Titan equivalent of salt flats are — surrounding these lakes.
Almost all of Titan’s lakes are concentrated around its north pole, which Cassini has been examining carefully. The spacecraft was able to discern differences — namely, a unique “bright material” in the surface around and between these lakes, indicating the presence of salt flats. Scientists believe the salt flats are produced by Titan’s weather cycle, which includes, much like ours, the evaporation of liquid from seas and lakes that leave the material behind.
Titan is the only known moon in the Milky Way that has a dense atmosphere, rich with methane. One of the awesome abilities of Cassini is that its instruments can see beyond the hazy atmosphere to give us a glimpse of all that lies beneath. The changes of the season and the lack of rain during Cassini flybys in July and September also helped.
Based on these observations and images, scientists conclude that Titan has a hydrologic weather cycle. During the rainy seasons, hydrocarbons from the methane clouds shower the planet and collect in the lakes — Cassini has documented the development of “new” lakes from such rains — and then eventually evaporates back into clouds, leaving the sediment behind. Scientists believe that the organic chemicals that once constituted Titan’s atmosphere then dissolved into the methane lakes, only becoming evident once the liquid evaporated.
Scientists are referring to the sediment left behind as salt flats because that’s our closest terrestrial reference point. They don’t actually know what this organic sediment is composed of, but whatever the material is, it isn’t salt. Like all organic material, it contains carbon, but that’s about all we know. Scientists also think that the environment on Titan is conducive to the kind of chemical soup out of which life on Earth arose. The finding also further confirms Saturn’s place as the coolest planet in the solar system. Forget about Mars — can’t we go here instead?