Scientists’ interest in Titan was piqued in the early 1980s, when Voyagers 1 and 2 sent back data revealing a complex chemistry in the moon’s atmosphere. Unfortunately, the twin spacecraft were not equipped to see beneath Titan’s haze.
For decades, Saturn’s largest moon looked like little more than a fuzzy orange ball.
That changed over the course of Cassini’s mission. Using its Visual Infrared Mapping Spectrometer, the spacecraft was able to take a closer look.
Cassini revealed that the Mercury-sized moon has vast deserts of rippling, sandy dunes at its equator...
...and seas of liquid methane and ethane at its poles.
It appears to be the only other place in the solar system that has a liquid cycle like we have on Earth. But on Titan, rain is made of methane rather than water.
Titan’s complex chemistry
In Titan’s atmosphere, solar energy prompts nitrogen and methane to react, producing a wealth of organic molecules.
The heaviest of these molecules can fall to the ground and wind up in Titan’s methane lakes and rivers. Other molecules make their way to the surface via rain.
Soluble molecules dissolve in the liquid methane, while insoluble ones tend to sink to the sea floor.
Before Cassini, scientists could see that the surface of Enceladus was unusually bright. But they didn’t know why. Cassini provided a shocking answer: The small, frozen moon has geyser-like jets that spew water and ice particles from an underground ocean out into space.
Some of the material in these plumes lands on Enceladus, helping to keep its surface smooth and bright. One of Saturn’s vast rings, the E ring, is also made up of material from the plumes.
Enceladus’ hidden ocean
In 2008, Cassini sampled one of the Enceladus plumes and detected nanoparticles that can be generated only when liquid water and rock interact at temperatures over 200 degrees Fahrenheit. That discovery suggests there might be hydrothermal vents on the bottom of the moon’s hidden ocean.
If so, the moon could be hospitable for life.
Meet Mimas, the “Death Star” moon. The 246-mile-wide moon has an enormous, 88-mile-wide crater that makes it resemble the planet-destroying space station from “Star Wars.”
An analysis of data collected by Cassini indicates that Mimas wobbles more than it should. Researchers have identified two possible causes of this unexpected behavior. It could be that Mimas has a football-shaped core, or it could have a subsurface ocean like Enceladus.
Orbiting Saturn at about the same distance that our own moon orbits the Earth, Dione continues to mystify scientists.
In 1980, the Voyager mission revealed that one hemisphere of the 349-mile-wide moon was covered in bright wispy features. At the time, scientists wondered if the wisps represented deposits of bright materials – snow or deposit from an ice volcano – that had perhaps erupted from the moon and then fallen back to its surface.
Cassini proved that theory wrong. The space probe discovered that the wisps were in fact bright ice cliffs that rose hundreds of feet high.
Hyperion is the largest non-spherical moon in the solar system. Shaped like a potato, it’s 204 miles long and has an extremely strange surface that resembles a natural sponge.
There’s a reason Iapetus has been nicknamed the “Yin and Yang” moon: One hemisphere is almost as dark as coal, while the other hemisphere is nearly as light as snow. This split had confounded scientists for centuries, but Cassini helped them figure out how it came to be.