Category Archives: Saturn’s Moons
Hello, Daphnis! On January 16, 2017, the Cassini spacecraft captured the best photo yet of Daphnis, a 5-mile-wide shepherd moon that orbits Saturn inside the Keeler Gap at the outermost edge of the A ring (and also just so happens to be my personal favorite moon of Saturn!) The raw image arrived on Earth today, and it’s just beautiful.
When you think of spacecraft landings on other worlds, you probably first think of Mars, the Moon, Venus, and comet 67P (if you’ve been following along over the past couple of years.) But—in addition to the asteroid Eros and hard impacts on a comet and Mercury—Saturn’s moon Titan was also visited by an alien (i.e., Earthly) spacecraft back in January of 2005. ESA’s Huygens probe, which traveled to Saturn onboard the Cassini orbiter, was deployed to the surface of Titan six months after Cassini arrived in orbit at Saturn. Huygens took 20 days to reach the cloud-covered moon, and during its two-and-a-half hour descent on Jan. 14, 2005 transmitted our first—and last—views from below Titan’s clouds and even from its methane-slush-covered surface. It was the first landing on a moon other than our own and the farthest landing from the Sun, but hopefully not the final time we’ll visit the fascinating surface of this icy moon.
Read more and watch the video of the Huygens probe landing on the Cassini mission site: Huygens: ‘Ground Truth’ from an Alien Moon
Saturn’s moon Dione (pronounced DEE-oh-nee) is a heavily-cratered, 700-mile-wide world of ice and rock, its surface slashed by signature “wispy lines” that mark the bright faces of sheer ice cliffs. But Dione has some strange colorations too, evident here in a global map created in 2014 from Cassini images. Its leading half—the side that faces “forward” as it moves around Saturn in its tidally-locked orbit—is pale and bright, while its trailing hemisphere is stained a brownish color, the result of surface interaction with charged particles in Saturn’s magnetic field.
Floating high above Titan’s hydrocarbon lakes, wispy clouds have finally started to return to the moon’s northern latitudes…but in much less numbers than expected.
Models of Titan’s climate have predicted more cloud activity during early northern summer than what Cassini has observed so far, suggesting that the current understanding of the giant moon’s changing seasons is incomplete.
Round and round they go… the animation above, made from 14 raw images taken by NASA’s Cassini spacecraft on August 23, 2016, shows the moons Prometheus and Atlas orbiting Saturn within the Roche Division gap between its A (top right) and F (center) rings. The gravitational tug of Prometheus (92 miles / 148 km long) is strong enough to pull on the fine, smoke-like icy particles of the F ring, creating streamer and “clump” features that follow it along.
The much smaller Atlas (23 miles / 37 km wide) follows a path around Saturn just past the outer edge of the A ring. It was once thought to be a “shepherd moon” of the A ring, but it’s now known that the pull of the more distant Janus and Epimetheus are responsible for that.
Atlas does have its very own ring, though—a very faint (i.e., not visible above) band of material that runs along its orbit named R/2004 S 1, discovered by the Cassini mission in July 2004.
Image credit: NASA/JPL-Caltech/SSI. Animation by Jason Major.
A crowning achievement of the Cassini mission to Saturn is the discovery of water vapor jets spraying out from Enceladus‘ southern pole. First witnessed by the spacecraft in 2005, these icy geysers propelled the little 320-mile-wide moon into the scientific spotlight. After 22 flybys of Enceladus during its nearly twelve years in orbit around Saturn, Cassini has gathered enough data to determine that there is a global subsurface ocean of salty liquid water beneath Enceladus’ frozen crust—an ocean that gets literally sprayed into space. Now, new findings from Cassini and researchers at the Planetary Science Institute—with a little help from a star called Epsilon Orionis—has shown that at least some of the vapor jets get a boost in activity when Enceladus is farther from Saturn.