Tethys and Saturn's rings

Sorry, just watched Gladiator again. One of Cassini’s newest images, aptly named Ices and Shadows, gives us another look at Tethys.

Tethys and rings shadow

Cassini’s vantage point gives us a nearly edge on look at Saturn’s majestic rings nestled behind Tethys.

From NASA:

The rings, which are seen nearly edge-on, are the dark bands above Tethys while their curving shadows paint the planet at the bottom of the image.

Those curving shadows look pretty cool, don’t you think? Earlier this month, NASA released this jaw-dropping image showing off shadows being cast by Saturn’s ring system.

Dione below Saturn's rings

It almost doesn’t look real. Cassini is looking at the unilluminated side of the rings at just 0.3 degrees below the ring plane. That little moon that appears to be hanging out right below the rings? That’s Dione. It might look like a tiny rock, but it’s actually about 600 miles across. Or, about a third of the size of Earth’s Moon.

My two favorite images of Tethys

Tethys Odysseus crater

Odysseus Crater

This stunning crater (on the right) is by far the largest on Tethys at 276 miles (445 kilometers) across. That’s just under half of the moon’s 660 miles (1,060 kilometers) diameter. Whatever slammed into Tethys, should have shattered the small moon. Why didn’t it? The crater’s structure gives us clues. See how the crater has mostly conformed to Tethys’ spherical shape? That tells us at the time of impact; Tethys was still partially molten. It would explain how the crater’s structure was able to collapse.

If Tethys wasn’t warm, we would see a crater similar to the ‘eye’ on Mimas, which better retains its structure.

Tethys and Janus

Tethys and Janus

I love this image. It perfectly demonstrates the difference between small moons and large moons. Why does Janus look more like an asteroid? Moons like Janus aren’t large enough for their own gravity to mold them into a sphere. Tethys, on the other hand, is.

Image credit: NASA