I originally planned a book review on a new asteroid book today but decided to hold off a couple days because of little time and other plans. Don’t worry, it’ll arrive in this space shortly. For fun I thought I’d share a recently released photo taken by the Cassini space probe of Saturn’s moon Tethys (TEE-this). This 660-mile wide ice ball orbits the planet every 1.9 days. In 6-inch and larger telescopes it’s a faint point of light hovering near the planet like a moth around a candle flame. Mimas is even closer to the great ringed one, zipping around it in just under a day.
Both it and another Saturnian moon, Mimas (MEE-muss) have large craters that size and appearance-wise are a good match for the concave disks of the superlasers in the infamous Death Stars, the moon-sized battle stations built by the evil Galactic Empire in the Star Wars movies. Mimas earned the nickname Death Star moon years ago, but Cassini proves that seen from the right angle, Tethys is just as capable of going over to the dark side.
Both moons have densities indicating they’re composed mostly of water ice. That tells us something about how bitterly cold (about 325 below F surface temp) it must be at Saturn’s distance from the sun for craters blasted from ice to remain sharp and clear 4 billion years after their origin.