... Titan Disguised . ... In the next few days, the Cassini spacecraft currently orbiting Saturn will release a probe that will descend toward Saturn's largest moon in mid-January. That moon, Titan, has a surface normally hidden from view by thick methane cloud decks. Titan Surmised . ... What used to be considered a hole in the sky is now known to astronomers as a dark molecular cloud. ... This bright white swath cutting across the surface of icy Jovian moon Europa is known as Agenor Linea. ...