Astronomy Picture of the Day . ... Seen from ice moon Tethys, rings and shadows would play across fantastic views of the Saturnian system. ... Visible light images show the central region of globular cluster 47 Tucanae is closely packed, with stars less than a tenth of a light-year apart. ... Water Ice in a Maritan Crater . ... What lies on the floor of this Martian crater? A frozen patch of water ice. The robotic Mars Express spacecraft took the above image in early February. ... February . ...