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? ... One of the nearest supernovas of recent years was discovered late last month in the bright nearby galaxy M51. ... July . ...