Its possible to stumble upon NASAs Web site via a random link only to emerge two hours later with a new ultra-high-resolution satellite image of Mt. Vesuvius for your computers desktop and a close familiarity with the inner workings of the Orion Nebula.
Proving that the stream of free space-related goodies is seemingly without end, NASA has made available a Mars Sunclock, a tool that tracks the current time of day on different parts of the red planet. Mars days (called "sols") are only 39 minutes and 35 seconds longer than Earth days, and the planets 25-degree tilt on its axis results in an Earth-like progression of the seasons. With the Sunclock, you can plot the location of the ailing Spirit and the still-functioningOpportunity rovers, as well as several other Martian landmarks, in relation to the time of sol on Mars.
Its true, you dont need the giant Vesuvius image, and you certainly dont need to know whether it is day or night in the Valles Marineris on Mars (its the middle of the night, as of this posting). But as is the common rationale to all of the cool freebies NASA has to give: Why not? —John Mahoney
Link (also, check out a similar Sunclock application for Saturns moon Titan here).