Astronomy Picture of the Day

Discover the cosmos! Each day a different image or photograph of our fascinating universe is featured, along with a brief explanation written by a professional astronomer.

2006 May 15

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Volcanic Bumpy Boulder on Mars
Credit: Mars Exploration Rover Mission, Cornell, JPL, NASA

Explanation: What created this unusually textured rock on Mars? Most probably: a volcano. Dubbed Bumpy Boulder, the strange stone measuring just under a half-meter high was found by the robotic Spirit rover currently rolling across Mars. Pits on the raged rock are likely vesicles and arise from hot gas bubbling out of hot rock ejected by an active Martian volcano. Several similar rocks are visible near Bumpy Boulder that likely have a similar past. The above true-color image was taken about one month ago. The Spirit rover, now in its third year of operation on Mars, is weathering the low sunlight winter of Mar's northern hemisphere on a hillside slope in order to maximize the amount of absorbable battery-refreshing sunlight.

Tomorrow's picture: space station below

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