Astronomy Picture of the Day

Explanation: Jupiter's moon Io is turning out to be our Solar System's geologic powerhouse. The churning moon was photographed again just recently on June 27th and again shows signs of violent activity. Shown above are photographs of the volcano Euboea Fluctus taken at different times. The black and white photograph on the upper left was taken by the Voyager 1 spacecraft when it flew by in 1979, the upper right and lower left photographs were taken in 1996 by the Galileo spacecraft, while the lower right photograph is a colour image taken by Voyager 2, also in 1979. The upper right Galileo picture has been artifically changed to simulate the colour sensitivity of the Voyager 2 mission. The marked difference in the two images is highlighted by new red and yellow deposits. These markings may indicate that Euboea Fluctus erupts in an unusual fashion, possibly caused by an obstruction near the volcanic vent.