After four years in orbit around Mercury, the NASA spacecraft Messenger ended its mission by crashing into the planet, after its fuel ran out. Because of Mercury's proximity to the sun, solar gravity affected Messenger's orbit, requiring it to burn fuel in order to stay in orbit. According to NASA, Messenger crashed at a speed of over 8,000 miles per hour and produced a crater 52 feet in diameter. During its mission, Messenger sent back more than 255,000 pictures to Earth, and found evidence of ice in Mercury's polar regions.
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