LYCOS RETRIEVER 
Mercury (Planet): Craters
built 655 days ago
Instruments provided a topographic profile of craters and other geological features on the night side of Mercury. The spacecraft ... discovered a unique feature that scientists dubbed "The Spider." This formation never has been seen on Mercury before and nothing like it has been observed on the moon. It lies in the middle of a large impact crater called the Caloris basin and consists of more than one hundred narrow, flat-floored troughs radiating from a complex central region.
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Radar observations first indicated, in 1992, that there is frozen water ice at Mercury's north pole. Such water is believed to exist at the permanently shaded bottoms of craters, where it is deposited by comets and/or gases from the planetary core.
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Craters