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  • What is the coldest place on Mercury?

    Posted on November 18th, 2010 admin No comments

    No correct answers to this one.  The floors of polar craters, where the Sun never shines, are the coldest places on Mercury.

    It was long thought that Mercury is tidally locked to the Sun, as the Moon is to Earth, keeping one side always facing the Sun.  There was once a hypothesis that the “dark side” of Mercury was among the coldest places in the Solar System.  Now we know this is false.

    In 1965, careful observations revealed that Mercury does indeed rotate with respect to the Sun.  It has no “dark side.”  All longitudes of Mercury are lit by the Sun at various times.  Only the deep craters near the poles of Mercury are permanently shaded, and these are thought to contain vast quantities of water ice.

    Mercury happens to have the smallest axial tilt of any planet in the Solar system.  This ensures that the Sun never lights the polar craters.  A crater at or near the poles of Earth, for example, would be lit by the Sun during that hemisphere’s summer, when that pole is tilted toward the Sun.  Mercury’s tilt is so small that its polar craters are permanently in shadow.

    More about Mercury:

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