Wikipedia:Today's featured article/August 25, 2006

Mercury, as photographed by Mariner 10

Mercury is the innermost and smallest planet in the Solar System, orbiting the Sun once every 88 days. It ranges in brightness from about −2.0 to 5.5 in apparent magnitude. The planet remains comparatively little known: the only spacecraft to approach Mercury was Mariner 10 from 1974 to 1975, which mapped only 40%–45% of the planet's surface. Physically, Mercury is similar in appearance to the Moon as it is heavily cratered. It has no natural satellites and no real atmosphere. The planet has a large iron core which generates a magnetic field about 1% as strong as that of the Earth. Surface temperatures on Mercury range from about 90 to 700 K, with the subsolar point being the hottest and the bottoms of craters near the poles being the coldest. (more...)

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