Transit of Mercury
November 12, 2006 Leave a comment
From a vantage point one million miles out in space the Solar and Heliospheric Observatory (SOHO) spacecraft captured images of the planet Mercury passing directly in front the Sun of the transit. Good views could also be seen from Americas, Hawaii, Australia, along the Pacific Rim.. The transit lasted for almost five hours. During the transit, Mercury’s tiny disk–jet black and perfectly round–glided slowly across the face of the Sun. Only a speck of the Sun’s surface is actually covered, so the Sun remains as dangerous as ever to look at. But with a proper filter or a spacecraft and a little imagination, the Transit of Mercury is a marvelous experience
Mercury is fantastically mysterious. More than half of the planet is unknown to us. When Mariner 10 flew by in the mid-70s, it managed to photograph only 45% of Mercury’s cratered surface. What lies on the other side? More craters? Or something totally unexpected? You’re free to speculate, because the next spacecraft to visit Mercury, NASA’s MESSENGER probe, won’t enter orbit until 2011. One of Mercury’s greatest secrets is the mysterious material at its poles. Radars on Earth have pinged Mercury and received a strong echo from polar craters. A favorite explanation is ice. While Mercury’s daylight surface heats up to 400 deg. C, the temperature in deep, and dark polar craters dips below -200 deg. C. If an icy comet landed in one of those craters (or made one of those craters), the comet’s ices, vaporized by impact, might re-freeze and stick around.
Source : Nasa