Wednesday, March 30, 2011

He’s really hot, really cold and maybe even a bit icy.

He is the planet Mercury, and this month he is ready for his extended close-up. On Wednesday NASA showed off some of the first pictures taken by its Mercury Messenger spacecraft, which entered the planet’s orbit on March 17. The Messenger is to spend at least a year photographing, measuring and studying Mercury.

The visit to Mercury is last frontier of planetary exploration that NASA will reach for a quite some time. The space agency has sent orbiters to five planets — Mercury, Venus, Mars, Jupiter and Saturn — but no plans are in place yet for trips to Neptune or Uranus (though a study on future planetary missions did express hope that an orbiter could be sent to Uranus in the coming years). NASA does have a spacecraft, New Horizons, that will zoom past Pluto in 2015, but Pluto is no longer considered a planet.

Mercury has been seen close up, but briefly, in half a dozen flybys by NASA probes: three by the Mariner 10 in the 1970s and three by the Messenger in the past three years. But now that the Messenger has pulled into an elliptical orbit around Mercury, planetary scientists will be able to get their first long look at the smallest of the eight planets. The day side of Mercury can broil at up to 800 degrees Fahrenheit. The night side drops to minus 150 degrees.

Particularly intriguing are the shadows in craters near Mercury’s poles. There, the Sun never shines, and in the frigidity, many scientists expect that the Messenger will find frozen water.


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