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Mercury shows wrinkles of age

WASHINGTON -The first pictures from the unseen side of Mercury reveal the wrinkles of a shrinking, aging planet with scars from volcanic eruptions and a birthmark shaped like a spider.

Some of the 1,213 photos taken by NASA's Messenger spacecraft and unveiled Wednesday help support the case that ancient volcanoes dot Mercury and that it is shrinking as it gets older, forming wrinkle-like ridges. But other images are surprising and puzzling.

The spidery shape captured in a photo is "unlike anything we've seen anywhere in the solar system," said mission chief scientist Sean Solomon of the Carnegie Institution of Washington.

The image shows what looks like a large crater with faint lines radiating out from it.

Mercury, the closest planet to the sun, has often been compared to Earth's dull black-and-white moon. But the new photos, which reveal parts of Mercury never seen, show the tiny planet is more colorful and once had volcanic activity.

The last time a NASA spacecraft went to Mercury was Mariner 10 in 1975. It took pictures of just 45 percent of the planet.

Messenger, which will do a couple more flybys of the planet before going into a long-term orbit, already has taken pictures of another 30 percent of Mercury, said instrument scientist Louise Prockter of Johns Hopkins University, which runs the Messenger mission for NASA. The rest will be seen eventually.

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Space walk

Two astronauts pulled off a riskier, trickier-than-usual spacewalk Wednesday, replacing a failed electric motor and giving the international space station a much-needed power boost. The station's power system still has problems: A joint for rotating one set of solar wings is mysteriously clogged with metal shavings and can't be fixed until later this year. Wednesday's successful operation, however, added to the power margin at the orbiting outpost and cleared the way for the deliveries of two science labs. Atlantis is supposed to lift off with the European Space Agency's Columbus lab Feb. 7 after a two-month delay. However, an inspection Tuesday uncovered a bent radiator hose in the shuttle's payload bay. NASA is reviewing the problem, which could affect the launch.

[Last modified January 31, 2008, 01:58:26]