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Scientists Slip Veil Off Mercury

Irene Klotz, Discovery News

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Jan. 30, 2008 -- Scientists waited 33 years for another look at the innermost planet of the solar system, and when they finally got a peek earlier this month, what they found left them astonished.

"It is not the planet we expected," Sean Solomon, the lead scientist for NASA's MESSENGER mission to Mercury said at a press conference Wednesday to release the team's first findings.

Most striking are the widespread signs of volcanic flows, places where the planet's pocked face, gouged by impact craters, has been smoothed by fresh coverings. Then there's the peculiar change in the planet's magnetosphere, which showed no trace of the energetic particles found during the Mariner flybys in 1974 and 1975.

And perhaps the most mind-bending find: a unique spider-like formation nearly dead center in one of the most prominent craters on the planet's surface, the Caloris basin. Scientists have no idea what caused more than 100 flat and narrow troughs to radiate like bicycle spokes from a 25-mile-wide central core which seems to be higher than the surrounding terrain.

"It looks like something pushed up," said Louise Prockter, with Johns Hopkins University Applied Physics Laboratory and the head of MESSENGER's camera science team.

One theory is that a volcano may have risen from the floor of the Caloris basin, causing the feature to rebound and crack after its formation.

Though many questions remain after MESSENGER's pass by Mercury on Jan. 14, the wait for answers is nearly over. MESSENGER, an acronym for MErcury Surface, Space ENvironment, GEochemistry and Ranging spacecraft, is due back in October for another flyby, and then again in September 2009.