for National Geographic News
Mercury is full of volcanoes and other surprises, reveals initial data from NASA's MESSENGER spacecraft—the first to conduct an in-depth investigation of the solar system's smallest planet in more than 30 years.
MESSENGER—which stands for Mercury Surface, Space Environment, GEochemistry, and Ranging—is Earth's second envoy to Mercury, after the Mariner 10 mission that launched in 1973.
In January MESSENGER made its first of three flybys planned before 2011, when the spacecraft settles into orbit around the enigmatic planet.
During the pass, MESSENGER snapped more than 1,200 images of Mercury's scorched sunlit side, including 21 percent of the surface Mariner 10 never saw.
(Related: "Weird 'Spider,' Volcanism Discovered on Mercury" [January 30, 2008].)
The images reveal a dynamic surface pockmarked by craters and volcanoes. They also shed more light on Mercury's magnetic field, which mirrors Earth's on a tiny scale.
And they reveal widespread slip faults, relics of a time when the planet's already-frozen surface weathered a spectacular collapse atop a shrinking, cooling core.
A suite of studies analyzing the flyby appears tomorrow in the journal Science.
James Head, a planetary geoscientist at Brown University in Providence, Rhode Island, and lead author on one of the studies, said that, unlike Earth's, Mercury's formative years haven't been concealed by weathering and erosion.
It's "a missing chapter in the history of Earth," he said. "Mercury now takes its rightful place in comparative planetology."
Volcanoes and Impacts
Questions about volcanism on Mercury go back to the first studies of Earth's moon, Head noted.
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