January 31, 2008A color image taken by the MESENGER spacecraft shows the side of Mercury previously unseen by human eyes.

The shot, released yesterday, is a mosaic of images from the craft's 11 narrow-band color filters.

Subtle patterns revealed by the filterswhich can capture light in wavelengths invisible to the naked eyewill help astronomers determine the mineral composition of the planet's surface.

The bright spots with a bluish tinge are relatively recent impact craters. Some of these have bright streaks, called rays. The streaks are made from crushed rock that was blasted outward during an impact.

The large, light-colored circle in the upper right of the image is the inside of the Caloris Basin. The only previous mission to Mercury, Mariner 10, viewed only the eastern (right) portion of this enormous impact crater.

MESSENGER has now shown that Caloris is filled with smooth plains that are brighter than the surrounding terrainthe opposite of the shading differences on Earth's moon.

Anne Minard

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