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On October 6, the spacecraft MESSENGER flew as close as 200 kilometers above the surface of Mercury, and then began to beam more than 1,200 high-resolution and color images back to Earth. The visit was the NASA craft’s second flyby of Mercury since its launch in 2004.

The above image, one of the first to be transmitted from MESSENGER, shows this other side of Mercury’s pock-marked surface. A vast network of rays, like lines of longitude, run from a young crater in the north to just south of a crater called Kuiper, which sits south of the center of the view shown here. Kuiper was originally identified in the 1970s by Mariner 10, the first spacecraft to venture to Mercury.

In addition to providing visual, gravitational, and topographical data on Mercury, this flyby gave MESSENGER a critical gravity assist. The planet’s gravitational field slowed MESSENGER’s speed and kept the spacecraft on its plotted course. MESSENGER is on a 7.9-billion–kilometer cruise that will take an estimated 6.6 years, all of which brings it closer to its ultimate goal — to be the first spacecraft to orbit Mercury. While most of MESSENGER's messages have yet to be analyzed, its arsenal of probing eyes will yield new ways to see the mysterious planet closest to the sun. — Laura Sanders