Mercury's Mysterious Bright Spot Photographed Up Close

A mysterious bright area on the surface of Mercury is seen near the top center of this 2009 image. The MESSENGER probe also imaged this spot in its second flyby of the planet on Oct. 6, 2008. Color images from MESSENGER's Wide Angle Camera reveal that the irregular depression and bright halo have distinctive color. (Image credit: NASA/Johns Hopkins University Applied Physics Laboratory/Carnegie Institution of Washington)

During its most recent flyby of Mercury, NASA?s MESSENGERspacecraft caught another glimpse of the innermost planet?s mysterious brightspot.

The MESSENGERprobe skimmed just 142 miles (228 km) above Mercury at its closest approachas it whipped around the planet during the flyby, the last of three designed toguide the spacecraft into orbit around the planet in 2011.

One of the new images shows a bright spot on the planet'ssurface, a feature that scientists cannotyet explain.

The new view was the third of the spot, which was first seenin telescopic images of Mercury obtained from Earth by astronomer RonaldDantowitz. The second view was obtained by the MESSENGER Narrow Angle Cameraduring the spacecraft's second Mercury flyby Oct. 6, 2008. At that time, thebright feature was just on the planet's limb (edge) as seen from MESSENGER.

Some of these craters are relatively fresh, formed by morerecent impacts. On Mercury, like the Earth's moon, even ancient impact craterscan be preserved on the surface because there is no atmosphere to cause erosionand no plate tectonics to recycle the rock, as there are on Earth.

MESSENGER was also able to image some of the same terrain asit did in its second flyby, but this time with slightly different lightningconditions. Different angles of sunlight can better show the topography of theplanet's surface.

The spacecraft is the first probe to visit Mercury sinceNASA's Mariner 10 mission in the mid-1970s.

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Andrea Thompson is an associate editor at Scientific American, where she covers sustainability, energy and the environment. Prior to that, she was a senior writer covering climate science at Climate Central and a reporter and editor at Live Science, where she primarily covered Earth science and the environment. She holds a graduate degree in science health and environmental reporting from New York University, as well as a bachelor of science and and masters of science in atmospheric chemistry from the Georgia Institute of Technology.