New images from NASA's Messenger mission to Mercury are providing scientists with new clues about the planet, the closest to the sun. Messenger was launched in 2004 and entered Mercury's orbit in March of this year. The above picture, acquired in August, shows the planet's south pole. New information from Messenger has shown widespread flood volcanism on the planet, much more sulfur than expected, and distinct "hollows" on the surface that may hint at ongoing geological activity.
Rebecca J. Rosen is a senior editor at The Atlantic, where she oversees the Family and Education sections.