Mercury/Magnesium

Element thought to exist on the surface of Mercury. It was detected in much higher abundancies by Messenger during a flyby than expected, when it was attempting to confirm its presence to imply it was on the surface.

Magnesium Detected in Mercury's Atmosphere (May 2009)

 * http://www.denverpost.com/headlines/ci_12267618
 * http://www.colorado.edu/news/r/3cc168fd0a6b2a95605dee1f60b4e03b.html