Hidden by the sun’s glare and dismissed as a heavily cratered rock no different than Earth’s moon, Mercury has for decades been relegated to the back burner of planetary research. But studies of the planet closest to the sun have now ignited. On March 17, NASA’s MESSENGER spacecraft became the first probe to enter orbit around the metal-rich body (SN Online: 3/17/11). MESSENGER — short for Mercury Surface, Space Environment, Geochemistry and Ranging — completes a lap every 12 hours, traveling an oval path that swoops close to the planet’s north polar region and keeps a greater dis... (p. 28)

A previously unknown reservoir of frozen carbon dioxide could periodically vaporize, thickening the atmosphere and allowing liquid water to flow on the Red Planet’s surface. (p. 8)

Europe is now on its own for two planned spacecraft to study black holes and gravitational waves.

Museums in New York, California, Florida and Virginia will display the four spacecraft after their final mission in June.

A hundred days of solitude for an experiment designed to rendezvous with the universe's missing mass put new limits on the elusive material's properties. (p. 12)