spacetoday.net: Scientists review spacecraft studies of Mercury

Posted: Thu, Mar 22, 2012, 6:33 AM ET (1033 GMT)
MESSENGER illustration (JHUAPL)

A year after entering orbit around Mercury, scientists said this week that NASA's MESSENGER spacecraft has provided key insights into the surface, interior, and magnetosphere of the planet. MESSENGER entered orbit around Mercury on March 17 of last year and just completed its one-year primary mission. Scientists said this week that some of the key discoveries from the mission include the fact that the planet's core is unusually large, with a radius of 85 percent of the planet itself, and is at least partially liquid. Other observations confirmed that "radar bright" regions at the planet's poles correspond with areas of permanent shadow, suggesting that they may be made of water ice or other volatiles, although scientists are still working to determine the composition of those regions. MESSENGER continues to operate on an extended mission for at least an additional year, with a greater focus on the planet's magnetosphere and tenuous atmosphere, as well as targeted observations of particular regions of the planet.