The innermost and smallest planet in the Solar System, Mercury, has always been difficult to observe. A basic understanding of Mercury’s structure was achieved when the spacecraft Mariner 10 visited the planet in 1974, but even today little is known about Mercury compared to other planets.
In these days, new insights are gained by the spacecraft MESSENGER which entered Mercury’s orbit in March 2011. One recent key result is that the planet’s core possesses an involved layered structure. Most astonishingly, the data recorded by MESSENGER suggest that below a thin mantle (approx. 400 km) of silicate minerals an extended outer core region is found which is mainly composed of iron sulfide. These large amounts of sulfur were not expected to be found, at least on the basis of the standard model of planetary evolution. The MESSENGER mission thus calls into question our knowledge of the Solar System’s history.
Read more:
http://www.sciencemag.org/content/early/2012/03/20/science.1218805
http://www.sciencemag.org/content/early/2012/03/20/science.1218809
Thomas Jagau