Mercury - 1

Mercury is extreme. Of all the planets in our solar system, it is the smallest, it has the oldest surface, it is closest to the Sun, it has the largest daily variations in surface temperature, and, until recently it was the least explored. NASA’s Mercury Surface, Space Environment, Geochemistry, and Ranging (MESSENGER) spacecraft, which inserted into Mercury orbit in March 2011 has changed all that! It has revealed rocky Mercury’s geologic history, the nature of its weak magnetic field, the structure of its core, and the composition of its thin exosphere. MESSENGER has even found hints of water at Mercury’s dark poles