Unmasking the Secrets of Mercury April 27, 2015April 27, 2015 / marilyngardnermilton To learn more about the minerals and surface processes on Mercury, instruments aboard NASA’s MESSENGER spacecraft have been collecting surface measurements since MESSENGER entered Mercury orbit on March 17, 2011. via NASA http://ift.tt/1zeU37k AdvertisementShare this:TwitterFacebookLike this:Like Loading... Related