The last mission to Mercury—three passes by Mariner 10 ... At least 40 percent of the surface consists of smooth plains, most of which are ancient lava flows. When Mariner 10 flew past, it ...

Just after MESSENGER's closest approach to Mercury (200 km above the surface ... This material was most likely excavated from a smooth plains unit that was buried by the lower-reflectance ...

Mercury's magnetic field ... faults cutting across and deforming older craters and relatively young smooth plains, which are interpreted as volcanic flows, have been observed in the Mariner ...