Mercury as Revealed by MESSENGER . ... Credit Copyright: MESSENGER , NASA , JHU APL , CIW Explanation: The planet Mercury has been known since history has been recorded, but parts of the Solar System's innermost planet have never been seen like this before. Two days ago the robotic MESSENGER spacecraft buzzed past Mercury for the second time and imaged terrain mapped previously only by comparatively crude radar . ... NASA Web Site Statements, Warnings, and Disclaimers . ...