Present Day Endogenic and Exogenic Activity on Mercury

Exogenic and endogenic activities dictate how planetary surfaces evolve. However, the present-day influence of each of these activities is not well constrained. MESSENGER (MErcury Surface, Space ENvironment, GEochemistry, and Ranging) temporal imaging recorded surface changes associated with these activities between 2011 and 2015. Here we present the results of a temporal investigation that identified 20 reflectance changes. One change exhibited bright rays extending from the site, consistent with the aftermath of an impact event. If all changes result from impact events, the present flux rate is 1,000 times higher than models predict. Consequently, we also report changes on slopes in areas with concentrations of tectonic landforms and identify a subset of changes that are on or adjacent to hollows, consistent with present-day endogenic activities. Therefore, we conclude that these observations captured endogenic and exogenic modifications to the surface.