A Shocking Discovery
This side-by-side comparison of Discovery rupes under two different illumination conditions illustrates the importance of MESSENGER's various imaging campaigns. The image on the left has an incidence angle, or angle between surface normal and the sun, of approximately 62°, whereas the image on the right has an incidence angle of approximately 85.6°. An incidence angle as high as 85.6° means that the sun is just barely skimming the surface of the planet, providing a unique opportunity to see certain morphological features that are otherwise difficult or impossible to see. For example, Discovery rupes, a sizable scarp that runs over 400 km from end to end, is practically invisible in the monochrome base map image to the left, yet it dominates the high-incidence-angle base map image to the right.
Release Date: July 2, 2012
Image Credit: NASA/Johns Hopkins University Applied Physics Laboratory/Carnegie Institution of Washington