MESSENGER Finds Unusual Groups of Ridges and Troughs on Mercury
The MESSENGER spacecraft has revealed families of extensional troughs, or graben, that are encircled by contractional wrinkle ridges arranged in circular rings on Mercury. The troughs can form complex patterns varying from the outlines of polygons inside the ridge rings to arcs that parallel the bounding ridges…
(read more: NASA Solar System Exploration)
(via: Lunar Planetary Institute)