Mare Crisium (638km dia.) is a fascinating mare but too often we see the whole sea portrayed in images and many of the most fascinating parts are missed because of that. Here we have the northern third of the polygonal mare. This image spans the region from Macrobius (66km) on the left, to the flat floored crater Eimmart (48km) near the right edge. In Crisium itself we see the wrinkle ridge, Dorsum Oppel that parallels the north shore of the mare for over 300km. with the two craters Peirce (19km) and Swift(10) at the mid-point. At the upper end is a similar sized crater Cleomedes F (12km). On the outside of the northeast (upper right) edge of the mare is the long winding Mare Anguis or the Sea of Snake with Eimmart in its middle. This strange mare stretches on north to the crater Delmotte (34km). Note how the mountains that make the northern wall of Crisium have been eroded with the outpouring of the lavas from the mare. This forms interesting passes through these mountains.
At the north interior of Crisium, not far from Cleomedes F, you can see a brilliant white spot. This had been reported as a “transient phenomenon” by observers over the years but a look at LROC QuickMap shows it to be a very fresh small kilometer sized crater at the top of a mountain that has an ejecta blanket spread over the mountains and the mare floor to the south. It has a very sharp and crisp rim indicating a young age. The interior appears bright as well. I have taken many images of this feature and have found it shows up very bright at a wide range of colongitudes. One might suspect this of being the caldera on a volcano, but the crater does not have the morphology of a caldera and the rays on the floor of Crisium indicate an impact. Look for it the next time you are in the area!
