Jansen (crater)

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Jansen is a 24-kilometer-wide impact crater in the northern part of Mare Tranquillitatis. It is named after Zacharias Janssen, a 17th-century Dutch optician, and lies east-southeast of the crater Plinius. The rim is low and narrow, with a notch on the western edge. The interior is relatively flat, which may mean it was flooded by lava. A small, prominent crater lies on the floor to the south-southwest, about halfway between the center and the rim. To the northwest of the rim is the rille called Rima Jansen, and to the east are wrinkle ridges on the mare. A low ridge runs from near the southeast rim toward the southeast. On lunar maps, nearby features are labeled with letters placed on the side of the crater midpoint closest to Jansen.