NASA - National Aeronautics and Space Administration

Mare Ingenii may be best known for its prominent lunar swirls, which are high albedo surface features associated with magnetic anomalies. However, lunar swirls are not the only unique geologic feature found in the farside "sea of cleverness."

Impact craters are visible everywhere on the moon, but pits are rare. This pit in Mare Ingenii, the "sea of cleverness," is about 130 meters (427 feet) in diameter! Image width is 550 meters (1,805 feet), illumination is from the upper right, LROC Frame: NAC M128202846LE. Credit: NASA/Goddard/Arizona State University
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The high-resolution cameras aboard the Japanese SELENE/Kaguya spacecraft first discovered this irregularly-shaped hole, visible in the above image at LROC's 0.55 m/pixel resolution. The boulders and debris resting on the floor of the pit are partially illuminated (left side of the pit, above image) and probably originated at the surface, falling through the pit opening during collapse.

Arrow indicates location of pit. "S" indicates one of the numerous lunar swirls located in this region. Image is a portion of LROC WAC mosaic, 200 meters per pixel resolution; image width is 160 km (100 miles). Credit: NASA/Goddard/Arizona State University
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A pit in the Marius Hills region, previously discovered by the JAXA SELENE/Kaguya mission, is thought to be a skylight into a lava tube in the rille-riddled region. Similar to the Marius Hills pit, the pit in Mare Ingenii is probably the result of a partially collapsed lava tube. However, the numerous volcanic features of the Marius Hills (such as the prominent rilles and domes) are not found in Mare Ingenii.