Geological Chronicle
Mare Cognitum, translated from Latin as 'The Sea That Has Become Known', is a circular lunar mare located in the southern near side of the Moon within the second structural ring of Oceanus Procellarum. Centered at 10.0° S and 23.1° W, the dark basaltic expanse spans 350 kilometers across. The underlying impact basin formed during the Pre-Nectarian epoch, while subsequent eruptions of basaltic lava flooded the structure during the Upper Imbrian epoch. The mare is bounded to the northwest by Montes Riphaeus, an arcuate ridge representing the rim of the degraded basin, and bordered to the east by the hummocky terrain of the Fra Mauro formation.
The region received its modern name in 1964 when the International Astronomical Union designated the formerly unnamed basaltic plain following the success of the Ranger 7 spacecraft. On July 31, 1964, Ranger 7 transmitted 4,308 high-resolution photographs during its final minutes of flight before impacting the mare floor. The images provided the first close-range views of lunar craters and surface texture, demonstrating that the lunar maria were structurally solid enough to support future robotic and crewed landings.
Exploration of Mare Cognitum expanded through NASA surface missions. On November 19, 1969, Apollo 12 astronauts Pete Conrad and Alan Bean landed their Lunar Module Intrepid at Statio Cognitum on the northern perimeter of the mare, touching down within walking distance of the robotic probe Surveyor 3, which had arrived in 1967. The astronauts gathered basalt samples with lower titanium concentrations than those from Apollo 11, giving the local terrain a slightly redder spectral hue. Laboratory dating showed the Apollo 12 basalts formed roughly 500 million years later than basalts from Tranquility Base, confirming that lunar mare volcanism occurred in distinct stages. Apollo 12 also recovered light-colored soil identified as ray ejecta from Copernicus crater, located hundreds of kilometers to the north.
In February 1971, lunar surface exploration returned to the eastern border of Mare Cognitum with the Apollo 14 mission. Astronauts Alan Shepard and Edgar Mitchell landed in the adjacent Fra Mauro formation to sample materials excavated by the impact that formed Mare Imbrium. The field data and returned samples collected around Mare Cognitum and the neighboring Fra Mauro ridges established foundational reference points for dating volcanic and impact sequences across the Moon.