Oceanus Procellarum

Oceanus Procellarum, meaning "Ocean of Storms," is the largest lunar mare on the Moon. Maria are vast, flat, dark plains formed by ancient lava flows that filled large impact basins. These basins, some hundreds of kilometers across, were created by asteroid impacts billions of years ago.12

Following these impacts, volcanic activity flooded the basins with magma, which then cooled and solidified into basalt. While visible from Earth, maria are not seas but are covered in a layer of pulverized rock and dust called regolith, formed by billions of years of meteoroid bombardment. Oceanus Procellarum is located on the near side of the Moon and contains features like craters, rilles (valleys), and ridges.12