Geological Chronicle
Riccioli is a lunar impact crater spanning 155.66 kilometers across near the western limb of the Moon. Located northwest of the larger crater Grimaldi, the formation appears strongly foreshortened when observed from Earth and is viewed almost from the side. To its southwest lie the craters Hartwig and Schlüter along the northeastern edge of Montes Cordillera, the ring-shaped range surrounding Mare Orientale.
Riccioli is older than the Orientale basin to the southwest, as ejecta from the impact that created the basin overlies the crater. This debris forms ridges that regionally trend northeast to southwest, but align parallel to Riccioli's northeast wall in that part of the crater. A system of rilles named Rimae Riccioli extends across the interior and crosscuts the ejecta ridges, while dark lava across the northern half of the floor covers some ridges and floods several rilles.
The crater is named after Giovanni Battista Riccioli, the Italian Jesuit astronomer who introduced the system of lunar nomenclature still in use today. He was also the first person to measure the rate of acceleration of a freely falling body.