Mars was approximately 10′ in diameter when Florida amateur Rick Ramsdell recorded the occultation of the red planet by the Moon on May 16, 1971.
Image: Rick Ramsdell/Sky & Telescope.

Periodically, the Moon passes in front of planets and other astronomical objects. This type of event is called an occultation. When the Moon occults a planet, only a small percentage of the Earth will be able to see the event. From St. Louis, the next planet to be occulted by the Moon is Mars, which occurs on December 8, 2022.