The Moon

node · earth · Moon

Earth's only natural satellite and the only body beyond Earth that humans have visited. Mean radius 1,737.4 km, mean distance from Earth about 384,400 km, surface gravity 1.62 m/s². It rotates synchronously, so one hemisphere permanently faces Earth. It has effectively no atmosphere: surface temperatures swing from roughly 120 °C in sunlight to below −170 °C at night, and its spin axis is tilted only about 1.5° to the ecliptic, so polar crater floors that have not seen sunlight for billions of years sit below about 100 K. Those cold traps are why the Moon, long assumed bone dry, is now understood to hold accessible water ice.