Geological Chronicle
Positioned near latitude 88.63° N, Peary is the closest large crater to the lunar north pole. Because the crater lies almost directly on the northern lunar limb from Earth's vantage point, detailed views of its structure remained unavailable until the United States Lunar Orbiter 4 spacecraft captured the first high-quality images from orbit. The 78.75-kilometer formation takes its name from American polar explorer Robert Peary.
The crater has a nearly circular outline with an outward bulge along its northeastern rim and an opening in its southwestern wall, where it joins the slightly smaller crater Florey. An eroded, mountainous outer rim casts long shadows over a relatively flat floor marked by small craterlets across its southeastern half. Due to the shallow angle of incoming sunlight, the southern third of the basin remains permanently shadowed, keeping average floor temperatures between 30 and 40 Kelvin.
In 2004, researchers analyzing Clementine spacecraft images determined that four mountainous regions on the rim appeared illuminated for the entire lunar day during northern summer. More detailed topographic data collected by the Lunar Reconnaissance Orbiter later showed that no point on the Moon receives perpetual light across all seasons. Peary's northern rim remains a candidate site for a future Moon base, where near-constant illumination would provide stable temperatures and continuous solar power near permanently shadowed areas that may contain frozen water.