WASHINGTON, USA, Oct. 19, 2026 - A study led by Smithsonian scientist Thomas R. Watters^[1] has produced one of the most precise estimates yet of how much the Moon is shrinking.^[2] Mapping of lunar faults indicates the Moon's radius shrank by about 45 metres as its interior cooled and contracted,^[3] with estimates ranging from 42 to 46 metres.^[4] The researchers identified more than 10,000 young fault movements across the lunar surface,^[5] combining more than 8,900 lobate scarps with more than 2,600 small mare ridges^[6] in images from NASA's Lunar Reconnaissance Orbiter Camera.^[7] The study was published in The Planetary Science Journal,^[8] and the mapped faults may also offer clues about moonquakes.^[9] Space Nugget. When a rocky world cools, its interior contracts. That squeezes the solid outer crust, which cracks and pushes up in places, leaving cliff-like scarps and wrinkled ridges at the surface.