About 100 artificial objects and footprints left by Armstrong and Aldrin remain at Tranquility Base. The descent stage of the Lunar Module remains at the original point of landing. According to Aldrin (with apparent confirmation from later Lunar Reconnaissance Orbiter photos), the US flag planted at the site during their moonwalk was blown over by the ascent rocket exhaust, but ostensibly remains there. A laser reflector was placed at the site to allow precise ongoing measurements of the distance to the Moon from Earth. A solar-powered seismometer was also left to measure moonquakes, but this stopped functioning after 21 days. A disc containing the Apollo 11 goodwill messages was left at the site, and various gear that was no longer needed for the return phase of the mission—including Aldrin's boots—was left behind to lighten the craft for return to lunar orbit.