The Lunar Module, a two-part spacecraft, allowed astronauts to land on the Moon during the Apollo missions. While the entire module did not return to Earth, parts of it remain on the lunar surface. These remnants serve as evidence of human exploration beyond Earth.
What Remains on the Lunar Surface
The lower section of the Lunar Module, the descent stage, was designed to remain on the Moon. These descent stages served as the landing platform and then as the launchpad for the ascent stage during liftoff from the lunar surface. Six descent stages are still present at their Apollo landing sites: Apollo 11, 12, 14, 15, 16, and 17.
These structures are intact, exposed to the harsh lunar environment. Images captured by NASA’s Lunar Reconnaissance Orbiter (LRO) show these descent stages, along with tracks left by astronauts and rovers. The LRO’s high-resolution cameras allow scientists to observe these artifacts from lunar orbit.
The Ascent Stage’s Journey
The upper part of the Lunar Module, the ascent stage, had a different purpose. After completing their mission, astronauts used the ascent stage to launch back into lunar orbit to rendezvous with the Command Module. This stage carried the crew and collected lunar samples, leaving the descent stage behind.
Once astronauts and samples were transferred to the Command Module, the ascent stage was jettisoned. Most ascent stages were intentionally deorbited to crash onto the lunar surface, providing valuable seismic data for experiments on the Moon. The Apollo 11 ascent stage was left in lunar orbit. The Apollo 10 ascent stage, nicknamed “Snoopy,” was sent into a heliocentric orbit and remains in space.
Why Equipment Was Left Behind
Leaving the descent stages and other equipment on the Moon was an engineering decision to reduce weight for the return journey to Earth. The Lunar Module was designed as a two-stage vehicle, with the descent stage serving as a landing platform and then discarded. This design allowed the ascent stage to be much lighter, requiring less fuel to lift off from the Moon’s surface and return to lunar orbit.
Beyond the descent stages, astronauts also left behind non-essential items to lighten the load for the return trip. This included scientific instruments, tools, spent backpacks, and human waste. Maximizing the amount of lunar rock and soil samples brought back to Earth was an objective, and every pound saved allowed for more scientific payload.
Their Enduring Legacy
The Lunar Modules and other artifacts left on the Moon are historical markers of human exploration. These sites mark humanity’s only direct presence on another celestial body. Some equipment left behind continues to provide scientific value, such as the Lunar Laser Ranging Retroreflector (LLRR) arrays.
These LLRR arrays, installed at several Apollo landing sites, are still used today to precisely measure the distance between the Earth and the Moon by reflecting laser beams sent from observatories on Earth. This ongoing experiment contributes to our understanding of lunar geology, the Earth-Moon system, and even provides data for testing theories of gravity. The presence of these modules on the lunar surface offers a tangible connection to a key era of human spaceflight.