1st Human Exploration of the Moon
Moon Landing and Science Missions
Apollo 16 sample #68815. (credit: NASA/AFP/Getty Images)
On July 20, 1969, about 4 pm (Eastern Daylight time), Armstrong and Aldrin landed on the Moon. They spent about 2 hours exploring the lunar surface, conducting scientific experiments and studies, and collecting about 22 kilograms of geological samples with specialized tools developed for this mission.
Robotic Imaging Spacecraft - the LRO
Over 40 years later, that landscape was re-imaged by the Lunar Reconnaissance Orbiter (LRO). Visible from a distance of 24 miles are the astronaut boot print trails, the Lunar Module and other pieces of equipment.
Weathering on Earth and Moon
The Moon possesses almost no atmospheric gas, no surficial water, no life, and its surface sustains no daily disturbances by passing thunderstorms, garbage trucks, lunch time kickball games on the school playground, or earthworms (Moonworms?) composting organic coffee grounds. So the Moon's surface is unweathered by the dominant forces of weathering on Earth.
Apollo 11 boot print on the Moon, showing the nature of the surface (fine, dry particles). Credit: NASA
That's why the astronaut boot print trails are clearly visible and largely undisturbed nearly half a century later.
However, processes of physical weathering continue to degrade the lunar surface, as a steady stream of electrically charged particles (including protons and neutrons) from the Sun (the "solar wind") slam into the Moon at speeds up to 1 million miles per hour. Micrometeorites and cosmic rays also physically "weather" the exposed rock and mineral matter. By these processes, the exposed rocky surfaces slowly break down into regolith (lunar "soil" as it's called) over the 4.5 billion years of the Moon's history. And early in the its history, the Moon was pummeled by asteroids and meteorites that excavated basins and craters. and the surface is today littered with debris from dust to boulders.
How long will the boot prints remain?
We can be assured, however, that these imprints of Man's first steps on an extraterrestrial body will endure for many more ages to come, but not "forever". The lunar surface is pitted with craters of all sizes, and no exposed rock remains pristine from the birth of the Moon.
How long? Your guess is as good as mine!