Fun fact 5 of 10
5. Footprints on the Moon may last millions of years
The marks left by the astronauts on the Moon between 1969 and 1972 are still there. With no wind, rain or rivers, nothing erases the footprints, and they may last millions of years.
A place where almost nothing moves
On Earth, a footprint in the sand disappears within hours, carried away by the wind, the water or animals. The Moon has no atmosphere to create wind, no liquid water on its surface and no life.
The lunar soil, called regolith, is made of fine, angular grains that lock together like pieces and hold the shape of a mark. It is different from beach sand, whose rounded grains slide and smooth out a footprint.
What wears down the Moon's surface, very slowly, is the constant fall of micrometeorites, tiny pebbles from space, along with radiation from the Sun. This process takes millions of years to smooth a mark away. A larger impact could erase a footprint before then, but that is rare.
In all, 12 astronauts walked on the Moon during the Apollo missions from 11 to 17, except Apollo 13, which suffered an accident and returned without landing. Besides the footprints, equipment, flags and even the vehicles used to drive across the surface were left behind.
Did you know? Gravity on the Moon is about one sixth of Earth's. A 60-kilogram person would feel the weight of about 10 kilograms, which is why the astronauts bounded along in little hops.
