Are the Apollo astronauts' footprints still on the Moon?

On Earth a footprint on a beach lasts until the next tide. On the Moon there is no tide, no wind, no rain and effectively no air, so there is nothing to smooth a print over. NASA's own estimate is that the tracks will stay for millions of years.

They are not just assumed to be there. Starting in 2009, the Lunar Reconnaissance Orbiter photographed every Apollo landing site from as low as 24 kilometres up. The pictures show the descent stages of the landers casting shadows, the scientific instruments the crews set up, and the paths worn between them: the astronauts' foot trails are visibly different from the twin tracks of the lunar rover. At the Apollo 17 site you can trace the last walk any human has taken on another world.

They will not last forever. The Moon is constantly peppered by tiny meteorites that slowly churn the top few centimetres of soil, so the sharp tread detail will blur over tens of thousands of years, and in some tens of millions the trails themselves will fade. By then, with any luck, there will be newer ones.