Space junk on collision course with moon

The moon is about to get walloped by a big piece of space junk. The leftover rocket will slam into the far side of the moon Friday. Experts think it is from a China launch from 2014, but China is dubious. No matter whose it is, the object will carve out a crater on the moon that could fit several semitractor-trailers. It may take weeks, even months, to confirm the impact through satellite images.

SpaceX originally took the rap for this lunar litter, but the asteroid hunter who discovered the collision course in January later concluded it was from China. The moon already bears countless craters, ranging up to 1,600 miles (2,500 kilometers).

With little to no real atmosphere, the moon is defenseless against the constant barrage of meteors and asteroids, and the occasional incoming spacecraft, including a few intentionally crashed for science's sake. With no weather, there's no erosion and so impact craters last forever.