More than fifty years ago, Apollo 15 photographed something unusual on the far side of the Moon. In a panoramic photograph taken from lunar orbit, two bright, sharply defined objects stood out from the otherwise subdued landscape on the floor of a crater called Paracelsus C.
Today we can take a much closer look.
By now, you have probably read or heard that our polluting ways have reached a critical point, where Earth is rapidly approaching total failure as a planet. Perhaps you have wondered how we humans could have managed to do so much damage in so little time.
Just like the dust that stubbornly besmirches your computer monitor, bookcase, and ancestral credenza, cosmic dust is now recognized to have a multiplicity of origins. For decades, astronomers thought that aging red giant stars produced most of the dust responsible for obscuring and reddening our views of nebulae and more distant stars ...
