Those carbon dioxide levels, in fact, have been dropping in the United States because of evolutions in the composition of electric generation from coal to natural gas, predicated on price structure and federal regulations.

FORBES: Lobbyists Try to Halt State Green Energy Standards

By observing the cloud of dust and gas kicked up by each impact, scientists knew they could obtain valuable data about the Moon's composition.

BBC: Nasa reveals new information about moon probes crash sites