A rocket carrying a NASA spacecraft was launched Wednesday on a first-ever mission to study mysterious clouds that float 50 miles (80 kilometers) above Earth. The noctilucent clouds, which cluster around the polar regions and can only been seen at night, have appeared more often and grown brighter in recent years. Scientists are puzzled by the changes, but some suggest they may be due to global climate change. The spacecraft, which will spend two years studying the ice clouds, will try to answer basic questions including why the clouds form and whether human-caused global warming is responsible for the changes. It is dubbed AIM, short for Aeronomy of Ice in the Mesosphere. "We are exploring clouds literally on the edge of space," principal investigator James Russell of Hampton University said at a press conference earlier this month.