A huge ice disk swirling in a river in Maine is stirring international interest. The City of Westbrook is inviting visitors to come down and check it out. A post on the city's official Twitter account says "It looks like the moon has landed." Scientists say the slowly rotating circular sheet of ice on the Presumpscot River is a rare, but naturally occurring phenomenon. The BBC features a video clip on its website, comparing the nearly 300 foot wide disk to an alien spacecraft, a carousel and even the Moon.