This image provided by NASA and photographed Sunday March 6, 2011, by an Expedition 26 crew member on the International Space Station shows Earth's thin line of atmosphere and a gibbous moon. (AP Photo/NASA)

This image provided by NASA and photographed Sunday March 6, 2011, by an Expedition 26 crew member on the International Space Station shows Earth's thin line of atmosphere and a gibbous moon. (AP Photo/NASA)