FILE PHOTO: A NASA astronaut is seen as the Earth's surface passes by in the background on the International Space Station, in this handout photo taken February 21, 2015, provided by NASA. REUTERS/NASA/Handout (OUTER SPACE - Tags: ENVIRONMENT SCIENCE TECHNOLOGY) FOR EDITORIAL USE ONLY. NOT FOR SALE FOR MARKETING OR ADVERTISING CAMPAIGNS. THIS IMAGE HAS BEEN SUPPLIED BY A THIRD PARTY. IT IS DISTRIBUTED, EXACTLY AS RECEIVED BY REUTERS, AS A SERVICE TO CLIENTS/File Photo