Hemispheric color differences on Saturn's moon Rhea are apparent in this false-color view from NASA's Cassini spacecraft in this March 2, 2010 file photo. (Photo by Reuters/NASA/JPL/SSI)
U.S. President Barack Obama speaks at the foot of the Edmund Pettus Bridge in Selma, Alabama March 7, 2015. With a nod to ongoing U.S. racial tension and attempts to limit voting rights, Obama declared the work of the Civil Rights Movement advanced but unfinished on Saturday on a visit to the Alabama bridge that spawned a landmark voting law. REUTERS/Tami Chappell (UNITED STATES - Tags: POLITICS ANNIVERSARY SOCIETY)
Afghan children play soccer in front of the war-damaged Darul Aman Palace in the suburbs of Kabul, Afghanistan, Wednesday, June 8, 2011. (Photo by Gemunu Amarasinghe/AP Photo)
Astronaut Donald R. Pettit would often rig an array of as many as six cameras in the cupola windows and set them all to fire continuously for events such as sunsets, which only last around seven seconds on the ISS. (Photo by Donald R. Pettit)
Muslim pilgrims pray around the holy Kaaba at the Grand Mosque, during the annual haj pilgrimage in Mecca September 30, 2014. (Photo by Muhammad Hamed/Reuters)
Passengers wait for a train to depart from the Hankou Railway Station in Wuhan, central China's Hubei province, Friday January 13, 2017. Officials expect that Chinese travelers will make almost 3 billion trips during the holiday travel rush that starts runs through Feb. 21. These trips include intercity flights, trains and local bus rides to villages for China's 1.4 billion people. (Photo by Chinatopix via AP Photo)