This artist's rendering illustrates the evaporation of HD 189733b's atmosphere in response to a powerful eruption from its host star. NASA's Hubble Space Telescope detected the escaping gases and NASA's Swift satellite caught the stellar flare. (Credit: NASA's Goddard Space Flight Center)

Kashmiri vegetable vendors assemble at a floating market in the interiors of the Dal Lake in Srinagar April 17, 2012. (Photo by Danish Ismail/Reuters)

Christian pilgrims from Brazil embrace after they are baptized in the water of the Jordan River during a ceremony at the Yardenit baptismal site near the northern Israeli city of Tiberias October 15, 2014. (Photo by Finbarr O'Reilly/Reuters)

The space shuttle Endeavour is transported to the California Science Center in Exposition Park from Los Angeles International Airport (LAX) in Los Angeles, California. (Photo by Kevork Djansezian)

A girl uses her mobile phone during the evening at the National Park in Khartoum, Sudan, April 24, 2015. (Photo by Mohamed Nureldin Abdallah/Reuters)

Senator Barack Obama (D-IL) (R) stands in front of Senator Hillary Clinton (D-NY) as they arrive for U.S. President George W. Bush's annual State of the Union speech to a joint session of Congress at the U.S. Capitol in Washington in this January 23, 2007 file photo. Hillary Clinton announced her second run for the presidency on April 12, 2015 starting her campaign as the Democrats' best hope of fending off a crowded field of lesser-known Republican rivals and retaining the White House. (Photo by Larry Downing/Reuters)

A woman sits in a cell at the Los Angeles County Women's jail in Lynwood, California April 26, 2013. (Photo by Lucy Nicholson/Reuters)

American soldiers with the 173rd Airborne Brigade Battle Company, on a battalion-wide mission in the Korengal Valley, looking for caves, weapons caches and known Taliban leaders, 2007. Tanner Stichter tends to Spc. Carl Vandeberge in the bushes moments after Vandeberge was shot in the stomach during a Taliban ambush, which killed one soldier and wounded two others. (Photo by Lynsey Addario)