A masked reveller poses near Saint Mark's Square during the Venetian Carnival in Venice January 31, 2015. (Photo by Stefano Rellandini/Reuters)

A man is silhouetted in front of the Allianz-Arena as he walks his dogs at sunrise in Munich, southern Germany, Friday, April 10, 2015. (Photo by Peter Kneffel/AP Photo/DPA)

In this photo taken late Thursday, May 7, 2015, a prison guard, left, and seated inmates cast shadows on a wall while waiting for the beginning of a rock concert by Romanian band Pro Musica, inside the Popa Sapca jail in Timisoara, western Romania. (Photo by Adi Piclisan/AP Photo)

A firefighter battling the King Fire watches as a backfire burns along Highway 50 in Fresh Pond, California September 16, 2014. The fire led officials to call on about 400 people to evacuate from areas threatened by the blaze, Cal Fire spokeswoman Alyssa Smith said. It has charred more than 11,500 acres (4,654 hectares) and was 5 percent contained on Tuesday. (Photo by Noah Berger/Reuters)

Backdropped by a night time view of the Earth and the starry sky, the Space Shuttle Endeavour is seen docked to the International Space Station on May 28, 2011. (Photo by Reuters/NASA)

Hundreds of festive, adorable canines and their owners took part in the annual “A Very Corgi Howloween” costume walk Saturday, October 25, 2014, at Green Lake in Seattle, Wash. The walk was put on by the Seattle-local “Corgi's R Us” MeetUp group. (Photo by Jordan Stead/AP Photo/Seattlepi.com)

History enthusiasts dressed as soldiers fight during the re-enactment of Napoleon's famous battle of Austerlitz near the southern Moravian town of Slavkov u Brna November 29, 2014. Hundreds of history enthusiasts took part in the re-enactment of the battle to mark its 209th anniversary. (Photo by David W. Cerny/Reuters)

Mount Sinabung volcano erupts, as seen from Tiga Pancur village, Karo Regency in Indonesia's North Sumatra province, in this October 8, 2014 file photo. (Photo by Y. T. Haryono/Reuters)