An American flag is visible in the windows of the cupola aboard the International Space Station. Thanks to a bill passed by Texas legislators in 1997 that put in place technical voting procedure for astronauts – nearly all of whom live in Texas – they have the ability to vote from space through specially designed absentee ballots. To preserve the integrity of the secret vote, the ballot is encrypted and only accessible by the astronaut and the county clerk responsible for casting the ballot. (Photo by NASA)

Children play in an outdoor shower as a soldier takes part in a surprise operation in the Manguinhos slum in Rio de Janeiro, Brazil, Thursday, January 18, 2018. Troops have been sent to Rio due to the increase of the violence, and in an attempt to help restore order, but so far have had little impact. The operation on Thursday took place three weeks ahead of Carnival, when thousands of tourists are expected to arrive in the city. (Photo by Leo Correa/AP Photo)

The fin of a tuna is seen on display in the outer part of the Tsukiji fish market, the Jogai Shijo, in Tokyo January 4, 2015. The famous Tsukiji wholesale fish and seafood market, is scheduled to leave its fabled 80-year-old halls to move into bigger, more modern facilities next year ahead of the 2020 Tokyo Olympics. The outer part of the market, the Jogai Shijo, that caters to the public will stay in its old place, but critics wonder about its chances for survival without the world's biggest fish trading place at its doorsteps. (Photo by Thomas Peter/Reuters)

Some of the most powerful narratives of the past decade have been produced by a forward-thinking generation of women photojournalists as different as the places and the subjects they have covered. National Geographic's “Women of Vision” exhibit features the work of 11 photographers and is on display at the Fernbank Museum of Natural History in Atlanta until January 3, 2016. Here: Nujood Ali stunned the world in 2008 by obtaining a divorce at age 10 in Yemen, striking a blow against forced marriage. (Photo by Stephanie Sinclair/National Geographic)

Britain's Red Arrows airplane display team perform during D-Day commemorations in Portsmouth in southern England on June 5, 2014. Several hundred surviving veterans of the 1944 D-Day landings are commemorating the 70th anniversary of the mission on both sides of the English channel. (Photo by Carl Court/AFP Photo)

A Kurdish girl wears her relative's assault rifle and ammunition belt as she waits at the Iraqi Kurdish Shaqouli checkpoint, some 35 kilometres east of Mosul, on November 10, 2016. Since the start of the Mosul offensive the Kurds have moved their border some 10 kms closer to Iraq's second city, marking it out with a line in the sand. (Photo by Odd Andersen/AFP Photo)

A couple chats at a park during sunset in Chihuahua November 15, 2014. (Photo by Jose Luis Gonzalez/Reuters)

Disguised participants strike poses on a car during the ancient carnival of Ituren, in the northern Spanish Navarra province on January 30, 2017. The yearly three day festivities, revolving mainly around agriculture and principally sheep hearding, run on the last Sunday, Monday and Tuesday of January where Navarra Valley locals from two villages dress up and participate in a variety of activites as they perform a pilgrimage through each village. (Photo by Ander Gillenea/AFP Photo)