This picture taken on July 8, 2015 shows 13-year-old jockey Purevsurengiin Togtokhsuren (R) watching a horse rolling in the dirt after a training session in Khui Doloon Khudag, some 50 kms west of Ulan Bator. Despite being only 13 years old, Togtokhsuren is riding for the fifth time in the national races for Mongolia's summer festival, known as Naadam, lining up against some 170 other child jockeys. (Photo by Johannes Eisele/AFP Photo)

An Afghan refugee family stands by trucks loaded with their belongings as they wait to go back to Afghanistan with others, at the United Nations High Commissioner for Refugees (UNHCR) office on the outskirts of Peshawar February 13, 2015. Afghan immigrants ordered out of Pakistan in what officials say is a bid to root out militants are, some analysts say, scapegoats being used to distract attention from the authorities' failure to end violence. (Photo by Fayaz Aziz/Reuters)

World Champion Matthias Dolderer of Germany flies over the Horseshoe Bend near Lake Powell in Page, United States during the transfer flight from Indianapolis to Las Vegas to prior the final stage of the Red Bull Air Race World Championship on October 12, 2016. (Photo by Predrag Vuckovic/AFP Photo)

“The power of nature”. Magma, ash and gas erupt from Mount Etna in December 2015, rising to a height of several kilometres. Winner: Nature. (Photo by Giuseppe Mario Famiani/SIPA Contest)

Children in Hiroshima, Japan, wearing masks to combat the odour of death after the city was destroyed by the first atom bomb. (Photo by Keystone/Getty Images). 1945

A boy jumps from a swing during sunset in Valras-Plage, southern France December 29, 2014. (Photo by Yves Herman/Reuters)

News personality Katie Couric, left, Jenna Dewan-Tatum, center, and model Chrissy Teigen mingle during the White House Correspondents' Association dinner at the Washington Hilton on Saturday, April 25, 2015, in Washington. (Photo by Evan Vucci/AP Photo)

In this May 8, 2015 photo, sisters Zoraida Infante, left, and Graciela Trujillo pray on Fishermen's Beach before therapeutic swimming in the Pacific Ocean in Lima, Peru. Under overcast skies, the bathers practice thalassotherapy, which derives from the Greek “thalasso”, for “sea”, and draws on the ocean's healing properties. (Photo by Rodrigo Abd/AP Photo)