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)

A tourist take a photograph of a sulphur lake in the Danakil Depression on January 23, 2017 near Dallol, Ethiopia. The depression lies 100 metres below sea level and is one of the hottest and most inhospitable places on Earth. Despite the gruelling conditions, Ethiopians continue a centuries old industry of mining salt from the ground by hand in temperatures that average 34.5 degrees centigrade but have risen to over 50 degrees. (Photo by Carl Court/Getty Images)

A West African Slender-snouted Crocodile is pictured in its enclosure at the zoo of Abidjan, Ivory Coast September 9, 2016. (Photo by Luc Gnago/Reuters)

A robot is seen on Mount Etna, Italy on July 4, 2017. Mount Etna, in Sicily, is a test bed for the approximately three-foot high, four-wheeled machine ahead of a future mission to the moon. It is being conducted by the German Aerospace Centre, the agency which runs Germany's space programme. (Photo by Antonio Parrinello/Reuters)

Girls rest on stairs at the China Digital Entertainment Expo and Conference (ChinaJoy) in Shanghai, China July 27, 2017. (Photo by Aly Song/Reuters)

A helicopter is silhouetted by glowing embers as it makes a water drop at the “Old Fire”, which burned in Calabasas, California, U.S., June 4, 2016. (Photo by Gene Blevins/Reuters)

A workman walks past a large mural on the side of a building during the “Sand Sea & Spray” Urban Art Festival in Blackpool, north west England on July 11, 2015. (Photo by Oli Scarff/AFP Photo)

Haitian policemen arrest a demonstrator with machetes at the end of a march, in Port-au-Prince, on November 26, 2015. Supporters of Fanmi Lavalas and Petit Dessalines political parties marched to protest against the results given by the Provisional Electoral Council (CEP), against the Haitian President Michel Martelly, and against the candidate of the ruling party Jovenel Moise. Provisional Electoral Council (CEP) confirmed this week that Haiti's presidential election will go to a runoff on December 27, between ruling party candidate Jovenel Moise and Jude Celestin, close to former president Rene Preval. (Photo by Hector Retamal/AFP Photo)