An aircraft passes over houses at it lands at Heathrow Airport near London, Britain, December 11, 2015. Picture taken December 11, 2015. (Photo by Neil Hall/Reuters)

People walk during a polluted day in Shenyang, Liaoning province, March 31, 2016. (Photo by Reuters/Stringer)

In this picture taken on Sunday, March 5, 2017, a Tehran's urban animal control worker catches a stray dog after being shot with his anesthetic dart on the outskirts of the capital Tehran, Iran. The shelter has been hired by the Tehran city government to take a new, more humane approach to deal with the burgeoning problem of stray dogs in the capital. It’s a sign of changing attitudes among officials in a country where Islamic authorities long saw dogs as “un-Islamic” and would at times confiscate them from people who kept them as pets. (Photo by Vahid Salemi/AP Photo)

A herd of wildebeest cross the skyline against the fading light in Masai Mara, Kenya, 25 August 2017. Stunning sunset photos silhouette Africa’s wildlife against streaks of orange and red sky. In August, German photographer Ingo Gerlach was on safari in the Masai Mara when he convinced his safari guide to stop and take in the sunset. The wildlife photographer was rewarded with his patience by an eye-catching sunset, which cast Africa’s wildlife into dark shadows against the vibrant skies. (Photo by Ingo Gerlach/Barcroft Images)

Family members watch on as a bride and groom leave their house to be married in West Mosul on November 3, 2017 in Mosul, Iraq. Five months after Mosul, Iraq's second-largest city was liberated from ISIL in a nine-month long battle, residents have returned to the destroyed city to rebuild their lives. (Photo by Chris McGrath/Getty Images)

A so-called “Supermoon” dominates the sky while traffic rolls in the streets in Naypyitaw, Myanmar, 03 December 2017. According to the National Aeronautics and Space Administration (NASA) a series of three “Supermoons” – dubbed the “Supermoon trilogy” – will appear in the sky on 03 December 2017, on 01 January 2018 and and 31 January 2018. A “Supermoon” commonly is a full moon at its closest distance to the earth with the moon appearing larger than usual. (Photo by Hein Htet/EPA/EFE)

In this picture taken on December 13, 2017, a woman commutes on a street on a cold day in Baoding. As temperatures dipped below freezing in a northern Chinese village, a group of parka-clad women tried to stay warm as they played mahjong around a small gas stove in a grocery store. (Photo by Fred Dufour/AFP Photo)

British fashion model Twiggy plays around on the bumper cars at the Bertram Mills Circus in London, England on January 10, 1967. (Photo by AP Photo)