A woman wearing a mask walk in a street in a Yonghegong Lama temple compound seen shrouded in smog in Beijing, China, 30 November 2015. Beijing issued an orange alert for heavy smog 30 November, the highest level this year. Authorities in the Chinese capital warned of 'severe pollution' and advised the capital's 20 million inhabitants to stay indoors. (Photo by How Hwee Young/EPA)

Humboldt Penguins swim in their pool as a keeper looks on through a spherical window during the annual stocktake press preview at London Zoo in Regents Park in London Monday, January 4, 2016. A requirement of ZSL London Zoo's license, the annual audit takes keepers a week to complete and all of the information is shared with zoos around the world via the International Species Information System, where it's used to manage the worldwide breeding programmes for endangered animals. (Photo by Alastair Grant/AP Photo)

Palestinian children warm themselves by a fire on a stormy day at Shati (beach) refugee camp in Gaza City January 18, 2016. (Photo by Mohammed Salem/Reuters)

Expedition 44 flight engineer and NASA astronaut Scott Kelly seen inside the Cupola, a special module which provides a 360-degree viewing of the Earth and the International Space Station. Kelly is one of two crew members spending an entire year in space. (Photo by Scott Kelly/NASA)

A man plays to the cameras as racegoers make their way home at the end of Ladies Day the second day of the Aintree Grand National Festival meeting on April 8, 2016 in Aintree, England. Today is Fabulous Friday and Ladies Day of the three-day meeting of the world famous Grand National Festival where fashion and dressing to impress is as important as the racing. (Photo by Christopher Furlong/Getty Images)

Boys play with water as they celebrate Myanmar's New Year Water Festival of Thingyan in Yangon, April 13, 2016. (Photo by Soe Zeya Tun/Reuters)

A topless activist of women's rights group FEMEN tries to break a segment of the Berlin wall which is on display outside the German embassy, during a protest against EU visa regime for Ukrainian citizens in Kiev, Ukraine, November 24, 2016. (Photo by Valentyn Ogirenko/Reuters)

An Indian man feeds peanuts to monkeys along a busy street in Ahmedabad on July 31, 2016. Feeding animals is sacred in Hindu society. (Photo by Sam Panthaky/AFP Photo)