The six-months-old female koala cub holds on to the back of zoo keeper Lena at the zoo in Duisburg, Germany, 23 October 2015. The yet unnamed baby weighs 580 grams. (Photo by Roland Weihrauch/EPA)

Ty, a 15-year-old boy, poses for a picture while collecting usable items at a landfill dumpsite outside Siem Reap March 19, 2015. Ty, who finished six-grade primary school, said he makes 5 USD per month working at the dumpsite. (Photo by Athit Perawongmetha/Reuters)

Tarah Kayne and Daniel O'Shea of the U.S. perform during the Pairs short program at the Skate America figure skating competition in Milwaukee, Wisconsin October 23, 2015. Fifty-six Olympic and world championship athletes are competing in the event, which is the first of six stops on the International Skating Union (ISU) Grand Prix of Figure Skating Series. (Photo by Lucy Nicholson/Reuters)

Nuns react at the arrival of Pope Francis at the St. Mary's school to attend a meeting of clergy and religious in Nairobi, Kenya, 26 November 2015. Pope Francis is on a six days visit that will take him to Kenya, Uganda and the Repulic of Central Africa from 25 to 30 November. (Photo by Daniel Dal Zennaro/EPA)

Astronaut Donald R. Pettit would often rig an array of as many as six cameras in the cupola windows and set them all to fire continuously for events such as sunsets, which only last around seven seconds on the ISS. (Photo by Donald R. Pettit)

Capgrossos de Mataro team members fall during the 25th Castells' contest at the Tarraco Arena in Tarragona, Catalonia, northeastern Spain, 02 October 2016. The “Castells” is a popular event in which people create human towers up to a height of between six and ten levels. (Photo by Jaume Sellart/EPA)