Lindsay Heimbach goes airborne while sledding down a hill on Mt. Lemmon December 27, 2008. (Photo by James Gregg/Arizona Daily Star)

This artist's rendering illustrates the evaporation of HD 189733b's atmosphere in response to a powerful eruption from its host star. NASA's Hubble Space Telescope detected the escaping gases and NASA's Swift satellite caught the stellar flare. (Credit: NASA's Goddard Space Flight Center)

Nikolai Vasilyev, 62, dressed as Father Frost, Russian equivalent of Santa Claus, water-skis along the Yenisei River outside Siberian city of Krasnoyarsk, Russia, December 10, 2015. Vasilyev, a teacher of the Krasnoyarsk Aerospace Academy, constructed the self-made water skis to travel on the water surface. The skis are made of plastic foam and the sticks are designed to propel him forward. (Photo by Ilya Naymushin/Reuters)

Revellers celebrate "Ash Monday" by participating in a colourful "flour war", a traditional festivity marking the end of the carnival season and the start of the 40-day Lent period until the Orthodox Easter,in the port town of Galaxidi, some 215 km (134 miles) north west of Athens, March 18, 2013. The revellers "fight" by throwing coloured flour, charcoal dust and powder painting until they essentially run out of supplies. (Photo by Yannis Behrakis/Reuters)

A view motorists have grown accustomed seeing, a military truck made by Oshkosh Corp. is taken for a test drive Thursday, April 11, 2013 in Oshkosh, Wis. Faced with deep cuts in U.S. military spending, and the end of the wars in Iraq and Afghanistan, Oshkosh Corp. is laying off 900 employees in its defense division based in Oshkosh. Approximately 700 hourly workers at the state's largest manufacturer will lose their jobs in mid-June, followed by approximately 200 salaried employees through July. (Photo by Mark Hoffman via The Journal Sentinel)

AP photographer Anja Niedringhaus laughs as she attends a swimming event at the 2004 Olympic Games in Athens, August 21, 2004. Niedringhaus, a veteran Associated Press photographer who had covered wars around the world was shot dead and another reporter was wounded on April 4, 2014 when an Afghan policeman opened fire on them in eastern Afghanistan, the news agency said. (Photo by Reuters/Staff)

In this Tuesday, July 29, 2014, photo, Syrian refugee Samah, 5, poses for a picture at Zaatari refugee camp, near the Syrian border, in Mafraq, Jordan. More than 2.8 million Syrian children inside and outside the country – nearly half the school-aged population – cannot get an education because of the devastation from the civil war, according to the U.N. children's agency, UNICEF. That number is likely higher, as UNICEF can't count the children whose parents didn't register with the United Nations refugee agency. (Photo by Muhammed Muheisen/AP Photo)

Women in kimonos look at pictures they took in front of paper lanterns during the annual Mitama Festival at the Yasukuni Shrine in Tokyo July 13, 2014. Over 30,000 lanterns light up the precincts of the shrine, where more than 2.4 million war dead are enshrined, during the four-day festival. The festival goes on till July 16. (Photo by Yuya Shino/Reuters)