Participants wearing superhero costumes attend the World DC Comics Super Heroes event in San Martin de Valdeiglesias, near Madrid, April 18, 2015. To celebrate the anniversary of the publication of the very first Superman story, DC Comics are asking fans to help set a new world record for the largest global gathering of people dressed as DC Comics Super Heroes. (Photo by Andrea Comas/Reuters)

Ants carry a leaf with a slogan reading “Merkel, Help!”, a reference of German Chancellor Angela Merkel, at the zoo in Cologne, Germany August 18, 2015. Some of the zoo's 500,000 leaf-cutting ants carry laser-cut leaves with slogans during a campaign to protect the Amazon rain forest, organised by the German branch of World Wild Fund for Nature (WWF) and Cologne Zoo. Picture taken through the glass of the display case. (Photo by Ina Fassbender/Reuters)

Surfer Arlen Macpherson sits on his board, which has an electronic shark repellent device installed, at Sydney's Bondi Beach in Australia, August 18, 2015. A spate of shark attacks in Australia has left some of world's top surfing beaches deserted and many people having second thoughts about taking a swim as the summer approaches. Macpherson paid A$390 for a device embedded in his surf board to repel sharks by emitting an electronic force field that overpowers its sensing organs. (Photo by David Gray/Reuters)

A handout phptopgraph made avaiable by NASA showing Russian support personnel roll the Soyuz TMA-19M spacecraft after it landed with with with Expedition 47 crew members Tim Kopra of NASA, Tim Peake of the European Space Agency, and Yuri Malenchenko of Roscosmos near the town of Zhezkazgan, Kazakhstan 18 June 2016. Kopra, Peake, and Malenchenko are returning after six months in space where they served as members of the Expedition 46 and 47 crews onboard the International Space Station. (Photo by Bill Ingalls/EPA/NASA)

Nepalese Hindu women pray to worship Lord Shiva during the first day of the Sarwan Brata festival, the month of fasting, at the premises of Pashupati Temple in Kathmandu, Nepal, 18 July 2016. Thousands of married and single Nepalese Hindu women will gather in temples for each Monday of the Sawan month (spanning from 16 July to 16 August) to pray for a long and prosperous life of their husbands or for a chance to find a good one. (Photo by Narendra Shrestha/EPA)

Elephants feast on fruits and vegetables during the elephant buffet prior to the start of the 2016 King's Cup Elephant Polo event in Bangkok, Thailand, 10 March 2016. The annual charity event, now in its 14th edition, runs until 13 March and will involve 18 elephants brought from tourist trekking camps in Pattaya as well as some unemployed in Surin. A total of 10 teams encompassing over 40 players will take part in the event directed at raising funds to improve the lives of elephants and elephant conservation. (Photo by Diego Azubel/EPA)

A 20 metre high spiral staircase in a tower used as an emergency exit, is seen inside a Federal Reserve bank (Bundesbank) bunker, prior to the bunker's official opening to the public in Cochem, Germany, March 18, 2016. West Germany's Central Bank (Deutsche Bundesbank) stored some 20 billion German marks of emergency notes in two underground bunkers, one in Frankfurt the other in Cochem, between 1964-1988 during the cold war. (Photo by Kai Pfaffenbach/Reuters)

Justin Nelzen, in red vest, joins others as they work to rescue up to 70 horses along Cypresswood Drive near Humble along Cypress Creek, Monday, April 18, 2016, in Houston. More than a foot of rain fell Monday in parts of Houston, submerging scores of subdivisions and several major interstate highways, forcing the closure of schools and knocking out power to thousands of residents who were urged to shelter in place. (Photo by Mark Mulligan/Houston Chronicle via AP Photo)