The Soyuz TMA-18M spacecraft is transported from an assembling hangar to its launch pad at the Baikonur cosmodrome, Kazakhstan, August 31, 2015. The Soyuz is scheduled to blast off with Aidyn Aimbetov of Kazakhstan, Sergei Volkov of Russia and Andreas Mogensen of Denmark to the International Space Station (ISS) on September 2, 2015. (Photo by Shamil Zhumatov/Reuters)

The Solar Impulse 2 airplane, flown by test pilot Markus Scherdel, flies off the coast of Oahu during a test flight from Kalaealoa Airfield in Kapolei, Hawaii, March 3, 2016. The solar-powered plane is ready to continue its revolutionary voyage around the world. After the craft was grounded in Hawaii last July due to overheated batteries, it was repaired and upgraded, and a recent initial test flight proved successful. (Photo by Eugene Tanner/Reuters)

In this photograph taken on February 18, 2016, Pakistani children ride on swings in the predominantly Pashtun Korangi District of Karachi. In a rundown district of Karachi, Rabia balks at a neighbour's proposal to vaccinate her children, demonstrating one of the biggest hurdles to eradicating polio in Pakistan by the end of the year: confused and frightened parents. (Photo by Asif Hassan/AFP Photo)

Aerial view of tourists in life vests and rubber rafts in the Grand Canyon of western Henan, Sanmenxia, China on August 5, 2017. (Photo by Imaginechina/Rex Features/Shutterstock)

A boy covers his head with fallen leaves as he enjoys a stroll with his family in a park in downtown Frankfurt, Germany, November 6, 2016. (Photo by Kai Pfaffenbach/Reuters)

A model presents a creation by Givenchy during men's Fashion Week for the Fall/Winter 2017/2018 collection in Paris on January 20, 2017. (Photo by Patrick Kovarik/AFP Photo)

An opposition supporter wearing a costume lies on the ground in front of riot police during a rally against Venezuelan President Nicolas Maduro's government and to commemorate the 59th anniversary of the end of the dictatorship of Marcos Perez Jimenez in Caracas, Venezuela January 23, 2017. The sign reads “Venezuelans starve. There is no food or medicine. The underworld kills us. Get out Maduro”. (Photo by Marco Bello/Reuters)

A man waits with his camel to take part in a camel decoration competition at the Nagaur Cattle Fair, where animals like camels, cows, horses, and bulls are brought to be sold or traded, in Nagaur, in the desert state of Rajasthan, India February 2, 2017. (Photo by Himanshu Sharma/Reuters)