Photographers gather to take pictures of pilot Andre Borschberg (C) ahead of the take off of Solar Impulse 2-a solar powered plane- in Nanjing, China, May 31, 2015. The world's largest solar-powered airplane, Solar Impulse 2, took off from eastern China's Nanjing on Sunday to continue its round-the-world voyage. The Swiss-made plane left Nanjing's Lukou International Airport at 2:39 in the early morning, with former fighter pilot Borschberg at the controls alone for the entire 8,200-kilometer flight from Nanjing to Hawaii, the toughest leg of its marathon adventure. (Photo by Reuters/Solar Impulse)

A Chinese woman wears a protective mask as she shops in a market on February 6, 2020 in Beijing, China. The number of cases of a deadly new coronavirus rose to more than 28000 in mainland China Thursday, days after the World Health Organization (WHO) declared the outbreak a global public health emergency. (Photo by Kevin Frayer/Getty Images)

Children wearing uniforms hold toy guns during a military parade game on China's National Day, at Beyou World, a centre children where can experience different kinds of professions, in Beijing, October 1, 2015. (Photo by Reuters/Stringer)

The Cotopaxi volcano, one of the world's highest active volcanoes, spews smoke as seen from El Pedregal, Ecuador, October 22, 2015. Ecuadorian authorities are monitoring activity at Cotopaxi volcano, which prompted Ecuador's President Rafael Correa to maintain a yellow alert for eruptions as bursts of ash keep spewing from the snow-encircled crater of the volcano and falling in gusts on residential communities. (Photo by Guillermo Granja/Reuters)

An activist takes a selfie during a protest ahead of the 2015 Paris Climate Conference, in Paris, Sunday, November 29, 2015. More than 140 world leaders are gathering around Paris for high-stakes climate talks that start Monday, and activists are holding marches and protests around the world to urge them to reach a strong agreement to slow global warming. (Photo by Christophe Ena/AP Photo)

U.S. players push head coach Adam Krikorian into the pool after they defeated the Netherlands in their women's water polo gold medal match during the Aquatics World Championships in Kazan, Russia, August 7, 2015. (Photo by Michael Dalder/Reuters)

German Oliver Struempfl competes to set a new world record in carrying one liter beer mugs over a distance of 40 m (131 ft 3 in) in Abensberg September 7, 2014. Struempfl carried 27 mugs over 40 meters to set a new record for the Guinness book of records. (Photo by Michael Dalder/Reuters)