Soldiers of China's People's Liberation Army (PLA) jump as part of their winter training in temperature of negative 26 degrees Celsius at China's border with Russia in Heihe, Heilongjiang province, December 14, 2015. (Photo by Reuters/Stringer)

U.S. Army soldiers with the 1st Battalion, 501st Infantry Regiment deployed to Combat Outpost Sabari, Afghanistan scan their area as they begin a multi-day air assault mission near the Pakistani border of eastern Afghanistan's Khost province May 2, 2012. (Photo by Staff Sgt. Joshua L. DeMotts/U.S. Air Force)

A handout picture provided by Solar Impulse on 18 March 2015 shows the Swiss solar-powered plane Solar Impulse 2, HB-SIB, taking off with Swiss explorer Andre Borshberg on board for the third leg Ahmedabad to Varanasi, of the Round-The-World, in Ahmedabad, India, 18 March 2015. Swiss explorers Bertrand Piccard and Andre Borschberg attempt to circumnavigate the world flying with an aircraft, with a 72 metres wingspan, powered only by solar energy without a drop of fuel. (Photo by EPA/Solar Impulse)

A paddler races in a giant pumpkin during the annual regatta on Lake Pisiquid in Windsor, Nova Scotia, Sunday, October 11, 2015. Participants hollow out the massive gourds and pilot them across the 500 meter course. (Photo by Andrew Vaughan/The Canadian Press via AP Photo)

Clearing skies await a tripod-toting photographer looking for a spot to capture the early-morning light at Portland Head Light, Thursday, January 17, 2013, in Cape Elizabeth, Maine. (Photo by Robert F. Bukaty/AP Photo)

Tourists gather to watch Mount Agung at Amed beach in Karangasem on Indonesia' s resort island of Bali on November 30, 2017. Thousands of foreign tourists were expected to leave Bali by plane on November 30 following a nearly three- day airport shutdown sparked by a rumbling volcano on the Indonesian holiday island. (Photo by Juni Kriswanto/AFP Photo)

Fans gather to watch a FIFA World Cup Russia 2018 football match between Brazil and Costa Rica on a giant screen at Alzirao neighborhood in Rio de Janeiro, Brazil on June 22, 2018. (Photo by Carl De Souza/AFP Photo)

A U.S. soccer fan pretends that Uruguay's soccer striker Luis Suarez is biting him as he takes a selfie next to an Adidas advertisement featuring Suarez near Copacabana beach in Rio de Janeiro, Brazil, Thursday, June 26, 2014. FIFA banned Suarez from all football activities for four months on Thursday for biting an opponent at the World Cup, a punishment that rules him out of the rest of the tournament. (Photo by Matt Dunham/AP Photo)