A partially burned American flag lies on the street near the spot where Michael Brown was killed before an event to mark the one year anniversary of his killing in Ferguson, Missouri August 9, 2015. (Photo by Rick Wilking/Reuters)

Max Gold, 20, of NYC, cruises on his skateboard as thousands gather on the National Mall for the March for Science on Saturday, April 22, 2017, in Washington, DC. Activists and scientists descend on the nation's capital to rally for environmental causes and government policies rooted in scientific research as part of the Earth Day and March for Science rallies. (Photo by Jahi Chikwendiu/The Washington Post)

Tourists visit the Corral Canyon Cave in Malibu, Calif., Friday, May, 6, 2016. The cave, better known by the misleading moniker “Jim Morrison Cave” is now closed to the public until further notice. Large crowds have shown up on a daily basis to see the often vandalized cave and in some cases add to the vandalism with graffiti of their own. (Photo by Damian Dovarganes/AP Photo)

Toyoda Gosei Co Ltd's personal mobility concept airbag car "Flesby" is displayed at the 44th Tokyo Motor Show in Tokyo, Japan, October 28, 2015. (Photo by Yuya Shino/Reuters)

A model presents a creation during the 2015 Victoria's Secret Fashion Show in New York, November 10, 2015. (Photo by Lucas Jackson/Reuters)

A heat-stressed koala waits as a resident pours water on its back on December 19, 2015 in Adelaide, Australia. Adelaide is experiencing an extreme heatwave, with temperatures reaching over 40 degrees for five consecutive days. (Photo by Morne de Klerk/Getty Images)

An army tank fires during a firefight against militants linked to al Qaeda near the southern Yemeni city of Zinjibar May 30, 2012. (Photo by Reuters/Yemen's Defence Ministry)

Crown line handler Bobby Marie controls “Chain Gang” as the balloon is inflated during the 43nd Annual Helen to the Atlantic Balloon Race and Festival, in Helen, Georgia, USA, 04 June 2016. The race is the oldest balloon event in the southern USA and United States' only long-distance hot air balloon race, according to the organizers. (Photo by Erik S. Lesser/EPA)