A couple covered in mud wait for it to dry at the Salt-works lakes near the Black Sea town of Burgas in Bulgaria on July 25, 2019. Thousands of tourists visit the red salt lakes for mud baths, which are believed to help the healing of muscular disorders and rheumatism. (Photo by Nikolay Doychinov/AFP Photo)

Protesters begin to gather ahead of the UK Student Climate Network's Global Climate Strike at Millbank in London, England on September 20, 2019. (Photo by Gareth Fuller/PA Images via Getty Images)

A zoo keeper carries a pelican to move it to its winter enclosure at Dvur Kralove Zoo in Dvur Kralove nad Labem, Czech Republic on November 5, 2019. (Photo by David W. Cerny/Reuters)

A member of the wingsuit flyers duo, known as the Soul Flyers, is seen in mid-air as he catches up and flies into the open door of Pilatus Porter plane, piloted by Philippe Bouvier, after B.A.S.E. jumping off the Jungfrau mountain, 4158 meters, in Lauterbrunnen, Switzerland, October 13, 2017. French athletes Fred Fugen and Vince Reffet had 2.45 minutes and a free fall distance of 3200 meters to complete their project “Door In The Sky”, coordinated by Yves Rossy know as the “Jetman”. (Photo by Thibault Gachet/Reuters)

A Chinese woman wears a mask to protect from particles blown in during a sandstorm as she walks in the street on May 4, 2017 in Beijing, China. Sandstorms are common in northern China during the spring season and are caused when heavy winds from Mongolia in the north brings sand and pollutants that can blanket Chinese cities and cause air quality to deteriorate. (Photo by Kevin Frayer/Getty Images)

Dancers perform during a general rehearsal of “Kreatur” (Creature) by German choreographer Sasha Waltz in collaboration with artist and fashion designer Iris van Herpen and light designer Urs Schoenebaum in Berlin, Germany on June 8, 2017. (Photo by Stefanie Loos/Reuters)

A man dressed as a demon poses for a picture as he participates in a ceremony known as Los Talciguines, as part of religious activities to mark the start of the Holy Week in Texistepeque, El Salvador, March 26, 2018. (Photo by Jose Cabezas/Reuters)

Revellers gather for the start of the Annual SantaCon Bar Crawl at Father Duffy Square, a section of Times Square, on December 14, 2019, in New York City. SantCon is an event where people make donations to charitable causes and dress up as a Christmas character and visit bars around the city. (Photo by Steven Ferdman/Getty Images)