Astronauts Harrison Schmitt (left) and Eugene Andrew Cernan practice taking geological samples at the Kennedy Space Center in Florida, in preparation for NASA's scheduled Apollo 17 lunar landing mission, on August 28, 1972. Schmitt is the Lunar Module Pilot and Cernan is the mission's Commander. They are training for their period of EVA (extravehicular activity) on the Moon. (Photo by Space Frontiers/Getty Images)

Wasibi, (r), yawns at backstage before the Algonquin Hotel’s Annual Cat Fashion Show in the Manhattan borough of New York City, New York, U.S., August 1, 2019. The theme of this year's show was “It's a Small World”. The cats represented countries including Ireland, Spain, the United Kingdom and the United States. (Photo by Jeenah Moon/Reuters)

“Contrails (short for “condensation trails”) or vapour trails are artificial clouds that are the visible trails of condensed water vapour made by the exhaust of aircraft engines. As the hot exhaust gases cool in the surrounding air they may precipitate a cloud of microscopic water droplets or, if the air is cold enough, tiny ice crystals”. – Wikipedia

Photo: An airplane leaves a vapor trail as it flies in front of he moon on January 17, 2007 above Hanover, Germany. (Photo by Alexander Hassenstein/Getty Images)

Tulane University graduates pop prosecco as they pose for graduation photos on a largely empty Bourbon Street, due to the coronavirus pandemic, in the French Quarter of New Orleans, Tuesday, May 12, 2020. (Photo by Gerald Herbert/AP Photo)

A young devotee of the Nine Emperor Gods has a large needle pushed through his cheek during the annual Phuket Vegetarian Festival in the southern province of Phuket on October 1, 2016. (Photo by Lillian Suwanrumpha/AFP Photo)

Two Inuit children at Point Barrow, Alaska, holding the tusks of a large walrus, probably killed for food, circa 1930. (Photo by General Photographic Agency/Getty Images)

Men slicing blubber off a large, dead whale. (Photo by Topical Press Agency/Getty Images). Circa 1912

A large brawl breaks out as people leave the track after Sydney Racing at Rosehill Gardens on December 07, 2019 in Sydney, Australia. (Photo by Mark Evans/Getty Images)