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)

A meteor streaks over the sky during the Perseid meteor shower at the Maculje archaeological site near Novi Travnik August 12, 2014. According to NASA, the annual Perseid meteor shower reaches its peak on August 12 and 13 in Europe. The fireballs from the meteorites are fast and plentiful, although a nearly full moon (Supermoon) makes it difficult to view them this year, the agency adds. (Photo by Dado Ruvic/Reuters)

This photo provided by NASA shows a full moon rising behind the United Launch Alliance Atlas V rocket with NASA's Mars Atmosphere and Volatile Evolution (MAVEN) spacecraft onboard at the Cape Canaveral Air Force Station Space Launch Complex 41, Sunday, November 17, 2013, Cape Canaveral, Florida. NASA's next Mars-bound spacecraft, the Mars Atmosphere and Volatile Evolution, or MAVEN, is the first spacecraft devoted to exploring and understanding the Martian upper atmosphere. (Photo by Bill Ingalls/AP Photo/NASA)

Giant pumpkins sit in the bed of a truck before the 40th Annual Safeway World Championship Pumpkin Weigh-Off on October 14, 2013 in Half Moon Bay, California. Gary Miller of Napa, California won the 40th Annual Safeway World Championship Pumpkin Weigh-Offgigantic pumpkin with a gigantic pumpkin that weighed in at 1,985 pounds. Miller took home a cash prize of $11,910, or $6.00 a pound. (Photo by Justin Sullivan/AFP Photo)

A woman walks on the stairs decorated with an image of two hands shaking to form the shape of the Korean Peninsula to support the upcoming inter- Korean summit, in downtown Seoul on September 17, 2018. South Korean President Moon Jae- in will fly to the North Korean capital on September 18, for his third summit with the North' s leader Kim Jong Un as a rapid diplomatic thaw takes hold on the peninsula despite stalled progress in denuclearisation talks between Pyongyang and Washington. (Photo by Jung Yeon-je/AFP Photo)