“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 polar bear fast asleep at London Zoo. (Photo by Fox Photos/Getty Images). 1961

Impala pictured in the Kruger National Park on December 7, 2007 in Mpumalanga, South Africa. (Photo by Warren Little/Getty Images)

German model Alena Gerber poses wearing a full chocolate dress during the presentation of chocolate dresses designed by German bakery group Lambertz on January 21, 2010 in Munich, Germany. (Photo by Alexandra Beier/Getty Images)

China has sent its first woman into space on a mission to dock with an orbiting station, the latest step in an ambitious programme to go to the moon and on to Mars.

Photo: China's first female astronaut Liu Yang, waves during a sending off ceremony before she departs for the Shenzhou 9 spacecraft rocket launch pad at the Jiuquan Satellite Launch Center in Jiuquan, China, Saturday, June 16, 2012. China will send its first woman and two other astronauts into space Saturday to work on a temporary space station for about a week, in a key step toward becoming only the third nation to set up a permanent base in orbit. (Photo by Ng Han Guan/AP Photo)

Growing cities, overuse of fertilizers and factory wastewater have degraded China's water supplies to the extent that half the nation's rivers and lakes are severely polluted. China aims to spend $850 billion to improve filthy water supplies over the next decade, but even such huge outlays may do little to reverse damage caused by decades of pollution and overuse in Beijing's push for rapid economic growth. Photo: Fishermen row a boat in the algae-filled Chaohu Lake in Hefei, Anhui province, June 19, 2009. (Photo by Jianan Yu/Reuters)

A man performs a split as he practices Kung Fu at Beihai Park in Beijing, China August 20, 2017. (Photo by Reuters/China Stringer Network)

A soldier shares a tender moment with his girlfriend while other soldiers rest during a rehearsal of a military parade a few days before the Independence Day in Kiev, Ukraine, Monday, August 22, 2016. Ukraine to mark the 25th anniversary of the Independence Day on August 24. (Photo by Efrem Lukatsky/AP Photo)