Sailors stand on the deck as the USS New York as it passes the Statue of Liberty during the start of Fleet Week May 25, 2011 in New York City. Fleet week, which has been held in New York City since 1984, celebrates the U.S. Navy and Marines Corps with a week of ship visitations and military demonstrations. Fleet Week concludes on Memorial Day with a military flyover to honor those killed while serving in the military. (Photo by Spencer Platt/Getty Images)

A gallery assistant at the Saatchi Gallery admires a sculpture by artist Dirk Skreber entitled “Untitled (Crash 1)” on May 26, 2011 in London, England. The sculpture features in the Saatchi Gallery's exhibition, “The Shape of Things to Come: New Sculpture” which showcases work from 20 international artists. (Photo by Oli Scarff/Getty Images)

Adult gentoo penguins keep an eye on their newly born chick at Edinburgh Zoo on June 10, 2011 in Edinburgh, Scotland. The gentoo chicks which started hatching in early May are looked after by both parents who regurgitate part digested food. When the chicks are hungry they peck the beaks of their parents to signal feeding time. (Photo by Jeff J Mitchell/Getty Images)

“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)

Female Chimpanzee “Fifi” eats carrots as she sits in her enclosure at Taronga Zoo on her 60th birthday May 21, 2007 in Sydney, Australia. Fifi is the oldest of the Zoo's chimp population, which consists of 19 individuals. (Photo by Ian Waldie/Getty Images)

An Afghan National Army (ANA) soldier assigned to the Mobile Strike Force Kandak fires a RPG-7 rocket-propelled grenade launcher during a live-fire exercise supervised by the Marines with the Mobile Strike Force Advisor Team on Camp Shorabak, Helmand province, Afghanistan, May 20, 2013. The Marines with the Mobile Strike Force Advisor Team instructed and mentored their ANA counterparts on how to properly utilize their weapons systems. (Photo by SSgt Ezekiel R. Kitandwe/RCT 7)

“Strike Through The Mothership”. Every May for the last 3 years I have driven down to Tornado Alley to capture some amazing storms. This supercell held so much promise to drop a tornado but one small shift in the atmosphere and all that it produced was an extreme lightning show. Photo location: Broken Bow, Nebraska. (Photo and caption by Vanessa Neufeld/National Geographic Photo Contest)

A woman is led aside as her partner is detained by Ukrainian security forces for being aggressive at an army checkpoint in the southeastern port city of Mariupol, on May 11, 2014. Residents’ attitudes appear to have hardened considerably with the deaths of dozens of pro-Russian activists in the city of Odessa this month and with reports that troops fired at a crowd in Mariupol last week. (Photo by Marko Djurica/Reuters)