People walk past a downed tree in Central Park on October 31, 2011 in New York City. Central Park may lose 1,000 trees following a freak October snowstorm while the park only lost 125 trees due to Hurricane Irene. (Photo by Mario Tama/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)

Darren Julien poses with two of Princess Diana's dresses which will be auctioned through WE tv & Wedding Central at Julien's Auctions in Beverly Hills on May 7th in celebration of the Royal Wedding, with a portion of the proceeds going to charity are shown at Times Square on April 20, 2011 in New York City. (Photo by Slaven Vlasic/Getty Images)

A pedestrian walks by an Apple Store following an announcement that Apple has become the world's most valuable brand on May 9, 2011 in San Francisco, California. In a report released by London based Millward Brown, Apple Inc. has surpassed Google to claim the top spot in a global ranking of brand value this year with an estimated value of more than $153 billion up 84 percent from last year. (Photo by Justin Sullivan/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)

Actress Penelope Cruz (L) and actor Johnny Depp arrive at premiere of Walt Disney Pictures' “Pirates of the Caribbean: On Stranger Tides” held at Disneyland on May 7, 2011 in Anaheim, California. Proceeds from the world premiere of Walt Disney Pictures' “Pirates Of The Caribbean: On Stranger Tides” will benefit the Boys & Girls Clubs of America. (Photo by Kevin Winter/Getty Images)

ESA astronaut Paolo Nespoli looks on after landing back on Earth from their Soyuz TMA-20 spacecraft on May 24, 2011 in Zhezkazgan, Kazakhstan. The mission of the Soyuz TMA-20 was launched last December to the International Space Station with the flight engineers Catherine Coleman from the United States, Russian cosmonaut Dmitry Kondratyev and Italian astronaut Paolo Nespoli. The next expedition is expected to launch this June. (Photo by Stephane Corvaja/ESA via 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)