NASA space shuttle Atlantis in Earth orbit is seen during a Rendezvous Pitch Maneuver, or back flip to enable space station crew members to take high resolution digital pictures of the shuttle's heat shield before docking for the last time with the International Space Station July 10, 2011 in space. Atlantis has embarked on a 12-day mission to the International Space Station where it will deliver the Raffaello multi-purpose logistics module packed with supplies and spare parts. This will be the final launch of the space shuttle program, which began on April 12, 1981 with the launch of Colombia. (Photo by NASA via Getty Images)

An arial view of Top Pearsy's Maize Maze in the shape of Harry Potter, on July 11, 2011 in York, England. Farmer Tom Pearcy has cut two portraits of Harry Potter in his crop of maize plants. With some subtle differences the two images create the world's largest spot the difference competition. At over 50m in diameter, and cut out of over 1 million living maize plants, the York Maze is the largest “Maize Maze” in Europe and one of the largest in the world. (Photo by Bethany Clarke/Getty Images)

Members of China Disabled Peoples Performing Art Troupe perform “Thousand-arm Goddess of Mercy” during a show on March 12, 2005 in Guangzhou of Guangdong Province, China. China Disabled Peoples Performing Art Troupe was established in 1987. It is an amateur mass art troupe composed of visually impaired, audibly impaired and physically and mentally challenged people. In the past nearly two decades, the troupe has visited more than 30 countries and regions, winning the hearts of audiences all over the world by their solid background of Chinese Culture and their colourful national charm. (Photo by China Photos/Getty Images)

A screen shows the new Automated Target Recognition software as a TSA employee, who couldn't provide her name, waits to walk into the advanced imaging technology unit to demostrate the new software that has been installed at Miami International Airport on August 23, 2011 in Miami, Florida. The new software is designed to enhance passenger privacy by eliminating passenger-specific images and instead auto-detecting potential threat items and indicating their location on a screen which shows a generic outline of a person. (Photo by Joe Raedle/Getty Images)

Patrick Boyle, The Earl of Glasgow and his son David, Viscount Kelburn pose at their home Kelburn Castle on August 30, 2011 in Largs, Scotland. The Earl of Glasgow has asked Historic Scotland if the graffiti can remain as a permanent feature of the Castle. The local council allowed the mural to be painted on the wall by Brazilian artists in 2007, with a three year limit put on the graffiti pending the start of rendering work at the castle.(Photo by Jeff J Mitchell/Getty Images)

The stern of the stranded cargo vessel Rena grounded on the Astrolabe Reef is seen on October 20, 2011 in Tauranga, New Zealand. Salvage crews continue to pump oil off the ship in an effort to remove as much as possible before bad weather predicted for the evening threatens to break the vessel and release more oil into the sea. Over 300 tonnes of oil has leaked from Rena since it hit the reef on October 5. (Photo by New Zealand Defence Force via Getty Images)

Tree trunks are seen in a forest on November 8, 2011 near Landau an der Isar, Germany. The German government is conducting a nationwide project to estimate the number, variety and geographic distribution of trees and forests in Germany, as well as their condition and health. Approximately a third of Germany is covered in woodlands, and though that territory has actually expanded since 1989, some analysts fear demand for wood will outstrip supply in coming years due to national growth in industry and bio-energy needs. (Photo by Johannes Simon/Getty Images)

People ride a prototype of a driverless vehicle as it is moves through a pedestrian area in Greenwich, east London, February 11, 2015. Britain has begun testing driverless cars in four cities, launching the first official trials ahead of a series of planned rule reviews to accommodate the new technology. (Photo by Suzanne Plunkett/Reuters)