A member of the United States Naval Academy freshman class wears body armor, helmet and carries a rifle through a mud-filled ditch as part of the “Wet and Sandy” challenge during the rigorous Sea Trials May 17, 2011 in Annapolis, MD. Under strict safety supervision, about 900 freshmen, or “Plebes”, faced 14 hours of 32 rigorous physical and mental challenges during the trials, a daylong, action-oriented event modeled after the Marine Corps 54-hour Crucible and the Navy's Battle Stations. (Photo by Chip Somodevilla/Getty Images)

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)

Two girls are detained outside the Currys electrical store in Brixton on August 8, 2011 in London, England. Widespread rioting and looting took place across many parts of London in the early hours of Monday morning in a reaction to earlier rioting in Tottenham in North London. Major disturbances broke out late on Saturday night in Tottenham and the surrounding area after the killing of Mark Duggan, 29 and a father-of-four, by armed police in an attempted arrest on August 4. (Photo by Dan Kitwood/Getty Images)

A South Korean soldier wear North Korea's military uniform, acting as North Korean soldier during an anti-terror and anti-chemical drill session held as part of the 2011 Ulchi Freedom Guardian (UFG) event on August 17, 2011 in Seoul, South Korea. The 11-day UGC, which features drills including the handling of chemical and biological attacks, is a regular joint exercise between US and South Korean troops to prepare for potential emergencies on the Korean Peninsula. (Photo by Chung Sung-Jun/Getty Images)

A Maasai boy bites a bull's heart during an initiation into an age group ceremony near the town of Bisil, Kajiado county, Kenya, August 23, 2018. Thousands of Kenyan boys had a blessing of milk and beer sprayed on them as part of a rare Maasai ethnic community initiation ceremony to mark their passing into early manhood. (Photo by Baz Ratner/Reuters)

Participants climb a 10km muddy obstacle course during the “Run Mud” race, on March 29, 2019 in the Israeli mediterranean coastal city of Tel Aviv. Over 6,000 participants took part in the obstacle race, with up to 18 artificial obstacles on three tracks (10 km, five km or two km). (Photo by Jack Guez/AFP Photo)

A farmer works in a paddy field at Reba Maheswar village, 56 kilometers (35 miles) east of Gauhati, India, Friday, July 3, 2015. Rice is one of the most important food crops of India and about 4,000 different varieties are grown in different parts of the country. (Photo by Anupam Nath/AP Photo)

Kale grows at Kajodlingen farm in Gothenburg, Sweden, September 28, 2016. They are doing it on the rooftops, on tower block balconies and even on a disused railway: Swedes have discovered a passion for urban gardening as a way of growing fresh food and getting back in touch with nature. Part of a global movement, an increasing number of Swedish city-dwellers are growing their own in window boxes and allotments or are visiting public gardens built in or on industrial or office spaces. (Photo by Maxim Shemetov/Reuters)