Revellers take part in the annual “Naval Battle” of Vallecas in Madrid, Spain July 19, 2015. The slogan for this year's water battle is “Get wet for Alfon, freedom for Alfon”, referring to Alfonso Fernandez Ortega, a Vallecas resident who was sentenced to four years in prison in June. The festival was started spontaneously in 1981 when some neighbours started to throw water at one another due to high temperatures during the Virgen del Carmen Festival. (Photo by Juan Medina/Reuters)

Among the fish populations that could be harmed by the Xayaburi dam in Laos is the critically endangered Mekong giant catfish, considered by the Guinness Book of World Records to be the world’s largest freshwater fish. The fish, which grows to 650 pounds and about 10 feet long, is only found in the Mekong River. It is migratory, moving between downstream habitats in Cambodia upstream to northern Thailand and Laos each year to spawn. Some experts fear the Xayaburi dam could block the migration and drive the giant catfish to extinction. (Photo by Courtesy of Zeb Hogan/University of Nevada, Reno)

This artist's scoreboard displays a fictional game between Mars and Earth, with Mars in the lead. It refers to the success rate of sending missions to Mars, both as orbiters and landers. Of the previous 39 missions targeted for Mars from around the world, 15 have been successes and 24 failures. For baseball fans, that's a batting average of .385. The United States has had 13 successes out of 18 attempts, or a “batting average” of .722. NASA's Curiosity rover, set to land on the Red Planet the evening of Aug. 5, 2012 PDT (morning of Aug. 6 EDT), will mark the United States' 19th attempt to tackle the challenge of Mars, and the world's 40th attempt. (Image by NASA/JPL-Caltech)

“I'm Josh Fancher, a 21 year old with an avid interest in photography, including macro, nature and wildlife, night photography, landscapes, cityscapes and architectural photography. Inspired by the beautiful and amazing water drop photography of Martin Waugh, I started doing water drop collisions in December of 2007. I use a 105mm Micro Nikkor lens for water drops, along with a pair of Nikon SB 600 flashes. I recently got a StopShot system (Nov 2009), which makes timing a lot easier. Before then, timing was manual, with an eye dropper, eye-hand coordination, and a lot of patience” – Josh Fancher. (Photo by Josh Fancher)

A woman at Foyles bookshop looks at a copy of J. K. Rowling's latest novel “The Casual Vacancy” which has gone on sale today starting at 8:00 am on September 27, 2012 in London, England. “The Casual Vacancy” is J. K. Rowling's first book aimed at an adult readership and is centered on a parish council election in a small West Country town. (Photo by Oli Scarf)