“Aurora Hunters”. Photographers taking part in a photography tour on the Lofoten Islands in Norway, pull over on the side of the road to take a photo of their first ever Aurora Borealis after spotting it from their tour bus. Photo location: Rystad, Lofoten Islands, Norway. (Photo and caption by Mark Gee/National Geographic Photo Contest)

Cars float up from a car garage in a mixture of storm water and gasoline in lower Manhattan as workers begin the process of pumping out the mess. (Photo by Carolyn Cole/Los Angeles Times/MCT)

A lunar eclipse appears behind a gargoyle atop the old red Dallas County Courthouse early Wednesday morning, October 8, 2014. The moon appears orange or red, the result of sunlight scattering off Earth's atmosphere. This is known as the blood moon. (Photo by Tom Fox/AP Photo/The Dallas Morning News)

A visitor walks on a giant chalk artwork called “Wasting Time” at the Chalk Urban Arts Festival in Sydney on October 25, 2014. The picture is the biggest 3-D artwork created in Australia by two artists, Leon Keer from Holland and Jenny McCracken from Australia. (Photo by Peter Parks/AFP Photo)

Yana Shcherban of Russia looks at the ball after failing to receive it during their FIVB Women's Volleyball World Grand Prix 2014 final round against Japan in Tokyo August 20, 2014. (Photo by Yuya Shino/Reuters)

The photography of Art Wolfe covers the globe, capturing landscapes, wildlife, and cultures from every continent; here he talks through a selection of his favourite images. Art Wolfe is an American photographer and conservationist. His photographs have been noted by environmental advocacy groups for their “stunning” visual impact. Here: Snowy owlets (Bubo scandiacus), Arctic National Wildlife Refuge, Alaska, USA. (Photo by Art Wolfe/Art Wolfe Stock)

Iraqi paramilitary troops fire towards Islamic State militants during a battle with Islamic State militants on the outskirts of the ancient city of Hatra near Mosul,Iraq April 26, 2017. (Photo by Reuters/Stringer)

A street vendor spreads vermilion powder used for worship during the Tihar festival, also called Diwali in Kathmandu, Nepal, November 9, 2015. Hindus all over Nepal are celebrating the Tihar festival during which they worship cows, which are considered a maternal figure, and other animals. Also known as the festival of lights, devotees also worship the goddess of wealth Laxmi by illuminating and decorating their homes using garlands, oil lamps, candles and colourful light bulbs. (Photo by Navesh Chitrakar/Reuters)