The 26th annual National Geographic Traveler Photo Contest is now accepting submissions. Official categories include: “Travel Portraits”, “Outdoor Scenes”, “Sense of Place” and “Spontaneous Moments”. The contest is accepting entries until June 30. Photo: “Forest lights”. Aurora Borealis over the forest of the Pyhae Luosto National Park, Finland. (Photo and caption by Nicholas Roemmelt/National Geographic Traveler Photo Contest)

The land-robot “teleMAX” of German company telerob stands next to soldiers during a trial at the German army base on May 18, 2010 in Hammelburg, Germany. ELROB provides an overview of the current state of affairs in European unmanned system technology and to evaluate commercial off-the-shelf products for military use. It is to show what is feasible in robotics, to support technological developments in Europe, and to find solutions for the current military challenges. (Photo by Ralph Orlowski/Getty Images)

Pakistani female police commandos attend a training session in Nowshera, near Peshawar Pakistan, Wednesday, February 11, 2015. Authorities formed a Special Combat Unit after Taliban militants stormed a Peshawar school on Dec. 16, 2014 and massacred 150 children and teachers. (Photo by Mohammad Sajjad/AP Photo)

In this artist's impression supplied by the ESO (European Southern Observatory) on April 25, 2007, the planetary system around the red dwarf, Gliese 581, is pictured showing what astronomers believe is the most earth like planet found outside our solar system to date. Using the ESO 3.6-m telescope in Chile, astronomers have uncovered the planet which could have water running on its surface. The planet orbits the faint star Gliese 581, which is 20.5 light-years away in the constellation Libra. (Photo by ESO via Getty Images)

An Afghan National Army (ANA) soldier assigned to the Mobile Strike Force Kandak fires a RPG-7 rocket-propelled grenade launcher during a live-fire exercise supervised by the Marines with the Mobile Strike Force Advisor Team on Camp Shorabak, Helmand province, Afghanistan, May 20, 2013. The Marines with the Mobile Strike Force Advisor Team instructed and mentored their ANA counterparts on how to properly utilize their weapons systems. (Photo by SSgt Ezekiel R. Kitandwe/RCT 7)

From house breaking in Johannesburg to hippos on the loose in Tbilisi to rioters attacking a policewoman in Burundi, Reuters photographers tell the story behind some of the most iconic pictures of the year. Here: Protesters drag a female police officer accused of shooting a protester in the Buterere neighbourhood of Bujumbura, Burundi, May 12, 2015. Goran Tomasevic: Protesters started throwing stones at a group of police, who then started to run away. The policewoman in the photo, Medikintos Inabeza, 33, got left behind and then some protesters started to push her, saying that she had shot a female protestor in the stomach with an AK47 rifle. I didn't see anything of that. There were 5 or 10 protesters pushing the policewoman at first, then others came and joined in. Up to 20 or 30 protesters were surrounding her at one point. The protesters kicked and beat her very badly; I also saw a couple of knives. I thought they were going to kill her... (Photo by Goran Tomasevic/Reuters)

People slide down a 1,082 feet (330 metre) long inflatable water slide in Hong Kong, China August 22, 2015. (Photo by Tyrone Siu/Reuters)