Riot security forces clash with demonstrators as a motorcycle is set on fire during a protest against Venezuelan President Nicolas Maduro's government in San Cristobal, Venezuela May 29, 2017. (Photo by Carlos Eduardo Ramirez/Reuters)

Indian Runner ducks march past farm buildings at the Vergenoegd wine estate near Cape Town, South Africa, May 16, 2016. Each day, a quack squad of killer ducks are released for the first of two sorties at South Africa's Vergenoegd wine farm in Stellenbosch. Their mission – seek and destroy thousands of pests out to ruin the season's harvest. Fanning out across the vineyards, some 1,000 Indian Runner ducks hone in on their hidden targets with uncanny precision, locating the tiny white dune snails feasting on budding vines. (Photo by Mike Hutchings/Reuters)

A police officer has weapons blessed by a Hindu priest during the Vishwakarma Puja festival in the outskirts of Agartala, India, September 17, 2016. (Photo by Jayanta Dey/Reuters)

“The Mikoyan MiG-31 (NATO reporting name: Foxhound) is a supersonic interceptor aircraft developed to replace the MiG-25 “Foxbat”. The MiG-31 was designed by the Mikoyan design bureau based on the MiG-25”. – Wikipedia

Photos: The Mikoyan MiG-31 “Foxhound”. Russia, April 2012. (Photo by Alexandr Pak; Source: LiveJournal)

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)

Thousands of species of amphibians are endangered and hundreds have already disappeared, but in recent years, a team of scientists and conservationists have re-discovered some of these “lost” species and uncovered previously unknown varieties. Here: Miniature glass frog. (Photo by Robin Moore)

People are seen on a street in Havana December 17, 2014. Stunned Cubans celebrated an apparent end to decades of conflict with the United States on Wednesday after both governments said they would restore diplomatic relations cut off in 1961. Many said they expected a restoration of ties would lead to the end of a U.S. economic embargo against Cuba, which is vilified daily in the official media and which Cubans accept as a key cause of widespread poverty on the island. (Photo by Reuters/Stringer)

A man stands next to a barricade blocking a road during a protest calling on the government to help ease the economic effects of an harmful algal bloom that had affected their livelihoods at Chiloe island in Chile, May 6, 2016. (Photo by Pablo Sanhueza/Reuters)