A tribesman loyal to the Houthi movement carries his rifle as he leaves a gathering held to show support for the group, in Yemen's capital Sanaa December 15, 2015. (Photo by Khaled Abdullah/Reuters)

An army soldier takes a tree branch from an anti-government protester who is blocking a major highway that links the capital Beirut to northern Lebanon, in the town of Nahr el-Kalb, north of Beirut, Lebanon, Friday, January 3, 2020. Lebanon is facing its worst economic crisis in decades, while protests against corruption and mismanagement have gripped the country since October. (AP Photo/Hussein Malla)

“Winter Climbing from inside Ben Nevis”. The view from inside the mountain, as a winter climber passes through the cave on Minus Three gully. Photo location: Ben Nevis, Fort William, Scotland. (Photo and caption by Daniel Wildey/National Geographic Photo Contest)

“NASA's Mars rover Opportunity just celebrated its ninth anniversary on Mars – a mission that was originally meant to last just 90 days...” – The Atlantic. Photo: NASA's rover Opportunity visits Victoria Crater, viewed from orbit by the High Resolution Imaging Science Experiment on NASA's Mars Reconnaissance Orbiter in october of 2006. Opportunity is a small dot on the crater's lip, at top right. Opportunity first reached the crater's rim on September 27, 2006. (Photo by NASA/JPL-Caltech/University of Arizona via The Atlantic)

A robin perches on a spade handle in a garden on a rainy day in Lixwm, north Wales. Researchers said this week that when European robins are subjected to human-produced noise, their behaviour changes. (Photo by DGDImages/Alamy Live News)

A cat walks past a Soyuz space ship installed at a museum, at the Russian leased Baikonur cosmodrome, Kazakhstan, Tuesday, November 15, 2016. The start of the new Soyuz mission to the International Space Station (ISS) is scheduled on early Friday, Nov. 18 local time. The Russian rocket will carry French astronaut Thomas Pesquet, Russian cosmonaut Oleg Novitsky and U.S. astronaut Peggy Annette Whitson. (Photo by Dmitri Lovetsky/AP Photo)

A cat sits in the flooding waters from Hurricane Matthew in downtown Nichols, South Carolina, October 10, 2016. (Photo by Randall Hill/Reuters)