In this May 4, 2014 photo, a miner holds an amalgam of mercury and gold he mined after working a 28-hour shift at an illegal gold mining process, in La Pampa, in Peru's Madre de Dios region. Thousands of artisanal gold miners sweat through the long shifts and endure, for a few grams of gold, the perils of collapsing earth, limb-crushing machinery and the toxic mercury used to bind gold flecks. (Photo by Rodrigo Abd/AP Photo)

Expedition 44 flight engineer and NASA astronaut Scott Kelly seen inside the Cupola, a special module which provides a 360-degree viewing of the Earth and the International Space Station. Kelly is one of two crew members spending an entire year in space. (Photo by Scott Kelly/NASA)

A man exercises in the early morning on a hilltop overlooking Kabul, Afghanistan March 3, 2016. (Photo by Mohammad Ismail/Reuters)

Lightning strikes during a storm over the Ionian Sea in Calabria, Italy on June 27, 2016. (Photo by Alfonso Di Vincenzo/Pacific Press/Rex Features)

The northern lights, or aurora borealis, appear in the sky over the Bamburgh lighthouse at Stag Rock in Northumberland, England on September 28, 2016. (Photo by Owen Humphreys/PA Wire via ZUMA Press)

In this September 17, 2010 file photo a little brown bat is photographed in La Crosse Wis. Researchers for the first time found that little brown bats appear to be showing resistance to white-nose syndrome, which has killed millions of bats across North America. (Photo by Peter Thomson/La Crosse Tribune via AP Photo)

A Kenya Wildlife Services (KWS) veterinarian and security personnel back away from a tranquilised black-Rhino calf August 30, 2017 after she appeared to prematurely overcome the sedative at the Nairobi National Park, during an identification-tagging excercise to ease quick identification of resident rhino during anti-poaching patrols. (Photo by Tony Karumba/AFP Photo)

Mercury and Maia, fueled and overhauled, are waiting in the Tay at Dundee, for favorable weather to start the flight to the Cape, a distance of 6,370 miles. The composite machine moored in the Tay River, at Dundee, on September 23, 1938. (Photo by AP Photo)