Germany plans to take all of its nuclear power plants offline by 2022, which means coal-fired power plants like the Kraftwerk Westfalen, in Hamm, Germany, will be a key component of the country's energy infrastructure. Lars Baron/Getty Images hide caption

itoggle caption Lars Baron/Getty Images

In this undated picture, Mount Everest, the world's tallest mountain at 29,029 feet, stands behind the Khumbu Glacier, one of the longest glaciers in the world. Nepal has more than 2,300 glacial lakes, and experts say at least 20 are in danger of bursting. Subel Bhandari/AFP/Getty Images hide caption

itoggle caption Subel Bhandari/AFP/Getty Images

A robotic arm breaks off a chunk of mineral-rich rock deep underwater. Nautilus Minerals of Australia hopes to develop and expand undersea mining by extracting copper, gold, silver and zinc from the seafloor. Nautilus Minerals hide caption

itoggle caption Nautilus Minerals

Researchers have analyzed the fossil imprints of of raindrops, like the ones shown here, to study the atmosphere of the Earth, as it was 2.7 billion years ago. The rule at the top is 5 centimeters, or about 2 inches, long. W. Alterman/University of Pretoria hide caption

itoggle caption W. Alterman/University of Pretoria

A drilling rig sits on Oooguruk Island off the coast of Alaska's North Slope. The 6-acre island was built by Pioneer Natural Resources so it could drill for oil on the Arctic Ocean. Steve Quinn/AP hide caption

itoggle caption Steve Quinn/AP

F. Sherwood Rowland, pictured here in 1989, was one of three chemists who shared the 1995 Nobel Prize for chemistry for work on discovering chemicals that deplete the Earth's ozone layer. University of California/AP hide caption

itoggle caption University of California/AP

Last year's earthquake and tsunami crippled the Fukushima Dai-ichi nuclear power station. Foreign journalists saw cleanup and recovery work in process on Feb. 28. Yoshikazu Tsuno/AFP/Getty Images hide caption

itoggle caption Yoshikazu Tsuno/AFP/Getty Images

A worker is given a radiation screening as he enters the emergency operation center at Tokyo Electric Power Co.'s tsunami-crippled Fukushima Dai-ichi nuclear power plant on Feb. 20. AFP/Getty Images hide caption

itoggle caption AFP/Getty Images

From left, enginers Eric Nicosia, Amin Ahmadi and Gavin Boogs work to solve an issue with part of a wind turbine at the Gamesa Corp. factory in Langhorne, Pa., on Feb. 10. Maggie Starbard/NPR hide caption

itoggle caption Maggie Starbard/NPR

This map shows what the Earth's landmass looked like in the Precambrian Era, about 738 million years ago. Chris Scotese/University of Texas at Arlington hide caption

itoggle caption Chris Scotese/University of Texas at Arlington

Natural gas is much cleaner than coal. But some energy analysts say an overabundance of the fuel could depress development in even cleaner energy sources like wind and solar power. Above, a rig in Washington, Pa., drills into shale rock to extract natural gas. Keith Srakocic/AP hide caption

itoggle caption Keith Srakocic/AP