Christopher JoyceChristopher Joyce is a correspondent on the science desk at NPR. His stories can be heard on all of NPR's news programs, including NPR's Morning Edition, All Things Considered, and Weekend Edition.
The Panel of Hands in the Cave of El Castillo in Spain. New dating methods suggest the paintings could have been drawn by Neanderthals, not humans, as previously thought.
Pete Vavricka conducts an underground train from the entrance of Yucca Mountain in Nevada in 2006. President Obama canceled the planned nuclear waste repository there in 2009.
Demand for natural gas has created a hydraulic fracturing or fracking boom; since 2008 over 5,000 new wells have been drilled nationwide. Workers at Chesapeake Energy, one of the biggest gas companies conducting fracking, are seen on the job site near Towanda, PA.
Conservator Angelyn Bass cleans and stabilizes the surface of a wall of a Mayan house that dates to the ninth century. The figure of a man who may have been the town scribe appears on the wall to her left.
Tyrone Turner/Copyright 2012 National Geographic
Researchers say our brains are probably wired from an evolutionary sense to encourage running and high aerobic activities. Above, a man runs past the Sydney Harbour Bridge on April 22.
Ryan Pierse/Getty Images
A wobbling of the Earth on its axis about 20,000 years ago may have kicked off a beginning to the end of the last ice age. Glaciers in the Arctic and Greenland began to melt, which resulted in a warming of the Earth, a new study says. Above, Greenland's Russell Glacier, seen in 1990.
Veronique Durruty/Gamma-Rapho/Getty Images
This NASA map shows the size of aerosol particles in the atmosphere. Green areas indicate larger, more naturally occurring particles like dust. Red areas indicate smaller aerosol particles, which can come from fossil fuels and fires. Yellow areas indicate a mix of large and small particles.
NASA Earth Observations