Glaciers in the Alps of Europe pose a scientific mystery. They started melting rapidly back in the 1860s. In a span of about 50 years, some of the biggest glaciers had retreated more than half a mile.
But nobody could explain the glacier's rapid decline. Now, a new study from NASA's Jet Propulsion Laboratory uncovers a possible clue to why the glaciers melted before temperatures started rising: Soot from the Industrial Revolution could have heated up the ice.