NASA's Dawn spacecraft has revealed the giant asteroid Vesta has its own version of ring around the collar. Two new papers, based on observations from the low-altitude mapping orbit of the Dawn mission, show volatile, or easily evaporated, materials have colored Vesta's surface in a broad swath around its equator.
With large swaths of oceans, rivers that snake for hundreds of miles, and behemoth glaciers near the north and south poles, Earth doesn't seem to have a water shortage. And yet, less than one percent of our planet's mass is locked up in water, and even that may have been delivered by comets and asteroids after Earth's initial formation.
Scientists have long believed that comets and a type of very primitive meteorite called carbonaceous chondrites were the sources of early Earth's volatile elements -- which include hydrogen, nitrogen, and carbon -- and possibly organic material, too. Understanding where these volatiles came from is crucial for determining the origins of both water and life on the planet.