A new study of images from NASA's Dawn mission examines remarkable, dark-as-coal material that speckles the surface of the giant asteroid Vesta. Scientists are using the images, taken by Dawn's framing camera, to understand the impact environment early in Vesta's evolution.

In the most comprehensive analysis of the dark material to date, Dawn scientists describe how this carbon-rich material tends to appear around the edges of two giant impact basins in Vesta's southern hemisphere.

The analysis suggests that the dark material was most likely delivered by the object that created the older of the two basins, known as Veneneia, about 2 to 3 billion years ago. Some of those materials were later covered up by the impact that created the younger basin, Rheasilvia.

The Dawn spacecraft orbited Vesta for more than a year, departing in September 2012. Dawn is now on its way to the dwarf planet Ceres, and will arrive in early 2015.

The paper, published in the November-December issue of the journal Icarus, was led by Vishnu Reddy of the Max Planck Institute for Solar System Research, Katlenburg-Lindau, Germany, and the University of North Dakota, Grand Forks.