Asteroid ( 596 ) Scheila was the first object for which the immediate aftermath of an inter-asteroidal collision was observed .
In Dec. 2010 , the 113 km-sized asteroid was impacted by a smaller asteroid of less than 100 m in diameter .
The scale of the impactor was established by observations of fading ejecta plumes .
Comparison of the light curves obtained before and after the impact allowed us to assess how much of Scheila ’ s surface was altered .
Cratering physics based on the impactor size suggests that the size of the affected area is larger than expected , ( effective radii of 3.5 – 10 km depending on the change in the albedo of the surface ) .
Similar but more localized albedo changes have been observed on Vesta and the Martian moons , but are not understood .
Empirical laws describing ejecta blankets however indicate that at distances between 3.5 – 10 km from the crater , Scheila ’ s surface would be covered by a thin layer 2 mm to 2 cm thick .
This dusting , possibly mixed with bright impactor material may be enough to explain to observed brightness increase .
Our results show that sub-critical impacts may play a significant role in processing the surfaces of asteroids .
The large effect of small impacts on asteroidal light curves complicate shape modeling .