NASA announced today that data from its Dawn probe show the giant asteroid Vesta is constantly "stirring" its surface, presenting a "young" appearance. The type of weathering that occurs on airless bodies, such as the moon, does not alter Vesta's surface in the same way.
Specifically, objects such as asteroids and the moon accumulate tiny metallic particles containing iron, which dulls their "fluffy" outer layer. Researchers using data from Dawn's visible and infrared mapping spectrometer (VIR) found no accumulation of the particles on Vesta.
"Getting up close and familiar with Vesta has reset our thinking about the character of the uppermost soils of airless bodies," said Carle Pieters, lead author of one of two Vesta studies published today in the journal Nature and a Dawn team member at Brown University. "Vesta 'dirt' is very clean, well mixed and highly mobile."
When Vesta was first photographed, researchers were puzzled by its light and dark splotches. The brightness range on the asteroid is among the largest observed on rocky bodies in the solar system.
NASA stated that "bright rays" of young features on Vesta degrade rapidly into the background soil, mixed by continual small impacts. Also, Vesta's unusually steep topography means landslides mix the surface as well.
The dark spots, which were originally thought to be the result of volcanic activity or high-speed impacts, have now been shown to be carbon-rich material from meteoroids. Researchers estimate, based on the amount of darkening, that around 300 asteroids with diameters between 0.6 to 6 miles likely hit Vesta in the past 3.5 billion years.
"This perpetual contamination of Vesta with material native to elsewhere in the solar system is a dramatic example of an apparently common process that changes many solar system objects," said Tom McCord, lead author of the other study and a Dawn team member at Bear Fight Institute. "Earth likely got the ingredients for life - organics and water - this way."
NASA's Dawn probe was launched in September 2007 and entered orbit around Vesta in July 2011. Dawn left its orbit around Vesta last month and is currently on course for the dwarf planet Ceres.