Colorful Vesta
Tonight’s press conference at the American Geophysical Union conference focused on the latest results from Dawn, orbiting the giant asteroid Vesta. Or to put it as scientist Vishnu Reddy put it, “Vesta is the most colorful asteroid in the solar system.”
At least, in geological terms. To our human eye the asteroid wouldn’t be so spectacular. However, the false color images released by the scientists show the global geological diversity of Vesta. From the press release:
In images from Dawn’s framing camera, the colors reveal differences in the rock composition associated with material ejected by impacts and geologic processes, such as slumping, that have modified the asteroid’s surface. Images from the visible and infrared mapping spectrometer reveal that the surface materials contain the iron-bearing mineral pyroxene and are a mixture of rapidly cooled surface rocks and a deeper layer that cooled more slowly. The relative amounts of the different materials mimic the topographic variations derived from stereo camera images, indicating a layered structure that has been excavated by impacts. The rugged surface of Vesta is prone to slumping of debris on steep slopes.
The data suggests that Vesta is divided into three regions.
- The south pole, which is an impact basin. This area is lightly cratered.
- The equatorial region, moderately cratered.
- The northern region, with the most cratering. This region has not been completely imaged.
The south region was formed due to a large impact. The formation of the other two regions they think were related to additional large impacts at other and probably earlier times. “Vesta is completely beat up,” noted Reddy.
In addition, the scientists are beginning to study the strange dark material that seems to trail away from or across some impact craters. Though they do not yet understand what caused the dark streaks, the data does strongly suggest that they were not formed by volcanic activity. One theory is that the dark material is the remains of the object that impacted the asteroid.
The lack of volcanic activity was unexpected. Meteorites thought to come from Vesta had suggested melting or volcanism. Instead, the scientists now think that this evidence of melting was caused instead by the many impacts that have bombarded the asteroid.
“Vesta is clearly a transitional object between small asteroids and planets,” noted David Williams of Arizona State University. The asteroid is unique in that no other asteroid so far studied is as differentiated geologically as Vesta.
If you want, you can browse the images from this press conference here.
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