NASA’s Dawn spacecraft has reached its high-altitude mapping orbit at 680km above the surface of asteroid Vesta and is producing extensive images. This false-colour map of the south pole of the body was created with stereo images from Dawn’s framing camera to give images with a horizontal resolution of about 750m/pixel.
In this image, the major circular structure is about 500km across, with about 15km relief between the interior and rim of the structure, possibly an impact basin.
These first results from Dawn’s visit to Vesta are already showing a striking variety of surface compositions, notably around craters, and a pattern of equatorial troughs running round the body, possibly formed as part of a giant impact.
The surface seems rougher than most asteroids, and preliminary dating suggests that parts of the southern hemisphere surface are younger than the northern hemisphere surface. If a giant impact played a part in shaping Vesta’s surface, the huge ring structure around the south pole may be especially significant.