Lutetia up close and personal
On July 10, 2010, the European Space Agency probe Rosetta passed just 3162 km (1960 miles) from the asteroid Lutetia, a lumpy rock 130 km (81 miles) end-to-end.
This image, taken at closest approach, shows how battered and worn Lutetia is. Craters pockmark the surface, including several that are many kilometers across. Like the Martian moon Phobos, grooves line the surface, which may be from boulders rolling around, perhaps ejected from some of the craters when they were formed. They may alternatively be stress fractures from impacts; there is still a lively debate over what causes these features in small bodies.
Much of the surface appears smooth, indicating great age for this object. Over billions of years it's been assaulted by dust grains moving at incredible speeds, as well as the solar wind. This has essentially sandblasted the surface, taking - literally - the edge off of the rims of craters.
We have very few high-resolution images of asteroids, and the more we get, the more we learn about them. Given that every now and again we get hit by them, I'm a big fan of understanding them better.
Credit: ESA 2010 MPS for OSIRIS Team. MPS/UPD/LAM/IAA/RSSD/INTA/UPM/DASP/IDA