Last July, the spacecraft Dawn slipped into orbit around Vesta, one of the largest asteroids in the solar system -- the first time a probe had ever orbited a main-belt asteroid. From its height of 16,000 km (almost 10,000 miles), it started mapping the 500 km (300 mile) wide rock, returning the first close-up pictures in amazing detail.
Over time, the height of the spacecraft over the surface was lowered, and it has now attained its lowest altitude orbit: a mere 200 km (120 miles) over the asteroid's cratered, battered terrain. I mean asteroidain. Whatever. Anyway, it's now sending back higher-resolution images than ever before, including this very cool one:
[Click to asteroidenate.]
This shows a region of Vesta about 18 km (11 miles) on a side, dominated by a ginormous impact crater. You can see how the crater's central floor is flat, and you get just a hint of a slightly raised rim around the edge of the crater. The shadow of the rim falling into the crater also suggests variations in the elevation of the rim top (though craters in the floor of the big crater distort the shadow's edge a little too). I like all the small craters inside the big one; they come in a variety of shapes, some deep, some shallow, and one (near the rim at the bottom of the picture) appears to be sliced in half; I suspect material flowing down the crater wall in a landslide half buried it. Light colored streaks pointing down the crater wall indicate slides do occur. Triggered by other impacts, maybe?
We'll be seeing lots of amazing images and science coming from this spacecraft over the next few months. Be sure to check the mission's Image of the Day pages to stay on top of what we're seeing on Vesta... but be quick, because time's running out. In May, Dawn will leave Vesta and start a new journey for a new target: the largest asteroid in the solar system, Ceres. It arrives there in 2015.
Image credit: NASA/ JPL-Caltech/ UCLA/ MPS/ DLR/ IDA