Last month the Chinese spacecraft Chang’e-2 (named after the Chinese moon goddess) had a very close encounter with asteroid Toutatis and was able to snap a few beautiful pictures. So what, you might say. It’s a space rock. What gives?
True, many asteroids fall into the “seen one, seen them all” category – Toutatis is pretty much one of those. An elongated potato-shaped rock about 3 miles long, slowly tumbling along its main axis – lots of asteroids we’ve got pictures of are like that. But what’s special about this encounter ?
First off, Chang’e-2’s primary mission was to explore and map the Moon. It did its duty, faithfully zipping around Earth’s companion, and once it was done the engineers sent it to a Lagrange point, a gravity-stable point in space where Earth’s and the Sun’s gravity are in exact balance. After hanging out there for some time, the engineers got the car-sized craft moving again so it was poised for a close up view of Toutatis as it zipped by.
We usually think of asteroids as slow-moving tumbling rocks in space – we’ve certainly seen plenty of them in every space-based science fiction show, along with plenty of popular science television features. The reality is quite different. Asteroids – like most space object, hurtle along at crazy speeds — for Toutatis that’s about 7 miles per second. That’s fast! And if you, the observer, also move (most likely also at a speed that would make the average speed trap go up in a sad puff of smoke), the asteroid appears to move even faster. For Chang’e-2, it meant that Toutatis was screaming by at a blistering 24,000 miles per hour.
Try to take a pictures of something that’s going that fast! And Toutatis was a paltry 2 miles away when it crossed Chang’e-2’s path. So you see, there’s some awesome engineering and science and technology involved to even get one single snapshot.