Japan landed a couple rovers on an asteroid… and that’s pretty cool. The Hayabusa 2 probe dropped off the two Minerva rovers on the asteroid named Ryugu, and they are sending back some great images.
Rovers are nothing new. They have landed and explored a number of locations throughout the solar system, but this is the first time they’ve been landed on an asteroid. Asteroids have hosted probes before. In 2001, the NEAR Shoemaker probe, launched by NASA, visited the asteroid Eros. After collecting a bunch of data, it set down on the surface, and continued collecting until it was shut down a couple weeks later. The predecessor to the Hayabusa 2 mission (aptly names Hayabusa), also landed on an asteroid (Itokawa). It had planned to land a Minerva rover, but after launching it, the rover never made the surface. After a couple of abortive attempts, the main probe did land, pick up some samples, and return them to Earth – an amazing feat.
Probe vs. Rover
So, what’s the difference between a probe an a rover? A probe may land and in some cases takes back off again. A rover… well, roves. It is an explorer that moves across the surface of whatever it is tasked with exploring. Mars has hosted a number of well-known rovers, as has our moon. Rover missions are also either planned or proposed to other moons, including Enceladus, Titan and Europa. So what’s the big deal about landing a rover on an asteroid?
One word: friction.
All the rovers we’ve landed have rolled around on a bunch of wheels gathering up their data. Pretty straight forward, really. But what allows the rovers to move is the friction between the wheels and the surface. Gravity enables that friction, and asteroids have almost no gravity. A wheeled rover on an asteroid would just spin its “tires” like a car stuck in Alabama mud. That’s why the Minerva rovers hop. The jump off the surface and land again to move around – and the gravity is so low, that they can take as long as 15 minutes to land!
Just getting to an asteroid is a big feat. But landing hopping rovers is pretty darned cool.