What is the fastest rover currently moving on the surface of another celestial body? At what speed with our technology currently does physics restrict our speed limits on the surfaces of solar system bodies?
The manned Apollo Lunar Roving Vehicle from Apollo 17 holds the record of 17km/h achieved by Eugene Cernan. Apollo Lunar Roving Vehicle was also present on Apollo 15 and 16.
For traditionally understood rovers - unmanned mobile landers, the fastest historically would be Lunokhod 1 and 2, capable of 2km/h.
At current time only two rovers are still active and operational: Curiosity: 0.14 km/h and Opportunity: 0.18 km/h.
Let's add for the record: Yutu: 0.2 km/h, Spirit, same as Opportunity: 0.18 km/h, Sojourner: 0.024 km/h. I believe this is the complete list of rovers that actually drove over the surface of remote celestial bodies to date.
The highest speed was recorded by an Apollo Lunar Roving Vehicle:
The rovers were designed with a top speed of about 8 mph (13 km/h), although Eugene Cernan recorded a maximum speed of 11.2 mph (18.0 km/h), giving him the (unofficial) lunar land-speed record.
Unmanned rovers have much lower top speeds. Their speed is limited by the amount of terrain they can see and by the amount of autonomy they have. Curiosity has 3 driving modes:
- fully programmed (using one sol's images to plan driving for the next sol in detail). This is the fastest mode.
- partly programmed
- autonomous, with image analysis (finding the safest route, checking for slope angles and obstacles) happening onboard. This is limited by onboard computer power, and is the slowest driving mode.
"Curiosity takes several sets of stereo pairs of images, and the rover's computer processes that information to map any geometric hazard or rough terrain," said Mark Maimone, rover mobility engineer and rover driver at NASA's Jet Propulsion Laboratory, Pasadena, Calif. "The rover considers all the paths it could take to get to the designated endpoint for the drive and chooses the best one."
Curiosity's top speed is 137 meters/h (0.085 mph).
To answer the second half of the question: rover speeds are primarily limited by practicality, rather than the physics or technology needed to drive on an extraterrestrial surface. As Elon Musk demonstrated, it's physically possible to send a very fast land vehicle out of Earth's gravity well. If you wanted to waste a lot of money, you could put a 200 kmh rover on another world. However, no scientific agency does this, because space launches are expensive and mass-limited. Every gram you use for motors, wheels, or suspension is a gram that you can't use for experiments or communications. No luxury seats with Corinthian leather either.
The Mars rovers have extraordinarily light weight wheels, and just enough motor to traverse the difficult terrain (with appropriate safety margins). High speed is neither necessary nor particularly desirable.