On big, big, big advantage here is that, unlike Mars for instance, robots on the Moon are literally 1.5 seconds away (3 seconds round-trip), as far as radio communications go. Remote-control in real-time isn't that hard. You'll have to go a little bit slow because of the 1.5-second delay in seeing what the robot sees, but it's perfectly manageable. The same just isn't true on Mars because it's around 5 minutes away (for a 10-minute round-trip).
This means you can send up big robots that have little to no intelligence or automation, and are not much more than giant R/C cars with webcams. Seriously, we could just launch regular heavy construction equipment (earthmovers, bulldozers, etc.) rigged with cameras and remote controls; the real problem is the power source, since all those things run on fossil-fuel-burning engines here. So the challenge is making versions of these things which are battery-powered and can somehow be recharged with solar power.
Oh yeah, I guess the other big difficulty is dealing with the Moon dust (regolith), which is notorious for getting in everything and fouling things up. But that shouldn't be that hard to deal with; our heavy equipment (and even things like cars) are already designed to handle harsh environments and dust. We'd probably need different elastomeric seals though since there's no atmosphere on the Moon.
Edit: fixed Earth-to-moon and Earth-to-Mars delay times
> robots on the Moon are literally 3 seconds away (6 seconds round-trip)
Moon's apogee (point of furthest distance from Earth) is 405,400km [1]. Speed of light is roughly 300,000km/s [2]. Robots on the Moon are 1.35 seconds away (2.7s round-trip). Even with equipment delays I can't see how you could arrive at 6 seconds round-trip.
> Mars [...] is a minimum of 15 minutes away.
Mars' aphelion (point of furthest distance from the Sun) is 1.67 AU [3][4]. Earth is about 1 AU from the Sun (by definition). Also, Sun is ~500 light-seconds away from Earth. Thus, at conjunction the distance from Earth to Mars is not more than 0.7 AU or 350 seconds (5.8 minutes).
This means you can send up big robots that have little to no intelligence or automation, and are not much more than giant R/C cars with webcams. Seriously, we could just launch regular heavy construction equipment (earthmovers, bulldozers, etc.) rigged with cameras and remote controls; the real problem is the power source, since all those things run on fossil-fuel-burning engines here. So the challenge is making versions of these things which are battery-powered and can somehow be recharged with solar power.
Oh yeah, I guess the other big difficulty is dealing with the Moon dust (regolith), which is notorious for getting in everything and fouling things up. But that shouldn't be that hard to deal with; our heavy equipment (and even things like cars) are already designed to handle harsh environments and dust. We'd probably need different elastomeric seals though since there's no atmosphere on the Moon.
Edit: fixed Earth-to-moon and Earth-to-Mars delay times