THanks for that link, Nick, that was a very thought-provoking piece, and a great thing for students.

Of course, it is easy to see how "obvious" plate tectonics would be from space-based reconnaisance, given that we're already familiar with the theory. How long would it take Martian geologists to come up with it?

It's possible that there is a grand and elegant model for Venus, for example, that could be inferred from our current data but which we just haven't been clever enough to figure out yet. I'm not sure that's the case; Venus may just be messier. It certainly looks less strongly ordered than global-scale features on the Earth, or maybe we're just not attuned to the right sort of patterns....