Frankly, if a robot had returned lunar samples at random, it would be almost equivalent to the Apollo programme return - precisely because impact gardening has randomly stirred the Moon's surface.

Add a filter to return a range of colours of rock, and you'd have everything we have now in the collections.

of course, it wouldn't have stirred the spirit the same way that I experienced in my teen years, but maybe we can derive similar levels of vicarious satisfaction from Robot missions. After all - how many of US got to visit the moon? (But it's still eerie sitting across a table from John Young, or another of the Moon Walkers...)

For Mars, I think we'll need something smarter - it does actually have geology. trouble is, it's so different to Earth geology, we gotta be careful not to teach our astronauts TOO much about how our Earth works. Sometimes, random collection or deliberately-variable sampling is a good way to find out things you DIDN'T already know...