Speaking of solar energy, just thought of a perfect place to use an autonomous vehicle powered by solar panels... on the moon! It would only need to travel at 10 mph to stay in perpetual sunlight. The advantage of being in constant sunlight is, that it could be on a continuous circumnavigation without losing power... ever! It could explore almost every square mile of the moon, excluding deep craters, and the closer it approached the poles the slower it would have to travel to stay in constant sunlight. It could explore the back side of the moon, which contrary to a famous old song, it isn't always dark.

It wouldn't need heavy batteries.

I just witnessed another impressive use of solar energy. It was a beautiful morning to view the solar powered International Space Station flying overhead. Although it dimmed and dissapeard as it approached sunrise, it was very bright for most of its 5 minute viewing time after it popped up in the western sky.