Yes, I really enjoyed that picture of Terra and Luna together in the same frame, au naturel. Gives you a direct feel of the scale of distance between them. (I wonder which continent of Earth is in view? Can anyone tell?)
Here's also a cool picture of a Rainbow on Mars, taken by the Opportunity rover:
This is a result of water droplets in the air, just like here on Earth.
Regarding understanding Mars, I think that we should use our constantly increasing supercomputing power to then model the weather on Mars in greater detail. The orbiters and planetside probes are generating large streams of data, and these could then be usefully plugged into a climate simulation on a supercomputer. Then we could explore terraforming ideas, to see how they might play out.