I think the real breakthrough on some of these probes to other planets isn't so much how they move around, but the growing possibility of self-directed action. Mars is between 3 light minutes and 22 light minutes away. Every command takes at least that long to reach a probe on Mars, then the same amount of time for NASA to be told "Yes, I heard you and did that".

The Curiosity rover has been on Mars for 6 years. It can travel 90m/hour. Theoretically, it could have moved 3,400km by now- that's more than once around the equator of Mars. It's managed almost 20km. While I'm sure there was much to pause and study, I cannot fathom that it could not have done more in it's time were it not constantly waiting for commands.

Saturn is, at closest approach, more than 1 light hour away.

I feel as though there's a real need to put a generic computer system that can be reprogrammed after launch into orbit around whatever planet we're studying. Give it higher-level commands of what we want to see happen, and send us back the highlight reel.