Given the power loss (dust, battery aging, that little heater that's stuck on), we're already down to 650Wh per day instead of 900. I don't know it could make it >10km, that'd be 20x the warranty! Of course the Viking lander kept running for five years(!), but that was nuclear powered.

If we could go that far, another option would be the terrain to the S/SW that gets different and brighter.

Where we REALLY need a 3km crater is at Gusev. I'm skeptical that we'll see anything but basalt flows at Bonneville. Unfortunately, that finding doesn't shut the door on the lake hypothesis; you can just assume the sediments are under a few hundred meters of lava. It'd be a shame to spend $400M and not have answered the question but we're headed that way. Maybe Gusev was a target that should have waited for pinpont landing systems so that we could put down with in reach of features that would have been more conclusive.