Day 1,464 of the Mars rovers' 90-day mission to Mars (for those of you keeping track), and Steve Squires, the head of science operations for the Spirit and Opportunity rovers is getting us up to date on their latest findings. Most important: serendipity in action. The Spirit rover's right front wheel has broken, so engineers turn the rover around, drive it in reverse, and drag the wheel behind the rover. As it slogs across the planet, it carves a trench. And my, what a trench it carves.