Mars Impact?

NASA Watch reports on an asteroid that may impact Mars. I mention this here because, although I'm fond of space access prizes, one of my favorite ideas for a prize - one that seems to me to fit very nicely with the advantages of prizes over other ways of getting things done, and one that perhaps doesn't even need to be in the millions of dollars to work - is a prize for detecting natural objects that will impact the Earth. I described this idea in one of my earliest posts (announcing the Planetary Society Apophis Mission Design Competition). One of the questions I asked about how the rules for such a prize should be designed was:

Would there be a bonus for detecting small impacts, or impacts to other solar system bodies, in advance so the impact can be monitored by scientific instruments?

At any rate, the (currently 4% with the data available) chance that we could see a decent-sized impact at Mars makes the Apophis competition all the more interesting.