[tortoise]

These odds estimates are based on a Monte Carlo probabilities, where several variables are each part of the matrix.

Its a little more complicated than that, but roughly true. They have not been able to nail down some of the parameters that would allow them to get at some extremely precise orbital elements. They'll be hovering around 1:43 until they get some better sensors looking at it; right now, that represents the margin of error for the models based on a lack of important parameters e.g. the rotational period and axis relative to the sun. It isn't as though they can't produce exceedingly precise orbital predictions but that they do not trust some of the data they have so far. Some of the unofficial analyses on the same data that tries to adjust for dubious data or bad calibration and giving missing parametric data "statistically representative" values is putting impact probability at closer to 1:20. But we still need better data, which will require the asteroid to be visible in the northern hemisphere to a significant extent, something which will happen in a bit. Right now, the rock is hovering around the South Pole.

[lwoodham]

I have been thinking about this. I agree that Monte Carlo analysis is surely being done on this. That means they know minimum(0 in case of a strike) and maximum distances of passage based on 1 in 43 odds. I have been trying to figure out if the maximum passage distance includes the moon within the possible strike cone. I realize that much more data will be required to know where the moon will be in orbit at that point in time. The rock hitting the moon would not probably cause any appreciable orbit change since the moon's mass is much greater, but would provide some incredible chances for science and the greatest light show of all time.