This is a first: a very small asteroid (or rock) has been discovered that is on course for an impact tonight in Sudan. This information is from various reports to posted to MPML (the Minor Planet Mailing List at groups.yahoo.com/group/mpml/). The impactor is only about 2 m across and will break up in the atmosphere, with no risk to those on the ground. (If something this size hit in the daytime, it would probably not be noticed, but at night it should put on quite show).
Alan Harris writes that this object, with the survey-assigned designation 8TA9D69, was discovered by the University of Arizona Mt. Lemmon survey and will almost certainly, tonight, become the first impacting bolide discovered before entry into the Earth's atmosphere. Steve Chesley (JPL) reports that atmospheric entry will occur on 2008 Oct 07 0246 UTC over northern Sudan.
Andrea Milani of the University of Pisa wrote the following: Today the object with the provisional designation 8TA9D69 was submitted to impact monitoring by using the normal software of the NEODyS system, by using the observations as reported by the MPC on the NEO Confirmation Page. Based on 26 optical observations from 2008/10/06.278 to 2008/10/06, the probability of impact is between 99.8% and 100%; in practice the impact can be considered sure and is for tonight. Our computation has already been confirmed independently by others, including the JPL NEO Program Office (with which we consult in all relevant cases of possible impact). The effect of this atmospheric impact will be the release, in either a single shot or maybe a sequence of explosions, of about 1 kiloton of energy. This means that the damage on the ground is expected to be zero. The location of these explosions is not easy to predict due to the atmospheric braking effects. The only concern is that they might be interpreted as something else, that is man-made explosions. Thus in this case, the earlier the public worldwide is aware that this is a natural phenomenon, which involves no risk, the better.
This is the first time an asteroid impact has been predicted, and it reflects the increasing capability of the Spaceguard Survey. There was one previous false alarm when, for a few hours around Christmas 2004, it appeared that an impact by a 30-m asteroid was possible, but this was ruled out by additional observations. The current case, however, seems much more solid.
David Morrison
