Dodged a bullet...
This appears to be good news. The illustration represents, the 'Updated Set of Possible Positions of 2004 MN4 on April 13, 2029'. A letter on Jerry's Pournelle's site asks a very interesting question.
"Predictions are that it's going to miss us by about 25,000 to 50,000 miles with a relative velocity of about 4 miles per second with a mass estimate of about 100,000,000 tons (9.4e+10 Kg). With 25 years to prepare the least we could do is land a probe or two on it, but what would it take to deflect it into either an Earth or a Lunar orbit?"
|Possibility of an Earth Impact in 2029 Ruled Out for Asteroid 2004 MN4
Don Yeomans, Steve Chesley and Paul Chodas
NASA's Near Earth Object Program Office
December 27, 2004
Over the past week, several independent efforts were made to search for pre-discovery observations of 2004 MN4. These efforts proved successful today when Jeff Larsen and Anne Descour of the Spacewatch Observatory near Tucson, Arizona, were able to detect and measure very faint images of asteroid 2004 MN4 on archival images dating to 15 March 2004. These observations extended the observed time interval for this asteroid by three months allowing an improvement in its orbit so that an Earth impact on 13 April 2029 can now be ruled out.
As is often the case, the possibility of future Earth impacts for some near-Earth objects cannot be entirely ruled out until the uncertainties associated with their trajectories are reduced as a result of either future position observations, or in this case, heretofore unrecognized, pre-discovery observations. When these additional observations were used to update the orbit of 2004 MN4, the uncertainties associated with this object's future positions in space were reduced to such an extent that none of the object's possible trajectories can impact the Earth (or Moon) in 2029.
In the accompanying diagram, the most likely position of asteroid 2004 MN4 is shown at the end of the blue line near the Earth on 13 April 2029. However, since the asteroid's position in space is not perfectly known at that time, the white dots at right angles to the blue line are possible alternate positions of the asteroid. Neither the nominal position of the asteroid, nor any of its possible alternative positions, touches the Earth, indicating that an Earth impact in 2029 is ruled out.
NASA JPL: Possibility of an Earth Impact in 2029 Ruled Out for Asteroid 2004 MN4