Confusing Mars Impact Predictions

I see the interest and excitement about a potential impact on Mars in January.

I was wondering if anybody could explane the curiosities in the predictions of it and 2004 MN4 Apophis. For WD5, it will pass only 50,000 km from and Mars and is said to have a 1:75 chance of impacting and "closing that gap daily". Apophis will pass within 35,000km and has a remote 1:45,000 chance. Any speculation on the wide discrepencies in these predictions? I assume it might be because the orbit for WD5 is less precise than that of MN4?

Regards,
Kevin

One estimate is based on Mars at its traditionally accepted size, and the other is for Mars at its new size, as proven in recent internet postings of "As large as the full moon."

Alex

I just spent a couple of hours at a JPL website, comparing the data on 2004 MN4 and 2007 WD5.

http://ssd.jpl.nasa.gov/sbdb.cgi#top

Just enter each object name (2004 MN4, and 2007 WD5) in the search bar to get the orbital data.

It looks like several of MN4's orbital elements are known to much better precision, about 100 thousand times better, than WD5's.

Also, play with the Orbit Diagram viewer for each object. The close approach to Earth for WD5 is around April 13, 2029. I had so much fun with that viewer, I forgot to eat dinner tonight.

sf