[BR-Crater] asteroid 1-in-75 chance to hit Mars on Jan 30

[Ian Kluft]

Some or most of you have probably already seen this in the news...

There is an estimated 1 in 75 chance that the asteroid 2007 WD5 will impact
Mars on Jan 30, 2008, just 5 weeks away.  This news will undoubtedly be
updated as astronomers get more observations.

Here's a google news search for it...
   http://news.google.com/news?hl=en&ned=us&q=asteroid+mars&btnG=Search+News

At 50m diameter, it's the same as the estimated sizes of the impactors in
the Tunguska 1908 event and Barringer Crater, Arizona (a.k.a. Meteor Crater).

1 in 75 seems like long odds.  It's on par with the worst concern we've
had yet for a potential Earth impact since studies began.  The asteroid
2004 MN4 (now 99942 Apophis) made news on Christmas Day 2004 that there
was a 1-in-62 chance of an Earth impact.  Of course, those chances were
based on what they'd observed at the time.  For 2004 MN4, observations
continued and then ruled out an impact with Earth in that case.  More
info is at http://en.wikipedia.org/wiki/99942_Apophis

JPL has an estimated band across Mars where the potential impact of
2007 WD5 could occur.  The Mars Exploration Rover Opportunity is near
but outside the area, and might have a chance to make observations of
the impact if probabilities turn in its favor.

Until more observations are made, we don't yet know whether 2007 WD5 will
tip toward or away from an impact with Mars.  They need more info to narrow
it down.  Actually, there are two reasons to hope it will hit Mars...
* An impact and new crater on Mars will be a nearly-endless source of
  scientific observations.
* If 2007 WD5 doesn't hit Mars, then Mars' gravity will change its orbit
  and require new observations to determine its trajectory.  Since its
  orbit also makes it a Near Earth Object (NEO), we'd all prefer see it
  removed from the pool of potential impactors of Earth.