Perhaps it’s fortuitous that an object similar to the asteroid that caused the Tunguska event in Siberia may put on a display for us on Mars. It’s only a one in 75 chance that 2007 WD5 will strike the surface, and those odds may change again as further data are analyzed, but if it does hit, the object could strike with much the same force as the Siberian explosion. This news story reports Tunguska as a 15-megaton explosion, though as we saw on Wednesday, new work at Sandia National Laboratories has re-considered that figure and now opts for the 3-5 megaton range.

The potential impact site is near the Martian equator. If we were to witness such a spectacle, it would bring back memories of the 1994 strike of comet Shoemaker/Levy 9, the famous ‘string of pearls’, on Jupiter. The devastation of that event was stunning, far greater than 2007 WD5 would produce, but the latter might deliver enough fireworks to produce a crater the size of Meteor Crater in Arizona. Is the Solar System trying to tell us something? If so, let’s hope the powers that handle the budgetary purse strings for critical planetary radars are listening.

So keep your eyes on this intriguing object. No one wishes Mars ill, but given the equipment we’ve now got orbiting that planet for close-up viewing, the image of what an asteroid strike can do in real time could become a powerful teaching tool. My guess is that as the new observations come in, the chances of an impact will lessen dramatically, but we won’t know for a while. Until we do, this particular game of celestial roulette should make us reflect on the odds as we consider how poorly prepared we would be if 2007 WD5 were coming at us.

Addendum: This asteroid is interesting, and unusual, in being both an Earth crosser and a Mars crosser. Says Steve Chesley (JPL):

“We estimate such impacts occur on Mars every thousand years or so. If 2007 WD5 were to thump Mars on Jan. 30, we calculate it would hit at about 30,000 miles per hour and might create a crater more than half-a-mile wide.”

Opportunity is exploring a crater of approximately this size right now.