Liberty's Blog

The Odds Keep Moving.

The astroid with the unimaginative name of 2004 MN4 has been observed, measured and reploted again, and the news is once again a little more negative. The impact probabality is now estimated at 2.2 Percent While Glenn Renolds warns us that its time for concern not Hysteria:

This asteroid, 2004 MN, is still unlikely to strike -- and it's not big enough to produce a Lucifer's Hammer kind of situation. It's more of a Krakatoa-level threat, which is bad enough, but not a civilization-ender. The big lesson, though, is that this sort of threat isn't just theoretical. Though the probability of a big hit is low, even a hit of this level -- which at 1/42 can't be called very low-probability at this point -- is serious. We're fortunate that nothing like this happened during the Cold War, when it might have triggered a nuclear exchange. But as nuclear weapons proliferate, there's more reason to try to ensure that we're not caught by surprise even by these smaller impacts.

Jay Manifold explains the carnage expected if it hits:

In any case, the projected energy of impact is 2,200 megatons. Now we turn to one of the earliest posts on Arcturus, Thinking About the Unthinkable, where I used some handy equations from Arsenal to find that the 5-psi overpressure radius (which may be regarded for the purposes of this discussion as the Bad Day radius) for a 10-kiloton explosion is just over 900 meters. These things scale inversely as the cube of yield, so ³√(2,200/0.01) × 0.9 km = 54 kilometers or thereabouts. The area thus affected, A = πr², is over 9,000 km², which at the average population density in the US of about 31 per km² (derived from this source) would contain about 280,000 people.

At the average population density of India -- which as I explained in my earlier post, is quite a bit nearer the probable impact site -- however, this works out to nearly 2.5 million people. Yikes.

A.E Brain explains the impact:

Note: this is not a "Dinosaur Killer", and anyone on a different continent from the impact will likely only be aware of it from news broadcasts, spacetacular sunsets, and a few slightly colder than normal seasons - much the same as if a number of major volcanos let rip simultaneously.

On the other hand, anyone within a hundred miles of the impact would likely have a tough time. The crater will be nearly 4 miles across. Anyone within 50 miles will get 200 mph winds, a bombardment of rocks ranging from golfball size to football size, and the equivalent effects of a magnitude 6.8 earthquake. (Data from the Impact Effects Calculator, with parameters of Velocity 12.59 km/sec, 0.44 km diameter size, Dense Rock, 45 degree impact angle).

The fact that it won't totally destroy the world or that it's almost 98% likely not to hit us is hardly comforting.

posted by Liberty @ 11:12 AM