[Geritol]

"I'll see your 0.19 Megaton and raise you 8 Megatons. Typical asteroid velocities are ~44 km/sec, which gives 8.19 MT"

The average speed may well be 5 or 10 times faster, but according to southack's calculations the actual speed of this object is ~15,000 miles per hour which I have rounded to 6.7 kilometers per second. Actual impact velocity would also include accelleration down our gravity well. Any idea how much affect that would have? I totally ignored that. I assume it would accellerate less than a similar object "dropped" from a stationary point some tens of thousand of miles out due to increased atmospheric friction, but I have no idea how to calculate it.

"If it is mostly nickel iron like earth .. try 5.5 gr/cm3 .... comes closer to .714 MT of KE"

In that case I am definitely off by a factor of 2 or 3 or even 4. Big difference between getting hit with a 30 meter rock of mostly metal and a dirty snowball.

[jpsb]

Impact speed can vary but 45,000 mps to 60,000 mps are the norm. Density can vary too, ice, rock or metal? Since there is no vapor trail, ice it not at all likely and the thing might be very dense making the chances of an inpact with the surface more likely. But it is going to pass us bye, this time.

[Lonesome in Massachussets]

Observations of meteors show that they typically enter the earth's atmosphere with somewhat less than 44 km/sec velocity. The sum of the escape energy from the earth at the top of atmosphere plus escape energy from the sun at the distance of the earth's orbit ~ 44 km/sec.