# Re: impacts are cool!

```Jeffrey Martz wrote:
>
> > Or the math is off.  The crater's only a couple hundred kilometers in
> > diameter even by the largest estimates, which is a heckuva lot smaller
> > than Mars.
>
>      A bullet can puch a hole in something quite a bit larger then its
> diameter.  The size of the crater and whatever global havoc the impact
> causes is indicative of the kinetic energy released by the impact, not
> just the size of the actual bolide.  Kinetic enery equals mass times
> velocity SQUARED; the speed of impact is more important in determining the
> destrcutive potential of an impact then the size of the projectile.

Look at what I wrote.  I never said anything about the size of the rock,
just the crater.  If it's gonna gouge out a volume of water equal to the
mass of Mars (the assertion the above was written in response to) your
rock's gonna need to leave a bigger crater than that, even if most of
it's energy is directed in toward the Earth.

>      As far as the crater being "smaller then Mars", not all of the energy
> is directed into producing the crater; energy directed upward and outward
> by  the impact wouldn't contribute much to making the hole, but could
> cause other effects; like vaporizing a whole lot of water. There are lots
> of different ways to play around with the numbers, but they are all BIG
> numbers. Nearly all impact scenarios predict a fairly impressive potential
> for shaking things up all over the planet.

Yeah, but I wasn't debating that.  I was debating the assertion that the
impact would vaporize an amount of water roughly equal to the volume of
Mars; no matter what your estimates, a volume like that equals a
scragged planet.

>      The fact that not all mass extinctions correlate in time with
> impacts, and the fact that other known impacts are not demonstratively
> tied to extinctions (or at least relatively smaller ones) certainly
> suggests that an impact is not by itself enough to trigger a major mass
> extinction; but it could certainly be an aggravating factor.

Chris

```