Are asteroids and comets equally destructive?

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Offline thedoc

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Are asteroids and comets equally destructive?
« on: 10/04/2013 06:30:02 »
David Gould asked the Naked Scientists:
Would an asteroid and a comet of comparable size cause the same damage if they entered Earth's atmosphere?

What do you think?
« Last Edit: 10/04/2013 06:30:02 by _system »


Offline CliffordK

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Re: Are asteroids and comets equally destructive?
« Reply #1 on: 10/04/2013 07:28:31 »
I would think that a comet would tend to melt and fragment more in the upper atmosphere, and may have less surface impact.  While an equivalent size non-icy asteroid would have a greater chance to have large chunks impacting the surface. 

Thus, for impact crater size, and surface damage, the rocky asteroid may be more damaging.

Of course, a large explosion and shock-waves generated a couple of miles in the air can cause widespread damage, potentially to a much larger area than a surface impact.  For this reason, the Hiroshima and Nagasaki bombs were intentionally exploded about km above the cities.

Thus, even if the comet exploded mid-air, it may actually affect a larger physical area with the primary explosion.

Apart from the primary impact, the secondary effects of dust and debris generated by, say a 10km object striking the earth could have global secondary effects, especially with respect to the climate.  I would think this would be worse with a larger object striking the earth than an atmospheric explosion and smaller surface impact.


Offline flr

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Re: Are asteroids and comets equally destructive?
« Reply #2 on: 10/04/2013 07:37:23 »
Comets can run up to 3 times faster than asteroids - that means up to 9 times more energy for the same mass. So, if the comet is faster it will release more energy.

If the comet and asteroid have equal masses and equal velocities, I believe asteroid is more destructive because  it is denser and the comet contains lots of less dense water. However that may depends on the distance from surface where comet explode ; at an optimal distance the reflection (from the ground) shock-wave can amplify the destruction.

If the diameter of the comet or asteroid is more than 20 miles,... well ...  I guess it does not matter anymore.

« Last Edit: 10/04/2013 07:43:44 by flr »