Need Calculations Billion Cubic Miles Ice Entering Earth Atmosphere?

Question

I saw this article "Did stardust trigger snowball Earth?" originally from NATURE:
http://www.bioedonline.org/news/news.cfm?art=1559
"Our planet may have frozen over in the past as it drifted though giant dust clouds in space. The result of the dust-bath would have been an almost complete overcoat of ice for the world, according to a new theory." I thought that ice would burn up on atmosphere entry and burn up the planet, but someone said the massive ice was a "heat sink". Is there any way to calculate if say, it was a billion cubic miles of ice caving in on earth's atmosphere, if that would be enough of a "heat sink" to offset the friction of entry?

Answer 1

You're misinterpreting the article. Nothing of consequence entered the atmosphere. The theory is that the dust cloud in space simply blocked a significant portion of sunlight from reaching earth, resulting in the earth becoming cold. Earth's surface then froze solid due to snow, glaciers, and sea ice originating from its own supply of water in the usual manner.

The eventual thawing of "snow ball earth" due to the build up of CO2 of volcanic origin is thought to have triggered the explosive evolution of animal life in the Cambrian that resulted in all modern phyla of animals (plus several now extinct phyla) evolving. It's refered to as "The Cambrian Explosion".

Answer 2

The previous answer is essentially correct, but I would offer a different angle on the problem. Please try to calculate the size of such mass of ice, based on the density. You will see that such an object (very, very roughly) will be of the same scale as our planet itself (somewhat smaller). It is incorrect, therefore, to consider it a heat sink as Earth would play a similar role (with dire consequences), and the effect of the atmosphere will be negligible anyway -- such an impact would ultimately result in the destruction of the Earth's crust and complete "resurfacing" of the planet with hot lava, with large amount of material being flung into space due to conservation of momentum. It would be a real bad weekend.

Answer 3

One cubic foot of water weighs 62.31 pounds. One cubic mile of water then weighs 9 x 10^12 pounds. If we then multiply this by a billion we get 9 x 10^21 pounds. This in effect would come close to doubling the mass of the Earth. Therefore, I would say that your theory is false.