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Description
More of my astronomical and space travel art can be seen in my DA "Space Art" gallery:

lexlothor.deviantart.com/galle…

I previously posted a picture of the ancient "Snowball Earth" as seen from the vantage point of a comet about to collide with it:

lexlothor.deviantart.com/art/I…

Around 650 million years ago the earth was entirely covered by ice. Known as the period of the "Snowball Earth" the seas were glazed in pack ice all the way to the equator. All of the landmasses were clad in continental glaciers.

Here I hypothesize the collision of the broken up remnants of a large comet at the moment before the first fragment hits the frozen surface of the Earth. The tremendous heating and vast turnover of atmospheric gases caused by an impact could have abruptly ended the ice house conditions of the Cryogenian. What might have been an "extinction event" in later ages of the planet's history may have actually improved the conditions for the evolution of multicellular life.

Most of the artistic and television CGI reconstructions I have seen of asteroid or comet impacts with Earth are entirely wrong. They usually depict a long fiery streak across the sky with yellow flame and smoke that looks like a skyrocket plummeting to the ground. Only a relatively small object striking the atmosphere at a very shallow angle would look anything like this. The atmosphere is simply too thin and the object is moving too fast for this to occur. For instance, the Chixalub asteroid that ended the Cretaceous was almost longer than the atmosphere is deep. One end of it could have touched the ocean floor while the other end was still sticking out of the troposphere.

A kilometers long extinction level object would simply light up the atmosphere with a light brighter than the sun from horizon to horizon. If an observer were anywhere to witness the actual impact he might well be vaporized faster than the image could travel down his optic nerves to the visual cortex of his brain. I depict here a ten kilometer comet nucleus just before it enters the atmosphere. It is seen at a point higher than the orbital altitude as the ISS. As it is traveling at 50km per second relative to the earth in its orbit, it punches all the way through the atmosphere and detonates in a matter of seconds.

The comet's tail would have cast its shadow across the face of the Earth. The shadows seen here are as long a North America is wide. Just before impact the gaseous coma surrounding the nucleus would have cast a refracted sunbow upon the surface that would have lensed from a penumbra as wide as Kansas down to a point in a few tenths of a second.

Depicting a comet striking Snowball Earth is a study of white on white. Snowball Earth would have reflected 90% of the sunlight reaching the surface. It would also have been so cold that the atmosphere would have been relatively free of clouds. In fact conditions may have been so frigid that dry ice may have snowed out of the atmosphere at the poles in winter. This could have sequestered more greenhouse CO2 and contributed to the runaway icehouse effect.

art & text (c) John P. Alexander

2.5" x 3.5" art card rendered in Prismacolor pencils, Tombow markers & acrylics

Description
More of my astronomical and space travel art can be seen in my DA "Space Art" gallery:

lexlothor.deviantart.com/galle…

I previously posted a picture of the ancient "Snowball Earth" as seen from the vantage point of a comet about to collide with it:

lexlothor.deviantart.com/art/I…

Around 650 million years ago the earth was entirely covered by ice. Known as the period of the "Snowball Earth" the seas were glazed in pack ice all the way to the equator. All of the landmasses were clad in continental glaciers.

Here I hypothesize the collision of the broken up remnants of a large comet at the moment before the first fragment hits the frozen surface of the Earth. The tremendous heating and vast turnover of atmospheric gases caused by an impact could have abruptly ended the ice house conditions of the Cryogenian. What might have been an "extinction event" in later ages of the planet's history may have actually improved the conditions for the evolution of multicellular life.

Most of the artistic and television CGI reconstructions I have seen of asteroid or comet impacts with Earth are entirely wrong. They usually depict a long fiery streak across the sky with yellow flame and smoke that looks like a skyrocket plummeting to the ground. Only a relatively small object striking the atmosphere at a very shallow angle would look anything like this. The atmosphere is simply too thin and the object is moving too fast for this to occur. For instance, the Chixalub asteroid that ended the Cretaceous was almost longer than the atmosphere is deep. One end of it could have touched the ocean floor while the other end was still sticking out of the troposphere.

A kilometers long extinction level object would simply light up the atmosphere with a light brighter than the sun from horizon to horizon. If an observer were anywhere to witness the actual impact he might well be vaporized faster than the image could travel down his optic nerves to the visual cortex of his brain. I depict here a ten kilometer comet nucleus just before it enters the atmosphere. It is seen at a point higher than the orbital altitude as the ISS. As it is traveling at 50km per second relative to the earth in its orbit, it punches all the way through the atmosphere and detonates in a matter of seconds.

The comet's tail would have cast its shadow across the face of the Earth. The shadows seen here are as long a North America is wide. Just before impact the gaseous coma surrounding the nucleus would have cast a refracted sunbow upon the surface that would have lensed from a penumbra as wide as Kansas down to a point in a few tenths of a second.

Depicting a comet striking Snowball Earth is a study of white on white. Snowball Earth would have reflected 90% of the sunlight reaching the surface. It would also have been so cold that the atmosphere would have been relatively free of clouds. In fact conditions may have been so frigid that dry ice may have snowed out of the atmosphere at the poles in winter. This could have sequestered more greenhouse CO2 and contributed to the runaway icehouse effect.

art & text (c) John P. Alexander

2.5" x 3.5" art card rendered in Prismacolor pencils, Tombow markers & acrylics