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Author Topic: How big was the prehistoric Earth atmosphere?  (Read 3762 times)

Titanscape

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How big was the prehistoric Earth atmosphere?
« on: 09/08/2006 07:05:19 »
Do you think that the Earth billions of years ago had a greater atmoshere extending beyond the magnetospere, and so a tail like the present Venusian atmosphere? One that blew away until a safe quantity remained beneath the magnetosphere as now?

Does the magnetosphere change and does the solar wind change?



Titanscape
« Last Edit: 01/07/2008 10:38:10 by BenV »

RD

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How big was the prehistoric Earth atmosphere?
« Reply #1 on: 14/07/2008 19:02:18 »
In the distant past earth rotated more rapidly, e.g. approximately half a billion years ago there were 400 days in a year.
I suspect a faster rotating Earth would have a stronger magnetic field due to the increased motion of liquid iron in the core.
« Last Edit: 16/07/2008 13:35:17 by RD »

Titanscape

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How big was the prehistoric Earth atmosphere?
« Reply #2 on: 16/07/2008 12:58:54 »
During polarity exchange is there a loss of atmosphere?

Off topic; might there be earthquakes?

graham.d

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How big was the prehistoric Earth atmosphere?
« Reply #3 on: 16/07/2008 13:08:03 »
I don't think there would be any reason for a loss of atmosphere and even less to any increase in earthquake activity. The main problem is the increase in ionising radiation that we would receive from the charged particles currently steered away by the earth's magnetic field.

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einfopedia

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Re: How big was the prehistoric Earth atmosphere?
« Reply #4 on: 19/03/2012 07:34:00 »
Shrunk
The Earth formed with the Sun 4.6 billion years ago. At this point, it was nothing more than a molten ball of rock surrounded by an atmosphere of hydrogen and helium. Because the Earth didn’t have a magnetic field to protect it yet, the intense solar wind from the young Sun blew this early atmosphere away.

As the Earth cooled enough to form a solid crust (4.4 billion years ago), it was covered with active volcanos. These volcanos spewed out gasses, like water vapor, carbon dioxide and ammonia. This early toxic atmosphere was nothing like the atmosphere we have today.

yor_on

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Re: How big was the prehistoric Earth atmosphere?
« Reply #5 on: 19/03/2012 17:12:47 »
"Using primitive meteorites called chondrites as their models, earth and planetary scientists at Washington University in St. Louis have performed outgassing calculations and shown that the early Earth’s atmosphere was a reducing one, chock full of methane, ammonia, hydrogen and water vapor. Chondrites are relatively unaltered samples of material from the solar nebula, According to Fegley, who heads the University’s Planetary Chemistry Laboratory, scientists have long believed them to be the building blocks of the planets. However, no one has ever determined what kind of atmosphere a primitive chondritic planet would generate.

“We assume that the planets formed out of chondritic material, and we sectioned up the planet into layers, and we used the composition of the mix of meteorites to calculate the gases that would have evolved from each of those layers,” said Schaefer. “We found a very reducing atmosphere for most meteorite mixes, so there is a lot of methane and ammonia.”

In a reducing atmosphere, hydrogen is present but oxygen is absent. For the Miller-Urey experiment to work, a reducing atmosphere is a must. An oxidizing atmosphere makes producing organic compounds impossible. Yet, a major contingent of geologists believe that a hydrogen-poor, carbon dioxide-rich atmosphere existed because they use modern volcanic gases as models for the early atmosphere. Volcanic gases are rich in water, carbon dioxide, and sulfur dioxide but contain no ammonia or methane.

“Geologists dispute the Miller-Urey scenario, but what they seem to be forgetting is that when you assemble the Earth out of chondrites, you’ve got slightly different gases being evolved from heating up all these materials that have assembled to form the Earth. Our calculations provide a natural explanation for getting this reducing atmosphere,” said Fegley." (2005)

And

"Earth’s early atmosphere may have flipped between two states before oxygenation, according to a new study.

Researchers at Newcastle University have published these findings in the journal Nature Geoscience. They found Earth’s early atmosphere would switch between a hydrocarbon-free state and a hydrocarbon-rich state. This kind of atmosphere, according to the researchers, is similar to that of Saturn’s moon, Titan.

Referring to the two states as “organic haze” and “haze-free”, the researchers say in the journal that intense microbial activity played a large part in this type of atmospheric switching.

The study offers a new look at how the Earth’s surface may have reacted to these different atmospheres and how climates effect the Earth’s environments.

Dr. Aubrey Zerkle from the School of Civil Engineering and Geosciences at Newcastle University led the atmospheric study. According to Zerkle, “Models have previously suggested that the Earth’s early atmosphere could have been warmed by a layer of organic haze. Our geochemical analyses of marine sediments from this time period provide the first evidence for such an atmosphere.”

What Zerkle’s team found next was a bit of a surprise for them, and introduced a new theory on how the Earth’s atmosphere operated before oxygenation.

“However, instead of evidence for a continuously ‘hazy’ period we found the signal flipped on and off, in response to microbial activity.

“This provides us with insight into Earth’s surface environment prior to oxygenation of the planet and confirms the importance of methane gas in regulating the early atmosphere.”" (2012)

http://www.universetoday.com/26659/earths-early-atmosphere/
http://www.nature.com/ngeo/journal/vaop/ncurrent/full/ngeo1425.html

As for "a greater atmosphere extending beyond the magnetosphere" Both studies found Titan to be closest to a prehistoric earth, so, does its atmosphere extend outside the magnetosphere? I don't know, and it should have to do with earths mass, the atmospheric envelopes density relative the magnetic field, and 'charge'(?) maybe. (and rotation, da*it:)

Couldn't find anything on that one as I looked, but I did find this :)
http://blogs.discovermagazine.com/badastronomy/2012/03/19/a-brief-bit-about-asteroid-2012-da14/

Memo to myself: Better buy a hardhat..
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Btw; This 'click to view.' doesn't work anymore in the new version of TNS, Hasn't for me anyway, which may be a good thing, or bad, depending :)
« Last Edit: 19/03/2012 17:23:12 by yor_on »

 

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