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View Full Version : Early Earth Had Toxic Oceans



Fraser
2005-Oct-07, 03:41 PM
SUMMARY: Researchers from NASA have confirmed that it would have been impossible for advanced life forms, like fish or mammals, to live in the Earth's early oceans because it was such a toxic environment. The scientists studied ancient rock formations, and found evidence of photosynthetic bacteria living as recently as 1.6 billion years ago. This bacteria would have required both sunlight and an environment rich in hydrogen sulfide - this environment would have been quite toxic for air breathing creatures.

View full article (http://www.universetoday.com/am/publish/early_earth_toxic_oceans.html)
What do you think about this story? post your comments below.

publiusr
2005-Oct-07, 05:41 PM
Near the smokers--it still does. Toxic to some life that is. If that were a tanker, it'd be called pollution.

cran
2005-Oct-07, 09:24 PM
Hmmm...
I read the NASA press release, and it seems like a bit of a jump to ascribe whole planet conditions based on a single deposit...
The environment being described is quite common today, in mangrove swamps... not exactly devoid of aerobic life despite high sulfides... and it doesn't seem to sit well with other reports of Archaean sites...
It sounds to me like someone found an Archaean microbiotic swamp... :think:

GBendt
2005-Oct-08, 12:42 PM
This is one interesting result, but it is only one.

If you examine a rock, manage to determine its composition and age, you may be able to tell a lot about that rock, but you cannot tell how the entire earth looked like at the time when this rock formed.

Today, there are areas at the bottom of the Black Sea, where nothing lives but sulphur-consuming bacteria. It is an oxygen-free zone. Imagine that future generations of geologists billions of years from now will find the rocks which will have formed from the deposits of the Black Sea from that area, they may derive from these rocks that no life but sulphur-consuming bacteria may have lived on earth at our times. We live today, and we know that they will be wrong.

To be able to find out that they are wrong, these geologists will have to study a lot more rocks from our time to be able to develop a more detailed image of the widespread diversification of life, and environments where it may flourish.

Unfortunately, it is not easy to detect different samples of rocks of the same age and from different areas of the world of that time. Each such sample would offer a valuable contribution to develop a more detailed and correct picture of the past.

If we are interested.

Regards,

GŁnther

Cohen the Barbarian
2005-Oct-08, 01:00 PM
My immediate reaction on reading this was "We've known this for years!"
The early atmosphere was a highly toxic (to modern life) mixture of gases which included many sulphur compounds. These were removed over many millions of years by sulphur bacteria. They, in turn, were followed by cyanobacteria which introduced, probably for the first time, oxygen, so bringing about conditions in which some of the life-forms with which we are familiar could evolve.

If I'm wrong, please tell me!

Roy

galacsi
2005-Oct-08, 05:44 PM
I think you are right . But i must add one precision : oxygen is also producted by water's photolyse. At a very small rate yes but enough along time to oxidize a planet . see planet mars.

Atmospheric Composition

Mars Earth

Carbon Dioxide 95% -

Nitrogen 2.7% 78%

Oxygen 0.13% 21%

Argon 1.6% 1%

Gullible Jones
2005-Oct-10, 03:15 AM
There's complex life living in the proximity of hydrogen sulfide vents. Oxygen-based metabolism is not the only sort of metabolism possible.

(That said, intelligent life probably wouldn't fair too well on sulfur-based metabolism - wouldn't provide enough energy to support a good-sized brain.)

Greg
2005-Oct-10, 07:37 PM
The question would be whether this is an excception or a representitive sample of the global environment that existed at that era. Thus, I need access to more research to make a determination.

Having done so, it would appear that this article describes research that is out of the norm for this time period (paleoproterozoic era). There is ample evidence that O2 producing organisms (photosynthetic) had been around for millions of years by then and had risen O2 levels from 1% to 15% by the time period in question in this article. I posted a link with relevant information below.

http://www.ucmp.berkeley.edu/precambrian/proterostrat.html