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Politics : Evolution -- Ignore unavailable to you. Want to Upgrade?

To: TigerPaw who wrote (1367)	5/24/2006 7:52:24 PM
From: Brumar89	Read Replies (1) \| Respond to of 69300

Perhaps life of a different kind might begin on another planet in the presence of oxygen. All the more reason to ask why its not happening here. I will remind you the issue of life and oxygen is one you raised to explain why we can't find life spontaneously arising all around us as we ought to if that can happen naturally. You raised the issue of oxygen in our atmosphere now as a reason. Now you are saying life might arise with oxygen after all. Your arguments contradict one another. This isn't the first time - remember the aggression of wasps being first related kinship and then unrelated to it.

To: TigerPaw who wrote (1367)	8/24/2006 5:48:01 PM
From: Brumar89	Read Replies (1) \| Respond to of 69300

Theories on oxygen may need revising New findings indicate it was in our atmosphere much earlier than scientists thought Reuters News Service LONDON — Scientists may have to rethink accepted theories of how prehistoric Earth's atmosphere developed after new discoveries in ancient sulfur raised serious questions, researchers said Wednesday. Up to now it has been generally accepted that Earth's atmosphere has been devoid of oxygen for some 80 percent of its existence. "The popular model is that there was little oxygen in the Earth's atmosphere before about 2.4 billion years ago," said Hiroshi Ohmoto of Penn State University. But Ohmoto's team has cast doubt on the theory after finding sulfur isotopes, indicating prevalent oxygen that predate the accepted start of atmospheric oxygenation. The key lies in the fact that while all isotopes of sulfur behave the same chemically, they have slightly differing masses according to the amount of atmospheric oxygen at the time. Isotopes from two sulfur samples the team studied — one 2.76 billion years old from a lake bed and the other 2.92 billion years old from the seabed — did not indicate an oxygen-starved atmosphere. Two possible explanations "We analyzed the sulfur composition and could not find the abnormal sulfur isotope ratio (indicating no oxygen)," Ohmoto said. "This is the first time that sediment that old was found to contain no abnormal sulfur isotope ratio." The team concluded that there were two possible explanations — either that prehistoric atmospheric oxygen levels fluctuated wildly over the millennia, or that sulfur showing no oxygen might have been produced in an oxygenated atmosphere as long ago as 3.8 billion years by violent volcanic activity. Either way, they said, the accepted theories needed to be re-evaluated. The findings were published in the science journal Nature. chron.com