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New Evidence Suggests Early Oceans Bereft of Oxygen for Eons
NewsWise ^ | 3/4/04

Posted on 03/07/2004 3:45:13 PM PST by LibWhacker

Description: Geochemists have uncovered evidence that Earth's ancient oceans were much different from today's. New data shows that Earth's life-giving oceans contained less oxygen than today's and could have been nearly devoid of oxygen for a billion years longer than previously thought.

Newswise — As two rovers scour Mars for signs of water and the precursors of life, geochemists have uncovered evidence that Earth's ancient oceans were much different from today's. The research, published in this week's issue of the journal Science, cites new data that shows that Earth's life-giving oceans contained less oxygen than today's and could have been nearly devoid of oxygen for a billion years longer than previously thought. These findings may help explain why complex life barely evolved for billions of years after it arose.

The scientists, funded by the National Science Foundation (NSF) and affiliated with the University of Rochester, have pioneered a new method that reveals how ocean oxygen might have changed globally. Most geologists agree there was virtually no oxygen dissolved in the oceans until about 2 billion years ago, and that they were oxygen-rich during most of the last half-billion years. But there has always been a mystery about the period in between.

Geochemists developed ways to detect signs of ancient oxygen in particular areas, but not in the Earth's oceans as a whole. The team's method, however, can be extrapolated to grasp the nature of all oceans around the world.

"This is the best direct evidence that the global oceans had less oxygen during that time," says Gail Arnold, a doctoral student of earth and environmental sciences at the University of Rochester and lead author of the research paper.

Adds Enriqueta Barrera, program director in NSF's division of earth sciences, "This study is based on a new approach, the application of molybdenum isotopes, which allows scientists to ascertain global perturbations in ocean environments. These isotopes open a new door to exploring anoxic ocean conditions at times across the geologic record."

Arnold examined rocks from northern Australia that were at the floor of the ocean over a billion years ago, using the new method developed by her and co-authors, Jane Barling and Ariel Anbar. Previous researchers had drilled down several meters into the rock and tested its chemical composition, confirming it had kept original information about the oceans safely preserved. The team members brought those rocks back to their labs where they used newly developed technology -called a Multiple Collector Inductively Coupled Plasma Mass Spectrometer-to examine the molybdenum isotopes within the rocks.

The element molybdenum enters the oceans through river runoff, dissolves in seawater, and can stay dissolved for hundreds of thousands of years. By staying in solution so long, molybdenum mixes well throughout the oceans, making it an excellent global indicator. It is then removed from the oceans into two kinds of sediments on the seafloor: oxygen-rich and those that are oxygen- poor.

Working with coauthor Timothy Lyons of the University of Missouri, the Rochester team examined samples from the modern seafloor, including the rare locations that are oxygen-poor today. They learned that the chemical behavior of molybdenum's isotopes in sediments is different depending on the amount of oxygen in the overlying waters. As a result, the chemistry of molybdenum isotopes in the global oceans depends on how much seawater is oxygen-poor. They also found that the molybdenum in certain kinds of rocks records this information about ancient oceans. Compared to modern samples, measurements of the molybdenum chemistry in the rocks from Australia point to oceans with much less oxygen.

How much less oxygen is the question. A world full of anoxic oceans could have serious consequences for evolution. Eukaryotes, the kind of cells that make up all organisms except bacteria, appear in the geologic record as early as 2.7 billion years ago. But eukaryotes with many cells-the ancestors of plants and animals- did not appear until a half billion years ago, about the time the oceans became rich in oxygen. With paleontologist Andrew Knoll of Harvard University, Anbar previously advanced the hypothesis that an extended period of anoxic oceans may be the key to why the more complex eukaryotes barely eked out a living while their prolific bacterial cousins thrived. Arnold's study is an important step in testing this hypothesis.

"It's remarkable that we know so little about the history of our own planet's oceans," says Anbar. "Whether or not there was oxygen in the oceans is a straightforward chemical question that you'd think would be easy to answer. It shows just how hard it is to tease information from the rock record and how much more there is for us to learn about our origins."

Figuring out just how much less oxygen was in the oceans in the ancient past is the next step. The scientists plan to continue studying molybdenum chemistry to answer that question, with continuing support from NSF and NASA, the agencies that supported the initial work. The information will not only shed light on our own evolution, but may help us understand the conditions we should look for as we search for life beyond Earth.


TOPICS: News/Current Events
KEYWORDS: astronomy; catastrophism; crevolist; geology; oceanography; oceans; oxygen; science
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1 posted on 03/07/2004 3:45:14 PM PST by LibWhacker
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To: PatrickHenry
Ancient anoxic oceans ping!
2 posted on 03/07/2004 3:48:45 PM PST by VadeRetro
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To: LibWhacker
Umm... I thought O2 was a poisonous waste for early life.
3 posted on 03/07/2004 3:57:18 PM PST by BikePacker
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To: LibWhacker
Kerry's brain is in a similar state as I type.
4 posted on 03/07/2004 3:59:48 PM PST by Atchafalaya
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To: VadeRetro
Once, pO2 increased, some of the critters' metabolism
could be used to make collagen (bones, skin, tendons; and then leave fossils).
5 posted on 03/07/2004 4:00:20 PM PST by Diogenesis (If you mess with one of us, you mess with all of us)
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To: BikePacker
Me, too . . . For very early life, that is. For nascent life. After it's established, though, you apparently need it to evolve higher forms. Thus, life arose early when O2 levels were low, then not much happened ito evolution until oxygen went through the roof.
6 posted on 03/07/2004 4:04:12 PM PST by LibWhacker
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To: Diogenesis
Yes. After a time there was a certain amount of oxygen-producing photosynthesis going on, but oxygen levels couldn't rise much until the surface iron ores were fully oxidized, etc.
7 posted on 03/07/2004 4:11:33 PM PST by VadeRetro
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To: *crevo_list; VadeRetro; jennyp; Junior; longshadow; RadioAstronomer; Physicist; LogicWings; ...
Oceanic PING. [This ping list is for the evolution side of evolution threads, and sometimes for other science topics. FReepmail me to be added or dropped.]
8 posted on 03/07/2004 4:21:51 PM PST by PatrickHenry (A compassionate evolutionist.)
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To: LibWhacker
"The scientists plan to continue studying molybdenum chemistry to answer that question, with continuing support from NSF and NASA, the agencies that supported the initial work."

So, whether there's any relevance to their theories or not, they WILL be getting funding from you and me.

Nice work if you can get it.

9 posted on 03/07/2004 4:30:40 PM PST by nightdriver
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To: PatrickHenry
The element molybdenum enters the oceans through river runoff, dissolves in seawater, and can stay dissolved for hundreds of thousands of years. By staying in solution so long, molybdenum mixes well throughout the oceans, making it an excellent global indicator. It is then removed from the oceans into two kinds of sediments on the seafloor: oxygen-rich and those that are oxygen-poor.

Thanks Patrick. This is very interesting.

10 posted on 03/07/2004 4:41:12 PM PST by Victoria Delsoul (The Passion is true to the Gospel, those who claim to know it and disagree...simply don't understand)
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To: nightdriver
So, whether there's any relevance to their theories or not, they WILL be getting funding from you and me.

Nice work if you can get it.

Nightdriver, have you checked with your moma to see if she smoked while she was pregnant with you?
11 posted on 03/07/2004 4:42:28 PM PST by LaMudBug
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To: VadeRetro
Here's a website about life in such an environment: Life in anoxic worlds. There could have been lots of anoxic life in the early oceans. Gone now. Poisoned by oxygen. Our kind of life has adapted to what may be regarded as a toxic environment.
12 posted on 03/07/2004 4:58:31 PM PST by PatrickHenry (A compassionate evolutionist.)
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To: PatrickHenry
Very nice! Had to go back and read the first two pages as well.
13 posted on 03/07/2004 5:20:23 PM PST by VadeRetro
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To: LaMudBug
"Nightdriver, have you checked with your moma to see if she smoked while she was pregnant with you?"

Hey, Looziana crawdad, I can come up with evolution theories that are a lot wilder than this one.

Now if I could just get you to pay me to investigate them! (?)

14 posted on 03/07/2004 5:48:54 PM PST by nightdriver
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To: VadeRetro
Karen Carpenter Ping!

Another Ancient anorexic ping!

Well, she's not using any oxygen now is she!?
15 posted on 03/07/2004 5:55:02 PM PST by tet68 ( " We would not die in that man's company, that fears his fellowship to die with us...." Henry V.)
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To: tet68
Kinda miss her. Never play any of her music, but she had a wonderful rich voice which might have been better used.
16 posted on 03/07/2004 5:59:06 PM PST by VadeRetro
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To: VadeRetro
you mean as in on key?
17 posted on 03/07/2004 6:06:12 PM PST by js1138
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To: js1138
Pulling her out of that stupid echo chamber her brother Richard had them in most of the time would have done it.
18 posted on 03/07/2004 6:09:06 PM PST by VadeRetro
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To: PatrickHenry
Thanks for the ping!
19 posted on 03/07/2004 8:07:41 PM PST by Alamo-Girl
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To: LibWhacker
Evolution didn't really get started until organisms learned to pronounce "molybdenum".
20 posted on 03/08/2004 1:11:45 AM PST by jennyp (http://crevo.bestmessageboard.com)
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