Stanley Miller's classic "primordial soup" experimental setup,
with a simulated ocean, lightning and broth
of hydrogen, methane, ammonia and water.
Posted on 04/08/2005 7:39:14 AM PDT by PatrickHenry
A new University of Colorado at Boulder study indicates Earth in its infancy probably had substantial quantities of hydrogen in its atmosphere, a surprising finding that may alter the way many scientists think about how life began on the planet.
Published in the April 7 issue of Science Express, the online edition of Science Magazine, the study concludes traditional models estimating hydrogen escape from Earth's atmosphere several billions of years ago are flawed. The new study indicates up to 40 percent of the early atmosphere was hydrogen, implying a more favorable climate for the production of pre-biotic organic compounds like amino acids, and ultimately, life.
The paper was authored by doctoral student Feng Tian, Professor Owen Toon and Research Associate Alexander Pavlov of CU-Boulder's Laboratory for Atmospheric and Space Physics with Hans De Sterk of the University of Waterloo. The study was supported by the NASA Institute of Astrobiology and NASA's Exobiology Program.
"I didn't expect this result when we began the study," said Tian, a doctoral student in CU-Boulder's Astrobiology Center at LASP and chief author of the paper. "If Earth's atmosphere was hydrogen-rich as we have shown, organic compounds could easily have been produced."
Scientists believe Earth was formed about 4.6 billion years ago, and geologic evidence indicates life may have begun on Earth roughly a billion years later.
"This study indicates that the carbon dioxide-rich, hydrogen-poor Mars and Venus-like model of Earth's early atmosphere that scientists have been working with for the last 25 years is incorrect," said Toon. In such atmospheres, organic molecules are not produced by photochemical reactions or electrical discharges.
Toon said the premise that early Earth had a CO2-dominated atmosphere long after its formation has caused many scientists to look for clues to the origin of life in hydrothermal vents in the sea, fresh-water hot springs or those delivered to Earth from space via meteorites or dust.
The team concluded that even if the atmospheric CO2 concentrations were large, the hydrogen concentrations would have been larger. "In that case, the production of organic compounds with the help of electrical discharge or photochemical reactions may have been efficient," said Toon.
Amino acids that likely formed from organic materials in the hydrogen-rich environment may have accumulated in the oceans or in bays, lakes and swamps, enhancing potential birthplaces for life, the team reported.
The new study indicates the escape of hydrogen from Earth's early atmosphere was probably two orders of magnitude slower than scientists previously believed, said Tian. The lower escape rate is based in part on the new estimates for past temperatures in the highest reaches of Earth's atmosphere some 5,000 miles in altitude where it meets the space environment.
While previous calculations assumed Earth's temperature at the top of the atmosphere to be well over 1,500 degrees F several billion years ago, the new mathematical models show temperatures would have been twice as cool back then. The new calculations involve supersonic flows of gas escaping from Earth's upper atmosphere as a planetary wind, according to the study.
"There seems to have been a blind assumption for years that atmospheric hydrogen was escaping from Earth three or four billion years ago as efficiently as it is today," said Pavlov. "We show the escape was limited considerably back then by low temperatures in the upper atmosphere and the supply of energy from the sun."
Despite somewhat higher ultraviolet radiation levels from the sun in Earth's infancy, the escape rate of hydrogen would have remained low, Tian said. The escaping hydrogen would have been balanced by hydrogen being vented by Earth's volcanoes several billion years ago, making it a major component of the atmosphere.
In 1953, University of Chicago graduate student Stanley Miller sent an electrical current through a chamber containing methane, ammonia, hydrogen and water, yielding amino acids, considered to be the building blocks of life. "I think this study makes the experiments by Miller and others relevant again," Toon said. "In this new scenario, organics can be produced efficiently in the early atmosphere, leading us back to the organic-rich soup-in-the-ocean concept."
In the new CU-Boulder scenario, it is a hydrogen and CO2-dominated atmosphere that leads to the production of organic molecules, not the methane and ammonia atmosphere used in Miller's experiment, Toon said.
Tian and other team members said the research effort will continue. The duration of the hydrogen-rich atmosphere on early Earth still is unknown, they said.
We don't need to run the whole abiogenesis experiment. What we need to understand is the processes. These will be broken down into small steps that can be studied in parallel.
Reverse engineering is faster than inventing.
It's the damning pronouncement of Chemistry (a true experimental science) that makes evolutionists back up hurriedly as they throw up their hands and say loudly: Our theory does NOT explain the origins of life.
As a chemist and a scientist, there are two problems with your statements. First, evolution does not relate to the transition from non-living to living. Evolution is an explanaition for how species change over time, not to how life first began.
Secondly, organic chemicals do not need to be formed by living things. See my post #213
"If you actually look at the organic molecules involved, you'll find an interesting catch-22. The molecules are required for life, yet can only be constructed by living organisms."
Organic compounds do not require life to exist. Organic compounds are any molecules that contain the carbon atom (relating or belonging to the class of chemical compounds having a carbon basis; "hydrocarbons are organic compounds"). Organic compounds were around long before life ever existed and exist on other planets where no life is yet to be found. I would suggest you rethink this catch-22.
There's a big difference in the chemicals formed in an interstellar hydrogen cloud and the chemicals required for the Krebbs Cycle. I believe I indicated that when I used the phrase "chemicals involved."
I guess I should have bolded the phrase if you actually look at the organic molecules involved. You're the second person to miss that.
The organic molecules found in an interstellar dust cloud, or on the surface of Titan are a far cry from the compounds used in the Krebbs Cycle.
"If you believe that the universe suddenly exploded into being from nothing you are of course rejecting not only evolution but the laws of physics as well."
I would completely agree with this assertion. I do not believe the big bang originated from nothing, but rather originated from everything packed into a tiny portion of space/time.
"I'd love to respond but I have a rule- any thread that goes over 200 posts has "jumped the shark"..."
You do realize that your statement fits into the "this is not here" category?
Miller has not been "completely discredited" either. I've about 2 hours of work before I have time to elaborate. Perhaps one of the other scientists on the board will respond before that.
I did not say cannot. I asked where it came from. If that is your scientific theory, it still needs to explain where carbon dioxide fits in.
Which molecule in the krebs cycle do you believe can only be created by living organisms?
Ever heard of racemization?
The problem with the Dawkins program, is that it assumes the existence of an alphabet.
Re-run the program using a random distribution of 26,000 dots (enough to form each letter of the alphabet in a 32x32 grid). Stir the dots randomly until an alphabet forms. You can't use the selection criteria, because the letters are the components of the words, and the selection operates on the words, not the components. So, it's purely random up to that point. Now congratulate yourself. You've just discovered evolution's inability to create irreducibly complex systems.
No, that's because the ToE addresses the dynamics of a system and not it's origins. What evolution requires to happen is simply the existence of imperfect self-replicators and it doesn't matter how these self-replicator originated.
So even if the first self-replicating molecules weren't the result of abiogenesis but the creation of a deity or some aliens "contaminating" our planet when they pooped before they left, doesn't render the Theory of Evolution invalid.
Yes. I started with a racemic mixture.
That is not racemization.
...and where did this tiny "packet of everything in space/time" originate?
"There's a big difference in the chemicals formed in an interstellar hydrogen cloud and the chemicals required for the Krebbs Cycle"
We also now know of life forms that do not use the krebs cycle as their basis of energy intake. Chemosynthesis has been found in animals near hydrothermal vents which use sulfur as their primary energy source.
"...and where did this tiny "packet of everything in space/time" originate?"
If physcists are correct that matter and energy can neither be created nor destroyed, I would have to say that it has always existed and was never created.
Acetyl coenzyme A would probably be a fair guess. Although alpha ketoglutarate would be another one.
And, please, don't try and argue that because we can synthesize it in a laboratory, it just happened to naturally form in a prebiotic sea somewhere, unless you are prepared to try and convince me that the pre-biotic oceans contained such substances as Adenosine 5'-Monophosphate, Pyrophosphate, Adenosine 5'-Triphosphate, Monobasic Potassium Phosphate (etc, etc,) all in the right molar concentrations as well as just the right concentration of buffer reagent for the reactions to occur as well as the correct amounts of Mangesium Chloride, Ferric Chloride, etc. etc. etc.
The whole "we find organic chemicals on Titan, therefore life can arise abiotically" falls on its face when you take the time to look at the actual chemicals involved in life.
Ping
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