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.
Disorder is not what entropy is to chemistry.
"Proto-life has been observed forming in the lab"
Now that some bright scientist has solved simulating millions of years in the lab, lets move on the real problem of synthesizing that pesky cell membrane.
After that we can throw those cells into a nourishing environment, stand back and watch something new crawl out of the petri dish.
Yogi! It really is you!
You make the mistake of assuming that there's a clear dividing line between life and non-life. Viruses and prions, just to give a couple of examples, are clear indications that there is a fuzzy gray area. I am not maintaining that viruses and prions were necessarily precursors to early life, but it seems reasonable that there were probably many steps between the first organic molecules and the first living cells. There may well have been some of these steps where it was unclear as to whether or not life had formed.
I see what you're getting at. Life is built OF non-living components. Now, do plants come from non-living atoms? They feed off of nutrients. They make reactions that provide energy. This does not make their food "living" though.
Nothing in any science is 100% certain. Every measurement contains some degree of error. Science, even quantitatively, can only be certain to within the limits of the errors in measurementor observation.
"I see what you're getting at. Life is built OF non-living components. Now, do plants come from non-living atoms?"
Atoms are not "alive"
" They feed off of nutrients. They make reactions that provide energy. This does not make their food "living" though."
Huh?
Well, then lets have the scientific community focus it's efforts on finding out how DNA came about without prior organization. Then this discussion will have meaning.
I'm not dismissing you, and what you said IS fascinating, but it seems to me this non-explored option of "life evolving" is being ignored in favor of assumptions.
His experiment also yielded a far greater proportion of compounds that are toxic to life. Furthermore, his "trap" for them removed products from an otherwise reversible chemical equation, where the amino acids would be destroyed again. His experiment did not use a closed system.
"Atoms are not 'alive'"
VERY GOOD! Now you know why it's called "non-living" ("dead matter" may suit you better)
"Huh?"
What was pointed out was that plants can make food out of raw materials (not by eating other living things)
Now, with that information at hand, go re-read my post.
I think you need to take a chemistry course.
It does not follow that an atmosphere containing 40% hydrogen cannot have changed into one containing 78% nitrogen. The gas giants today are the hydrogen-containing planets simply because they are big enough to prevent the hydrogen from escaping. Hydrogen molecules, since they are much lighter, have a much higher average velocity at a given temperature than do nitrogen and oxygen (and CO2 and any other gas) molecules. At terrestrial temperatures, this velocity typically exceeds the earth's escape velocity, so the hydrogen escapes. On gas giants, the escape velocity is higher than the molecular velocity, so the hydrogen is retained.
As far as going from 40% hydrogen to 78% nitrogen goes, for simplicity consider a small atmosphere containing 166 molecules, 66 of which are hydrogen, 78 are nitrogen, 21 are oxygen and one is argon. This atmosphere then contains 66/166 = ~40% hydrogen, 78/166 = ~47% nitrogen, 21/166 = ~12.5% oxygen and 1/166 = ~0.5% argon. Now allow all of the hydrogen molecules to escape and you are left with an atmosphere containing 78 nitrogen, 21 oxygen and 1 argon molecule. This atmosphere then has a composition that should be familiar, ie. 78% nitrogen, 21% oxygen, and 1% argon.
Maybe we have mis-understood each other if you believe that.
Lets try this: explain your position about autotrophic organisms.
You're willing to ignore one type of science (quantum psychics) in exchange for another science(evolution)that agrees with your "beliefs."
"Selective science" is then just another form of religion. It's all based on your personal choice of theories.
If you read correctly, this statement is a hypothetical. ie, IF the earth's atmosphere were hydrogen-rich, as we have shown, then organic compounds could have easily been produced. Photochemical reactions of hydrogen and carbon dioxide are in fact readily carried out in lab experiments. There's no reason to believe that in an atmosphere with high concentrations of CO2 and H2, that there'd be any problem carrying out similar photochemical reactions. The photochemistry involved in this process is very well understood.
As for the outer planets, the mean surface temperature refers to the extreme upper atmospheric layers since these planets have no defined surface boundary so it is difficult to make absolute comparisons of physical properties between the inner planets and the gas giants. The point from the post I replied to was the presence of hydrogen on the early Earth. The gas giants still retain their hydrogen because of their intense gravity. The inner planets would have lost their atmospheric H2 because their combination of lower gravity and higher temperature pushes a significant proportion of the hydrogen molcules past escape velocity based on their Boltzmann distribution of speeds.
So, you are saying that one can have organic compounds without the existence of life?
Are you then denying that at one time there was an earth without life? Whether created by God or created as a result of ambient environmental conditions and the laws of chemistry, if there hasn't always been life on earth, then life must have arisen from non-life at some point. That doesn't even seem to me to be in question. The question is not whether life arose from non-life, but rather how it did so. That is where the disagreement is.
Once again, laws in physics are descriptive not prescriptive.
Hope I could clear that up.
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