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.
Well, I will simply give you the description you have earned, you are inane and patronizing.
No you weren't. You were "talking" about teaching.
Rational speculation is not mysticism, but a part of the scientific process and what I've described is a reasonable conjecture. That is part of the scientific process. Us scientists have to start with a hypothesis based upon some form of rational speculation, then develop experimentation to test it. Repeat the process iteratively and you develop theories.
In this case, to assume existing cellular mechanisms exisited during biogenesis, as AndrewC has suggested, is also speculation. However, a mechanism outside the "chicken vs egg" cirular logic is more reasonable, even though such a theory does not exist at this time.
I don't recognize that suggestion. My suggestion, if any such statement exists, would be that current theories are not even close to providing a plausible explanation for the simplest replicating thing to have formed from reactions plausibly available on a violently reactive and hot earth.
Finally, this statement "Speculation, not supported by evidence. Another no-no." was entirely correct in describing your flight of fancy in post 286. You have established that with the "I can state with certainty that we don't know what chemical soup we will find on Titan", so you were speculating.
Based on your own arguements, scientist should not engage in speculation. Well, as I've posted before, speculation is a part of the scientific process. Get used to it becasue it's been that way from the start. What you call my "flight of fantasy" re #286 is no such thing. Your (Mathemagician's) guess of finding thor's Hammer in a valley would be. My speculation is rooted in knowledge and experience in organic chemistry. Your "Thor's Hammer" supposition lacks a basis in reality, unless you are trying to disprove a negative. If given a complicated mixture of hydrocarbons in an environment such as Titan, it is reasonable to expect to find a wide variety of chemical species. I used the term "unexpected" because there is no established reference for what the chemical composition and distribution is on Titian. Therefore, any result would necessarily be unexpected. On a deeper level, complex hydrocarbon mixtures can contain a wide variety of trace species. That is well known principle to anyone who has actually done analytical chemistry. I'm talking on the ppm, ppb and ppt levels. There is no chemistry, that I'm aware of, that would deny this description, but that does not mean it cannot happen. Hence, a hypothesis has been created. The next step would be to test it experimentally and see what the results would be. You have merely stated that there is no evidence of this, therefore you cannot say that. I retort that complex mixtures of hydrocarbons previously studied on Earth have yielded interesting, diverse species on the forementioned levels. Therefore, it is not an unreasonable supposition to find complex mixtures wherever hydrocarbons are found.
When I said "We don't know if the first living things were even cellular like what we see today... There may well be an initiation mechansim that is unknown to us at this time..." is a valid description. There are other chemical phenomena, as I outlined in post #425, that functon in an analagous matter. Extrapolation is a valid method for generating a hyposthesis as I've done. It's not "Speculation, not supported by evidence. Another no-no." as has been written. It is construction of a hypothesis based upon existing knowledge of chemistry. To say there is a mechanism we may not know was an improper statement. It should have been more emphatic. There must be a mechanism that, at this time, is unkown to us is a more proper statement. That goes right back to the circular arguemnt of chemicals only used by living things that could only have come from living things. Since we know the world was without life and life arose from abiogenesis, then there must be a mechanism(s) independent of the current cicle of life. The challenge is to define and test those mechanism(s). Miller's experiment is only a small fragment of information towards a more complicated puzzle. In other words, we don't know what the mechanism is, but we can, based on existing knowledge define it's constraints.
Why even discuss anything? By that definition, Science has no predictive ability.
It was and remains a flight of fancy. You yourself limited the species available by discussing it thereby limiting the available universe of possibilities to your speculation which remained unsupported by evidence. If it were supported by evidence then your flight of fancy would be expected which is counter to your statement above.
Finally, Since we know the world was without life and life arose from abiogenesis
I do not accept the sought after conclusion of a proof as an axiom in the said proof.
"Now why does the universe and all that it contains has these properties and no others? Well, I don't know."
Actually, this is the point I was getting at. Not the "how" but the "why"
I wasn't aware of your first response, but your second one I can answer.
2. in machining (turning or milling) there is a range of optimal speeds, feeds, and angles for each kind of material for removing the desired chip profile and producing the desired surface on the workpiece. Too slow is just as bad as too fast.
I do a bit of turning myself, and while I can agree that the fastest safe speed is best, it also takes in to account angle and other factors on if its best. Cutting in to deep at a slow speed may nik the surface, but cutting to deep at too high a speed will destroy it.
So while it is easiest to cut, it also makes the risks higher, and if you don't control your hand VERY well at higher speeds, you may find yourself cutting several centimeters you hadn't intended to. This is due to the additional mechanics involved.
Do you mind mailing me some of the list if you recall them?
Thanks for the response :)
"There is a range of temperatures for which things proceed. Most living things survive over a large range of temperature. Some are more fragile than others."
that part I was aware of. Microbacteria and other such things tend to survive easier at higher temperatures. A virus strain (yes, I know it's argueable if it's "alive" or not) can survive at even more extreme temperatures (hot or cold) and since they still contain protein coding, that's where my question arose. Is coding itself still viable (and possibly more likely) at higher temperatures? "Living things" was a step beyond that.
"I rather doubt that any brute force research project will create life from scratch."
This is being stated with respect, so please don't flame me.
The begining of life WAS "brute force research"
There was no control group, no white coats, nobody controling temperature. "Life" was a MASSIVE step from oblivion. As someone else showed earlier, there are "stages" of protein formations leading to DNA. But information from nothing?
It goes against my understanding as one who works with computers all day long. Something had to "bootstrap" it in. Brute force will show that.
"Nothing is universal."
Then why bother to look for an origin? Everything leaves it's mark in some other aspect of existance. Even ideas and principles.
Would evolution predict the order of genes on the human genome to be more similar to the mouse or the chicken?
You do realize that the patron saint of ID, Michael Behe, fully endorses common descent, dont you?
I don't have a religious problem with common descent, I have a problem with common descent being treated religiously. What would happen to a biologist who thought outside the box & proposed a separate origion for each of the six (or five) kingdoms?
Information, like cloud pictures, is in the eye of the beholder.
We have very simple molecules that self replicate. They obviously aren't life, but there is an easiness about self replication that suggests it is a common attribute of chemistry. Why this would be so you are free to speculate upon, but replication with occasional errors is evolution.
Selection is the source of information.
This is is some sense tautological. Since most of the proposed kingdoms are dominated by single celled or colonial organisms, it could be difficult to find a common ancestor that is not a DNA sharing population. There is a point at which the attempt to trace a lineage becomes futile, because lineage only makes complete sense in sexually reproducing organisms.
"Information, like cloud pictures, is in the eye of the beholder."
A beholder would imply conciousness.
I'll try to get the names of some journals later. I don't have access to the review journals from this computer.
What do you mean by that? Is this some "Charles's law" that we have missed up to now?
I mean simply that self-replication in and of itself does not require life.
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