Conditions on primitive Earth

[krumov]

Hi there all,
I'm a student in Molecular Biology with an interest in Biochemistry and this is what I'm going to specialize in the future.I am currently doing a coursework (a review article) in one of my favourite research fields in science - the origin of life and the evolution of metabolism so you are probably already guessing why I am writing in the Earth Science section.I am slightly lost among all those papers regarding the early conditions of our planet and It's hard for me to form an opinion.And this is very important since I have to be able to discuss the process of abiogenesis with respect to these conditions.So I need some help from a person with a good background in Geology and Earth science.
I see that the earliest views regarding the early Earth are that the atmosphere was considered reductive in character (which will support the famous Urey-Miller experiment) - mainly composed of chemicals like methane, amonnia and hydrogen.However, It seems that the views have changed and in the last decade there is also an opinion that It has actually been neutral to slightly reductive - richer in compounds like carbon dioxide.Despite that in some recent papers I read that the concept of a reductive atmosphere is not dead (which with respect to the origin of life will make the Urey-Miller experiment still relevant).Can someone help me to get an orientation about the current model regarding the primitive conditions of Earth?

(I saw the homework section but I decided to create a topic here since I think this is not a question with a precise and simple answer and maybe requires to be discussed.Besides, I think that early Earth was a pretty interesting place )

Thank You

[arc]

Hi krumov, and welcome to SFN.

 

You might take a look at the four Galilean moons of Jupiter; Io, Europa, Ganymede, and Callisto.

They are some of the largest moons in the solar system, Ganymede is even larger than Mercury. They may even have been at their early beginnings, solar orbiting planets that were captured by Jupiter. The outermost have been held in somewhat cryogenic conditions, possibly retaining their early earth like chemistry under their layers of ice. The four moons display through their varied orbital distances from Jupiter, a graduated exposure to gravities and radiation that has allowed them to all develop in their own unique way. Europa and Ganymede have chemical trace atmospheres with Ganymede being the "only satellite in the Solar System known to possess a magnetosphere, likely created through convection within the liquid iron core."

 

These moons are likely our best chance to find ext-life in the coming decades.

 

[Mike Smith Cosmos]

Hi there all,

I'm a student in Molecular Biology with an interest in Biochemistry and this is what I'm going to specialize in the future.I am currently doing a coursework (a review article) in one of my favourite research fields in science - the origin of life and the evolution of metabolism so you are probably already guessing why I am writing in the Earth Science section.I am slightly lost among all those papers regarding the early conditions of our planet and It's hard for me to form an opinion.And this is very important since I have to be able to discuss the process of abiogenesis with respect to these conditions.So I need some help from a person with a good background in Geology and Earth science.

I see that the earliest views regarding the early Earth are that the atmosphere was considered reductive in character (which will support the famous Urey-Miller experiment) - mainly composed of chemicals like methane, amonnia and hydrogen.However, It seems that the views have changed and in the last decade there is also an opinion that It has actually been neutral to slightly reductive - richer in compounds like carbon dioxide.Despite that in some recent papers I read that the concept of a reductive atmosphere is not dead (which with respect to the origin of life will make the Urey-Miller experiment still relevant).Can someone help me to get an orientation about the current model regarding the primitive conditions of Earth?

(I saw the homework section but I decided to create a topic here since I think this is not a question with a precise and simple answer and maybe requires to be discussed.Besides, I think that early Earth was a pretty interesting place )

Thank You

?

.

I just bought a Trilobite fossil from the Ordovician Period . Found in Erfoud, Morocco . I was yesterday at Lyme Regis , along the Jurasic Coast in the U.k.

 

Trilobites , One of the very early creatures, according to Richard Faulty palaeontologist of note in the u.k.

This is from approx 460 million years ago. I know this is not very early rock earth, but it is very early animal earth . ( or at least Ocean ) .

 

I am currently looking this creature in ' the Eye ' across 460,000,000 years ! It's eyes have got a bit calcified over that time . But the man in the shop showed me one of the eyes of a more expensive trilobite , through a hand held microscope , " it was awesome " .

 

See attachments

 

( trilobite 2-3 inches long )

 

Sketch of what I saw of the eye of the Trilobite . Very Black eyelid, fragmented eyes ( sort of like a fly's eye) ( calcite eyes that is the trilobite)

 

Edited December 8, 2015 by Mike Smith Cosmos

[Ophiolite]

Mike, interesting as your contribution is, it has nothing to do with the OPs questions. Please do not derail thread's with your own musings. I have requested, via the Report function, that your post be split off to its own thread.

 

Krumov, you raise interesting points. Debate on the nature of the primitive atmosphere is, to my knowledge, on going. I share your understanding that current thinking is that the atmosphere was neutral to slightly reducing. However, this is an area of active research and surprises are turning up all the time. For example, in the November 24th PNAS there is this article discussing Potentially biogenic carbon preserved in a4.1 billion-year-old zircon. That pushes the evidence for life back a further 300 million years and hence has massive implications for the nature of abiogenesis.

 

The importance of the Miller-Urey experiment is, to my mind, seriously misunderstood. The results of the experiment were unimportant. The fact of the experiment was hugely important, as it demonstrated it was possible to investigate what may have happened on Earh four billion years ago. Until that point abiogenesis was essentially off limits as a valid field of investigation (Haldane and Oparin, not withstanding).

 

If you have access to a good library I suggest seeking out The Earth Science Review, published annually, for a review article on the topic. There is almost certain to be one within the last five years.

 

Good luck with your study.

[Moontanman]

Hi there all,

I'm a student in Molecular Biology with an interest in Biochemistry and this is what I'm going to specialize in the future.I am currently doing a coursework (a review article) in one of my favourite research fields in science - the origin of life and the evolution of metabolism so you are probably already guessing why I am writing in the Earth Science section.I am slightly lost among all those papers regarding the early conditions of our planet and It's hard for me to form an opinion.And this is very important since I have to be able to discuss the process of abiogenesis with respect to these conditions.So I need some help from a person with a good background in Geology and Earth science.

I see that the earliest views regarding the early Earth are that the atmosphere was considered reductive in character (which will support the famous Urey-Miller experiment) - mainly composed of chemicals like methane, amonnia and hydrogen.However, It seems that the views have changed and in the last decade there is also an opinion that It has actually been neutral to slightly reductive - richer in compounds like carbon dioxide.Despite that in some recent papers I read that the concept of a reductive atmosphere is not dead (which with respect to the origin of life will make the Urey-Miller experiment still relevant).Can someone help me to get an orientation about the current model regarding the primitive conditions of Earth?

 

(I saw the homework section but I decided to create a topic here since I think this is not a question with a precise and simple answer and maybe requires to be discussed.Besides, I think that early Earth was a pretty interesting place )

 

Thank You

 

 

This link may help you find a starting point, as i understand it Earth had a silicate atmosphere for several decades after the Moon formed ,

 

http://forces.si.edu/atmosphere/02_02_00.html

 

Oxygen also has a strange history.

 

http://www.ux1.eiu.edu/~cfjps/1400/atmos_origin.html

 

Evidently there is more than one viable hypothesis.

 

http://www.astrobio.net/topic/solar-system/earth/geology/earths-early-atmosphere/

[Essay]

I was wondering how (and when) the Late Heavy Bombardment (4.1 to 3.8 billion years ago) fit into the question, and I found an interesting blog that seems to reliably summarize (with some good, well-cited but un-linked, references on) this topic.

 

http://sanuja.com/blog/late-heavy-bombardment

 

"The material ...added to Earth resulted in physical and chemical alterations of the hydrosphere, biosphere, atmosphere, and lithosphere."

 

"The increased temperature of liquid water established hydrothermal vents, which had the potential to shelter pre-bombardment life or host post-bombardment life. All necessary conditions for life were present on Earth before the LHB, including continental crust, liquid water, and a primitive atmosphere (Martin et al., 2006)."

 

"Earth’s atmosphere endured both loss and gain processes, which altered the pressure and composition of the atmosphere. Impact erosion, as described by Hamano and Abe (2010), ...due to impact was minor, however the atmospheric pressure increased during the course of the bombardment, mainly due to buildup of CO and CO2 (De Niem et al., 2012)."

 

"...creating topographic dichotomy 3-4 km high (Grieve 1980)."

...gosh, think of the erosion back then!

===

 

But it seems the early atmosphere may have varied somewhat, perhaps more than once, between periods dominated by highly reducing or moderately or mildly reducing or even neutral conditions.

~

 

[Mike Smith Cosmos]

I was wondering how (and when) the Late Heavy Bombardment (4.1 to 3.8 billion years ago) fit into the question, and I found an interesting blog that seems to reliably summarize (with some good, well-cited but un-linked, references on) this topic.

 

 

...gosh, think of the erosion back then!

===

 

But it seems the early atmosphere may have varied somewhat, perhaps more than once, between periods dominated by highly reducing or moderately or mildly reducing or even neutral conditions.

~

 

..

 

I think the early earth is a very interesting subject.

 

From 4,600,000,000 years ago, up to the Cambrian times at approx 500,000,000 years ago. ( namely up to the Trilobite times )

 

I have been reading about the change from a total sea of Magma to Crusts.

Both the formation or the first crusts ( ocean crusts ) . Then the first continental crusts.

All apparently caused by the upwelling of convecting ,Red Hot , magma at the mid ocean , spreading, accreting *. , the continental crusts and sub ducting , back into the mantle as a techtonic plate mechanism , right from those early times!

 

All this crust matter being ' lighter' than the mantle matter . Hence why it floats on top!

 

Incredible !

 

Ref :- David Waltham PhD Physics, Lecturer Royal Holloway , University of London . Head of Earth Science 2008- 2012 . Book " Lucky Planet " Pages 50 -64

 

* Accreting Like a bull dozer see Accreting . :- http://www.physicalgeography.net/fundamentals/10j.html

 

 

Mike

Edited December 11, 2015 by Mike Smith Cosmos

[puppypower]

The original Miller-Urey experiment used a reduced gas mixture of methane, ammonia, hydrogen and water which had been in vogue, for the early earth, at the time of his experiment.

 

In recent years, studies have been made of the amino acid composition of the products of "old" areas in "old" genes, defined as those that are found to be common to organisms from several widely separated species, assumed to share only the last universal ancestor (LUA) of all extant species. These studies found that the products of these areas are enriched in those amino acids that are also most readily produced in the Miller–Urey experiment. This suggests that the original genetic code was based on a smaller number of amino acids – only those available in prebiotic nature – than the current one.^[33]

 

 

Professor Jeffrey Bada, himself Miller's student, inherited the original equipment from the experiment when Miller died in 2007. Based on sealed vials from the original experiment, scientists have been able to show that although successful, Miller was never able to find out, with the equipment available to him, the full extent of the experiment's success. Later researchers have been able to isolate even more different amino acids, 25 altogether. Professor Bada has estimated that more accurate measurements could easily bring out 30 or 40 more amino acids in very low concentrations, but the researchers have since discontinued the testing. Miller's experiment was therefore a remarkable success at synthesizing complex organic molecules from simpler chemicals, considering that all life uses just 20 different amino acids.^[7]

 

Variations of the original Miller experiments have demonstrated that neutral gases could also be used to make amino acids. In practice gas mixtures containing CO, CO₂, N₂, etc. give much the same products as those containing CH₄ and NH₃ so long as there is no O₂. The hydrogen atoms come mostly from water vapor.

 

In fact, in order to generate aromatic amino acids under primitive earth conditions it is necessary to use less hydrogen-rich gaseous mixtures. Most of the natural amino acids, hydroxyacids, purines, pyrimidines, and sugars have been made in variants of the Miller experiment.

 

MacNevin did an experiment where he was passing 100,000 volt sparks through methane and water vapor and produced "resinous solids" that were "too complex for analysis." His experiments suggests abiogenesis fossil fuels may have been made without life and fossils. Life may have infiltrated after the fact.

 

 

​

 

​

[Moontanman]

 

MacNevin did an experiment where he was passing 100,000 volt sparks through methane and water vapor and produced "resinous solids" that were "too complex for analysis." His experiments suggests abiogenesis fossil fuels may have been made without life and fossils. Life may have infiltrated after the fact.

 

 

​

 

​

 

Thomas Gold suggested a similar abiogenic origin for fossils fuels in his book "The Deep Hot Biosphere"

[Essay]

MacNevin did an experiment where he was passing 100,000 volt sparks through methane and water vapor and produced "resinous solids" that were "too complex for analysis." His experiments suggests abiogenesis fossil fuels may have been made without life and fossils. Life may have infiltrated after the fact. ​

...speaking of abiogenesis fossil fuels:

 

I was surprised to learn the main reason why humus was “little studied” for much of the 20^th century, was that it also was “too complex for analysis” or too difficult to reliably isolate and characterize …or as Steinberg [2003] says on page ten, in Ecology of Humic Substances in Freshwaters, “The fact that these matters are little studied is certainly due to the traditional view that Humic Substances are (with the exception of photolytic cleavage) inert, refractory, or in some other way passive in ecosystems.” He concludes by noting, “This idea is at best outdated, if not false.”

===

 

Now that science has begun to characterize the variety of molecules that comprise humus (which broadly includes humic substances (HS), humic acid, fulvic acid, humin, and humic acid precursors), it is easy to see how these relatively simple molecules are converted into ‘fossil fuels’ after being geologically concentrated and then variously compressed and heated.

 

And if these molecules occur naturally, then it is probably no coincidence that some of these same molecules, which are created as part of the resinous or "oily scum" and "yellow-brown" goo in various abiogenesis experiments, are some of the same molecules that have been identified as intermediates in the normal biochemical pathways found in common physiological systems.

===

 

This would also explain how, as Steinberg writes on page 36, “Humus or at least HS-like molecules become established in ecosystems independently from life and death events and play a definitive role in early evolution.”

 

He adds:

“The HS are to be granted the role of an independent ecosystem component, such as atmosphere, water, or light, since they come into being simultaneously with early life.”

 

That is a paradigm shifting idea, isn’t it? When we formed our worldview, evaluated our resources, and developed our economic ideologies, did we overlook accounting for an important fundamental?

 

...but back on the topic:

“This means that living organisms have to adapt to humus or HS-like materials with which they come in contact from the very time they evolve.”

Wow!

 

For one thing, any HS would have been scavenging reactive radicals, “which otherwise inhibit or prevent the synthesis of amino acids, carbohydrates, and nucleic acids.”

===

 

Steinberg continues on page 37, noting that “Once organisms have evolved, and through the formation of humus from dead biomass, the quality of HS becomes more diverse and its quantity greater. For organisms, the adaptive pressure rises.”

 

So it seems, since life developed and lives within a virtual ‘aether’ of humic substances, it is not surprising that, “…the transformation (detoxification) systems are very conservative, occurring in only slightly altered forms in organisms from bacteria to mammals.”

~

Edited December 12, 2015 by Essay

[Ophiolite]

Clearly my education is deficient. (No surprise there - the natural consequence of being an autodidact.)

 

I had always understood humus to be that ingredient in soil that was a product of decomposing vegetation and animal matter. Since soil, as known to us today, and terrestrial vegetation, are comparative novelties, younger even than multi-cellular organisms and hard shelled creatures, I don't understand how humus could be present in the subsea environment to which life was pretty well restricted for 80% or more of its time on Earth. Since most hypotheses for abiogenesis place it somewhere in the sea, how could this terrestrial material - humus - "come into existence simultaneously with the first life".

 

Would you explain what simple fundamental I have totally failed to grasp.

[Essay]

The conclusion I took away from this, which I hoped the quotes would suggest, is that essentially the "pre-biotic soup" would be equivalent to an ocean of humus. Sure it would be very dilute humus, in most places; and this is using the broadest definition of humus, which includes those simple molecules identified in the abiogenesis experiments, as well as the many resinous and oily, yellow-brown, molecules that were not identified in those same experiments.

 

But the process of humus production, as well as humification and diagenesis, would still operate in marine environments and on seafloors; and as Steinberg points out, "the quality of HS becomes more diverse" as life evolved, and so especially after it moved up onto land. Probably there should be different words for 'pre-biotic humus' and 'post-biotic humus' (and 'post-Cambrian humus'), but since this is a "little studied" topic, the terminology is still developing. Your view was right, for the relevant circumstances; but now this word is being applied to a much broader canvas, so the definitions get broadened ...or words to that effect.

 

~

[Ophiolite]

Thank you for the clarification Essay. I agree completely with you that distinct terms are required. Humus has, at least until now, a fairly precise definition and context. This attempt to broaden its range is - at least for me - misleading and counterproductive.

[puppypower]

The bottom line is the earth's water played a pivotal role in abiogenesis. Water was not just a reactant for most of these abiogenesis mechanisms, but water via the generation of lightning was a major source of high energy needed for making organic materials from simple gases.

 

If we start with an atmosphere of varied gases plus water, with the water forming huge thunderstorms with lightning, many of the gases will be sequestered into higher boiling point liquids, such as amino acids and humus. Reduced gaseous material will be stripped from the atmosphere and converted to liquids that will enter the oceans.

 

This cases the atmosphere to evolve toward simpler nonreactive gases like CO2, N2. Miller based experiments show that even these can form animo acids with the less reduced atmosphere, allowing animo acids with resonance structures. The water is cleaning and changing the atmosphere while adding materials to the ocean water and land, for further development. Once life begins to generate O2 through photosynthesis, there is a shifting with CO2 sequestered and traded for higher O2. This ends the Miller aspect, since O2 tends to reverse its reactions. Life has been jump started.