Earth’s atmosphere before the age of dinosaurs

Posted: April 7, 2012 by Rog Tallbloke in atmosphere, Carbon cycle, climate, general circulation, Geology, Gravity, Ocean dynamics, Solar physics, Tides, volcanos

This is a long but very readable reposted paper which presents a convincing argument built up from several lines of investigation to arrive at the conclusion that the young Earth’s atmosphere was like the planet Venus’ is today. Venus has a very thick heavy atmosphere consisting almost entirely of carbon dioxide, CO2. The implications won’t be lost people following the development of the new theory of climate on this blog, or those considering the history of the Sun’s evolution.

Octave Levenspiel is professor emeritus of chemical engineering at Oregon State University (Corvallis, OR 97331-2702; 541-753-9248; octave@che.orst.edu).

Thomas J. Fitzgerald is a senior scientist in the space technology division of TRW Inc. (Redondo Beach, CA 90278; 562-596-8674).

Donald Pettit is a mission specialist (astronaut) at the National Aeronautics and Space Administration, Johnson Space Center (Houston, TX 77058-3696; 281-461-0630).

An earlier article in Chemical Innovation (1) showed that if you believe that biology’s mouse-to-elephant curve also applies to the flying creatures of the past, and if you also trust aerodynamic theory (which applies equally to flying insects, birds, and airplanes), then the giant flying creatures of the dinosaur age could only fly if the atmospheric pressure was much higher than it is now: at least 3.7–5.0 bar.

If this is so, it raises several interesting questions. For example, how did the atmosphere get to that pressure 100–65 million years ago (Mya)? What was the pressure before that? And how did it drop down to today’s 1 bar? Although we have no definite answers to these questions, let us put forth reasonable possible explanations.

Figure 1. Three possible alternatives for the atmospheric pressure early in Earth’s lifetime, given that it was at ~5 bar, ~100 Mya.

What was the air pressure for the 97% of Earth’s life before the age of dinosaurs? We have three possible alternatives, as shown in Figure 1.

  • The pressure could have been at 1 bar throughout Earth’s earlier life, risen to 4–5 bar ~100 Mya (just at the time when the giant fliers needed it), and then returned to 1 bar (curve A).
  • The pressure could have been ~4–5 bar from Earth’s beginning, 4600 Mya; and ~65 Mya, it could have begun to come down to today’s 1 bar (curve B).
  • The atmosphere could have started at higher pressure and then decreased continuously through Earth’s life to ~4–5 bar ~100 Mya and down to 1 bar today (curve C).

The third alternative seems to be the most reasonable, so let us pursue it. We will also look into the composition of Earth’s atmosphere, but we will first discuss Earth’s surface and see how it affects the atmosphere.

Earth’s surface

Because the atmosphere is largely influenced by the characteristics of Earth’s surface, let us consider its history. Evidence shows that fresh mantle material upwells at fractures in midocean, spreads to the continents, and then sinks back into the interior. Recent measurements (2) show surface movements of 2–30 cm/year or more. Although this may seem to be very slow to us on the human timescale, it is not slow on Earth’s timescale. For example, measurements indicate that South America and Africa separated a mere 125 Mya (3); you could have walked directly east from New York to the Sahara Desert 155 Mya (4). The Atlantic and Pacific Ocean floors are swept clean and are replaced by fresh upwelled material roughly every 200–300 million years (4). Given that Earth is 4600 million years old, enough time has elapsed for >15 exposures of completely fresh solids on the ocean floors.

During this period, the crust floating on the mantle has wandered about. Current thinking is that today’s continents were all part of a super landmass <200 Mya. What about the previous 4400 million years? How many times did the crust split apart and rejoin? Our clues come from the distribution of various life forms. For example, because dinosaur skeletal remains have been found on all continents, this suggests that the landmasses were joined 135–65 Mya.

All of this indicates that Earth’s surface is plastic, deform able, and mobile, with much mixing with the interior. We believe that this movement greatly influenced the atmosphere.

Earth’s original atmosphere

Geologists believe that most of the carbon on the young, hot Earth, >4000 Mya, was in the form of gaseous carbon dioxide, carbon monoxide, and methane. With time, the CO and CH4 reacted with oxide minerals and were transformed into CO2. These reactions did not change the total amount of carbon in the atmosphere.

Our sister planet and nearest neighbor, Venus, has an atmosphere of 90 bar pressure, consisting of 96% CO2 (5). Why should Earth be so different? Ronov measured the equivalent of at least 55 bar of CO2 tied up as carbonates around the world (6), whereas Holland estimates that at least 70 bar of CO2 is bound as carbonate materials (7). These carbonates had to come from the atmosphere, by way of the oceans, so we propose that, after the original oxidation of CH4 and CO, Earth’s early atmosphere was at very high pressure, up to 90 bar, and that it consisted primarily of CO2.

If we are correct, why did Venus’s atmosphere remain at 90 bar while Earth’s decreased to a few bar during the age of dinosaurs and then declined to the 1 bar it is today? What happened to Earth’s CO2 and by what mechanism did it virtually disappear?

Figure 2. Comparison of Venus with Earth. p = atmospheric pressure, r = radius, and ρ = density.

We compare Venus and Earth in Figure 2. The two planets are about the same size; however, Venus has no moon, whereas Earth has one of the largest moons in the solar system. Our moon has the same density as Earth’s crust, which suggests that the moon was formed by stripping Earth of some of its then fluid crust. If not for this loss, Earth’s crust, now only 5–30 km thick, might be 42 km thicker. Therefore, Earth’s crust should be thinner than that of Venus.

Being thinner, Earth’s crust was fragile and broke up under the action of the mantle’s convective forces. In contrast, Venus’s thicker crust remained rigid and did not permit the mechanisms that removed the CO2 from its bound state.

In addition, because Venus is closer to the Sun and hotter than Earth, free liquid water cannot exist on it, whereas Earth has giant oceans that cover two-thirds of the planet. The oceans played an important secondary role in removing CO2 from the atmosphere.

Dissolution of CO2 in Earth’s oceans

At an atmospheric pressure of ~90 bar, a considerable amount of CO2 would dissolve in the oceans. CO2 dissolves in water according to the equilibrium relationship

where H is the Henry’s Law constant. H depends on temperature, but is ~876–1000 bar per unit mol fraction of CO2 (8, 9).

If we assume that Earth’s oceans are 2 km deep, the values given above imply that at equilibrium, for each mole of CO2 in the atmosphere, there is one mole of CO2 dissolved in the ocean. So an atmosphere originally consisting of 90 bar of CO2 would decrease to 45 bar of CO2 by dissolution alone; however, another factor acts to lower the concentration of CO2 in the atmosphere even further.

Reaction of CO2 with upwelling minerals

Figure 3. The upwelling of Earth’s mantle material causes rejuvenation of the ocean bottoms

As mentioned earlier, our picture today is of continents “floating” above a circulating layer of mantle, which rises at mid ocean ridges and sinks elsewhere (Figure 3). The upwelling brings fresh minerals, including oxides of calcium, magnesium, and other elements, up from Earth’s interior. The oxides dissolve in ocean water and then combine with dissolved CO2 to form carbonate deposits.

We assume from reaction kinetics that the rate-controlling step of this reaction is the upwelling of the alkaline oxides at the tectonic plate boundaries and not the solution and transport of CO2 from the atmosphere to seawater. On the basis of a conservative assumption of a roughly constant spreading rate of the seafloor, this means that the concentration of CO2 in the atmosphere decreased roughly linearly with time (zero-order kinetics). When the carbonates sink back into the mantle, they are heated and decompose, releasing captured CO2, which returns to the atmosphere through volcanic eruptions and to the ocean from vents in the ocean floor (Figure 4).

Figure 4. Circulation and progressive removal of CO2 from the atmosphere.

Today, vast deposits of sedimentary carbonate rocks are found on land and on ocean bottoms, >1,000,000 km3 throughout Earth’s crust. Above the continents, the CO2 was taken up by rainwater and by groundwater. This CO2-rich water reacted with rocks to form bicarbonates, followed by transport to the ocean and precipitation as calcium and magnesium carbonates. In the ocean, dissolved CO2 combined with the calcium hydroxide to form deposits of chalk, or it was taken up by coral, mollusks, and other living creatures to form giant reefs. A study of the distribution through time of these deposits gives us clues to the history of CO2 in the atmosphere.

Figure 5. History of deposition of CO2 as carbonates. The red area represents continental deposits that “float” on denser material and are not subducted. The blue area represents ocean deposits. These are frequently subducted and therefore relatively young.

A detailed analysis by Hay (6) of the extensive measurements taken from around the world by Ronov and Yareshevsky (10) is summarized in Figure 5. Hay’s analysis shows that today the continents contain at least 2.82 × 106 km3 of limestone, which are the remains of deposits over the past 570 million years that have not been washed to sea or subducted back into Earth’s interior. This is equivalent to a CO2 atmospheric pressure of 38 bar. If we add the carbonates found on the ocean floor, the equivalent CO2 atmospheric pressure rises to 55 bar. Integrating the values plotted in Figure 5 gives the progressive depletion of CO2 from the atmosphere (Figure 6). Thus, CO2 is recycled: 55–70 bar or more is accounted for on the surface of Earth (6, 7), and ~30 bar is in the process of being recycled in the planet’s interior.

Figure 6. Progressive lowering of CO2 pressure due to carbonate formation and deposition on Earth’s surface.

Figure 5 verifies the earlier statement that the present oceans are relatively young because they contain limestone not older than 200 million years. On the other hand, the continental landmasses are much older because, 100–65 Mya, the oceans and the atmosphere shared the free CO2 equally. Consequently, the pressure of CO2 in the atmosphere was ~8–10 bar in the age of the flying creatures (Figure 6).

The geological evidence is consistent with and lends support to the physiological and aerodynamic arguments (1) that the atmospheric pressure was definitely higher in the age of dinosaurs than it is today. If you reject this argument and if you prefer to believe that the atmosphere was at 1 bar throughout Earth’s history, how do you explain where the measured 55–70 bar of CO2 in limestone and other carbonates came from?

The astronomical argument

From the viewpoint of the modern theory of stellar evolution, Sagan and Mullen discussed the “faint early sun” paradox, which asks why Earth’s surface did not freeze in its early days, given a 25–40% lower solar luminosity at that time (11). These values represent the range of five estimates. With these lower luminosities, Earth’s average temperature would have been somewhere between –5 and –21 °C instead of the present 13–15 °C. With frozen oceans covering our planet, how could life have established itself and thrived under these inhospitable conditions?

One reasonable answer to this question is that CO2, the atmosphere’s efficient greenhouse gas, was present at high concentration in those early times. Kasting and co-authors suggest a factor of 100–800 times as high as today, all at 1 bar (12, 13); however, he did not consider the possibility of a higher total pressure of the atmosphere, as we do here.

Earth’s history

As our young planet cooled and condensed into a solid, it was surrounded by a thick, soupy atmospheric mixture. Hydrogen and hydrogen-containing compounds combined with oxygen to form the water that became oceans, while the carbon-containing compounds, principally CO and CH4, combined with oxygen to form CO2 at high pressure. All this took about half of Earth’s lifetime, and it left the atmosphere depleted of oxygen.

Life probably got its foothold in the oceans of the barren planet as blue-green algae and cyanobacteria—organisms that did not need oxygen to live. Photosynthesis had not yet been invented by plant life. So the reaction that sustained these life forms was

These algae spread throughout Earth’s oceans.

After about a billion years of additional experimentation, life came up with its most important invention, photosynthesis, and so learned to live off the abundant CO2 of the atmosphere plus sunlight and thereby invade the landmasses. Land plants evolved and lived by the reaction

During the Carboniferous period, 350–280 Mya, these plants proliferated widely, covering the land surfaces with lush forests of giant ferns, trees, and plants of all types. Because the atmosphere was rich in CO2, but very poor in oxygen, dead plant material did not decompose rapidly, so layer upon layer of it was laid down in thick blankets that would transform over time to coal.

It is estimated that each 1-m thickness of coal comes from the compression of a 10–20-m layer of dead organic matter (14), so that today’s 10-m thick coal seam represents an original 100 m of decayed material. Such a thick layer of decaying matter is something that we do not see anywhere today. Tropical forests today only support a very thin layer of decaying matter because of rapid oxidation. Thus, 100-m-thick layers can only occur if the atmosphere discourages oxidation. This is additional strong evidence that the atmosphere in those distant times was rich in CO2, but poor in oxygen.

With time, the concentration of CO2 steadily decreased, primarily because of the formation and deposition of limestone and other carbonaceous materials. CO2 was also lost by photosynthesis followed by the deposition of carbonaceous substances such as coal, petroleum, peat, oil shale, and tar sands; however, this loss was quite minor. Calculations show that the deposit of what are now considered fuel reserves lowered the atmospheric CO2 by <<1 bar.

At the same time, the concentration of oxygen slowly rose. These two changes, the decrease in CO2 and the rise in oxygen, thinned the forests and the dead material began to be oxidized more rapidly, so that dense layers of dead organics were no longer deposited. Evidence of this change in atmospheric conditions is that we cannot find any massive coal deposits younger than 65 million years.

Figure 7. Earth’s proposed atmospheric history.

Animal life found this changed atmosphere to its liking, so mammals and dinosaurs flourished, first as very small creatures but then increasing in size as a result of evolutionary competition. This led to the giant flying creatures close to the end of the dinosaur age. It could be that these creatures died out as the total pressure of the atmosphere dropped below their sustainable level (Figure 7).

Limestone caves

There are many limestone caves throughout the world, some of which are several kilometers long. These caves are all relatively young, most of them <100 million years old, and were carved by running water, which dissolved the limestone. This tells us something about our atmosphere as well.

Because of its high concentration in the atmosphere, CO2 dissolved in rainwater and groundwater, and the reaction

Calcium hydroxide/carbonate equilibrium

was driven to the right. When the atmosphere becomes lean in CO2, the reaction shifts to the left. The fact that the limestone caves were formed relatively recently indicates that the CO2 concentration in the atmosphere was very high long ago, leading to the deposits of limestone, but became very low recently, allowing limestone to dissolve.

Experimental verification

Besides the general findings supporting the theory of plate movement, perhaps the most tangible and unambiguous evidence for the recycling of Earth’s material from crust to deep mantle and back again comes from a recent report by Daniels and co-authors (15).

In high-CO2 atmospheres and other hostile environments, life forms can take advantage of free energy in an amazing range of environments: above the boiling point and below the freezing point of water, in pressures as high as 300 bar, in oxygen-rich and oxygen-poor environments, and in the presence and absence of sunlight (16, 17). On a more familiar level, the microbe that produces champagne bubbles operates at pressures up to 7 bar of CO2.

Other estimates of CO2 concentrations

Researchers have speculated that the CO2 concentration may have been somewhat higher in the past than it is today. Studying carbon exchange between mantle and crust, Des Marais suggests that 3000 Mya, the atmosphere contained at least 100 times as much CO2 (or 0.03 bar) as it does today (18).

Holland (7) estimates that Earth’s earliest atmosphere contained up to 20 bar of CO2 and that ~10 bar could conceivably have persisted for several hundreds of millions of years (19). Many other such proposals have been put forth.

Plant growth at high CO2 concentrations

It is pertinent to ask whether any experiments have been performed to suggest whether life could thrive at higher CO2 concentrations. Pine and aspen trees grown at the University of Michigan’s biological station at Pellston, were found to respond dramatically to elevated CO2 levels. They grew 30% faster than normal trees at about double the normal CO2 level (700 ppm) (20).

However, to test our speculation we need to see if plants can survive, not at double today’s CO2 concentration, but at thousands of times higher. We put this proposal to the test by growing plants in 32 sealed containers (1- and 2-L plastic soda bottles containing weighed amounts of CO2) at pressures from 2 to 10 bar. These conditions gave CO2 partial pressures 3000–27,000 times greater than normal, or 50–90% CO2.

Of the species tested, Taxodium, Metasequoia, Araucaria, Equisetum, and Sphagnum grew best at these higher pressures; one specimen of Taxodium grew 7 cm over 2 years at 2 bar (50% CO2). In general, however, plant growth was considerably slower than at 1 bar. Mosses, ferns, and flowering plants died within a month at these high CO2 levels.

The poor growth observed in these experiments is most likely due to the buildup of product gases in the sealed containers, rather than high CO2 pressure, and therefore these results could be flawed. We would expect that vigorous growth would be observed in a continually rejuvenated atmosphere. Although present-day plant life is probably not adapted to living at the very different atmospheres and pressures of the past, our preliminary experiments do suggest that a dense CO2 atmosphere could have existed on early Earth without violating any known constraints on the planet’s evolution.

Making sense of it all

If we assume that Earth’s early atmosphere was very different, both in composition (mainly CO2) and total pressure, that would answer some puzzling questions from a variety of disciplines.

    • How did the flying creatures from the age of dinosaurs have enough energy to fly when physiology, biology, and aeronautics say that this was impossible?
    • How could life have developed on Earth when astronomy says that Earth was too cold to sustain life?
    • If Earth’s atmosphere had stayed at ~1 bar throughout its history, where did the equivalent of 50–70 bar of CO2 in limestone and other carbonates on Earth’s surface come from?

This picture of high CO2 concentration and high pressure in the past also explains why most massive coal seams are older than 65 million years and why most limestone caves are younger than 100 million years.

Although we do not know the values for the atmospheric pressure in those early times, and although each of the arguments in this paper only leads to suggestions, when taken together, the evidence from these various sources leads to the same conclusion: The atmospheric pressure was higher in the past than it is today and consisted primarily of CO2. This hypothesis presents a picture of our evolving planet that should be examined and that could have interesting consequences.

References

  1. Levenspiel, O. Chem. Innov. 2000, 30 (5), 47–51.
  2. The Earth’s Fractured Surface. Map; National Geographic, April 1995.
  3. Wegener, A. Origin of Continents and Oceans; Biram, J., Translator; Dover: New York, 1966.
  4. Sullivan, W. Continents in Motion; McGraw-Hill: New York, 1974.
  5. CRC Handbook of Chemistry and Physics, 66th ed.; Chemical Rubber Company: Cleveland, 1986; p F-129.
  6. Hay, W. W. Potential Errors in Estimates of Carbonate Rock Accumulating through Geologic Time. In Geophysical Monograph Series, Vol. 32; Sundquist E. T., Broeker, W. S., Eds.; American Geophysical Union: Washington, DC, 1985, pp 573–583.
  7. Holland, H. D. Chemical Evolution of the Atmosphere and Oceans; Princeton University Press: Princeton, NJ, 1984.
  8. Hougen, O. A.; Watson, K. M.; Ragatz, R. A. Chemical Process Principles, Part 1, 2nd ed.; John Wiley: New York, 1954; p 182.
  9. International Critical Tables, McGraw-Hill: New York, 1928; Vol. 3, p 279.
  10. Ronov, A. B.; Yareshevsky, A. A. Chemical Composition of the Earth’s Crust. In Geophysical Monograph Series, Vol. 13; Hart, P. J., Ed.; American Geophysical Union: Washington, DC, 1969, pp 37–57.
  11. Sagan, C.; Mullen, G. Science 1972, 117, 52–56.
  12. Kasting, J. F. Photochemical Consequences of Enhanced CO2 Levels in Earth’s Early Atmosphere. In Geophysical Monograph Series, Vol. 32; Sundquist E. T., Broeker, W. S., Eds.; American Geophysical Union: Washington, DC, 1985, pp 612–622.
  13. Kasting, J. F.; Pollack, J. B.; Crisp, D. J. Atmos. Chem. 1984, 1, 403–428.
  14. Stach, E.; Machowski, M.-T.; Teichmüller, M.; Taylor, G. H.; Chandra, D.; Teichmüller, R. Coal Petrology, 2nd ed.; Gebrüder Borntraeger: Berlin, 1975; p 18.
  15. Daniels, L.R.M.; Gurney, J. J.; Harte, B. Nature 1996, 379, 153–156.
  16. Lutz, R. A.; Fornari, D. J.; Haymon, R. M.; Lilley, M. D.; Van Damm, K. L.; Desbruyeres, D. Nature 1994, 371, 663.
  17. Adams, M.W.W.; Kelley, R. M. Chem. Eng. News 1995, 73 (51), 32–44.
  18. Des Marais, D. J. Carbon Exchange between the Mantle and the Crust, and its Effect upon the Atmosphere: Today Compared with Archean Time. In Geophysical Monograph Series, Vol. 32; Sundquist E. T., Broeker, W. S., Eds.; American Geophysical Union: Washington, DC, 1985, pp 602–611.
  19. Walker, J.C.G. Origins of Life 1986, 16, 117–127.
  20. Chem. Eng. News 1991, 69 (42), 20.

Comments
  1. Ronaldo says:

    The figures do not appear but are visible on the original post.

  2. tallbloke says:

    Thanks, I’ll fix that.

    UPDATE Fixed, I think

  3. Graeme M says:

    Not sure if this has been floated here before, but David Esker has proposed this on his website:
    http://www.dinosaurtheory.com/index.html

  4. tallbloke says:

    Hi Graeme, yes, it was mentioned in this post.
    http://tallbloke.wordpress.com/2012/01/26/greenhouse-gases-cool-planets-volcanos-warm-them/

    I find this paper more convincing to be honest, though David Esker’s ideas are worth a read, because there is broad agreement except for magnitude of pressure.

  5. Graeme M says:

    TB I find that broad agreement intriguing. Before I’d read David Esker’s ideas I had never heard that there was any suggestion that atmospheric pressure differed in the past, but as an explanation for dinosaur size and pterosaur flight it seems a viable hypothesis at first blush.

    As a kid I as always pretty interested in dinosaurs, like most kids. But it never occurred to me to wonder at their size and the physical principles involved. Although I have to admit to always wondering exactly how the large sauropods actually ate enough to stay alive. Given that they are partly believed to have been so big to aid digestion, it seems unlikely that they had such small heads. What would be the volumetric efficiency of such a small intake area? If air pressure were as today, they’d expend enormous energy in just driving their body, let alone movement. If you look around today, no herbivore has such an extreme head/body ratio. I can’t imagine how hard they’d have to eat to get enough food in to fill that size stomach!

    Still, perhaps this has been figured out somewhere along the line, I just never read anything about it back then.

  6. LL says:

    The article is mistaken in what it has to say about biology.

    http://en.wikipedia.org/wiki/Cyanobacteria

    Cyanobacteria and blue-green algae are different names for the same thing. And they are the original photosynthetic organisms. The authors appear to believe that photosyntheses originated in terrestrial forms a billion years later which is simply wrong.

  7. tallbloke says:

    Hi LL and welcome. Yes, I too was bemused by the similarity of the two equations, given the distinction drawn in the text at first. But when you read more closely what they are saying becomes clear.

    “Photosynthesis had not yet been invented by plant life. So the reaction that sustained these life forms was

    [eq2]

    These [phtosynthesising] algae spread throughout Earth’s oceans.”

  8. LL says:

    @tallbloke

    These algae spread throughout Earth’s oceans.

    After about a billion years of additional experimentation, life came up with its most important invention, photosynthesis

    I can’t charitably read this in a way which makes it correct. Blue green algae (also known as cyanbobacteria) invented photosynthesis.

    This is what peer review is for but it doesn’t work if errors are not corrected after being pointed out. The authors may mean archaebacteria which recently (in the past several decades) were deemed a separate kingdom of life apart from eubacteria. Archaebacteria which include extremophiles that can digest iron and sulfur without either oxygen or CO2 are thought to be the original life forms emerging some 3.5 billion years ago. A billion years after that eubacteria emerged and these include cyanobacteria which were the first photosynthetic organisms and which took in CO2 and gave off O2 as a waste gas.

    I don’t believe this mistake really detracts from the narrative but it certainly changes the timeline by a billion years and such a fundamental mistake detracts from the general credibility of the paper and makes it clear that there has been no serious peer review. Certainly anyone who has taken an introductory class in oceanography, which is a common enough class for anyone with a BS degree, knows that cyanobacteria and blue-green algae are the same organism and that it uses photosynthesis to make a living.

  9. LL says:

    Other criticisms come from here, or rather are corroborated here:

    http://books.google.com/books?id=idta6AVV-tIC&pg=PA60&dq=Pterosaur+oxygen&hl=en

    The authors of the book correctly point out that L/D (lift to drag ratio, I happen to be a pilot among other things) does not change with increased air density. The primary thing about pterosaur flight that is not understood is how they acheived takeoff speed as this does decrease in a denser air. Pilots have to deal with these things as taking off from tiny airports in popular mountain resorts such as Mammoth Mountain in California is a lot different from flying in and out of Catalina Island. Unless turbocharged your engine generates a lot less power at Mammoth Mountain and takeoff speed for the same aircraft is substantially higher at the mountain resort. Critters as big as pterosaurs fly all the time toda’s modern thin atmosphere – they’re called hang gliders. ;-) But they don’t take off on flat ground and without a denser atmosphere it’s unlikely pterosaurs could take off from flat ground either although this is open to question because without a density increase a simple increase in partial pressure of oxygen enables better power-to-weight ratios in muscles in the same fasion that it makes for better p/w ratios in internal combustion engines.

    Or maybe pterosaurs were just like modern hang gliders and they had to hoof it up a tall hill in order to take flight. In that same era there were also dragonflies with wingspans of 24 or more inches. These aren’t gliders and use different means of acheiving flight. Denser air would not help them.

    Denser air, in and of itself, only helps for lighter-than-air flight. Fish “fly” through the water but they float to stay “aloft”. It works the same way in air. Flight speeds, and critically takeoff speeds, are reduced in denser atmospheres but it doesn’t take less energy to remain aloft because as density increases so does drag so lift-to-drag ratio for powered flight is uneffected. The big advantage is greater availability of oxygen but this can gained either from increased density or simply more oxygen and less nitrogen without any increase in density.

  10. tallbloke says:

    Hi LL, thanks for your further observations. Unfortunately, the authors are not aware that I have posted this, so they won’t benefit from the ‘peer review’, but we will.

    Your points about algae and bacteria are well taken, and I agree now that you are right.

    Regarding pterosaur flight:
    The lift/drag ratio issue is clearly important. presumably, smooth skinned reptiles present quite a bit less drag to the air than feathered birds do. We could perhaps see the development of feathers as a response to a cooling world with a thinner atmosphere, and so this would argue for the thesis rather than against.

    For acrobatic flight, drag is necessary for sharp turns and quick decelerations as you’ll know being a pilot. Birds can spread tail feathers and perhaps the unusual ‘flag’ like structures on the tails of some pterosaurs fulfilled a similar function. They are proportionally small compared to bird tail-fan capabilities, and taking into account the pterosaur’s higher mass/wing area ratio. Those details seem to support a higher density thesis I think.

    We know comparitively little about the nitrogen cycle but considering it’s a fairly inert gas I don’t see any reason to assume extra oxygen there may have been (due to abundant plant life) would have displaced the existing mass of nitrogen. The ability to fly in an oxygen rich world would be a distinct advantage for escaping lightning ignited forest fires, which would have been pretty awesome if oxygen was much higher than today.

    Lots to consider, keep the ideas and obs coming!

    Thanks – TB

  11. tallbloke says:

    Heh, nice read Tim, thanks. Pity some of the diagrams are so small.

  12. gallopingcamel says:

    Fascinating speculation!

    My reservations center on the effect of pressure on a planet’s surface temperature. Let’s start with 60 bars and a TSI of 1,362 Watts/m^2.

    According to N&K equation (8) the surface temperature would be 550 K (277 degrees Centigrade). This would cause a minor probem as there would be no liquid water at the surface. The bulk of the atmosphere would be composed of steam which would raise the surface pressure by another 320 bars. Recalculate the surface temperature for a total pressure of 380 bars and you get 1147 K. Finally, Jim Hansen’s “Runaway Greenhouse Effect”.

    Jim is right about one thing, if this condition were to occur it could not be reversed absent a huge loss of atmosphere. As we are here discussing it I can safely say none of this happened.

    Let’s try again, assuming Sagan’s “Dim Sun” delivering only 60% of the present TSI (817 W/m^2). Now with a 60 bar atmosphere the surface temperature is down to 484 K (211 degrees Centigrade), still hot enough to vaporize the oceans.

    My contention is that somehow the CO2 pressure must have fallen much earlier than the authors assume and before most of the water arrived.

    Come to think of it, does anyone know when the water arrived? If it was here when the planet’s surface was molten how did it managed to condense into water?

  13. Hans says:

    channon says: April 7, 2012 at 6:25 pm
    http://www.xenology.info/Xeno/11.3.3.htm

    Thanks Tim for all these impressive statements derived from calculations. Yet, I have been told that it is scientifically proven that a bumble bee cannot fly in earth´s atmosphere!

  14. Hans says:

    gallopingcamel says: April 7, 2012 at 7:14 pm

    “Come to think of it, does anyone know when the water arrived? If it was here when the planet’s surface was molten how did it managed to condense into water?”

    To state the problem correctly is half of the solution. Congratulations.

  15. archonix says:

    LL mentioned huge insects, which I think is interesting, as insect size is strictly limited by how dense the atmosphere is. Modern insects can’t get more than a few inches in length; any larger and they wouldn’t be able to breathe. Those much larger prehistoric insects likely couldn’t have survived without a much denser atmosphere.

  16. Tenuk says:

    Much of the ‘high pressure’ atmosphere premise seems to rely on supposition, the use of proxy data and a vivid imagination. I think that evidence for flying dinosaurs is fairly pivotal to this idea, but the current meme regarding these creatures could be completely wrong and open to a differnt interpretation.

    I don’t think that pterodactyls flew, rather they used arms and feet membranes to glide around the landscape using trees to avoid predators, and ambush small prey. Today we have the flying squirrel family (Pteromyini), which operate successfully in a similar manner.

    So, could pterodactyls climb trees? Many specimens have curved hooks on the front of their elbows and sharp hooked talons on their feet, so yes, I think it is possible.

    The other problem I have with flying dinosaurs is the small size of the dinosaur brain, which is even less developed than modern reptiles. It takes a lot of processing power and good eyesight to manoeuvre in 3-D space. Modern birds are equipped to deal with the problem of flying and they figure high up on the animal intelligence league table.

  17. archonix says:

    Oops forgot to add: You could assume that it’s a higher partial pressure of Oxygen that allowed them to survive, but that requires there to be a lot more oxygen in the atmosphere then than now, which seems rather to be begging the question.

  18. Hans says:

    archonix says: April 7, 2012 at 7:29 pm

    “Modern birds are equipped to deal with the problem of flying and they figure high up on the animal intelligence league table.”

    About brain size. The smartest bird managing to survive the Swedish winter has been proven to be “talgoxen” (Parus major) in a big scientific test. Its weight is about 10 gram and its brain must be included in that weight. It needs to eat about 1/3 of its own weight every day if I got it right. Some expert might correct me.

  19. gallopingcamel says:

    Birds have the ability to fly at altitudes that would render you and I unconcious in less than a minute. I think that implies that their cardio-vascular system is much more efficient than ours.

    The current altitude record for birds is 37,900 feet, held by the Ruppell’s Griffon (a vulture):
    http://wiki.answers.com/Q/What_species_of_bird_flies_at_the_highest_elevation

  20. tallbloke says:

    GC: According to the article,

    “As our young planet cooled and condensed into a solid, it was surrounded by a thick, soupy atmospheric mixture. Hydrogen and hydrogen-containing compounds combined with oxygen to form the water that became oceans, while the carbon-containing compounds, principally CO and CH4, combined with oxygen to form CO2 at high pressure. All this took about half of Earth’s lifetime, and it left the atmosphere depleted of oxygen”

  21. Tenuk says:

    Hans says:
    April 7, 2012 at 8:18 pm
    archonix says: April 7, 2012 at 7:29 pm
    “…’Modern birds are equipped to deal with the problem of flying and they figure high up on the animal intelligence league table.…’ About brain size…”

    Hi Hans, that was my comment. The bird in question, Talgoxen or Great Tit, as we would call it, has a brain to body mass ratio of ~1:12, compared to humans ~1:40. So perhaps size isn’t a good indicator of intelligence, although I expect much of the Great Tits brain is used for the difficult job of flying and navigating 3-D space.

  22. Richard111 says:

    All very interesting but not a single mention of banded iron formations (BIFs). That was responsible for the removal of a lot of oxygen from the atmosphere.

  23. Zeke says:

    What is it with these people and Big Bangs?

    Hydrogen and oxygen combining to make water:

  24. Have a look at the video Robotic Flying Bird here http://secretofflight.wordpress.com/birds/

  25. LL says:

    Tenuk says:
    April 7, 2012 at 7:27 pm

    “Much of the ‘high pressure’ atmosphere premise seems to rely on supposition, the use of proxy data and a vivid imagination. I think that evidence for flying dinosaurs is fairly pivotal to this idea, but the current meme regarding these creatures could be completely wrong and open to a differnt interpretation.

    I don’t think that pterodactyls flew, rather they used arms and feet membranes to glide around the landscape using trees to avoid predators, and ambush small prey. Today we have the flying squirrel family (Pteromyini), which operate successfully in a similar manner.”

    I’ll see your flying squirrel and raise you a flying fish. The fish doesn’t even get the luxury of an elevated launch platform!

    http://en.wikipedia.org/wiki/Flying_fish

    Distances up to 50 meters above the surface which is sufficient to make a predator chasing it say to say to itself WHERE THE F*** DID MY LUNCH GO?

    Gliding dinosaurs are a whole lot more credible than flying dinosaurs. The difference in size between giant species of yore and modern species is usually attributed to a higher partial pressure of oxygen in the atmosphere. Giantism and dwarfisim today tend to happen on islands with isolated populations and prey/predator relationships all askew. If there’s an abundance of food it’s giantism and not much food dwarfism. It happens fast too in an eyeblink of geologic times. Thousands of years not millions.

  26. tchannon says:

    If I read that site correctly cementafriend it is yet another no banana.

    I don’t understand why on so many things people get bogged down on detail whilst missing the fundamental. You can fly a brick with no fancy stuff involved at all, extremely inefficient, an irrelevancy.

    The basic fundamental is a fluid has mass, and mass can be accelerated, has inertia and therefore force can be created by inertial reaction, resistance to acceleration. Flying involves accelerating a mass of fluid exactly sufficiently to support the weight (not mass) of the body.

    The best way to go about this is a detail. Side effects are a detail.

  27. LazyBoy says:

    How do I get me one of them runaway greenhouse things? I want one in my back yard so it’ll generate dry steam for a turbine and produce endless free electricity for me. Well that’s not counting wear and tear on the turbine but there’s no fuel cost for it.

    Y’all do realize, doncha, that if you have a surface illuminated with 1000 watts of light it ain’t possible to get more than 1000 watts of power back out of it. Something emitting 1000 watts per square meter is 365 degrees Kelvin and if she’s hotter than that she’s pumping out more power than that and if she ain’t got that much power going in to her she’s a done right perpetual source of free energy. Don’t try to patent it they’ll march ya straight out of the office with no questions asked. The reject things like that out of hand because if they appear to work they’re invariably a fraud of some sort.

    Just sayin’

  28. LazyBoy says:

    gallopingcamel says:
    April 7, 2012 at 7:14 pm

    “Recalculate the surface temperature for a total pressure of 380 bars and you get 1147 K. Finally, Jim Hansen’s “Runaway Greenhouse Effect”. ”

    Yeah boy! That’s more than hot enough for a stream turbine!

    “As we are here discussing it I can safely say none of this happened.”

    Yeah, that’s pretty safe to say at 93 million miles from old sol. She can barely heat water to boiling at standard temperature and pressure at high noon under a glass ceiling on the space station. Impossible on the surface with atmospheric attenuation bringing the practical maximum noontime temperature for anything to 1000 watts per square meter or 92C. Gotta use mirrors or a lens to concentrate the sunlight onto a smaller spot but that of course puts some adjacent spot in shadow so you’re just borrowing from Peter to boil Paul in that case.

    “Let’s try again, assuming Sagan’s “Dim Sun” delivering only 60% of the present TSI (817 W/m^2). Now with a 60 bar atmosphere the surface temperature is down to 484 K (211 degrees Centigrade), still hot enough to vaporize the oceans.”

    Let’s try yet again. With 817W/m2 in you can’t get more than 817W/m2 out. That’s a temperature of only about 74C. Nothing’s gonna boil. In fact when that solar constant is spread out across a sphere with a radiating surface area 4x greater than a flat plane it isn’t even enough to melt water to say nothing of boiling it. Hence the Faint Sun Paradox which remains unexplained to this day. I suspect internal heat of the planet was a lot more billions of years ago because it had less time to bleed off, radioactive isotopes were far more abundant because they have subsequently gone through some or many of their various half lives in the few billion years since then. A hotter mantle with more magma plume and a far greater ring of fire (underwater seams where new crust is formed from oozing magma) should be enough to keep the ocean melted.

    “My contention is that somehow the CO2 pressure must have fallen much earlier than the authors assume and before most of the water arrived.”

    The water arrived pretty early. It was here within a billion years of formation. The sun was still faint.

    “Come to think of it, does anyone know when the water arrived?”

    Yes, about 3.5 billion years ago. Minerals that only form in the presence of water are found in that strata.

    “If it was here when the planet’s surface was molten how did it managed to condense into water?”

    It didn’t. The earth cooled enough for a liquid ocean in the first few hundred million years after its birth. Comets then supplied the water over the next several hundred million years. First life appears around the end of that first billion years. Archaebacteria. Extremophiles that eat iron and crap sulfur and so forth. They’re still around today lurking in extreme places where modern life forms can’t survive.

  29. Tim, people tell me I am humourless (but I enjoyed and still do the Goons on radio/CD especially the mental vision of shooting someone with a banana, and the battle of the prisons).. I am not sure what you mean by another no banana. Is it scientists getting hypotheses wrong? I have said before from my reading there is no so-called climate scientist who understands heat and mass transfer or fluid dynamics (or reaction kinetics).
    My take on the work by Prof Johnson and the other authors is that turbulent vortices play an important part in reduced pressures which create lift.
    I saw on TV scenes of containers and truck semi-trailers being lifted in a Texas tornado. Of course there are many stories of raining “cats and dogs” and fish. The negative pressure in these tornadoes and cyclones cause significant lift.
    That, then, comes back to the effect of a denser (higher pressure) atmosphere. Not only will there be more buoyancy but there is the potential of more turbulent vortex lift.

  30. vukcevic says:

    Hi Steven
    Great minds (don’t) think alike.
    http://tallbloke.wordpress.com/2012/04/06/fossilized-raindrops-dampen-theory-of-ancient-warming/#comment-22408
    I am losing track on the JC’s blog, thanks for the effort.

  31. tchannon says:

    cementafriend,

    Ah, I was referring the immediately preceding comment, about the “secret” of flight.

  32. Q. Daniels says:

    gallopingcamel,

    At 60 bars, water boils at ~275 C.

  33. Eric Barnes says:

    Who says all that carbon has to be in the atmosphere at the same time?
    IMO, the rate carbon got cycled into the atmosphere was highest when the earth first formed and has been declining ever since as the carbon cycle has slowed.
    The arctic and antarctic ice caps are a symptom of lower atmospheric pressure from carbon (and other gases) not being replaced as quickly. Notice that the frequency of ice ages has decreased.
    “gallopingcamel says:
    April 7, 2012 at 7:14 pm

    My reservations center on the effect of pressure on a planet’s surface temperature. Let’s start with 60 bars and a TSI of 1,362 Watts/m^2.

    According to N&K equation (8) the surface temperature would be 550 K (277 degrees Centigrade). This would cause a minor probem as there would be no liquid water at the surface. The bulk of the atmosphere would be composed of steam which would raise the surface pressure by another 320 bars. Recalculate the surface temperature for a total pressure of 380 bars and you get 1147 K. Finally, Jim Hansen’s “Runaway Greenhouse Effect”.

    Jim is right about one thing, if this condition were to occur it could not be reversed absent a huge loss of atmosphere. As we are here discussing it I can safely say none of this happened.”

  34. Doug Proctor says:

    Currently: 1. High pressures cause nitrogen and CO2 to accumulate in the bloodstream, causing nitrogen narcosis and something CO2 to begin with, and death afterward.

    2. High CO2 pressures will cause high CO2 in the water, but will there be enough oxygen in it to supply biological processes?

    Significant biological process differences are required for very high initial atmospheric pressures.

    Historically:
    1. Previous epochs, the Ordovician, Silurian, Devonian had relatively bizarre levels of carbonate deposition, Today carbonates are rare even in the temperature areas where they are created. The oceans lack Fe and other elements necessary for life: it could be that the older oceans were rich in elements lacking now: perhaps this would occur under a high CO2 atmosphere? Or high pressure, high CO2 atmospheres would cause a different type of chemical erosion that would show up in the rock record? The iron-silica deposits of Michigan were, I understood, to occur during an anoxic-oxygen transition and seasonal overturn of iron-rich, oxygenated waters into oxygen-depleted deeper waters. Is that the signature of I’m thinking of?

    2. There are salt deposits from the Silurian through the Jurassic I have seen on my dinner table. There are a lot of “impurities” in salt that are removed before you sprinkle the white stuff on your ‘fries: these would hold the key to the chemistry of the waters precipitating out the salt. I wonder what this says of the earlier ocean chemistry? Unlike other deposits, salt/halides/evaporites are untouched once they dewater. They should be time capsules to their histories.

    I wonder: have the paleo-biologists noted odd things in the record that might make sense in light of the very high pressure, CO2 atmosphere? And the evaporite chemists: have they also noted anything odd but PROGRESSIVELY becoming less odd through time in their deposits?

    Just wondering.

  35. People seem to be forgetting clouds. It has been found that clouds (composed of H2O droplets, ice particles, dust, solid CO2 particles, etc) result in net cooling of the surface. The clouds reduce insolation but still allow some radiation from surfaces, particularly water surfaces (which have an high emissivity at liquid temperatures (including the high temperatures under pressure), to space which is at about 4K. The evidence is that it rained lots. Note the deposition of sedimentry deposits. Further, the advance of glaciers is from an increase of snow and ice at the head.

  36. gallopingcamel says:

    Q. Daniels says, April 8, 2012 at 10:02 am
    “At 60 bars, water boils at ~275 C.”

    Thanks for that! I checked my steam tables and you are right, so the dim sun (817 W/m^2) could not boil the oceans if the atmospheric pressure was 60 bar.

    However, if the starting condition was a steam atmosphere, the pressure would be 320 bar due to the steam alone plus whatever partial pressure might be provided by CO2, Nitrogen etc. My steam table stops at 200 bar (366 C).

    My guess is that water boils at around 415 C at 320 bars, so the rain would not reach the ground (650 C) even assuming a “Dim Sun”.

  37. gallopingcamel says:

    Doug Proctor, April 8, 2012 at 7:02 pm
    Here is a link that attempts to answer some of your questions. It seems likely that most of the carbon was locked up in ocean sediments long ago:

    http://www.greenworldtrust.org.uk/Science/Scientific/CO2-flux.htm

    Slightly off topic. The site includes a link to Glassman who explains the physical processes that underlie the ice core observations showing CO2 concentration lagging temperature. If CO2 drives temperature at all, it must be a much weaker effect than the extent to which temperature drives CO2 or there would have been a “Runaway Greenhouse Effect” in the past. As Richard Lindzen points out we would not be here if that had happened.

  38. davidmhoffer says:

    cementafriend says:

    April 9, 2012 at 2:19 am

    People seem to be forgetting clouds. It has been found that clouds (composed of H2O droplets, ice particles, dust, solid CO2 particles, etc) result in net cooling of the surface.
    >>>

    You are half right. When insolation is high enough that the surface would otherwise be warming, clouds cause net cooling. When insolation is low enough that the earth surface is cooling, clouds result in it cooling more slowly.

    I grew up in a harsh climate. Trust me, when you wake up in the morning in January and the sky is bright blue, that means -40C. Winter cloud=less cold. Summer cloud=less hot.

  39. tempestnut says:

    Quick question; when did water condense and form the oceans? It didn’t just appear and must have been the result of some form of chemical reaction. And given that our planet is mostly metals any water could well have turned back into an oxide and hydrogen, which would have combined with?

  40. tallbloke says:

    TN: According to the article,

    “As our young planet cooled and condensed into a solid, it was surrounded by a thick, soupy atmospheric mixture. Hydrogen and hydrogen-containing compounds combined with oxygen to form the water that became oceans, while the carbon-containing compounds, principally CO and CH4, combined with oxygen to form CO2 at high pressure. All this took about half of Earth’s lifetime, and it left the atmosphere depleted of oxygen”

  41. gallopingcamel says:

    LazyBoy, April 8, 2012 at 5:18 am,

    “The earth cooled enough for a liquid ocean in the first few hundred million years after its birth. Comets then supplied the water over the next several hundred million years. First life appears around the end of that first billion years.”

    Somehow I missed your comment. You provide a plausible scenario that would explain why we don’t have a steam atmosphere.

    I was under the impression that there are very few old rocks to be found on Earth so how far back does Earth’s geology take us? I have been told that our moon has far more old rocks than Earth does.

    [ http://news.nationalgeographic.com/news/2008/09/080925-oldest-rocks.html --Tim]

  42. Jim S says:

    The earth was smaller:

  43. gallopingcamel says:

    Another dumb question. If Earth picked up its oceans from comets, why is there so little water in the Venusian atmosphere?

  44. Hans says:

    gallopingcamel says: April 10, 2012 at 4:55 am

    “Another dumb question. If Earth picked up its oceans from comets, why is there so little water in the Venusian atmosphere?”

    Answers according to my opinion:
    There are no dumb questions but for sure there are very dumb statements made in the name of science.
    The statement that earth picked up its oceans from comets is at best an unverified hypothesis.
    Water vapour will be lifted to the top of the Venusian atmosphere and be split into H2 and O2. Some of the former will leave the planet. It might also be split to H, too. It will happen even when water is in the form of small ice chrystals (sublimation).

    A good question is if this process can be verified to happen in earth´s atmosphere. I simply don´t know. I believe it has been verified to happen in the Martian atmosphere which keeps a minor amount of water ice and water vapour.

  45. Hans says:

    Jim S says: April 10, 2012 at 4:24 am
    “The earth was smaller”

    Another dumb question: From where did earth get the energy to expand and from where did the water come? The metoritic bombardment on earth stopped about 4 billion years ago. The history can be seen on the lunar surface where the big impacts still can be seen as a consequence of limited erosion and deposition of matter.

    An intriguing fact is that the inner planets are denser than the outer ones. Higher density might follow from greater age?

  46. tchannon says:

    I think hairy explanations are in order here.

    The tail of Venus reaches to Earth so it is likely some material is transferred, apart from which the Sun is pouring out Hydrogen.

    A twist to this is a factor to do with the magnetosphere.

    http://www-ssc.igpp.ucla.edu/personnel/russell/papers/merc_mag/

    http://www-ssc.igpp.ucla.edu/personnel/russell/papers/venus_mag/

    http://www-ssc.igpp.ucla.edu/personnel/russell/papers/earth_mag/

    http://www-ssc.igpp.ucla.edu/personnel/russell/papers/mars_mag/

    http://www-ssc.igpp.ucla.edu/personnel/russell/papers/jup_mag/