Lush Venus? Searing Earth? It could have happened

Rice University scientists propose that life in the solar system could have been very different

This image shows planets (composite). CREDIT Composite image by Arie Wilson Passwaters/Rice University

This image shows Earth and Venus (composite). CREDIT Composite image by Arie Wilson Passwaters/Rice University

If conditions had been just a little different an eon ago, there might be plentiful life on Venus and none on Earth.

The idea isn’t so far-fetched, according to a hypothesis by Rice University scientists and their colleagues who published their thoughts on life-sustaining planets, the planets’ histories and the possibility of finding more in Astrobiology this month.

The researchers maintain that minor evolutionary changes could have altered the fates of both Earth and Venus in ways that scientists may soon be able to model through observation of other solar systems, particularly ones in the process of forming, according to Rice Earth scientist Adrian Lenardic.

The paper, he said, includes “a little bit about the philosophy of science as well as the science itself, and about how we might search in the future. It’s a bit of a different spin because we haven’t actually ­­­­done the work, in terms of searching for signs of life outside our solar system, yet. It’s about how we go about doing the work.”

Lenardic and his colleagues suggested that habitable planets may lie outside the “Goldilocks zone” in extra-solar systems, and that planets farther from or closer to their suns than Earth may harbor the conditions necessary for life.

The Goldilocks zone has long been defined as the band of space around a star that is not too warm, not too cold, rocky and with the right conditions for maintaining surface water and a breathable atmosphere. But that description, which to date scientists have only been able to calibrate using observations from our own solar system, may be too limiting, Lenardic said.

“For a long time we’ve been living, effectively, in one experiment, our solar system,” he said, channeling his mentor, the late William Kaula. Kaula is considered the father of space geodetics, a system by which all the properties in a planetary system can be quantified. “Although the paper is about planets, in one way it’s about old issues that scientists have: the balance between chance and necessity, laws and contingencies, strict determinism and probability.

“But in another way, it asks whether, if you could run the experiment again, would it turn out like this solar system or not? For a long time, it was a purely philosophical question. Now that we’re observing solar systems and other planets around other stars, we can ask that as a scientific question.

“If we find a planet (in another solar system) sitting where Venus is that actually has signs of life, we’ll know that what we see in our solar system is not universal,” he said.

In expanding the notion of habitable zones, the researchers determined that life on Earth itself isn’t necessarily a given based on the Goldilocks concept. A nudge this way or that in the conditions that existed early in the planet’s formation may have made it inhospitable.

By extension, a similarly small variation could have changed the fortunes of Venus, Earth’s closest neighbor, preventing it from becoming a burning desert with an atmosphere poisonous to terrestrials.

The paper also questions the idea that plate tectonics is a critical reason Earth harbors life. “There’s debate about this, but the Earth in its earliest lifetimes, let’s say 2-3 billion years ago, would have looked for all intents and purposes like an alien planet,” Lenardic said. “We know the atmosphere was completely different, with no oxygen. There’s a debate that plate tectonics might not have been operative.

“Yet there’s no argument there was life then, even in this different a setting. The Earth itself could have transitioned between planetary states as it evolved. So we have to ask ourselves as we look at other planets, should we rule out an early Earth-like situation even if there’s no sign of oxygen and potentially a tectonic mode distinctly different from the one that operates on our planet at present?

“Habitability is an evolutionary variable,” he said. “Understanding how life and a planet co-evolve is something we need to think about.”

Lenardic is kicking his ideas into action, spending time this summer at conferences with the engineers designing future space telescopes. The right instruments will greatly enhance the ability to find, characterize and build a database of distant solar systems and their planets, and perhaps even find signs of life.

“There are things that are on the horizon that, when I was a student, it was crazy to even think about,” he said. “Our paper is in many ways about imagining, within the laws of physics, chemistry and biology, how things could be over a range of planets, not just the ones we currently have access to. Given that we will have access to more observations, it seems to me we should not limit our imagination as it leads to alternate hypothesis.”

###

The National Science Foundation supported the research.

Read the abstract at http://online.liebertpub.com/doi/abs/10.1089/ast.2015.1378

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133 thoughts on “Lush Venus? Searing Earth? It could have happened

  1. ACS’ climate change tool kit has a section on the difference between a supposed zero atmosphere S-B BB of 255 K at 240 W/m^2 compared to a surface temperature of 15 C, 288 K. This 33C difference is supposedly due to the GHE and all the following thermo & heat transfer nonsense, 390 W/m^2 up-welling, net 333 down welling, “back” radiation, etc.
    The 240 W/m^2 & 255 K are WITH an atmosphere. The 240 W/m^2 are after the deduction for albedo (atmosphere) measured at the 100 km ToA (atmosphere).
    No atmosphere means no water, no atmospheric gases, no albedo, no vegetation, a naked dirt ball. Would that be different? Well, duh! And the temperature? Anybody’s guess, educated, perhaps, but still a SWAG.

    • Nocholas,
      Yes, your are absolutely correct. Without an atmosphere, the Earth would have the approximate albedo as the Moon (0.13) and its average temperature would be slightly below freezing, however, in the tropics, it would still be well above freezing.
      The ‘consensus’ conveniently ignores he fact that GHG’s (primarily water) also increase the albedo through clouds and ice which is a strong negative feedback like cooling influence that acts on the surface. So, the supposedly 33C increase includes about 16C of cooling that the same GHG’s are responsible for. The net warming is only about half of the claimed effect.
      Of course, errors of a factor of 2 or larger are very common throughout all of climate science which the consensus requires in order to have the necessary wiggle room to support an otherwise impossible result.

      • “The excessive mass of CO2 on Venus, relative to its primordial mass on Earth leads me to believe that Venus had a much larger atmosphere at one time and the lighter gases were ripped away by the solar wind and lack of magnetic field.”
        Very interesting speculation, co2isnotevil. Thanks.

    • This paper is at least a week old and does the same crap as most dodgy climate “science”. It posits the idea that the earth is balanced on a knife’s edge of positive feedback via either heat death or snowball earth depending on which way it randomly falls. The is uses simulations and models using this assumption to show how lucky we are to have survived without ever hitting either heat death or snowball.
      The ironic thing is that snowball earth *has* occurred. In their paper they assume this is “game over man”. Every simulation which hit this condition was considered a “no life scenario”. And yet here we are.
      As for their Venus vs Earth C trapping idea. It is nice that finally climate scientists recognize that C is a scarce resource constantly being eliminated by pesky life forms, but somehow they fail to realize the chicken/egg nature of the problem. The earth was 2 billion years old before the oxygen crisis. Did the CO2 decide to go on vacation for those 2 billion years? So yes is is interesting that Venus has a *way* bigger atmosphere than Earth, but the idea that (1) life made it this way and (2) life could not have started without this already being the case is … fucking stupid.
      I literally laughed out loud when I read it.

    • Hey it is very simple; even I can understand it.
      Simply switch places between Earth and Venus, and voila ! (izzat French) we have a cooked Earth and a green Venus.
      Told ya’ it was simple.
      g

      • How many more post are we going to see that pretty much say “we don’t know anything about anything but maybe this could happen or maybe not”?

      • Except for one glaring difference which is that the mass of the CO2 on Venus is comparable to the mass of Earth’s oceans and exceeds the amount of carbon available on earth by orders of magnitude. I suspect that Venus started out as a small gas giant which migrated inward and whose H2 and He has been stripped away by the solar wind. Otherwise, the amount of CO2 Venus has can not be adequately explained.

      • The vast, vast majority of earths CO2 is locked up in carbonates and other geological formations.

        • Mark,
          True, but there are not enough carbonates to support primordial CO2 levels anywhere near that of Venus and presumably, we came from the same part of the primordial disk. To account for all the missing carbon, the required mass of carbonates would need to be the same order of magnitude as the mass of all the Earth’s oceans and/or there would be orders of magnitude more oil and gas in the ground than anyone could possibly consider.

      • There’s only one other planet in the solar system besides Venus with a retrograde rotation around its axis and that’s Uranus whose retrograde rotation is thought to have occurred by collision with something about the same mass and currently unidentified, but considered to have been absorbed. Gas giant to gas giant collisions would seem to be more elastic than two solid bodies colliding, especially if they are colliding at a relatively low velocity which could be the case for two gas giants in similar orbits, but spin and trajectory can be significantly altered, for example in pool. I also understand that it was difficult to get planetary formation simulations to reproduce our solar system, especially as related to the formation of Venus, without hypothesizing a wandering Jupiter passing through the inner solar system. The excessive mass of CO2 on Venus, relative to its primordial mass on Earth leads me to believe that Venus had a much larger atmosphere at one time and the lighter gases were ripped away by the solar wind and lack of magnetic field. If Venus was what collided with Uranus many billions of years ago, it’s a plausible explanation for many things that are currently not very well explained. It’s very slow rotation is why it has no significant magnetic field (its core is surely still molten) and the only thing we know of that can slow the rotation down by that much is a collision with something about the same size as it was.

      • co2isnotevil July 7, 2016 at 2:35 pm: “The excessive mass of CO2 on Venus, relative to its primordial mass on Earth leads me to believe that Venus had a much larger atmosphere at one time and the lighter gases were ripped away by the solar wind and lack of magnetic field. . .”
        It has been suggested, of course, that Venus was untimely ripped from the planet Jupiter, and made its way to the inner Solar System leaving chaos in its wake. Might that account for all that CO2? I won’t mention the author’s name, as it’s controversial, but it begins with V.
        /Mr Lynn

        • LE,
          Possibly, but a different planet seems more likely as a Venus size chunk stripped by gravity from Jupiter would have been all gas. Note that even a small a gas giant heading towards the inner planets owing to a collision with another (I think this is necessary to explain its very slow retrograde rotation) would have the same effect as the variations of the wandering Jupiter theory.

      • co2isnotevil said: ” True, but there are not enough carbonates to support primordial CO2 levels anywhere near that of Venus and presumably, we came from the same part of the primordial disk. To account for all the missing carbon, the required mass of carbonates would need to be the same order of magnitude as the mass of all the Earth’s oceans and/or there would be orders of magnitude more oil and gas in the ground than anyone could possibly consider.”
        Forget CO2. If you look at the amount of nitrogen in Venus’ atmosphere, there is about four times the amount on Venus compared to Earth. Earth was involved in a massive collision early in solar system history. That would explain the loss of much of it’s primordial atmosphere.

        • scarlet,
          Perhaps, but Venus was involved in an even bigger collision in its past. While our Moon is hard to explain without a big collision, the retrograde rotation of Venus is even harder to explain without an even bigger one. Why didn’t that collision do the same to Venus as what happened to Earth and leave a Moon behind, or at least rings? Wouldn’t a collision powerful enough to stop a planets rotation and even reverse it slightly be powerful enough to eject all sorts of matter into orbit around it? The other planets in the solar system (except Mercury which is tidally locked to the Sun) have day lengths on the order of an Earth day or less (Uranus is also retrograde, but has a short day). The Venusian day is about 225 Earth days and if you could perceive the Sun from the surface, it would rise in the West and set in the East. After over 100 days of continuous solar energy the 2650 W/m^2 it receives from the Sun is affecting half of the planet resulting in an average input of 2650/2 = 1325 W/m^2 which would be 1153 W/m^2 assuming a .13 surface albedo and a temperature of 377K assuming no atmosphere, which is slightly above the boiling point of water. A common mistake is to divide the incident energy by 4, like we do for the Earth, however, the Earth rotates fast enough to distribute the energy across the either surface, while Venus rotates so slowly (like the Moon relative to the Sun), only half of the planet would be involved.

    • Snark aside, I think this modeling exorcise will tell us nothing more than the assumptions and expectations of the modelers.
      .
      .
      .
      Wait… we already have those models.

    • HR
      You noticed the –
      “could have happened” précis, too.
      Yeah.
      It could have happened . .
      Auto – noting I didn’t.
      Noting also that better purveyors of this sort of ‘Science’ include Asimov, Heinlein and Clarke – and many – very many – others, all in the private sector.
      If my story sells, I eat.
      And the estimable Rice U?
      I make up stories, and the tax-payer enriches me. Manifold.
      And if not – the tax-payer enriches me. Manifold.
      Auto.
      Maybe letting some cynicism creep through . . . . . . . .

      • Or you could have been any one of the 57 total genders, or even a hermaphrodite, which for some reason is not one of the 57 on the list.
        g

    • The Goldilocks zone is defined as that place where life happened and can happen.
      How else could it be ??
      Well also it should have warm porridge.
      g

      • Well anything that can happen, does happen, and just as soon as it can happen and not before it can happen, or after, because nothing waits for anything.
        So the Rice thesis is baloney.
        It couldn’t happen so it didn’t happen.
        We called this one Earth, and we called that one Venus. Wishing we had done the opposite, is like saying we should have made electrons be positive charge, instead of negative charge.
        We didn’t, so we won’t .
        g

      • Don’t forget the chair, George. Must have a chair that’s just right. No one would think of these things if they had to stand up all of their life. (I’m beginning to believe in intelligent design, If we didn’t have knees, we couldn’t sit down at our computers and think up this stuff.)

    • Blind faith doesn’t belong in science. All observed evidence supports life existing only on earth.

      • It takes just as much faith to believe that there is no life out there as it does to believe that there isn’t.

      • Saying ” I don’t believe there is. ” is NOT the same as saying ” I believe there is not. ”
        The first is NOT a belief; it simply says I dunno ! The second IS a belief and could be considered an act of faith.
        No useful purpose is served by believing in the existence of anything for which there is not a shred of evidence, or even a hint of a shred of evidence.
        We could fill our entire existence by talking about all of the things we could believe in for none of which is there any physical evidence of any kind.
        G

      • Pointman,
        “Correct, and most probably wrong outside the caveats it was expressed inside.”
        Most probably? Isn’t that a statement of faith ?

      • @MarkW
        “It takes just as much faith to believe that there is no life out there as it does to believe that there isn’t.”
        ????? Maybe I need more coffee?
        (N.B. coffee = life and as best I know, there is no coffee on Venus)

      • Pointman,
        “No, it’s called a conjecture.”
        On my planet conjecture can be based on faith . . so, your response is . . evasive or indicative of a lack of self awareness in my eyes.

  2. I think everyone who reads WUWT probably has surmised that the beginnings of life on any planet is tricky at best. The authors just put our collective thoughts into the form of a spitball paper so that they could ask for grant money to retirement.

    • Don’t know about. Life on the earth formed only about 100 million years after the crust cooled enough for liquid water to form.
      It took another 3.5 billion (or there about) years for life to go from single cell to multi-cell.
      And from there several hundred million years to arrive at complex life forms.
      Life, in the form of single celled creatures, may be fairly easy to get started.
      Complex life on the other hand may be extremely rare.

      • So if life may be easy to get started all by itself; how much easier then would it be for our best chemical and biochemical minds to do it deliberately ??
        So I’d like a nice pet one of a kind for my next birthday.
        See that it gets done please.
        g

      • “Life, in the form of single celled creatures, may be fairly easy to get started.”
        ?? You mean like little green monkeys may fly out of your butt tomorrow ; )

  3. It is rather sad that modern scientist act mostly like entertainers or prophets of some scary things or some hysterical shysters promising revolutionary and unbelievable things. All these agencies and foundations are funding some obvious garbage. It all started with Albert Einstein who became celebrity of science. At least he actually was great physicist. But now this system deteriorated to level of Neil Degrasse Tyson and Michio Kaku (on the higher level) and Michael Mann, Ken Caldeira and these dudes who wrote this article (on the lower level). What to do?….

      • I used to respect Neil Degrasse Tyson until he placed himself on the same intellectual level as Bill Nye.
        What a waste.

      • Higher level of shysterism, higher level of notoriety, exposure, income… higher level of bs…

    • Not sure what puts Tyson on the high side except his mentor Carl Sagan. Tyson’s CV lists all of 14 papers, most of which have him in the “et al” section. Hardly impressive. Essentially, he worked in imagery and made no important contributions to the field.

    • Tyson and Kaku are scary given the Non-Science (= nonsense) they foist on the general public. Who funds these nitwits?
      For example, Tyson’s attempt to update Carl Sagan’s “Cosmos” was pitiful in its pandering to CAGW. What a missed opportunity!

  4. They forgot the spin. Venus rotates very slowly on its axis so that the Venusian day is longer than the year, which means that half of the planet would fry during the “day” and freeze during the “night.”

    • The slow rotation is why Venus turned into such a hothouse. Within the very first day, all of the molecules in the surface that could combined to turn into a gas where in fact turned into a gas and released to the atmosphere. The surface accumulated so much energy from being heated for 116 days straight that it reached 500C on the very first day. Strong winds in the very thick atmosphere spread,the energy around to the dark side. Simple joules/second calculation.

      • As in, it did not take any time at all.
        Surface solidifies. But 2700 hours straight of sunlight with the surface absorbing 0.008 joules per second just like on Earth means that the surface never falls below 773 kelvin and all the volatiles are released into the atmosphere as a gas and the surface never gets cold enough for anything but hellish conditions.
        From day 1, the rotation rate meant that the fate of Venus was sealed.

    • Except that the Venusian surface temperature, like the temperature of the Earth’s surface under the deep ocean, shows no diurnal or seasonal variability.

        • Mark,
          So your conjecture is that Venus surface heat from its interior and the 100% cloud coverage has kept it from cooling enough for liquid water to form in the last 4+ billion years? If Earth started the same, it cooled enough for liquid water to form almost instantly as compared to 4+ billion years.
          Keep in mind that Venus without clouds would have a much cooler surface as even at 100 atmospheres or CO2,, the transparent window in the atmosphere covers more than half of the emission spectrum (especially without water vapor) and an even larger fraction at higher temperature whose energy moves up and away from the primary 15u absorption lines.

      • So, slow rotation=very hot=all volatiles to gas=90 atmospheres=always hot everywhere. Most forget that 90 atmospheres=hot even if it were not mostly CO2. It would be almost as hot here at 90 atmospheres even with our atmospheric composition.

        • Jim,
          Yes, you are exactly correct. Another way to understand this is by identifying the surface of Venus that is in equilibrium with the Sun. The bottom of our oceans are at a constant temperature for much the same reason (pressure/density profile of water) and they do not contribute to the surface of Earth in direct equilibrium with the Sun and whose temperature we care about. That surface encloses the top of the ocean and the little bits of the solid surface that pokes through. All of the Venusian solid surface is at the bottom of the Venusian ‘ocean’ which in this case is CO2, which at the solid surface is even a supercritical fluid.
          The surface of Venus in equilibrium with the Sun is layer high in its clouds at a pressure of a few tenths of an atmosphere. Heat from this cloud layer then heats the surface below, which is dictated by an inverse lapse rate. The source of Earth’s atmospheric heating is also the surface in equilibrium with the Sun, except that the lapse rate is reversed since this surface is below the atmosphere and not above.

  5. There are a lot of problems with this Venus has no moon to stabilise how it rotates. The moon stops the planet flipping over and regulates our rotation.
    Also Venus’s day is longer than it’s year so one side is constantly being roasted by the Sun. It also has a weaker magnetic field than the earth. These all need to be taken into consideration.
    If Earth was closer with the moon in tow it might be fine in Venus’s orbit, but the moon is so important to how the earth evolved.

  6. What about the Moon, is next closest to Earth???
    Why not “looking” at it?
    Why it is the way it is………..How can we tell about other planets far far far away in far far far away solar systems…………and ignoring our closest “neighbor”????!!!!
    Why? why, when every thing suggests that it could help and aid us in a better understanding of our own Earth?
    How can that ignoring be excused or justified?!
    cheers

  7. Seems pretty simple … life “as we know it” would probably require a goldilocks zone location, but life “as we don’t know it” might not. The latter category of possible life is probably larger than the other category of what we are familiar with. So our search for extraterrestrial life should not make too many assumptions about where to look. Our current explorations will shed more light on this over time.

  8. Actually, the juxtaposition of ideas, venus green, earth scorching is entirely bone-headed.
    If Venus were green, it’d have to have a cooler sun, for the sun-venus (☉ ↔ ♀) distance. If that were the case, Earth would be freezing. Ice world. UNLESS it had a huge atmosphere load of greenhouse gasses.
    But then it might not be scorching: Venus receives 2.2 times as much sunlight as Earth.
    Point is, if EITHER planet is habitable, the OTHER planet most likely would not be.
    GoatGuy

  9. We assume earth’s configuration as it is is the final outcome when it could just be a phase in a process we can do nothing about.
    Such is the complete lack of actual knowledge of history of the solar system we can only guess, and publish those guesses, and many refer to those guesses as some sort of facts. 😀

    • Mark,
      Earth’s final outcome is to run out of carbon leading to the demise of all life. Life is continuously sequestering carbon as biomass falls to the bottom of the ocean, eventually to be subducted and converted into fossil fuels and as life transforms carbon into carbonates. Returning this sequestered carbon to the atmosphere is the best thing we can do to insure our long term survival.
      This is why the long term (multi-million year scale) CO2 concentrations have been steadily declining. Only as life benefits from warmer temperature are natural sources of CO2 recaptured by life, temporarily building up atmospheric concentrations to the levels required to support the increased biomass. We see this in the ice cores where the amount of Earth’s surface conducive to life is proportional to atmospheric CO2 concentrations.

  10. We are on earth and we still flimflam to explain Earth’s geological history, the folly of making any claims about Venus is pure comedy gold.

  11. The catastrophe of the proto-Earth being hit by a celestial object large enough to cause the lunar mass to spin off probably led to the creation of a lot of the conditions required for life to start and thrive on what became the Earth we know today.
    The catastrophe apparently blasted away a great deal of crust, leaving great basins in place. The Earth was shattered and a subduction/sliding tectonics process was permitted to continue, lubricated by the H2O that filled the great basins. Life tied up huge amounts of carbon and calcium, enabling a sedimentary and erosion process to thrive. The Earth’s rotational axis was put into a geometry that allowed for seasonality without wild extremes. The lunar mass coalesced in what we now see in our nightly sky, acting as a brake on rapid rotational speeds and creating tides in the oceans. the energy it took to slow both Earth and moon rotation must have released a lot of internal heat in both. Something kept the Earth’s magnetosphere in place strong enough and long enough to protect Earth from the sun’s deadly embrace. Earth was able to acquire and hold onto oceans of water, and an atmosphere dense enough to sustain life. And life itself was able to modify it and continue it… self-tuning it to the requirements of life on Earth. And all of these semi-independent processes have been sustainable over giga-years of time, despite asteroids, stellar fluctuations, long term axial wobbles, and God only knows what else. An interesting and providential chain of macro-events indeed.

    • The axial tilt alone is absolutely required at our distance from the Sun. Without the seasonal summer Sun, the snow would never melt at the poles.
      The climate at the poles would always have been April-like. This would have lead to NO snow melt ever and then 10 km high glaciers, glaciers building toward the equator, Albedo rising to 60% and then a permanent Iceball Earth.

  12. This is not a report of results so much as a speculation paper that suggests novel lines of research.

  13. The composite image contrasting Earth with Venus is a nice visual complement to the theme in Neal Stephenson’s novel, SEVENEVES. I’ve only read it halfway, but recommend it, especially if you like Stevenson’s work. I now return you all to your discussion of the Rice paper, to which this observation is a mere distraction. Apologies if I’ve strayed beyond the rules of the house.

  14. I wonder how much having a relatively large moon affects both Earth’s rotation and plate tectonics. Mars has a similar rotation period, but insignificant moons, but not plate tectonics.

    • The only impact that the moon has on plate tectonics is that the collision that gave the Earth the moon, also gave the Earth a core that was much larger than Mars’. As a result Mars’ core cooled off and turned solid millions of years ago.

  15. Isn’t hydrogen able to reach escape velocity on Venus? If so, I don’t see how water sticks around if hydrogen can escape the atmosphere.

    • Hydrogen can escape Earth, yet we have lots of water. The real question is why does Venus have so much CO2 while the Earth has an equivalent mass of H2O.

        • Mark,
          So were are all the carbonates? The mass of the CO2 on Venus is about the same as the mass of the Earth’s oceans, so where are all these gazillion tons of carbonates hiding? It would need to be at least a mile thick layer covering the entire surface and the geological record does not support this.

      • “Because life turned the CO2 into carbonates.”.. and wood, coal, oil, & natural gas (although a significant portion of the latter two may be abiotic).

        • Louis,
          Yes, CO2 is converted into carbonates and yes CO2 is a greenhouse gas.
          As I asked in my response to others, where are all the carbonates? Based on the relative amount of CO2 on Venus, if Earth turned the same amount into carbonates, there would need to be a layer of carbonates more than a mile thick covering the entire surface of the planet and there would be a virtually infinite supply of fossil fuels underground.

  16. Big G says “So the Rice thesis is baloney.”
    Agree.
    Intensity of Venus’ magnetic filed is tiny and life wouldn’t have ever started, whatever the temperature of the goldilock’s porridge happen to be. It’s not only the location, location it is also the life killing radiation, radiation.

  17. I’ve always thought that the early bombardment period has a lot to do with why Mars, Earth, and Venus are the way they are. Earth was lucky enough to have been hit by enough watery comets and hit the right way for it to rotate at the right speed.

    • RW,
      But this would mean the Venus was unlucky enough to be hit with a far larger proportion of dry ice comets. I don’t see this as plausible given how close Earth and Venus are relative to the distribution of matter in the primordial disk. Mars is too small to have enough gravity to keep the water bound to it, although it was able to keep most of its CO2 which even today is more mass per column of atmosphere than we have on Earth. If Earth had the same amount of CO2 in the atmosphere as Mars (.006 ATM), it would be about 6,000 ppm.

  18. “The paper also questions the idea that plate tectonics is a critical reason Earth harbors life. “There’s debate about this, but the Earth in its earliest lifetimes, let’s say 2-3 billion years ago, would have looked for all intents and purposes like an alien planet,” Lenardic said. “We know the atmosphere was completely different, with no oxygen. There’s a debate that plate tectonics might not have been operative.”
    Weathering of rocks has released more and more magnesium and calcium ions into the ocean. The insolubility of their carbonates leads to the gradual removal of carbon dioxide from the atmosphere and the depositing of calcium and magnesium carbonates on the ocean floor, where it would remain in the absence of plate tectonics. The increase in calcium and magnesium ions in the ocean has limited the amount of CO2 to levels that are sometimes referred to as “CO2-starvation” compared with the past. Although some of the planet’s original carbon dioxide was converted to oxygen by photosynthesis, the largest reservoir of carbon dioxide is in the crust of the earth in the form of these carbonate minerals. (Note: Some sources ignore that amount of carbon dioxide in the crust and show the ocean as the largest reservoir.) Without plate tectonics, there would be even less CO2 in the atmosphere than there is today.
    See Figure 2 in http://globecarboncycle.unh.edu/CarbonCycleBackground.pdf

  19. and I thought the high temperature on Venus had more to do with the density of its atmosphere – 90 Earth atmospheres. More like a pressure cooker.

  20. Hmmm. This looks to me like the planetologists are going to seminars run by the climatologists. “How To Get More Funding By Simply Denying Physics.”
    Early Earth didn’t have tectonic activity? Really? Just been whacked not very long ago (geologically) by another protoplanet that stripped off a big chunk of crustal material? Which material reformed as the largest moon in the Solar System (relative to its primary)? And was MUCH closer at the time, with a MUCH more powerful tidal effect?
    Riiight…

  21. You use the same Goldilocks argument with the level of gravity in the universe, dark energy, etc., etc.

  22. So, what did this paper contribute to human understanding of our universe? Who paid for it? Are all scientists of this ilk members of Star Trek fan clubs? So many questions … and all I can do is ask questions, or perhaps say, FFS!

    • If you pay taxes, you paid for this nonsense through the National Science Foundation.
      I think it is time to cut their budget.

  23. There is a basic assumption by many that the solar system was formed as we see it now in basic detail. But is this right? We have no real evidence as to how the solar system was at the beginning.
    I do remember reading a while back that the ancient Sumerians left many clay tablets with incredibly detailed and accurate depictions of the sky at that time (circa 3000BC). The strange thing was that Venus was not represented even though it is the brightest object after the sun and moon. When Venus did appear it was shown rising in the west. This was put down to a “silly mistake” but all other details were very accurate.
    Could this be an indication that Venus joined the party long after after the initial birth of the solar system? It might explain some of the very different attributes of Venus. Who knows for sure, I try to keep an open mind on this and many other “facts”.
    SteveT

  24. If conditions had been just a little different an eon ago, there might be plentiful life on Venus and none on Earth.
    The idea isn’t so far-fetched, according to a hypothesis by Rice University scientists and their colleagues who published their thoughts on life-sustaining planets, the planets’ histories and the possibility of finding more in Astrobiology this month.

    Hmmm…Just how many biological samples from “Astro” sources has this magazine reported on?
    Sounds like it deals with a bunch of theoretical “what if”‘s rather than an examination of “what is”.
    Don’t get me wrong. I wouldn’t mind if my wife could be mistaken as a daughter of Venus. I’m sure she wouldn’t mind if I could be mistaken for a son of Mars. But their are no facts to say we were not the offspring of earth. Just thoughts and theories.

  25. The first thing to do is to find Earth-like and Venus-like planets and compare them to ourselves.
    In order to find and study these kinds of planets, we need bigger telescopes.

  26. Come on now, Venus does not have a moon and is in a retrograde orbit. One side faces sun. If earth did not have moon like Venus. All water wold be frozen on cold side to start. Thus no oceans, thus major build up of co2 with out question. Without moon, earth would look like Venus.

  27. Here’s an interesting paper about conditions on the earliest Earth (the Hadean Period). The atmosphere was about 100-200 bars of CO2 and the air temp about 500 K after the original silica vapor atmosphere cooled and rained out into the magma ocean.
    So a lower pressure of CO2 is not the reason why Earth did not become Venus-like. In my view, the collision with the Mars-sized planetoid blew off almost all of the lighter crust, exposing the top of the magma mantle. This allowed tectonics and subduction to occur in direct contact with the atmosphere. Note that on Venus, any subduction occurs below a fully intact surface crust. Venusian CO2 is not exposed to this.
    Earth’s mantle overturning at the surface, radiated heat away early on much more efficiently than could Venus with a globally intact crust. With the later arrival of cometary water, surface cooling of Earth could become more efficient.
    So, it was that early-on collision that did it for Earth. Had it alternatively hit Venus, and removed most of the crust, and given Venus a moon, maybe clement conditions and life would have emerged there, instead.

    • The 100-200 bars of CO2 is qualified with this line from the paper:
      “Zahnle et al. 2007 recently developed a speculative narrative”
      which is indeed speculative as it assumes that primordial CO2 on Earth was the same as on Venus and that a runaway GHG effect was in effect. Apparently, they didn’t bother to figure out where all this carbon went and since it cited a runaway GHG effect (which is actually precluded by COE), this slipped right on past peer review. There are just not enough carbonates and fossil fuels to account for all of the extra carbon. Also, if you look at their plot, there’s a precipitous decrease in CO2 over a short period of time in order align to where the data can start to suggest (after a complex set of assumptions) how much CO2 was in the early atmosphere.

    • The total amount of terrestrial surface carbonate plus kerogen is estimated to be equivalent to an atmosphere of 60-80 bars of CO2, here. The authors mention that if the earlier magma ocean was iron-rich, it would have absorbed some of the very earliest CO2 as Fe_melt + CO2 –> 2FeO + Fe/C_dissolved.
      The same 60-100 bar CO2 atmosphere is mentioned here (pdf), based on the same evaluation of the total surface carbon inventory.

      • Our oceans contain enough water to sustain a steam atmosphere with a surface pressure of >200 bars. If Hansen is right this planet could end up an atmosphere composed mainly of steam.

      • Pat,
        Some places claim calcium carbonate comprises 4% of the crust, which is almost enough CaCO3 to account for 100 bar of CO2. However, this conflicts with the geological assessment of the crustal components which shows CaO as the primary Ca compound in the crust and the CaCO3 content is so small, its not even worth mentioning. Perhaps there is some confusion with the fraction of crustal Ca which is about 4%.
        https://en.wikipedia.org/wiki/Crust_(geology)

      • Glad you said IF Hansen is right.
        But he isn’t.
        Water vapor (aka steam) doesn’t absorb nearly enough solar spectrum radiant energy to maintain its Temperature at the TOA, so eventually visible clouds must form, and with all of that steam in the atmosphere, those clouds would be totally opaque to the high energy solar photons, which go deep into the oceans, and warm the oceans.
        Surface level solar insolation would be virtually zero, so there would be massive precipitation, until the cloud level got down to what can support some stable surface Temperature.
        Similar problem occurs if you assume zero water in the atmosphere (on earth with its oceans).
        Peter Humbug did that one on his play station, and got all of the atmospheric water back in about three months.
        If you assume that the earth system has two possible stable Temperature (regimes); one at a higher Temperature with all of that steam and a lot of clouds, and the other at a lower Temperature with not too much clouds, then the region between those two Temperatures must be unstable and will diverge to one end or the other.
        So far, nobody has proved that the stable high Temperature regime, is different from the stable low Temperature regime. IE there is no proof that earth’s climate system has two stable Temperature regimes.
        And as I said Peter H has shown that the zero H2O (in the atmosphere) is unstable. (gives you the mother of all forcings, with nearer to 1362 W/m^2 at the earth surface, rather than 1,000.
        I don’t have a Play station like Peter Humbug, so I just wing it, and my back of the envelope / restaurant table cloth chicken scratchings, says the Sauna Senario is equally unstable, and it is merely a conjecture of mine that the Birdseye case (as in quick frozen) and the Sauna case both decay to exactly what we have now.
        There’s no proof of that so don’t say so in you PhD orals, or you will flunk.
        But I’m always open to a formal proof that the earth climate system has two stable points; or for that matter, there could be more than two, in which case they should come in pairs, with stable regimes between each pair and unstable regions between the two members of the pair.
        G
        Don’t sweat it Mates, it will all come out in the wash, so she’ll be alright !

      • Pat
        The clue to the different fates of Earth and Venus is in this statement from Abe’s paper.
        The upper bound of planetary flux is about 307 W/m^2 for the case of 100% humidity. Above this value, the atmosphere is in a runaway greenhouse state. (Abe, 1995)
        Abe is referring to the early Earth with atmosphere of 60-100 bar CO2 similar to Venus. Earth’s average solar insolation was 240 W/m^2 due to the faint sun (30% dimmer than present). This is below the critical value for a runaway greenhouse effect. But Venus was at 460 W/m^2, above the critical value. Apparently Earth is teeming with life because it is in the Goldilocks zone much to the dismay of astrobiologists.

    • “Earth’s mantle overturning at the surface, radiated heat away early on much more efficiently than could Venus with a globally intact crust.”
      So why didn’t earth’s top mantle cool into a globally intact crust? Kelvin estimated it would only take 100 million years to cool the mantle into solid. Of course Kelvin didn’t know about nuclear energy in the 19th century. So is it radioactive elements that kept plate tectonics alive and made life possible?

    • “In my view, the collision with the Mars-sized planetoid blew off almost all of the lighter crust, exposing the top of the magma mantle. This allowed tectonics and subduction to occur in direct contact with the atmosphere. Note that on Venus, any subduction occurs below a fully intact surface crust.”
      The Big Whack came before the formation of the solid crust. Earth and Venus have similar basalt crust. The is difference is earth has more granite that makes up the continental plates. Granite has lower density than basalt. Granite floats on basalt. This allows subduction to occur on earth’s surface. In my view, the formation of granite was due to earth’s hotter mantle from the kinetic energy of the Big Whack
      “With the later arrival of cometary water, surface cooling of Earth could become more efficient.”
      Bulk of earth’s water didn’t come from comets. It came from earth’s interior. Water-bearing silicate minerals in the mantle have 25x more water than the oceans.
      “Had it alternatively hit Venus, and removed most of the crust, and given Venus a moon, maybe clement conditions and life would have emerged there, instead.”
      Surface water would still evaporate due to high solar insolation. The atmosphere would be high on water vapor and CO2 and greenhouse effect. I think Venus would still be hot as hell

      • “Had it alternatively hit Venus, and removed most of the crust, and given Venus a moon, maybe clement conditions and life would have emerged there, instead.”
        Venus did get hit by an even bigger rock. Otherwise, its slow, retrograde rotation can not be explained.

  28. A billion years ago Earth’s atmosphere was composed mostly of CO2 just like Venus, yet there was liquid water and life.
    The important difference was that the surface pressure on Venus was/is 90 times that of Earth. Venus is not suffering from “Runaway Global Warming” caused by CO2. It simply has a much denser atmosphere than Earth.

  29. “The idea isn’t so far-fetched, according to a hypothesis by Rice University scientists and their colleagues who published their thoughts on life-sustaining planets, the planets’ histories and the possibility of finding more in Astrobiology this month.”
    Venus is the way Venus is because Venus could not be otherwise.
    Theories are great but there were good reasons why empiricism was favoured during the Enlightenment. We may not know the laws of the universe and we may never know them. But we can try to predict backwards and forwards. So what if most of the time we are wrong.
    If you toss a coin and it comes up heads, you say it was random. But even Heisenberg would admit that what is, is. Even when we cannot perceive what is.
    For more on entity realism check out Ian Hacking and Nancy Cartwright.
    But I offer this. When you bump into a specific oak tree within a forest, depending on how fast you were walking, you will confirm that the tree is real. But is the species “oak” real? Or is that a theory? Is the forest real? Or a mental construct applied to a collection of trees?
    Does the planet Venus in this hypothetical other universe “real” in any way?
    Is what these researchers are doing related to science in any way? Or merely a form of computer gaming?

  30. Are they bonkers? Searing Earth and a cool Venus? Have they forgotten that Venus is 1/3 closer to the Sun than Earth?

  31. Funny astrobiologists:
    “If we find a planet (in another solar system) sitting where Venus is that actually has signs of life, we’ll know that what we see in our solar system is not universal,” he said.
    Because that exoplanet doesn’t have 460 C surface temperature. Hint: it’s not because it is close to the star. Venus is hotter than Mercury
    “Earth in its earliest lifetimes, let’s say 2-3 billion years ago, would have looked for all intents and purposes like an alien planet,” Lenardic said. “We know the atmosphere was completely different, with no oxygen. There’s a debate that plate tectonics might not have been operative.”
    It would look like earth, the only planet with lots of water. The oceans were formed over 4 billion years ago. Plants don’t need oxygen. They created the oxygen in the atmosphere. There’s no debate among geophysicists about plate tectonics. Astrobiologists can debate but they can’t stop the oceanic and continental plates from moving.
    “Yet there’s no argument there was life then, even in this different a setting. The Earth itself could have transitioned between planetary states as it evolved. So we have to ask ourselves as we look at other planets, should we rule out an early Earth-like situation even if there’s no sign of oxygen and potentially a tectonic mode distinctly different from the one that operates on our planet at present?”
    Yes there were plants and microbes but no hairless apes even the dumb type. The aliens could be solar powered intelligent machines or pond scums that don’t need oxygen.

    • Looks to me that there is an assumption that the orbits of the planets is unchanged over the eons. Astronomers don’t think that is true.

  32. Who really cares about such a crazy hypothesis anyway. It can be of no benefit or detriment to us here on earth.

  33. Seems science fiction is now a part of science. None of this matters in the least. “Could have” is irrelavent. Only what DID happen matters. Alternate timelines and outcomes in the past belong in the fiction writers section. What a waste of time and money when real science needs attending to.

  34. Our solar system COULD have had two habitable planets, if a star the size of Alpha Centauri B , about half as luminous as our sun, replaced our sun. Venus would have been in a similar situation to Earth 4.5 billion years ago. As the star heated up, there would have been a runaway greenhouse on Venus, but that would have happened after 7 or 8 billion years, not after a few hundred million years, as happened in our solar system.

    • “Venus would have been in a similar situation to Earth 4.5 billion years ago. ”
      No. Its day is far too long and its max daytime solar input would be twice of what it would be for a faster rotating planet. Earth spins fast enough we can consider the entire surface to be equilibrium with the Sun, while Venus spins so slowly, that if it the surface was actually in DIRECT equilibrium with the Sun. the average input is half the total power from the Sun and not only 1/4 as it is for the Earth.

  35. One thing I notice in the US is that a moral dimension to everything is inescapable. Any bad thing that happens to a person, any hard times they experience, are always due to “poor choices”. Even dying, of cancer for instance, is a sign of moral weakness, of not having fought hard enough to live. Climate science is needless to say intensely moralistic, and this narrative only continues this trend. Now the inhospitable climate on Venus is a result of “poor choices” by that planet. Of course the ultimate goal of morality is violence. Moral opprobrium is the perfect basis for violence against individuals. The more moralistic a society is, the more violent.

  36. Venus rotates in opposition to the planets, all other arguments containing the topics regarding “Big G” mass retention can be excommunicated as non-compliant.

  37. alignment in the thread, better :
    ptolemy2 on July 8, 2016 at 1:14 pm
    +1 to the ‘moral club’ vs. ‘bad luck’ dichotomy.

  38. And then there’s that urban myth, a guy pretending to board a ship in finnis terrae crossing the oceans for ‘free trade’ with some already known ‘indians’.
    Last SMS or e-mails saying his, Columbus’, columbians struggling against amerigos.
    Or that other urban myth there’s such thing as ‘South Pole’ – who needs such speculations, stop funding.

  39. Any effort to discover what happened in the past is not only based on the accuracy of evidence we find today and the principals of observed physics,, but equally based on the accuracy of our imagination.
    Only the observer of the past events themselves can truly and absolutely know what happened, provided of course, that they are a good observer.

  40. This article is a good example of simplistic thinking. It ignores the presence and function of Earth’s massive Moon and the lack of an equivalent in the case of Venus or Mars. Moon stabilizes Earth’s axis, such that it’s inclination from a vertical to the plane of the ecliptic has never deviated more than a degree from its present 23½ degrees. Had Moon not been there, the axis would have been able to swing freely, allowing such inclinations around 90 degrees, which would have presented Earth’s polar regions to direct insolation for significant periods during the solstices. Earth’s oceans would not have survived the ensuing 24/7 insolation and would have first evaporated and then photodissociated, leaving Earth with a much-diminished hydrogen-to-deuterium ratio, such as is found on both Mars and Venus, both of which have lost their oceans due to insolation made possible by uncontrolled swings of their rotational axes. Interestingly, the hydrogen-to-deuterium ratio is lower on Venus than it is on Mars, indicating its more comprehensive loss of water. The “Godlilocks” model of life formation with simple distance from the primary star is obsolete, and should be discarded.

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