Why Didn't the Young Earth Freeze Into an Ice Ball?

By Andrew Moseman | April 2, 2010 12:24 pm

SnowballEarthThe “young sun paradox” just won’t go away. For decades, scientists like Carl Sagan have tried to resolve this mystery of the early solar system—how the newborn Earth stayed warm enough to keep liquid water—but it continues to bob and weave around an answer. In the journal Nature, a team led by Minik Rosing proposes an alternate solution to the leading theory, which relies on the greenhouse effect hypothesis. But don’t expect the debate to end here.

The problem is this: The young Earth received much less heat from the sun. Four billion years ago, a lower solar luminosity should have left Earth’s oceans frozen over, but there is ample evidence in the Earth’s geological record that there was liquid water — and life — on the planet at the time [Space.com]. So what gives? The traditional explanation going back to the 1970s has been that a powerful greenhouse effect, far stronger than the one we experience today, kept the Earth basked in enough warmth to keep water sloshing around the planet’s surface as a liquid and not packed in solid ice. In 1972, Sagan and colleague George Mullen wrote that such an effect would have required intense carbon dioxide concentrations in the atmosphere during that period, the Archaen.

But the evidence isn’t there, Rosing argues. To research the greenhouse hypothesis, he and his team studied banded iron formations in Greenland ice dating back 3.8 billion years. They focused on two minerals, magnetite and siderite, that can provide a bellwether of the CO2 concentrations in the atmosphere. Too much CO2, and magnetite can’t form, whereas the opposite is true for siderite [ScienceNOW]. According to Rosing’s analysis, the CO2 concentration in the atmosphere could have been as high as three times what we see today, but that’s not nearly enough to account for the warmth that would’ve been needed to stave off a snowball Earth.

So, Rosing puts forth his own solution. Back then, he says, the continents were smaller and thus more of the Earth’s surface was covered by water. Since water tends to absorb more heat than land, an ultra-watery Earth could have helped conserve warmth. Secondly, he says, the early earth wasn’t a cloudy place back then, due to the fact that life had just arisen. The droplets of water that make up clouds form by glomming on to tiny particles, called cloud condensation nuclei, many of which are chemical substances produced by algae and plants, which weren’t present on the Earth at that time [Space.com]. You see the same effect today, he says, in areas of the open ocean that have neither much marine life nor much cloud cover. And if the young Earth truly had few clouds, more sunlight reached the surface.

Atmospheric scientist James Kasting says that if Rosing’s team is right, the idea could have consequences beyond our own planet’s history—it could widen the habitable zone for exoplanet hunters seeking extraterrestrial life. But regarding the young sun paradox, he says, this new answer is incomplete. “I think their mechanism fails because they just barely get up to freezing point,” Kasting said, adding that it also fails to take into account the reflectively of the planet’s ice [Discovery News].

Related Content:
DISCOVER: The Fast Young Earth
DISCOVER: Did Life Evolve in Ice?
DISCOVER: Snowball Earth
DISCOVER: Our Solar System’s Explosive Early Years

Image: Wikimedia Commons / Neethis

CATEGORIZED UNDER: Environment, Space
  • http://www.wesleyan.edu/av/gronican.htm R. White

    We don’t know how much compatible (with humans) life exists in the Universe. It’s very possible that we’re unique beings. Such a shame that we’re using our limited energy and time in killing each other and destroying the planet through waste. I wonder why humans bother having children if those progeny won’t have a future. We seem to consider resources in terms of a hundred years instead of thinking of the far future and the descendants of our children. We should be exploring our resources, conserving them, exploring the oceans and learning to live there as well as developing platforms in space, on the moon, the asteroids and planets such as Mars. I hope that one day, soon, we’ll stop acting like destructive termites and begin adopting the mantle of intelligent beings, “Human Beings,” as the ancient American Indians once referred to themselves.

  • BillWhite

    See, there IS something good about global warming!

  • scott

    Fascinating…but please, brilliant scientists…quit arguing, experimenting and doing research on something that went on 4 billion years ago (since nobody was there, it is still speculation) and please use your brain power, time and research money to help put things in better balance and in better shape now (pollution control, clean energy, ecology, etc)…

    It’s great to spend billions to smash protons and learn about new funky particles that exist for a trillionth of a second that emerge from distant dimension, and great to spend another few billions on a probe that can scoop up some sand on Mars and test for organic molecules but lets focus on that after we – clean up the pacific garbage patch, create (perfect and put into use) new forms of clean energy, make state of the art sewer treatment plants, etc, etc….

    I’m just saying….I am worried about the planet now, not the state of it 4 billion years ago. Maybe early life grew on/under the ice like a modern day Europa? How do we really know it was not like that that long ago? Even the greatest minds, with the best theories, calculations and tests can still, only speculate.

  • Daniel J. Andrews

    Scott, sometimes lines of these lines of thoughts have pay-offs in our understanding of things now, or where things will be going in the future.

    Even if they didn’t though, the same curiosity and passionate desire to understand what happened in the past is the same curiosity that resulted in things like computers, air flight, medicine, and other modern conveniences.

    Incidentally, if we try and solve all problems here on earth first we’d have never gotten to the moon, and many of those spin-off technologies wouldn’t have been developed till much later, if at all (Velcro!) :)

    Finally, take a look at how much the US spends on science and research and compare that to other expenditures. You’ll see it is a very small fraction of the budget. It may seem like a lot of money is being spent on out of this world things, but compare it to other expenditures. If anything, we should be demanding more money go into science, not less.

  • William F Davis

    Enough for a moment with all the political and monetary views, and back to the science…

    It’s been suggested that the moon was created by a Mars sized object slamming into the young Earth. If so, how long would it take for the thermal footprint of that event to settle down?

    It just seems to me that something that enormous would leave Earth with a hot crust for a very long time. Also, the early moon was a lot closer than it is now. Wouldn’t tidal forces be a factor in warming the young Earth? Earth likely would have been bombarded for a long time from gravitationally collected debris from that huge event, another possible source of heat.

    Another possibility is that the young Solar System might have been traveling through a dense dust or gas cloud, perhaps the very same nebula that it was born in. There may have been exposure to thermal transfer between the Sun and the Earth due to high volumes of dust and gasses from the nebula, and also the Sun’s own planetary disk. A few hot super giant stars nearby may have been a contributing factor as well. After 4.5 billion years, traces of that nebula are probably long dissipated, it’s super giants exploded long ago, all stirred back into the soup of our Milky Way.

    I don’t know if any of the above could actually fits within the time line that includes the young Earth’s early oceans, but I thought it might be worth tossing it out there.

    Now about how our money is spent… Actually, the study of science, like that in the above article, is an exploration that may help us understand better what is happening to us now. To understand how (and why) something that is played out long ago, may be applied to a better understanding of what we discover today. That may help us better navigate our human existence and survival on this Earth. But it does usually require scientific minds to fully grasp how the connections between past events and today’s discoveries relate, and how this new knowledge may be applied to help us cope with, and possibly solve, today’s many complex problems. Examples include better medicine, better and cleaner energy sources, better food and agriculture production, better control of a stable climate… the list goes on and on!

    As far as politics… good healthy debate between opposing scientific views, met with dedicated actions to seek the truth under full cooperation and exchange on all sides, will serve us best to solve many of humanities problems. Politicians must step aside long enough to allow for best conclusions to be made, and not take sides ahead of the actual knowledge, a knowledge that assumes the best probability models based on actual observation and physical facts. For example, global warming is still in early scientific debate and should be better funded for continued study from all angles, and with full unconditional cooperation from within the science community. Our partisan politicians must refrain from taking sides and making a field day out of unfinished science. In good time, we may know the pros and cons of global warming, and find ways to adapt and resolve issues relating to it. Yes I said “pros”, because some will find good side effects in it. We should be looking at those pros as a means to help adjust, not just the cons as some all-doom scenario. This way, we may avoid being so drastic in our resolves. And that will surely keep the costs down!

  • scribbler

    My money’s on thermonuclear generation of heat in the core…
    ;-)

    Raises some interesting questions, at the very least…

  • Lucas

    KILL ALL HUMANS! That’s the solution.

  • Paul

    What happened to the hypothesis that the early atmosphere had much higher pressure, due to it having more nitrogen? Pressure broadening would have made CO2 more effective as a greenhouse gas, without requiring so much CO2 to be present that overly-reflective CO2 clouds would have formed in the mesosphere.

  • William F Davis

    Paul makes a great point about CO2, nitrogen, and higher pressure. I believe that if we assume the planet as we see it now, the model has it’s problems. But if we take in account the planet’s past features, which would have been a lot different, then maybe the model makes better sense. I would even bet there was much more CO2 along with that pressure Paul mentions. Along with the belief that the core was much warmer, and having a shallow unstable crust, it looks like a recipe for warmth. Might have been a bit too warm for glaciers for all we know! Earth was slowly cooling as the Sun was slowly warming, so baby bear’s porridge was just right!

  • m

    HUH?

    i had thought all this resvolved…the Earth didnt freeze away back then because the mantle wasnt thick enough. More of the interior fusion “seeped” up. Kinda like the way Venus is now, with its thin crust.

    *shakes head*

    it’s a shame Discover doesnt read more of its own articles from the past. In fact, I’ve got the issue right here in my hand Discover. But – I’m not going to do the work for you. Here’s a hint though…there are 2 issues and both appeared within the last 8 years.

    But that’s all the hint I’m going to give you.

    Start reading.

  • Ikelos

    I agree with the post above. It makes sense that the earth was warmer back then because it had only freshly formed. At one point (briefly) the earth’s surface was completely liquid from the heat and because the core temperature was higher the crust was thinner.
    The opposite is the problem with Mars. Supposedly it once was home to liquid water, but now its core has cooled too much and its crust is too thick. Any water that just happens to be liquid despite the colder temperature of Mars sinks too far into the crust to appear on the surface.

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