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Space Science

Updated Model Puts Earth On the Edge of the Habitable Zone 264

Posted by Unknown Lamer
from the living-on-the-razor's-edge dept.
cylonlover writes with news of an update to the model used for calculating the habitable zone around stars shifting things out a bit. From the article: "Researchers at Penn state have developed a new method for calculating the habitable zone (original paper, PDF) around stars. The computer model based on new greenhouse gas databases provides a tool to better estimate which extrasolar planets with sufficient atmospheric pressure might be able to maintain liquid water on their surface. The new model indicates that some of the nearly 300 possible Earth-like planets previously identified might be too close to their stars to to be habitable. It also places the Solar System's habitable zone between 0.99 AU (92 million mi, 148 million km) and 1.70 AU (158 million mi, 254 million km) from the Sun. Since the Earth orbits the Sun at an average distance of one AU, this puts us at the very edge of the habitable zone."
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Updated Model Puts Earth On the Edge of the Habitable Zone

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  • by Anne_Nonymous (313852) on Monday February 04, 2013 @08:07PM (#42791693) Homepage Journal

    by deciding to include my neighborhood.

  • GW solution (Score:5, Funny)

    by GrahamCox (741991) on Monday February 04, 2013 @08:09PM (#42791715) Homepage
    This then suggests a simple fix for global warming - we just need to move Earth into a slightly higher orbit. A few hundred well-placed nuclear bombs ought to do it.
    • No way! The temperature where I live is just right.. In fact, I wouldn't mind if the temps climbed a bit more.

    • by oodaloop (1229816)
      A few hundred million, maybe. The earth is pretty big.
      • by MightyYar (622222)

        What if each bomb were moon-sized? :)

        • What if each bomb was let of on the moon instead? Each boom moves the Moon a little faarther out, pulling the Earth with it. I may a few centruies but we could move better position.

          Though if they all went of together, we have "Space 1999" with a Moon size interplanetary ship. Will take awhile to get anywhere but at least we would be traveling.

          • I don't see how moving the moon into a higher orbit would change the earth-sun dynamic. If the moon's further away, it'll just have a smaller average tidal effect. It'll pull the earth less in all directions assuming the orbital eccentricity remains the same.

            • It would change things quite a bit if the moon was pushed completely out of orbit. The mass of the earth-moon system would be significantly smaller if it were just earth.

            • The earth and moon orbit around the combined center of mass (barycenter: http://en.wikipedia.org/wiki/Barycenter#Astronomy [wikipedia.org]). Moving the moon moves that center of mass. Though it's not a necessarily efficient method to move the earth; the assumption is that the earth-moon system is in a stable orbit. Move one hard enough in the wrong way, and it may destabilize to where the model doesn't work. Also, destabilizing the moon's orbit could be a potential hazard.
              • by Plekto (1018050)

                I once calculated this out, in fact. We need to move the Earth a bit over 2 feet per year to outdistance projected solar warming as our sun ages. This is within theoretical limits of our technology to accomplish in the next few hundred years.

                The other option is to make an artificial ring to block out about 1% of The Sun's energy.

          • by rossdee (243626)

            Gravity is an inverse square force - if you move the moon away from the earth it would have less effect . You could knock the moon completely out of the solar system and the earth would remain pretty much in the same orbit. (Space 1999 anyone?)

            • if you move the moon away from the earth it would have less effect

              Well obvious answer then, move it closer for an even stronger effect!

        • by oodaloop (1229816)
          Do we have a lot of those in stock?
    • Re: (Score:2, Informative)

      by Anonymous Coward

      You probably mean more like our entire combined worldwide nuclear arsenal all going off at once in a single location.

      Even then, I doubt it would have enough effect. The earth has been hit by countless enormous hunks of rock during its creation, each with power in the multitudes of times greater than our arsenal, and they didn't manage to move the world.

      • Re:GW solution (Score:4, Insightful)

        by amicusNYCL (1538833) on Tuesday February 05, 2013 @12:54AM (#42793637)

        The earth has been hit by countless enormous hunks of rock during its creation, each with power in the multitudes of times greater than our arsenal, and they didn't manage to move the world.

        That's patently false. If any mass hits the earth, we move. How much? Depends on how much mass hit us, but we certainly move. There isn't a threshold where we start moving over a certain amount of mass, the question is how much we move based on the force that was exerted on the planet and the mass of the planet. If anything at all hits us, that number is never exactly 0.

      • Re:GW solution (Score:5, Informative)

        by MrNemesis (587188) on Tuesday February 05, 2013 @07:32AM (#42795205) Homepage Journal

        Not directly related, but the XKCD "What If" scenario on just changing the rotation of the earth enough to avoid having leap-seconds would require 50,000 4m diameter rocky asteroids hitting the earth every second.

        http://what-if.xkcd.com/26/ [xkcd.com]

        Back-of-a-fag-packet calculations that every nuclear and non-nuclear explosion in the history of civilisation wouldn't give enough oomph to move us more than a few km away from the sun (although that didn't stop anyone making films about it). http://www.imdb.com/title/tt0054790/ [imdb.com]

    • by PvtVoid (1252388)

      This then suggests a simple fix for global warming - we just need to move Earth into a slightly higher orbit. A few hundred well-placed nuclear bombs ought to do it.

      Let me guess: you fell for this [venehammerschlag.com] too.

      • by AC-x (735297)

        This then suggests a simple fix for global warming - we just need to move Earth into a slightly higher orbit.

        Nah, we could simply drop a giant ice-cube into the ocean every now and then. Of course since the greenhouse gasses are still building up it will take more and more ice each time, thus solving the problem once and for all!

        • by mjr167 (2477430)

          You may think you are jesting but... my husband works in the nuclear industry and the nuclear plant down near New Orleans gets it's water intake that it uses for cooling from the Mississippi River. One summer they had record highs and the electric company was making money hand over fist running the plant because demand was at record highs. It was hot enough that the temperature of the water they were pulling out of the river was getting too high for them to keep running the plant at the current output and

    • by macraig (621737) <(mark.a.craig) (at) (gmail.com)> on Monday February 04, 2013 @08:24PM (#42791881)

      Nah... we just need a planet-sized pair of Stargates.

    • Re:GW solution (Score:5, Informative)

      by girlintraining (1395911) on Monday February 04, 2013 @08:37PM (#42792027)

      A few hundred well-placed nuclear bombs ought to do it.

      If the goal is a nuclear winter, sure. If you're trying to move the planet... how can I put this as succinctly as possible: If we detonated every nuke we had on one side of the planet, we'd succeed only in leaving one side of the planet uninhabitable. It wouldn't move the planet by any appreciable amount. The subsequent earthquakes would probably do more, by affecting spin. People seem to forget in orbital mechanics, to move in one direction, you have to displace an equal amount of mass x energy in the opposite direction. All a nuke would do is move the air around and leave a hole in the ground. Nothing would be ejected into space, and therefore, no movement.

      I know you're trying to be funny, but after awhile, I get tired of the "a nuke is powerful enough to do anything!" thinking. I blame Bruce Willis.

      • Re:GW solution (Score:5, Informative)

        by budgenator (254554) on Monday February 04, 2013 @09:02PM (#42792257) Journal

        I get tired of the "a nuke is powerful enough to do anything!" thinking. I blame Bruce Willis.

        My Organic instructor was a real math geek, one day she demonstrated that a quarter inch of rain falling on Manhattan resulted in the same release of energy as the atomic bomb dropped on Hiroshima, she was good at estimating cube roots of 4 digit numbers in her head too.

        • she was good at estimating cube roots of 4 digit numbers in her head too.

          No great trick given there only a dozen or so integers that produce 4 digit results ... some basic gut feel for a cubic function will get you pretty close every time.

    • Re:GW solution (Score:5, Informative)

      by Nimey (114278) on Monday February 04, 2013 @08:51PM (#42792165) Homepage Journal

      Niven's way ahead of you. It's a simple matter of knocking Uranus into a cometary orbit and using its gravity to move Earth further out.

      • Niven's way ahead of you. It's a simple matter of knocking Uranus into a cometary orbit and using its gravity to move Earth further out.

        I'm reading Larry Niven's "A World Out Of Time" now (after another slashdotter recomended it), and I'm almost where this is going to be explained. Good read so far, page 72 and it's already 3 million years into the future!

    • Meh. All we need is a cable of sufficient length and tensile strength, two exceptionally strong anchors, and a mars rocket. Let angular momentum take care of the rest.

      • You want to slow Earth down and plummet it into the Sun? Mars is traveling slower than Earth in a larger orbit with less mass...

    • This then suggests a simple fix for global warming - we just need to move Earth into a slightly higher orbit. A few hundred well-placed nuclear bombs ought to do it.

      Yes, but not a new idea. The slogan for Earth Day 2012 was "Mobilize The Earth": [earthday.org]

      For Earth Day 2012 we are mobilizing the planet simply to say one thing: the Earth won't wait. It seems that environmental issues have been put on the back burner as we are in the midst of a global recession. It is time for us to Mobilize the Earth

      However, I was disappointed when their implementation did not even begin to approach my own vision. [google.com]

      • Did you just put a rocket booster in the south pacific? I am not impressed. That's going to lower property values.

    • by CRCulver (715279)

      This then suggests a simple fix for global warming - we just need to move Earth into a slightly higher orbit.

      Larry Niven already proposed this four decades ago in his novel Ringworld [amazon.com] , where the alien race the Puppeteers had moved their planets away from their sun to cool them. This was long before fears of global warming, but Niven felt that technological advancement would inevitably lead to problems with waste heat.

    • Easy calculation (Score:5, Informative)

      by iris-n (1276146) on Monday February 04, 2013 @10:14PM (#42792777)

      Hmm, not in my definition of "few hundred". The calculation is actually easy to make:

      The earth is about 1,5E11 m away from the Sun, let's say that 1% is the variation that we want, so we get it to 1,515E11 m. So the difference in energy that we need is GMm(1/R1-1/R2) \approx 5E31 J; quite a lot.

      The best (or worst, depending on your point of view) nuke we ever exploded is the Tsar Bomba [wikipedia.org], which was 57 megatons or better 2,4E17 J.

      So if we managed to use this energy with 100% efficiency (which we obviously can't) to move the Earth, we would need 10^14 nukes. Well, guess we're stuck here.

      • So if we managed to use this energy with 100% efficiency (which we obviously can't) to move the Earth, we would need 10^14 nukes.

        Sounds pretty good, only four nukes!

        Better use five. From Orbit. Just to be sure.

    • by siride (974284)

      Yes, and then when we screw it up, we'll need massive volcanoes to keep the poles cool while people live in squalor for a thousand years. Not what I'd like to see.

    • If we can get a small asteroid to gradually move a bigger asteroid around the solar system in a controlled orbit, then we could make such asteroid steal momentum from Jupiter or Saturn bit by bit to put Earth's orbit out a bit more. It would take several thousands of years, though. It's within our current technology because we just to use smaller objects to move & control progressively bigger objects by leveraging the big planets. It's somewhat similar to how we used Jupiter's gravity to speed up the Ne

  • by Anonymous Coward on Monday February 04, 2013 @08:14PM (#42791791)

    ...time for some terraforming?

  • Wow (Score:5, Informative)

    by Arancaytar (966377) <arancaytar.ilyaran@gmail.com> on Monday February 04, 2013 @08:31PM (#42791941) Homepage

    The whole "Earth is fine-tuned for life" stuff has been debunked for ages (but still circulates thanks to creationists), but it's pretty amazing to consider our planet could be more than 1.5 times as far out as it is now, and still remain habitable.

    Also, note that the Earth's perihelion places us at 0.983AU. If these numbers are correct, our orbit actually leaves the habitable zone for a brief period every year.

    • We're on the ragged edge of survival! The preppers are right!

      Grab those guns, stock up on the freeze dried. Hunker down, it's gonna be a wild ride!

      (Remember, this is a pretty soft call, lots of things in the model that aren't accounted for: clouds for one. Don't get all worked up just yet. In the end, we're our own worst enemy, the Universe is merely indifferent.)

      • by d.valued (150022)

        There is a lot in the model that isn't fully accounted for. But they're getting better.

        Still, shoot me for at least acknowledging the anthropic principle.

    • Re:Wow (Score:5, Informative)

      by dryeo (100693) on Monday February 04, 2013 @10:57PM (#42793061)

      You do realize that the habitable zone has been moving out over the life of the solar system? The Sun converts hydrogen to helium, helium is more dense, increasing the density of the Sun causing it to burn hotter. Estimates are that some billion years ago the Sun was 25% cooler which would have shrunk the habitable zone quite a bit, perhaps to the point where Venus was habitable. Also with the Sun getting hotter, in perhaps half a billion years the oceans will boil and the Earth will be much more similar to Venus.

    • by riverat1 (1048260)

      Of course as you moved the orbit out the Earth would be colder and the the evolved biosphere would likely be very different than it is now. The habitable zone doesn't mean it's necessarily habitable for humans, just life in general.

  • Sure (Score:2, Insightful)

    by Exitar (809068)

    Every month or so astronomers find something that, according to their knowledge, should not exist.
    I bet they'll soon find a planet outside this new defined zone that has liquid water on its surface.

    • Re:Sure (Score:5, Interesting)

      by Jason Levine (196982) on Monday February 04, 2013 @09:28PM (#42792453)

      Surface? No, but Europa is believed to have an icy surface hiding a massive liquid water ocean. Although it is far from the habitable zone, gravitational interactions with Jupiter generates heat which keeps the oceans liquid. Add in some organic materials (which asteroids might supply) and life could have developed deep under the surface of Europa. Perhaps right now, as I type this, some big Europan fish-like creature is swimming through the cold oceans on the moon. (Or perhaps there are just Europan bacteria... even single celled alien life would be a major find.)

    • Mars (Score:5, Interesting)

      by Eric Coleman (833730) on Monday February 04, 2013 @09:39PM (#42792549)
      Mars had liquid water at some point and is outside the habitable zone, for some definitions of habitable zone. So it is entirely possible that planets with liquid water can exist outside the habitable zone. The real issue is with stability. An interesting take on this is to consider the flux of radiation from the Sun hitting the Earth. For a disk the size of the Earth, one can calculate the distance where water freezes and where water boils as a rough estimate of a "zone" of sorts. When looked at in this way, the Earth is at a point just barely above freezing. That we have the climate that we do beyond that near freezing point is due entirely to greenhouse effects.
      • Mars had liquid water at some point and is outside the habitable zone, for some definitions of habitable zone. So it is entirely possible that planets with liquid water can exist outside the habitable zone.

        Am I correct in assuming that the liquid which must have flowed on Mars doesn't necessarily have to be water, or has there been proof that the liquid was specifically water? That's a real question by the way, I'm not trying to be sarcastic. If anyone knows, I'd appreciate an answer.

        • by riverat1 (1048260)

          I'm not aware of anything that's liquid at the right temperatures and pressures and likely to be available in a large enough quantity to substitute for water. The only possibility I can think of would be ammonia and it seems it would likely have somewhat different effects than water because of its reactive nature.

        • Re:Mars (Score:5, Informative)

          by tgd (2822) on Tuesday February 05, 2013 @09:27AM (#42795757)

          Mars had liquid water at some point and is outside the habitable zone, for some definitions of habitable zone. So it is entirely possible that planets with liquid water can exist outside the habitable zone.

          Am I correct in assuming that the liquid which must have flowed on Mars doesn't necessarily have to be water, or has there been proof that the liquid was specifically water? That's a real question by the way, I'm not trying to be sarcastic. If anyone knows, I'd appreciate an answer.

          The presence of water is proven on Mars. The existence of minerals that only form in the presence of water is proven on the surface of Mars. Massive liquid-based erosion is proven on the surface of Mars. Its reasonable to assume they're all related. And, frankly, the fact that water is found damn near everywhere in the solar system where it hasn't been torn apart by radiation, or heat makes is really implausible that there wouldn't have been water on Mars -- water that got there the same way it got to Earth, during a period of time in which Mars was more conducive to surface water than Earth.

          IMO, the whole "finding water on Mars" thing is more akin to the "seeing a giant squid alive in the ocean". Everyone knows its there, but scientists just like to see things with their own eyes. The search is the fun part, so... search away.

  • by trims (10010) on Monday February 04, 2013 @08:41PM (#42792061) Homepage

    This is interesting, since all the scientific data I've seen says that ultimately, Venus is far better than Mars as a target for Terraforming, yet this research is claiming that Venus is far outside the habitable zone, while Mars is smack in the middle of it.

    Mars simply lacks two things: (1) the ability to generate a good strong magnetic field (too small, and no molten iron core), so it gets constantly bombarded with far more solar radiation than terrestrial life can stand outdoors, and (b) its much smaller mass and lack of magnetic field make is impossible for Mars to hold an atmosphere that's much more than it has now. So the result is that, while Mars superficially seems a better place for life now, there's no good way for us to transplant onto Mars without having to either live underground or under thick domes.

    Venus, on the other hand, already generates a good magnetic field, and has no problem holding a significant atmosphere. It's just too hot and toxic. But a couple thousand tons of bacteria into the upper atmosphere will solve that problem, so Venus is actually the best candidate to turn into an Earth-like place.

    I guess we'll have to look for two criteria: (1) which planets are most likely to have Earth-like indigenous life on them, and (2) which planets are best suited to be terraformed for occupation by us.

    Like I said, interesting...

    -Erik

    • So exactly how does one eliminate a high pressure atmosphere from Venus? One way of lowering the atmospheric pressure is reducing the mass of venus (thereby having weaker gravity, and unable to hold a high pressure atmosphere), but say you managed to instantaneously precipitate half of venus's atmosphere into solid form, and reduced its atmospheric pressure by half -> wouldn't its gravity tend to move the atmosphere back into a high-pressure equilibrium with the planet?

      • by Dr. Spork (142693)
        You drop the temperature and all that atmosphere will come raining/snowing down. Probably the best way to drop the temperature is to unfurl a very large, semi-permiable membrane at the liberation point between Venus and the sun, to reduce the amount of solar flux reaching the surface. Eventually, we could do all that shading with a gigantic array of solar panels at L2 - just large enough so that the solar flux hitting the surface of Venus is the same amount as what hits the Earth (this requires 50% coverag
    • by NalosLayor (958307) on Monday February 04, 2013 @09:23PM (#42792409)
      Issues with removing the atmosphere aside:

      1. I'm pretty sure that Venus doesn't have an appreciable magnetic field.

      2. Even if it did, its day is about the same length in its year (e.g. about 250 earth days) so nobody could live in any fixed place on the planet without freezing or melting, even if we got rid of the thick atmosphere. You'd have to live in trucks rolling slowly around the planet in the ... pardon the pun ... twilight zone.

      Mars on the other hand has normal days and could be warmed up with a greenhouse effect. Also, the thicker atmosphere would provide additional sheilding at the surface level. One could imagine the last few percentage points of shielding being made up with local magnetic field "bubbles" around settled areas, powered by fusion reactors, assuming we have that technology in the next century or so.

    • by erice (13380)

      Venus, on the other hand, already generates a good magnetic field, and has no problem holding a significant atmosphere. It's just too hot and toxic. But a couple thousand tons of bacteria into the upper atmosphere will solve that problem, so Venus is actually the best candidate to turn into an Earth-like place

      Venus doesn't have enough hydrogen to support hydrocarbon based life. Your cyanobacteria will simply die unless you hit Venus with a preposterous mass of comets. You may also need to get rid of the excess CO2 so your bugs don't they don't get too cooked.

    • by Svartormr (692822) on Monday February 04, 2013 @10:34PM (#42792907)

      Alas, you are wrong about Venus. It has a negligible magnetic field (likely due to no core convection) and cosmic rays and the soloar wind freely interact with the upper atmosphere causing hydrogen loss. As well, if Venus was a black body and had no incoming radiation it would take on the order of 600+ years to cool off.

  • by bagorange (1531625) on Monday February 04, 2013 @08:43PM (#42792085)
    Surely you all know the habitable zone is exactly 20ft wide? Someone told me once, so I believed them [ning.com]
    • by rubycodez (864176)

      It's True! I went on the sun deck on the rooftop of the building with the lockers at the local pool. It was 10 ft. up in the air and I got a terrible sun burn! that's because I was out of the habitable zone! Good thing I didn't go up there at night when the sun was on the other side of the world, I'd surely have frozen to death being outside the HZ

  • As the authors explain "Testing these predictions quantitatively using 3-D climate models should be a fruitful topic for future research." i.e. they need to keep paying mortgages, car loans,... next few years. The model is so embarrassingly inadequate, that considering how much room for fudging one has with toy models, they still barely managed to get Earth to come inside the "habitable zone."

    I also wonder how will politicians translate this 1-D toy model into a story in which we are somehow responsible for

  • Simulation of being just a bit further away from the Sun sounds like it would effect what happened in the Maunder Minimum, with reduced Solar output where millions of people starved to death in Europe alone.

  • It seems he's saying that the Earth is almost too close to the Sun to sustain life, so I have to ask... are we talking about the same Earth here? You know, the one that's had dozens of ice ages?
  • by Dishwasha (125561) on Tuesday February 05, 2013 @03:07AM (#42794293)

    While everyone debates how many nukes it would take to adjust earth's orbit, I decided to see if our current solar distance under the new guidelines was actually a problem. I fired up Celestia [shatters.net] and although I'm not sure what kind of factors it takes in to effect at both a macro and micro level, I figured it would give a decent representation of our solar orbit trends for the next 10 millennium at least.

    It looks like around Jul 16, 2013 we're at our farthest solar orbit of around 1.0164au and around December 31, 2013 we're out our closest solar orbit at around 0.98333au. Fast forward 11970 years and around June 30, 13983 we are at our furthest solar orbit of around 1.0151au and around December 30, 13983 we're at our closest solar orbit of around .98390au. And if you advance even further to over a million years in Celestia we're still looking at solar distances right around the same range.

    Sure, the close range may mean that we're too close to the sun by only 0.00667au and our saving grace is that it won't stay at .98333au all year round, but somebody may want to inform the researchers that we are outside of their range and the earth appears to be quite habitable. And for the rest of you, let's not try to solve a problem that doesn't exist and won't exist for a very, very, VERY long time.

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