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Updated Model Puts Earth On the Edge of the Habitable Zone
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."
piss!
by deciding to include my neighborhood.
Could there be some variation? If another Star was slightly bigger or slightly smaller, wouldn't the habitable zones be different?
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.
it MUST be correct.
With all the fluctuations over 4B years, how then have we remained in the zone to maintain life?
All scientific papers should be published with a full list of all grant money sources received over the past 24 months.
Call me naive but doesn't the energy output of the star matter too? I would think a larger star with a higher energy output could/would have a habitable zone potentially much larger (greater diameter) than our own.
--AC
Personally I would much have our global climate be what it is rather than have 40 degree oceans if we were further from the Sun.
call me FOSS im the boss with the sauce and the source
I smell a new political platform to run on, this orbit is just too damn high!
...time for some terraforming?
It also means Mars is just within the newly-defined habitable zone
This puts Mars right in the middle of the habitable zone (1.38 AU)
Wonder how many other systems have multiple planets within the habitable zone.
Shucks, if only that were possible, eh?
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.
It's a study that evaluates the conditions optimal for an Earthlike, carbon-and-water-cycled ecosystem with no clouds (they do adjust for them, but modeling clouds would require serious time on big iron). Instead of just relying on "too hot" and "too cold" they're looking at things like greenhouse effects based on known absorption values and whether or not liquid water can exist on the surface, which brings the scope of this research into politically-sensitive AGW territory (they note that they deliberately underestimate the effects of CO2 as a greenhouse gas in this model). They also model for varying sizes of planets as well, like you'd expect, using both early Mars and recent Venus as prime examples of planets that stray from the habitable zone. All and all an interesting step forward for astronomers everywhere that owes a clear debt to ongoing climate change research here on Earth.
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.
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
There are always four sides to every story: your side, their side, the truth, and what really happened.
Surely you all know the habitable zone is exactly 20ft wide? Someone told me once, so I believed them
Well, given a thousand years or so we could probably dump enough asteroid material on it to bring the mass up. By then, we should have enough fusion tech to scarf hydrogen from Jupiter, fuse some of it up to oxygen, fuse more up to nitrogen, and combine the rest with some of the oxygen for water. Then seed with microbes, algae, etc; that ought to take another few hundred years. But after all that, sure, Mars ought to be nice.
And by the time that's done with we could probably set up a Nivenesque drive system on Neptune and use it to pull Venus out to the habitable zone and get started on it. :)
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 the Earth's distance from Sun and need to pay them for it.
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.
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.
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, 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.
entropy happens
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?
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 New Horizons probe.
Table-ized A.I.
Wasn't Earth stuck in frozen-ice-ball phase about a billion years ago? If we were a little further out, we may still be stuck in that phase even today.
Maybe the habitable zone varies over time depending on the planet's conditions and chemical makeup.
Table-ized A.I.
A qucik look and Mars is 1.5 Au from the sun. I guess thats good enough! AWG solved just by moving next door!
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?
There is more to being habital than simply being in the habital zone.
Nah, fission on Mars to split Fe to O2/N2. And we'd probably need to pull it into the asteroid belt to get all the asteroids to it, and we'd need nearly the entire belt to get it a noticeable gain in mass.
And I'd use the Niven drive to push all the gas giants together. See how star-like the result is. Then move that gas super-giant towards earth, and set Earth, Mars, Venus, and all the Jovian moons around, crashing Europa into Mars for the mass/water, and then using the Niven drive to move the small star-cluster into intergalactic space, if there ever is an issue with our Sun. (may have to do the Europa/Mars thing first, so as to not destroy Europa with the planet combining)
Learn to love Alaska
I know that was not your point, but just wanted to make sure that we are not confusing apples and oranges.
I KNEW this would really be about greenhouse gases. Fascinating how science is so easily bent to political will, and how so few scientists have any insight into the situation.
(Because this "proves" just how fragile our biosphere is and that we are on the edge of a mass extinction event if we don't submit to the political solutions being dreamt up by our betters, which largely involves crippling the middle and lower classes with high energy prices.)
This habitable zone idea needs to die. We have 1... that's ONE example of a inhabited planet. Out of and infinite number of habitable planets. We have no idea what life can live on, and no, we're not a good example. As far as we know, we'll find life on every planet, moon and asteroid in this system. We're not even entirely sure life can't be living on the surface of the sun. We need liquid water to survive, I doubt the trillions of other species out there are even remotely similar to us.
Remember that Bo Vie Bo Michael Mann, the Anthropocene Mann, is home at Penn State. Therefore all departments MUST bow and kiss his ass and sign a 20 year agreement for prostitution to fulfill his Mannly needs.
The larger the planet the more atmosphere it will have and therefore the more heat retention capacity it will have and therefore the habitible zone (range of radii the planet can sit in and maintain liquid water) will be further out than for lthe ighter and less atmospheric planets.
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.
"There is more worth loving than we have strength to love." - Brian Jay Stanley
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!
"There is more worth loving than we have strength to love." - Brian Jay Stanley
Sorry but I have to say the word is habitable. Habital sounds like something I do as a result of a habit.
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 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.
it will be revealed that earth (terra, aka sol 3) is NOT a planet, it is a habitoid.
They are taking greenhouse effect into account? If it goes further this way, by 2050 habitable zone for Earth will be between 1.10 and 2.05 AU, because of amount of CO2 we pump to atmosphere. And this will give us a clear conscience - it is not our fault for making Earth inhabitable, it is just in wrong place in orbit for our pollution needs.
I wonder if our ancestors, barely surviving ice ages, would also agree that 0.99AU is way too close to Sun...
Sorry but I have to say the word is habitable. Habital sounds like something I do as a result of a habit.
habitual
After coming into contact with a religious man I always feel I must wash my hands. Friedrich Nietzsche
Conveyor belt of asteroid-habitats transferring momentum, then?
Well, given a thousand years or so we could probably dump enough asteroid material on it to bring the mass up.
Not sure where you'd get all that asteroid material from, as if you dumped the entire mass of the asteroid belt on Mars you'd only increase its mass by 0.5%.
The Kuipler belt is much more massive, maybe 10% the mass of Earth, but that's mainly frozen ices rather than rock.
Interesting. The orbit of Mars is at 1.38-1.67 au, which is at the other end of the habitable zone. So our solar system actually has two planets in the habitable zone!
Stellar evolution of sun like stars suggests our Sun was ca. 20% dimmer 4 billion years ago, and early opinions were the Sun was too dim and the Earth too cold for liquid water. In the 1970s, Carl Sagan proposed an Ammonia rich atmosphere that produced an efficient Greenhouse effect, but later work on the redox state of the Mantle indicated out gassed volatiles produced a hydrogen rich (mildly reducing atmosphere) that did not easily produce a strong greenhouse. Despite this later research, looking at stable isotopes, suggested the early earth was quite warm ~50 to 60 degrees Celsius. The reappraisal of the Habitable Zone may help dispel the "Faint Young Sun Paradox".
Yes, but reheating and restarting the core to get a proper magnetic field would be a bitch.
What can I say Earthlings
Venus and Mars were always in the habitable zone, although this new definition excludes the former. But that only means that it's not physically impossible for liquid water to exist on them. We have good evidence that Mars had liquid water, but it has disappeared since then. To get liquid water on Mars, we would first have to replace its lost atmosphere, and for that atmosphere to remain, we would have to give it a magnetic field, which is pretty much impossible for the foreseeable future.
So mars is near the other edge of the habitable zone. This seems more like they're adjusting the zone for wishful thinking. They really really want mars to be habitable, but it's not. And they really really want earth to be on the verge of disaster for some reason. Or maybe they've got it right.
Billions of years ago, when Earth's oceans first formed, the sun was much cooler. As a result, the habitable zone was much closer to the sun. At this time, Earth would have been close to the *outer* edge of the habitable zone (as it then existed). Billions of years later (i.e. now), after the sun has slowly, continuously warmed, Earth is now close to the *inner* edge of the habitable zone.
This implies that planets that are close to the outer edge of their host star's habitable zone are less likely to have intelligent life (due to not having spent very much time in the habitable zone). Conversely, planets close to the inner edge of their host star's habitable zone are more likely (the most likely?) to have intelligent life (due to having spent billions of years in the host start habitable zone).
I thought the idea to terraform venus was to provide a solar shade to cool it down. Why not do the same thing for the earth, build a pair of solar plants in space that also act as a shade. Then we should build two and make the earth had some really cool looking sunglasses, to cool it down.
They may have overlooked an important factor. It would not be the first time. Carl Sagan went overboard with is "nuclear winter" scenario based on 1-D atmospheric profiles, land-only model 20 years ago. Later 2-D mixed land/ocean models were more moderate.
Sure. The best way? Find some bacterium that will thrive in Mars' current atmosphere, feed on it's minerals and excrete the right combination of gasses. Dump them en masse and watch the atmosphere grow!
yeah, I had misremembered the estimated mass of the asteroids. Oh well. We could still do the atmosphere thing, but with 0.38 gravities at the surface, I'm not sure how long the air would stay on Mars. May be better to just go straight to the Venus plan.
Way too close. I call gerrymandering.
#o#
O Moo.
How come the moon is not habitable?
The whole damn world seems uninhabitable then.
"A conservative estimate for the width of the HZ from this model in our Solar system is 0.95-1.67 AU."
Ergo, the "but Earth is sometimes within 0.983 AU of the sun" comments can stop. As amusing as the idea is, we don't leave the habitable zone.
They were referring to the older model.
This is new:
"According to the new model, the water loss (inner HZ) and maximum greenhouse (outer HZ) limits for our Solar System are at 0.99 AU and 1.70 AU, respectively, suggesting that the present Earth lies near the inner edge."
My mistake.
Since the Earth orbits the Sun at an average distance of one AU, this puts us at the very edge of the habitable zone.
Take that aliens, out planet has the edge!!!!!
Sure enough, the cow costume was hanging up next to the superhero outfit and sailors uniform. (S,Spud)