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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."
by deciding to include my neighborhood.
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.
They adjust the "habitable zone" for each star already.
How can I believe you when you tell me what I don't want to hear?
TFS already indicates that the change affects where the Solar System's habital zone is calculated to be; even without looking at TFA it is clear that the "habitable zone" is star-specific.
...time for some terraforming?
You're right, we shouldn't build models based on math. We shouldn't even try to understand the universe using such abstract tools. We should rely on thought experiments and push models around in sand. We can dress in togas and burn heretics.
W..w..W - Willy Waterloo washes Warren Wiggins who is washing Waldo Woo.
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.
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
He should not have published anything until his model matched up in some meaningful way with known facts about climate history. Obviously the lack of accounting for such a massive element is what probably is leading to this ridiculous idea that we're somehow almost too hot to support life, which is why we've had dozens of ice ages, including some which arguably devolved into 'snowball earth' scenarios where the virtually the whole planet was frozen. If your model doesn't fit major facts, it sucks, and it should be completely retooled at a minimum, or even discarded, because models that don't fit facts are nothing but incomplete masturbations.
I support the Slashcott and will not be reading or commenting from 2/10/14 to 2/17/14. Beta is steaming pile of dog shit
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.)
My sci-fi novel, Ghost Thief, is now available from Amazon.com.
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
Clouds not only affect sunlight on the day side of the planet but also also radiative heat transfer from the surface on both the day and night sides. Ever notice how much warmer it can be on a cloudy night than on a clear night? Current research indicates that clouds overall probably have a slightly positive effect on global warming but much research still needs to be done.
So clouds have an effect but greenhouse gases still dominate the equations. That affects the accuracy of model he uses but it's likely not an order of magnitude off and so is useful as a starting point to further refine the science.
This binary thinking that something has to be 100% right or it's completely wrong is not how science works.
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.