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."

Meaning at 1.5AU Mars Is In The Habitable Zone Too

[Anonymous Coward]

...time for some terraforming?

But for Terraforming?

[trims]

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

Re:Well if a "scientist" makes a model then

[ElectricTurtle]

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.

Re:But for Terraforming?

[NalosLayor]

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.

Re:Sure

[Jason Levine]

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

[Eric Coleman]

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.

Re:GW solution

[CrimsonAvenger]

I'm sorry, I must have missed the string holding the earth and the moon together.

We like to call it "gravity".

Yes, altering the moon's orbit would affect Earth's orbit, and could, theoretically, be used to move the Earth.

It would take more than a few million nukes, and longer than a few thousand years (probably), but it could be done.