34 ms·

A few zones some think need to overlap and be dialed-in to come close to offering a habitable place: water habitable zone ultraviolet habitable zone photosyn

by EA 11y ago

A few zones some think need to overlap and be dialed-in to come close to offering a habitable place: water habitable zone ultraviolet habitable zone photosynthetic habitable zone ozone habitable zone planetary rotation rate habitable zone planetary obliquity habitable zone tidal habitable zone astrosphere habitable zone

saiya-jin 11y ago
quite a few of those are not relevant for habitability. for example tides, really? or you wouldn't survive if day would have 40 hours???
- SapphireSun 11y ago
  I think it's more like if the day was 100 msec that you have to worry about. Also, if the day is too slow, then one side of the planet bakes while the other side freezes. Think of the rotation axis as a spit roaster.
  - Ecco 11y ago
    Nice metaphor :)
- dandelany 11y ago
  They are relevant, you're just misinterpreting. None of these are meant to imply "X must be like Earth for the planet to be habitable," they mean "X is an important factor for habitability and must be considered in our models if we want them to be meaningful, unlike the ESI which captures a mere handful of variables". For example, "tidal habitable zone" doesn't mean "we need [ocean] tides to survive," it means "tidal heating effects have an enormous impact on planetary conditions". For example, an Earth analogue in orbit around a tiny red dwarf in a seemingly "habitable zone" would be subject to tidal heating effects which would bake the surface, whereas a similar planet in a similar orbit around a sun-like yellow dwarf would not. Similarly, "rotation rate habitable zone" doesn't mean "the planet must have a ~24 hour day", it means "all else being equal, a planet's rotation rate can greatly affect habitability," mostly due to weather patterns and air/heat circulation. By including rotation rate in our models, some planets previously thought to be inhabitable may turn out not to be, and vice versa.
drzaiusapelord 11y ago
Pretty sure these all apply for Mars and Venus and they're dead planets. Not sure why everyone is assuming some exo-planet must have life when the two other examples we have don't.
- ericson578 11y ago
  The earth similarity index for venus is 0.44, and for mars is 0.70
  - drzaiusapelord 11y ago
    I understand, but that's a synthetic benchmark. We actually have no idea why Earth has life and other planets don't and similarity to Earth may not be a big factor (see theories on life in Europa's seas for example or non-carbon based life). I just feel everyone gets excited over nothing solely because its extra-solar. Our own solar system is fairly diverse. If life was common, we'd probably be seeing more of it here.
    - ericson578 11y ago
      maybe life is common enough, but doesn't typically overlap in time. Maybe life on mars or venus died out a billion years ago. We'll have a better picture when we study our solar system in more detail. Maybe 100 years? I agree that speculation this early in the game isn't enough to get excited over.
anew 11y ago
I'd put magnetosphere in that list
- ghshephard 11y ago
  I'd put it up fairly high on the list... http://www.windows2universe.org/glossary/plasmaspheric_gain.html http://www.windows2universe.org/glossary/plasmaspheric_gain....

by EA 11y ago

saiya-jin 11y ago

quite a few of those are not relevant for habitability. for example tides, really? or you wouldn't survive if day would have 40 hours???

SapphireSun 11y ago
I think it's more like if the day was 100 msec that you have to worry about. Also, if the day is too slow, then one side of the planet bakes while the other side freezes. Think of the rotation axis as a spit roaster.
- Ecco 11y ago
  Nice metaphor :)
dandelany 11y ago
They are relevant, you're just misinterpreting. None of these are meant to imply "X must be like Earth for the planet to be habitable," they mean "X is an important factor for habitability and must be considered in our models if we want them to be meaningful, unlike the ESI which captures a mere handful of variables". For example, "tidal habitable zone" doesn't mean "we need [ocean] tides to survive," it means "tidal heating effects have an enormous impact on planetary conditions". For example, an Earth analogue in orbit around a tiny red dwarf in a seemingly "habitable zone" would be subject to tidal heating effects which would bake the surface, whereas a similar planet in a similar orbit around a sun-like yellow dwarf would not. Similarly, "rotation rate habitable zone" doesn't mean "the planet must have a ~24 hour day", it means "all else being equal, a planet's rotation rate can greatly affect habitability," mostly due to weather patterns and air/heat circulation. By including rotation rate in our models, some planets previously thought to be inhabitable may turn out not to be, and vice versa.

drzaiusapelord 11y ago

Pretty sure these all apply for Mars and Venus and they're dead planets. Not sure why everyone is assuming some exo-planet must have life when the two other examples we have don't.

ericson578 11y ago
The earth similarity index for venus is 0.44, and for mars is 0.70
- drzaiusapelord 11y ago
  I understand, but that's a synthetic benchmark. We actually have no idea why Earth has life and other planets don't and similarity to Earth may not be a big factor (see theories on life in Europa's seas for example or non-carbon based life). I just feel everyone gets excited over nothing solely because its extra-solar. Our own solar system is fairly diverse. If life was common, we'd probably be seeing more of it here.
  - ericson578 11y ago
    maybe life is common enough, but doesn't typically overlap in time. Maybe life on mars or venus died out a billion years ago. We'll have a better picture when we study our solar system in more detail. Maybe 100 years? I agree that speculation this early in the game isn't enough to get excited over.

anew 11y ago

I'd put magnetosphere in that list

ghshephard 11y ago
I'd put it up fairly high on the list... http://www.windows2universe.org/glossary/plasmaspheric_gain.html http://www.windows2universe.org/glossary/plasmaspheric_gain....