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Just remember being in a "habitable zone" is but one, small necessary (and by itself absolutely insufficient) condition for actually being "habitable" or sustai

• 3825 13y ago
  That's what I was thinking. Isn't Mars in a habitable zone as well?
  • Zardoz84 13y ago
    It's in the border. In theory can be terraformed.
  • arethuza 13y ago
    Looks like it depends how you define "habitable zone" - it seems that if you are conservative about it (i.e. Earth sized planets remaining habitable) then Mars is actually outside of that zone: http://en.wikipedia.org/wiki/Circumstellar_habitable_zone http://en.wikipedia.org/wiki/Circumstellar_habitable_zone
    • chc 13y ago
      I see don't see where that article suggests that Mars is outside the habitable zone by any reasonable estimate. The only part I see questioning Mars's position suggests that Mars might actually not be as close to the edge as we think. Mars's lack of habitability is partly because of its position, but also partly due to other factors like its lack of a magnetic field and atmosphere. If you somehow "poofed" a copy of Earth into Mars's place, I think it would be considered habitable (but still not really for humans), though I'm not really qualified to say that with any certainty.
      • arethuza 13y ago
        In the diagram in that article the dark green band is the conservative habitable zone - the orbit of Mars looks to be pretty much completely outside of that area.
  • jerf 13y ago
    Venus is right on the edge too. We don't have to be wrong by much for it to be habitable, in theory. One can imagine a world covered in clouds, but with a habitable surface, or some set of geological structures that go high enough to be cool enough to live on. Earth life might not like it there, but we've got extremophiles already here on Earth living in similar conditions. Mars and Venus provide instructive examples on why being in the zone is merely one small prerequisite. We talk about it because it's just about the only characteristic of these planets we can see, not because it's the only important characteristic. Mars has too little atmosphere, among other problems, and Venus has way the hell (word chosen advisedly) too much.
    • CodeCube 13y ago
      we built this (cloud) city on rock and roooollll!
      • 3825 13y ago
        I didn't understand your comment until I glanced at the wikipedia article for the atmosphere of Venus[1]. With a surface air pressure of 92x and carbon dioxide making 96.5% of the atmosphere, the surface of Venus is a no-go even before considering the extreme winds. >The atmosphere of Venus is much denser and hotter than that of Earth. [...] The main atmospheric gases are carbon dioxide and nitrogen. Other chemical compounds are present only in trace amounts. >Despite the harsh conditions on the surface, the atmospheric pressure and temperature at about 50 km to 65 km above the surface of the planet is nearly the same as that of the Earth, making its upper atmosphere the most Earth-like area in the Solar System, even more so than the surface of Mars. Due to the similarity in pressure and temperature and the fact that breathable air (21% oxygen, 78% nitrogen) is a lifting gas on Venus in the same way that helium is a lifting gas on Earth, the upper atmosphere has been proposed as a location for both exploration and colonization. [1]: https://en.wikipedia.org/wiki/Atmosphere_of_Venus https://en.wikipedia.org/wiki/Atmosphere_of_Venus
  • afterburner 13y ago
    No; no liquid water at the surface. http://www.astro.sunysb.edu/fwalter/AST101/habzone.html http://www.astro.sunysb.edu/fwalter/AST101/habzone.html http://en.wikipedia.org/wiki/Circumstellar_habitable_zone http://en.wikipedia.org/wiki/Circumstellar_habitable_zone EDIT: to be more precise, the conditions aren't right for there to be liquid water at the surface.
• cryptoz 13y ago
  So our sun has three rocky planets near the habitable zone. One of them evolved intelligent, space-travelling, radio-communicating species. The other two have robots on them. If we're using our own system as a kind of model for projecting ideas about Gliese 667c, I'd be pretty optimistic about the chances.
  • stouset 13y ago
    Except you have no idea of the relative probability of these events. Two of them have robots on them precisely because of the space-travelling, radio-communicating species on the third. But we have no firm data on the likelihood of a random planet in a star's habitable zone being rocky, having an active core, and a slow enough rotation for a stable atmosphere. Nor for that matter the expected percentage of time that such a planet should be expected to be populated with intelligent life over the span of its existence. You're effectively saying, "Somebody else has discovered a swan. The only swan I've seen is white. Therefore, I expect that this new swan is white as well."
  • Sharlin 13y ago
    If we're using our own system as a kind of model for projecting ideas about Gliese 667c, I'd be pretty optimistic about the chances. The problem is that we cannot do that without succumbing to selection bias. We don't know how many things had to go just right to give rise to life, let alone a technological civilization, we just know that it has happened (at least) once in the whole universe. http://en.wikipedia.org/wiki/Selection_bias http://en.wikipedia.org/wiki/Selection_bias https://en.wikipedia.org/wiki/Anthropic_principle https://en.wikipedia.org/wiki/Anthropic_principle
  • xenophonf 13y ago
    And on one of those two planets, all the robots are DEAD. If that isn't the setup for an awesome Doctor Who/Culture cross-over fanfic, I don't know what is.
• mbell 13y ago
  > Just remember being in a "habitable zone" is but one, small necessary (and by itself absolutely insufficient) condition for actually being "habitable" or sustaining life. It's not even a necessary condition. The 'habitable zone' is based on the possible presence of water on the surface of the planet, which it is argued makes it more likely life could have evolved. But, it isn't a requirement, at least as we understand it. For example, Europa, a moon of Jupiter, is well outside the habitable zone but is believed to have a sub surface water ocean that could be capable of spawning life.
  • mparlane 13y ago
    We are outside the habitable zone :\ ref: http://www.newscientist.com/article/dn23118-earth-and-others-lose-status-as-goldilocks-worlds.html http://www.newscientist.com/article/dn23118-earth-and-others...