SLD
Contributor
There's an interesting article in this month's Scientific American about super hospitable worlds. It argues that super earths around a K type star are the best for harboring life for a long time.
You can find the article here if you have a subscription (if not you'll have to buy the mag): http://www.scientificamerican.com/a...table-than-earth-may-be-common-in-our-galaxy/
The author argues that our earth is actually only marginally suitable for life. He may have a point, but I found the article failed to answer some important questions. I posted the following comment on their website for the article, but it doesn't appear that there is a lot of discussion nor does the author appear to be interested in engaging discussions on his piece, at least not yet. So here is my posting and questions which I throw out for discussion with this erudite crowd of my fellow infidels:
Well, I enjoyed the article, and hope the author monitors these comments for reply to questions. But the article raises more questions than it answers honestly. It left a lot unsaid that would be interesting and important to know.
1) what would be the effect of such a significant increase in Gravity and atmospheric pressure on the evolution of land animals? Would it not really prevent them from evolving in any significant way? I suppose Marine life would not have a problem growing in size. But there would still be different requirements to maintain buoyancy.
2) what about the effect of solar flares? For a K dwarf star, the habitable zone is closer in, much. Much closer in. Solar flares would be far more of a problem for such a world. Would the stronger magnetic field though be enough to protect it? IIRC, smaller stars tend to have more issues with flares than G2 types.
3) the article states that an archipelago type world would promote biodiversity. Maybe, but what size islands are we talking about? Australia is an island of sorts. But so is Guam. Big difference and a big difference on what kind animals can evolve in such an environment. I would suspect that the evolution of really large complex life forms would require continental size masses. Smaller islands tend to have much smaller species on them for a variety of reasons - think Homo Floriensis and their associated fauna. Separating islands, even if by shallow seas, would seem to isolate genes and thus not result in much biodiversity.
4) the article states that being closer to the sun would be necessary to have an active plate tectonics that would drive the all important carbon cycle. But it doesn't say why that is so. Why would being closer to the star make such a huge difference in plate tectonics? I was under the impression that our plate tectonic activity was only minimally influenced by tidal factors from the sun and moon. Io is very different though.
5) speaking of tides, in an archipelago world with minimal higher mountains, the tides might be huge being so close to their star, and especially a gas giant. They would swamp lower lying islands. Right?
All in all these problems seem to me unanswered by the article. The planets might be great for the evolution of certain types of life and even for long periods, but I am skeptical that they would harbor significant land life that could evolve intelligence. It seems to me that if we expect to find intelligent life in the Galaxy we need to focus on G2 type stars, or very similar ones. Fortunately there is one really close by. No signs yet from Alpha Centauri yet though, but we cannot rule out an earth like planet in its habitable zone. And while I am a natural procrastinator, maybe now is the time to find one so close whether than waiting 1.6. Billion years - then it might be too late!
Cheers!
SLD
You can find the article here if you have a subscription (if not you'll have to buy the mag): http://www.scientificamerican.com/a...table-than-earth-may-be-common-in-our-galaxy/
The author argues that our earth is actually only marginally suitable for life. He may have a point, but I found the article failed to answer some important questions. I posted the following comment on their website for the article, but it doesn't appear that there is a lot of discussion nor does the author appear to be interested in engaging discussions on his piece, at least not yet. So here is my posting and questions which I throw out for discussion with this erudite crowd of my fellow infidels:
Well, I enjoyed the article, and hope the author monitors these comments for reply to questions. But the article raises more questions than it answers honestly. It left a lot unsaid that would be interesting and important to know.
1) what would be the effect of such a significant increase in Gravity and atmospheric pressure on the evolution of land animals? Would it not really prevent them from evolving in any significant way? I suppose Marine life would not have a problem growing in size. But there would still be different requirements to maintain buoyancy.
2) what about the effect of solar flares? For a K dwarf star, the habitable zone is closer in, much. Much closer in. Solar flares would be far more of a problem for such a world. Would the stronger magnetic field though be enough to protect it? IIRC, smaller stars tend to have more issues with flares than G2 types.
3) the article states that an archipelago type world would promote biodiversity. Maybe, but what size islands are we talking about? Australia is an island of sorts. But so is Guam. Big difference and a big difference on what kind animals can evolve in such an environment. I would suspect that the evolution of really large complex life forms would require continental size masses. Smaller islands tend to have much smaller species on them for a variety of reasons - think Homo Floriensis and their associated fauna. Separating islands, even if by shallow seas, would seem to isolate genes and thus not result in much biodiversity.
4) the article states that being closer to the sun would be necessary to have an active plate tectonics that would drive the all important carbon cycle. But it doesn't say why that is so. Why would being closer to the star make such a huge difference in plate tectonics? I was under the impression that our plate tectonic activity was only minimally influenced by tidal factors from the sun and moon. Io is very different though.
5) speaking of tides, in an archipelago world with minimal higher mountains, the tides might be huge being so close to their star, and especially a gas giant. They would swamp lower lying islands. Right?
All in all these problems seem to me unanswered by the article. The planets might be great for the evolution of certain types of life and even for long periods, but I am skeptical that they would harbor significant land life that could evolve intelligence. It seems to me that if we expect to find intelligent life in the Galaxy we need to focus on G2 type stars, or very similar ones. Fortunately there is one really close by. No signs yet from Alpha Centauri yet though, but we cannot rule out an earth like planet in its habitable zone. And while I am a natural procrastinator, maybe now is the time to find one so close whether than waiting 1.6. Billion years - then it might be too late!
Cheers!
SLD