If you count moons, then it is practically unlimited. Not just the habitable zone either. On Earth we have not just Ceres Europa and Ganymede, even Titan, and Encladus and some speculate about Triton and Pluto having sub surface water or oceans.
I think that these may possibly be the most abundant habitats in the galaxy. If so, then the big thing is - can complex life and even intelligent life evolve in these habitats?
If it can then this may be the most common habitat for ETs. We may be very unusual to live on the surface of a planet rather than in a subsurface ocean.
But ETs in those subsurface oceans would probably not have advanced technology - hard to develop fire for instance. And might be totally unaware that the rest of the universe exists, as - how could they possibly know about it? Maybe detect subtle changes in gravity - but that needs complex technology which they probably don't have. Or things like neutrinos ditto.
They may be billions of years long lived civilizations without technology and none of them know that any of the others exist. It's just a guess / hypothesis :). And if we were lucky, we might have civilizations in these habitats even within our own solar system and we wouldn't know about them, and they wouldn't know about us, not yet.
It is just a fun, rather way out theory at the moment. Most likely place perhaps Europa because it is thought to have an oxygen rich ocean because of the effect of the radiation from Jupiter on the ice dissociating it into hydrogen and oxygen with the oxygen eventually making its way into the ocean. So that could theoretically support a complex multi-tier ecosystem, even intelligent life quite possibly.
Anyway - so that makes the number - well not totally unlimited - but vast surely. Even could have habitats like that in the Oort clouds if it turns out that Pluto does have a subsurface ocean.
Here is the article about the Pluto subsurface ocean hypothesis
A Subsurface Ocean on Pluto?
If this was confirmed - then that would mean you could have subsurface oceans by similar processes throughout the Oort cloud.
I think that these may possibly be the most abundant habitats in the galaxy. If so, then the big thing is - can complex life and even intelligent life evolve in these habitats?
If it can then this may be the most common habitat for ETs. We may be very unusual to live on the surface of a planet rather than in a subsurface ocean.
But ETs in those subsurface oceans would probably not have advanced technology - hard to develop fire for instance. And might be totally unaware that the rest of the universe exists, as - how could they possibly know about it? Maybe detect subtle changes in gravity - but that needs complex technology which they probably don't have. Or things like neutrinos ditto.
They may be billions of years long lived civilizations without technology and none of them know that any of the others exist. It's just a guess / hypothesis :). And if we were lucky, we might have civilizations in these habitats even within our own solar system and we wouldn't know about them, and they wouldn't know about us, not yet.
It is just a fun, rather way out theory at the moment. Most likely place perhaps Europa because it is thought to have an oxygen rich ocean because of the effect of the radiation from Jupiter on the ice dissociating it into hydrogen and oxygen with the oxygen eventually making its way into the ocean. So that could theoretically support a complex multi-tier ecosystem, even intelligent life quite possibly.
Anyway - so that makes the number - well not totally unlimited - but vast surely. Even could have habitats like that in the Oort clouds if it turns out that Pluto does have a subsurface ocean.
Here is the article about the Pluto subsurface ocean hypothesis
A Subsurface Ocean on Pluto?
If this was confirmed - then that would mean you could have subsurface oceans by similar processes throughout the Oort cloud.
About the Author
Robert Walker
Writer of articles on Mars and Space issues - Software Developer of Tune Smithy, Bounce Metronome etc.Studied at Wolfson College, Oxford
Lives in Isle of Mull
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