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Name: Cody
Status: other
Grade: other
Location: NV
Country: N/A
Date: N/A

Can a gas giant be a host to life both in its own atmosphere and on the surface of a moon in the while orbiting inside the habitable zone?

Dear Cody,

Very good question. Only on the surface of the moon orbiting a planet inside its habitable zone. The gas giant itself does not orbit in any zone. Also the period for such life to evolve would be much shorter than here because the star is later on the H-R diagram.


David H. Levy

Hello Cody,

I think the answer is possibly, but it depends on a great number of conditions. In short, I do not think we have any way of reliably saying YES or NO to your question at this time (and I would say anyone that is giving you a firm answer has not thought about it enough).

Part of the question involves what you mean by life. That is a huge question just by itself. I think the likelihood of finding "simple" life (so like bacteria) on a gas giant moon is reasonably good. Given the right conditions life very different from what we think of as normal could arise. Given the simply staggering number of stars (and hence planets) in the galaxy, let alone the universe, I have a hard time imagining the rest of the universe as bereft of life. If we were betting on the likelihood of finding at least some kind of simple life on a moon somewhere in this solar system, I would bet on the "yes" side. That said, I have lost plenty of bets and we have not found any life outside of earth at the moment.

Simple life may even be possible in gas giants themselves. Would it be large multi-celled organisms that inhale O2, exhale CO2, enjoying temperatures in the narrow range of 10-40 Celsius, needing sunshine and a firm place to stand? Probably not (I think Carl Sagan's idea of giant "floaters" was clever, but probably not very reasonable either). But just because the environment of a gas giant is so different from what we think of as needed for life does not preclude it (in my mind) from having the potential for at least some simple life in the right conditions. Perhaps nature is clever enough to even have more complicated life on gas giants in the right circumstances.

So I suppose my unqualified answer (I am not an astrobiologist) is this: Given the right set of circumstances and the shear number of planets and moons in the universe, I would say it is very likely for at least simple life to exist on both a moon and a gas giant somewhere.

There is a very, very interesting story about life outside of earth that we do know fairly well. While we have not discovered life elsewhere in the solar system, we have taken it out with us and seen that at least some organisms are capable of surviving the vacuum of space. Apollo 12 was able to retrieve microbes from earlier probes launched to the moon. These microbes had to survive for years in a harsh vacuum, extreme temperature and without any support. So have we found extra-solar life? Not yet, but it is reasonable that some very simple life may actually be more ubiquitous than we often think.



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