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Question: What Is The Best Candidate In Our Solar System (Apart from Earth) As An Abode For Extraterrestrial Life?

While I know that the darling candidates in our Solar System for those into astrobiology, although I still prefer the term “exobiology”, are Mars* and Europa (with an ocean beneath an icecap), I am going to vote for Jupiter (and to a slightly lesser extent Saturn). Why? Firstly Jupiter (and Saturn) have extensive resources of the four basic chemical elements that make up life as we know it – Carbon; Hydrogen; Oxygen; Nitrogen). Secondly their atmospheres contain many organic compounds responsible for the colorful cloud bands as well as water vapor. Thirdly there is a lot of mixing in those turbulent atmospheres bringing together organic compounds in various combinations. Lastly, while the interiors of Jupiter (and Saturn) are really hot (Jupiter outwardly radiates more heat than it receives from the Sun), the outer atmospheres are really cold. That means that there must be a Goldilocks temperature realm that is in-between the two extremes compatible to our terrestrial temperatures. Given four and a half billion years plus the sheer volume of these giant planets, and that is an awful lot of time and real estate volume for Mother Nature to strut her biological stuff.

*Based on the Viking results; the detection of underground water reserves; methane in the atmosphere; the likely transfer of terrestrial material to Mars (ballistic panspermia); and of course that Mars rock (ALH 84001) with four separate and apart biological indicators present.

Question: What Is The Best Terrestrial Analog For An Extraterrestrial?

What would be the best terrestrial analog for an intelligent alien, as in extraterrestrial? Well firstly the organism would have to look alien, something other than just having two arms, two legs, and one head sticking out of a torso. Secondly, the organism should inhabit a relatively 'alien' (to us) environment. Thirdly this creature would need to be able to manipulate its environment. Lastly, the critter would have to have a relatively high degree of intelligence. And so, the ideal candidate, IMHO, is the humble octopus!

johnprytz 7 Sep 12

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Just to be "That Guy", Venus, Earth and Mars are the only planets of our solar system in the Goldilocks or circumstellar habitable zone. Anywhere else and the moon would be simpler.

@johnprytz No longer relevant? You mentioned it in your original post. Albeit, on a planetary scale. CHZ may not be as limiting a factor in moving the odds of life existing on a planet or moon above zero. However, the chances of finding life is greatly increased on planets within the Goldilocks Zone.

Jupiter and Saturn are off the table for me because of their size. If you go deep enough to reach an zone where the temperature I above 0, what's the pressure like.

When you're talking about abiogenesis, you almost need liquid-gas interface to facilitate reactions and introduce reagents.

The chance of the discovery of a liquid water aquifer on Mars is our best bet.


I am under the impression that Jupiter presents the possibility of hydrogen or nitrogen based life forms (which would likely be thin and wide spread, like a sheet), whereas Europa may present the possibility of more familiar carbon based life forms.


I am under the impression that Jupiter presents the possibility of hydrogen or nitrogen based life forms (which would likely be thin and wide spread, like a sheet), whereas Europa may present the possibility of more familiar carbon based life forms.


I am under the impression that Jupiter presents the possibility of hydrogen or nitrogen based life forms (which would likely be thin and wide spread, like a sheet), whereas Europa may present the possibility of more familiar carbon based life forms.

@johnprytz If I recall correctly, scientists were hypothesizing that the gravity of Jupiter makes finding carbon based life forms there unlikely. It’s been a while since I read the articles, though. Now that I’m thinking about it, I want to say that they were actually talking about the possibility of methane based life forms.

@johnprytz Hold the phone. Looked it up. They were talking about Titan, not Jupiter. As I said, it was a while ago. []


My best guess would be Jupiter's moon Europa. Liquid water and heat energy gives this the best shot at a version of life as we know it.

@johnprytz Very true, but we have versions of life on Earth that have pretty much that situation. Deep trench geothermal vents have extremophiles who meet the criteria.


Any space that possesses liquid anything.


Never say never, but I am skeptical that any form of life as we know it, could exist for long in the atmospheres of the gas giants.

The reason being, that these planets as I understand it, produce tremendous amounts of ionizing radiation that life does not tend to thrive in well.

All right, you've convinced me. I did some more reading into it, and it seems like the ionizing radiation is more a feature of the planet's magnetosphere than the atmosphere. Like our own Van Allen Belts, it looks like you don't want to be orbiting near the inner moons without effective radiation shielding. The radiation emanating from the planet itself appear to be in the radio wave and microwave bands and non ionizing.

So your hypothesis looks just as likely to me as any other. Maybe there's some tardigrades or something similar floating around there.


Probably the center of the sun. It’s plenty warm and with all that hydrogen there’s probably enough water to sustain life.

@johnprytz What about plants? They love the sun. It seems like the center of the sun would be perfect for them. There could even be plants like Audrey from Little Shop of Horror that feed on blood and everything.

@johnprytz You know, what is today’s fiction may be tomorrow’s fact. There was a movie once called The Right Stuff and it chronicled man’s first journey to the moon. Wouldn’t you know it in 1957 Sputnik was launched and it happened almost exactly as the film predicted.

So I wouldn’t be so quick to discount the notion that a population of Little Shop of Horrors type plants are living in the center of the sun.

@johnprytz Too points. First, yeah I might have got some details wrong. The fact remains that a work of fiction become reality. I must admit though, I never knew we put a man on Mercury. I’ll have to watch that movie.

Second, I’m sure it’s hot inside the sun. It’s probably over 100 degrees. I don’t think I would want to live there because I like jacket weather. I still think plants would love it.

Third, the other night when I was organizing my salt collection I was thinking about what you said about water disassing. Wouldn’t the water fall to the center of the sun? Water is heavier than fire and the sun is made of fire.

@johnprytz I did some research on Ask Jeeves and found out the first hydrogen bomb was made by the Germans and it was called the Hindenburg. There’s even video footage that someone captured on a really old black & white phone. If you watch it you can see people running out of the fire, so it can’t be that hot.

Now you say water can’t survive on the sun, but is water really alive? Well, maybe. I saw a movie called The Abyss, and it had a creature that was made of water. So, I guess it’s possible. People may say water creatures are impossible, but they said the same thing about putting a man on Mercury. Yet we did it, and anyone can look it up on IMDB.


Personally I suspect we will find microbial life all over the Solar System once we have the means to look for it. Which is a matter of money and engineering. Basically sample return probes that can retreive samples from deep locations where life might be, or very sophisticated lander laboritories. Both are being worked on. To answer the question more on point, I think Mars is the best place to look, because of its proximity and relatively benign surface environment. If Mars turns out to be lifeless, I suspect the odds of finding it elsewhere drop considerably.

@Heathen_555 It's still an argument from big numbers and glosses over the fact that our database of planets that have known life is one. And SETI keeps coming up with nada. It's certainly possible there is something else out there, but it's also possible that there are as yet unknown factors that made us a unique accident.


i have to agree with those who have mentioned enceladus, which is what was on my mind when i read the question.

i can't help wondering whether an intelligent life form there might wonder if there was extraenceladusian life anywhere in its solar system.


Probably not, it's too hot nearer the Sun for life to exist.

@starwatcher-al but the extraenceladusians might not be looking in that direction. they might be looking out the other way, farther from the sun, as they do their wondering. it's a big solar system.


@genessa Yup, sure is and we don't know even a tiny bit of what's out there yet.

@starwatcher-al we, of our generation, likely never will. it all takes so long! maybe some day, if we don't blow our own planet up, someone will know a little more.



nothing wrong with floating creatures in the atmosphere of Jupiter. The icy moons also have the elements for life also. Titan's life would be soo weird but still not impossible. Just look at the extremophiles on this planet from boiling ocean vents to the coldest places. As far as Mars, there's not much life there except on Saturday night, then the place gets jumppin.


The problem with the gas giants is their turbulent and chaotic environment, even in the theoretical "goldilocks zone". For life to arise, the basic ingredients not only have to be there, but a stable environment has to endure for millions of years for life to get underway -- much less intelligent life. Still, it's not impossible. For all we know, the Cassini probe, in being crashed into the atmosphere of Saturn, clobbered the Grand Procter of Silex of Greater Saturn, and as we speak, they are mounting a retaliatory strike.

@johnprytz Diurnal rhythms are no inherent problem, but there's still a solid bottom under it all on Earth. I would envision the contents of the Saturnian goldilocks zone occasionally continuing to up or down-well out of said zone. But maybe it's more stable than that.


enceladus titan mars be extreme etxremophiles though if it has passed microbial stage of developement to more complex organisms


When you consider that humans have only just scratched the surface when it comes to exploring our solar system over the past century it seems unlikely that even if there were other life forms living on the other planets in our solar system that they would be in sync with humans technologically. Even if the life forms, should they exist, were within the technological window we are in now, give or take a thousand years, that would be extremely unlikely and they would either be unable to communicate with us or be uninterested in communicating with us, particularly if they shared no common interests with us due to cultural, anatomical and ethical interests.

@johnprytz The cultures inhabiting the Americas when Europeans 'discovered them' were only a few centuries apart but look at what became of those cultures in less than a century.

@johnprytz Correct again, at least in theory, the only way to know for sure is if and when contact with an extraterrestrial species is made.


I'd have to say microbe on Mars since that is where most effort is being Put right now.
Next would be a moon of Jupiter they've already found complex carbon compounds in the Jets coming out of the geysers on Escalades.
But hey, let's just keep killing and starving each other it's so much more rewarding and closer to home.?


I cannot answer this. It's hard for me to see life on another planet and that lifeform being one that we know from our own planet.


Saturn's moon Titan is touted as a candidate for having life. No evidence as yet but it's hypothesised that simple life forms may exist beneath the frozen surface.

There is a great sci-fi movie on Titan called "Gattaca", although it's more of a philosophical-ethical movie, imo. It's one of my all-time favorites!

I must check this out, thank you for the heads up.

Data from NASA's Cassini probe has strengthened the probability of there being liquid water beneath the frozen surface.

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