Most liveable alien worlds ranked

[Deckerd]

Scientists have published in the Journal of Astrobiology speculation as to which moons and planets are "most likely to harbour alien life", which is a bit far-fetched but even scientists gotta dream.

I think the most habitable index is more interesting, from a human perspective, although I don't know why Saturn and Jupiter are on there.

link-o-rama

 

[YellowSubmarine]

Which of that sounds far-fetched for you? Both rankings go against what my gut tells me, and I'm uncertain if they are a good representation of what we know, but then again I don't think you can have a good ranking right now – you create several that represent different sets of the things we think are important. I don't see how they are in any way far-fetched.

My only complaint is that they limit themselves to two indices. There should be at least one targeting conditions for known life, one that favours liquid water for example. Europa and Enceladus should top at least one ranking. Callisto and Ganymede also might have subsurface oceans.

 

[Deckerd]

That's what I meant about far-fetched. Why aren't the moons of Jupiter and Saturn in the list, rather than the gas giants, which let's face it, are totally far-fetched.

 

[Shatnertage]

I'm particularly flummoxed that Mars scored as high as it did. After all, it ain't the kind of place to raise your kids.

 

[Alidar Jarok]

Cold builds character

 

[YellowSubmarine]

And breathable air spoils the children.

 

[Shatnertage]

Yeah, but there's no one there to raise them, if you did.

 

[Kai Winn]

Don't discard Venus. Has lots of water vapor and CO2 in it's atmosphere, that has just to be cooled down, and chopped up in C and O. That's a project for geo-engineering, and it's in the neighbourhood. The long rotation period of Venus is a bitch, however. 243 of our days.

 

[Deckerd]

I don't think there's much water vapour in Venus's atmosphere. Certainly not enough to be useful.

 

[YellowSubmarine]

I guess Venus is boring as a candidate for life, but the pictures from the surface that the Russians took during Venera rank at the top of my most amazing pictures of all time. I think we should definitely send hardened nuclear powered robots there. And more of them.

 

[Alidar Jarok]

If the atmosphere were better, Venus probably would be habitable. It's closer to the sun, yes, but it's got about the same mass and I don't think it's too close.

 

[YellowSubmarine]

Though it's not the temperature that's a problem. It's that the planet is boring, unvaried, homogeneous. On the surface, there's no weather, no potential differences, no flow of energy, no nothing. It's hot and boring.

 

[Deckerd]

Though it's not the temperature that's a problem. It's that the planet is boring, unvaried, homogeneous. On the surface, there's no weather, no potential differences, no flow of energy, no nothing. It's hot and boring.

By that criterion, there isn't any rocky planet ever found that beats the one we evolved on. All of them are either too hot, too cold, too heavy or too light.

 

[YellowSubmarine]

Mars is far more interesting than Venus. It has winds and storms at the surface. It has much more energy added to its surface during the day. Hell, it has a day, since Venus doesn't even have a temperature differential across the surface. Things heat up and cool down. Venus stays the same. The only thing that possibly goes on is volcanism, but even there, Enceladus beats it – it's having eruptions of water, and all the fun is happening in the water.

 

[Deckerd]

I don't know what you mean by 'energy'. Comparing Mars and Venus, Venus has thousands more times energy in its atmos than Mars. Any colony, which would probably have to be subsurface on Venus, would have limitless engergy from the atmos, whereas Mars has got a many times weaker atmosphere than Earth. Mars' 'storms' would be summer zephyrs on Earth. AFAIK Venus doesn't have an active core; it isn't producing convection which would produce vulcanism, so it's either very hot and keeping the surface very hot or it's much cooler than it should be.

 

[YellowSubmarine]

There's some evidence for volcanism (which was a surprise to me), but it's probably far less geologically active than the Earth.

Any way, the point is not to have energy as an absolute value, but to have energy that you can use. Useful energy input. You can't extract energy from heat. For example, you'd be unable to set a colony inside the sun due to the lack of extractable energy. If you had energy, you could use it to cool down the colony enough so you can safely stay inside the sun. But you simply can't find the energy to use to cool your colony down, which is why you can't have a colony inside the sun.

Venus is a less extreme example of that.

(Well, you could run a fission reactor on Venus or a fusion reactor on the Sun, so it's not completely out of the question, but beside that, nothing.)

 

[Deckerd]

Why can't you use extract energy from heat? Run that by me again? Ignoring your Sun comments which are silly.

 

[YellowSubmarine]

Devices that extract energy from heat are otherwise known as perpetual motion machines of the second kind. I do hope and believe we will make such at some point in the future (otherwise we are doomed), but we certainly can't make them now.

 

[Deckerd]

So any settlement on Venus would necessarily have to take a lot of water and the means for producing more water. And if they apply the atmospheric heat to that water in, oh I don't know, off the top of my head, a pressure vessel; they wouldn't be able to make any use of that whatsoever. Uhuh.

 

[YellowSubmarine]

I have no idea what you're suggesting, but they could apply the atmospheric heat once, after that they'd need to find ways to cool it down. But perhaps you could build a perpetual motion machine – you extract energy from the initial heating and use it to cool the water down after that.

What's a pressure vessel and what does it do?