hobbsyoyo
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That's the way I look at it. But what would I know?
Alpha Centauri has a planet
- Thread starter choxorn
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That's the way I look at it. But what would I know?
Because the idea buried deep down is that we're the only ones.
_random_
Jewel Runner
Only if we assume that all other intelligent life is created in the Image of God and that the Image of God expressly refers to physical characteristics. I don't see much reason to assume either.
Angst
Rambling and inconsistent
Actually, especially the philosophers will have a fun time trying to revise, reexamine and redefine the length of the philosophic tradition; aliens as a subject matter has only been slightly touched upon lately, and usually in shallow hypotheticals.
Epistemology? Theology? Existentialism? Everything will have to be expanded upon. Humans were the subject matter of everything, with the insane being counterexamples to what defined humans and human experience. Aliens, now? What the heck, screw 2000 years of philosophical development.
Think about it. Everything we have done is anthropocentric somehow - necessarily so, of course, but all the humanities will get a good kick in the shins.
It's super effective!
I'm all for extra-solar exploration, but as Arthur C. Clarke assumed, I'm not sure whether it's better for there to be intelligent, contactable life out there or not. I am certainly not expecting it to be humanoid.
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Diverse in Unity
That Venus had oceans has been established, I think. There is even a hint it might have had plate tectonics in the early stages of its evolution, before the oceans evaporated.
We have pretty significant supporting evidence that Venus had large bodies of water on its surface early in its history. There is disagreement on whether it was like Earth-like oceans, or a pressure cooker (150°C water kept from evaporating by a dense atmosphere).
The point is, there is sufficient scientific base for me to go with this scenario in my fictional project
Because that argument is a logical fallacy. Should we stop developing cures for cancer because there are millions of otherwise healthy people starving and dying from diseases which we can easily cure? Should we stop researching lakes under glaciers in Antarctica and instead use the money to fund more clean water projects in Africa? I could go on like this for days.
I don't know why people always bring this up when we speak of space exploration, and not, say, Olympic games or something like that. The existence of poverty, hunger, and all kinds of problems on Earth are not an argument against making humanity a space-faring species.
Precisely. Case in point - Envisat and all the other probes and satellites that help us observe the environment and determine what needs to be done to better protect it.
I don't subscribe to narrow, too "Earthly" definitions of habitability. My Venus (in this alternate universe it's known by its Greek name, Aphrodite) has two small moons like Mars, they're just called differently. The planet is bigger than Mars and spins a bit faster than Earth (whose rotation period has got slower in time due to the Moon's influence) so the axial tilt doesn't change that much (180° is too extreme. 20-30° is more imaginable). Aphrodite is definitely a harsher place for life (more asteroid impacts due to its proximity to the main asteroid belt, frequent supervolcanic eruptions, ice ages, etc.), but this has led the biosphere to "adapt" to frequent mass extinction events. Life is less finely specialized, there are more "jack of all trades" species capable of dealing with rapid changes in their environment
This is how it went in my thought experiment:
Spoiler :
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I am pretty sceptical about life on Venus. There is practically no water (vapour) left, and the altitudes in the atmosphere where temperatures are acceptable are full of nearly 100% sulphuric acid aerosols. I don't even think Venus had oceans for long enough for life to develop, much less to evolve in forms which could then survive its hellification.
Mars is an infinitely better candidate. There probably is liquid water *underground*, near geothermal vents or something similar to it, and life could have retreated there easily as Mars began losing its atmosphere over the period of hundreds of millions of years.
Europa and other outer planets' moons are a wild card, I dare not make predictions there.
I seem to recall Professor Brian Cox doing a programme about Titan's methane seas and about how liquid methane behaves in a very similar way to water, so there could in theory be methane-adapted life just lying around the universe waiting to be discovered.
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Yeah, if there is one thing certain, it's that the Universe will continue to surprise us. I am fairly sure we'll eventually find some preeettty exotic life-forms.
hobbsyoyo
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If there is life on Venus, it will be fundamentally different from Earth life and possibly even unrecognizable. The only reason I say there could be life on Venus is that there is plenty of energy to sustain it and lots of interesting (and still not completely understood) chemistry going on there. If life was capable of forming without or surviving without water, Venus would be a good place to look.
For similar reasons (interesting chemistry), people think life on Titan is plausible. I posit that there just isn't enough energy there to develop or sustain life. Even the very slow kind (Ben Bova style), I don't think could happen as the random chemical interactions that would've been needed to develop life in the first place would have taken far too long for it all to work out. If life is a random thing that happens given enough trillions and trillions of interactions over time, well the slow rate of interactions in a low energy environment like Titan will require more time than has passed IMO.
Eh, I'll give this too you for the sake of argument but I'm not entirely sold. Most of the things we know about Venus are circumstancial and speculative in nature gleaned from radar and spectroscopic investigations. We have done next to no direct investigation there.
I'd like to see that evidence please. I'm not calling you out - I'm genuinely curious.
Maybe I wasn't clear enough before, but I'd don't go by too Earthly definitions of habitability or even Earth-similar life. That's why I think it's possible for life to be on Venus right now, after all.
180 degrees is not too extreme at all, Mars does in fact do this. It's hard to believe but over time without some stabilization effects, small planets like Earth, Mars and Venus will wobble significantly. I do take that Venus could rotate faster than the Earth (though I don't think this is a given - Mars rotates as slowly as Earth without any big moons to slow it down) and this could make it's axial tilt more stable. (However if you say that it would still have a much thicker atmosphere, this would slow down the rotation and without the stabilization effect of a close-up Sun, it would thus still wobble.)My Venus (in this alternate universe it's known by its Greek name, Aphrodite) has two small moons like Mars, they're just called differently. The planet is bigger than Mars and spins a bit faster than Earth (whose rotation period has got slower in time due to the Moon's influence) so the axial tilt doesn't change that much (180° is too extreme. 20-30° is more imaginable). Aphrodite is definitely a harsher place for life (more asteroid impacts due to its proximity to the main asteroid belt, frequent supervolcanic eruptions, ice ages, etc.), but this has led the biosphere to "adapt" to frequent mass extinction events. Life is less finely specialized, there are more "jack of all trades" species capable of dealing with rapid changes in their environment
But consider that it will still wobble (and let's just split the difference and say it wobbles 60 degrees instead of 180 or 30), that would have a huge impact on the development of life. Factor in the drastic atmospheric and climate changes brought on by periodic mega-volcanism, and the more constant asteroidal bombardment brought on by proximity to the asteroid belt and Jupiter, and you have one hellish environment. And on top of that is the remaining fact that Venus would still recieve 50% of the solar energy that Earth does. Granted, it could possibly trap it far better than Mars - but I don't think it would have a runaway greenhouse in that orbit and possibly no greenhouse at all - but it would still be a far lower energy environment than Earth.
Finally, the hint of past plate tectonics is not actual, active plate tectonics. If they aren't happening now and haven't happened for a long time (if ever) then that's still a major problem for life.
All together, the scenario you outlined is still very difficult for life to adapt. As you say, the best it could probably achieve is basic, jack of all trades microbial forms. I'm not even sure that is possible, but I will give you that in a pinch it could happen.
I really do appreciate your thought experiment. It's very cool and well thought out.
I hope you don't think I'm trying to knock the whole thing - just some of the finer details!
And now that you have clarified that you think life would only be very simple in your hypothetical Venus, I have much less objection. I had been under the mistaken belief that you thought a Venus at Mars' orbit would have complex life like the Earth.
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Diverse in Unity
Available energy is one criterion, there are others. More important in this regard is energy gradient, IMO, but I don't want to really go into that. Venus simply doesn't seem to me as a good place for carbon based life, even microbial. Water isn't there, the environment is extremely hot, the pressure is very high (so much so that the lower segments of the atmosphere are in fact oceans of supercritical CO2 fluid), there isn't much sunlight at the surface, and too much UV radiation above the sulphuric acid clouds, etc. etc. etc.
I of course don't rule anything out, but I remain highly sceptical.
As far as I remember, there are multiple sources of indirect evidence - the amount of heavier hydrogen atoms in the atmosphere (consistent with the theory of evaporated oceans), the presence of rocks which may be the same which on Earth form in the presence of water, and the sheer composition of the atmosphere itself. Venus and Earth are of roughly the same size, so they should have similar amounts of nitrogen present. Well, it turns out that if you removed the CO2 from Venus' atmosphere, you'd end up with a nitrogen atmosphere close in mass/pressure to Earth's. Conversely, let Earth's ocean evaporate and you'll end up with a Venus like atmosphere eventually. It seems to fit together nicely.
Of course, until we actually land probes on the surface and start sampling the rocks, we won't know for sure, just as we didn't know about Mars' oceans.
What's the source on that? The most I've read about was Mars' axial tilt wobble in ranges 13 and 40 degrees. Extreme compared to Earth's, but not any kind of pole reversal.
Yet the real Venus' axial tilt is very small (yes, I know it rotates in reverse), and that's a planet which rotates slow so it doesn't benefit much from the gyroscope effect. I just don't take claims like "you need a large moon to stabilize the axis" as some sort of iron rule of the universe.
1) Larger planets tend to rotate faster (pirouette effect). Earth rotated much faster in the early days. Much of this energy was transferred to the Moon, which is what made it raise its orbit significantly.
2) Not much thicker atmosphere. Here's what I came with for Aphrodite (I really need to get back to it one day
):Spoiler :
It wobbles, but much less than you think. I used the Mars figures known to me. My Aphrodite has a greater axial tilt, which makes its season more severe (with CO2 snowstorms at the poles during mid-winter
). As for the rest: impact are more frequent, just as volcanism and ice ages. That doesn't kill life, it just forces it do adapt. Aphrodite is far from hellish, it's an advanced biosphere every bit as complex as Earth's. Just... different. (It's DNA-based life which shares the same origin as the Earth one - in my scenario, nobody is sure on which planet it began and to which planet it spread in meteorites).
The atmosphere is denser and has more CO2, which makes it retain plenty of heat. The growing seasons are twice as long as on Earth, which of course greatly influenced the evolution of plant and animal life. In general, the hottest areas around the equator are about as hot as the Mediterranean zone here on Earth.
As I said, I had lots of fun with this project
Real Venus doesn't have plate tectonics now. Aphrodite does, albeit slower.
Not at all. I don't underestimate life
That's exactly what I am saying
Forests, animals, everything.
hobbsyoyo
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Basically, this is my main objection to the theory of Venusian oceans.
You're right, I was too extreme. The Axial tilt page on wikipedia says it wobbles as much as 60 degrees, but even that's disupted.
I should also state that I didn't mean pole reversal. I meant 180 degress as the distance it would go for the North pole pointing East to it pointing West. (like how Uranus does, but flopping to point in the other direction too). This isn't the standard method for measuring tilt. I should've said something more like +/- 90 degrees. I just took 180 degrees as the total difference between these two states (pointing East to pointing West), I didn't mean that it went from pointing North to pointing South.
Venus' axial tilt is huge. It's 177 degrees. It rotates in reverse because it's north pole is facing directly south. The article is mum on how it got this way. I take it it's either asteroidal impact or just plain jane axial wobbling.
Though I'm no expert, I don't discount that you need a large moon to stabilize the axial tilt simply because I've heard it and read it in so many places.
All I'm saying is that all of those factors (impacts, volcanism, axial wobble) are extremely signficant. All they have to do is change the climate in a relatively small amount of time to kill off huge chuncks of the biosphere. Earth is lucky in that it's so stable. I'm just thinking that all of these factors for Aphrodite are significant enough to kill off most life periodically or even keep it from forming.
Huh? Then I misread your earlier post. I don't think this would be likely, but I've already stated as much.That's exactly what I am saying
Sorry I keep making the conversation go around in circles.
Crezth
i knew you were a real man of the left
People who are skeptical that space research is useful let alone necessary must not use GPS or cell phones or check the weather.
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Diverse in Unity
Well, that's why I said I realize that it rotates in reverse
If 0° = 180° (in the sense that the axis is perpendicular to the orbital plane), then Venus' axial tilt is mere 3 degrees, much less than the Earth's - and Venus lack both a large moon and a quick rotation period. To me this suggests that axial tilt wobbling isn't a given and that the lack of a large moon isn't an automatic guarantee of insurmountably unstable climate.Sure, I am fine with that. It makes sense and I count with it in my AH scenario, it's just that I tend to be sceptical toward absolute claims
Well, I don't think so. I think we often underestimate the powers of evolution. These factors would prevent evolution of the same kind of advanced life we have on Earth, but that in my opinion doesn't preclude the evolution of life which has adapted to survive periodical hardships. If mass extinction-level events are common enough, then they create a selective pressure that favours plants and animals which are flexible, adaptable, not too specialized, and capable of enduring long periods of sub-optimal environmental conditions. Something like our mammalian ancestors who lived through the two most severe mass extinctions in Earth's history (the Permian and K/T).
For example, I posited that most of Aphrodite's animals have evolved the ability to hibernate because of the planet's long seasons. Clearly, the ability to survive a year in a coma-like state is incredibly useful when an asteroid hits and the planet is plunged into years of darkness and cold, or when a supervolcano erupts with pretty much the same effect.
(And let's face it - this exercise would be far more boring if all there was were single-cell organisms
I wanted to create an interesting world I can play with, so I took some liberties. But I do think I haven't ventured beyond what's acceptable in science fiction I've got some very good feedback from other people, who sometimes corrected my naive misconceptions about certain things (chiefly molecular biology ), and that made it even more interesting to me. But enough about that, this is probably not the best place.)
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Or watch the news. Or use frying pans.
hobbsyoyo
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Oh hey, I found this on axial tilt wrt a large moon on wikipedia (emphasis mine):
http://en.wikipedia.org/wiki/Axial_tilt
I thought that the mammals didn't start showing up until well after the Permian Extinction.
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