Gliese 581d -could- have a complete water-cycle climate
- Thread starter Cairan
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there. 
fsci123
Future Dubstar and Rocketkid
It wil be super funny if we send a quadrillion dollar probe there only to find out its an iron ball with a hydrogen atmosphere... Or if we arrive there to find a billion berzerker probes...
garyw
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This 'water cycle' is based on the planet being in the goldilocks zone and that's no guarentee of it being able to sustain water in liquid form. Give it a few years and hopefully some of the Earth bound and orbital telescopes can get a spectrogram of the atmosphere.
fsci123
Future Dubstar and Rocketkid
Well we kinda knew that it could support water... Think about it... Water is blue and has a low albedo so it absorbs more heat... THe only objection to this rule would be if it migrated from the outer reaches of the system and may still be covered in a layer of ice... SO now you would have a planet with a layer of ice on top of a layer of water on top of a layer of ice...:rofl:
Actually, water is colourless. Large bodies of water appear blue due to light scattering effects.
Generally though, oceans tend to have low albedos. Clouds tend to have high albedos though, too...
If Gliese 581d is a world ocean, which could be probable, then it'd probably have quite a boring biosphere, unfortunately. :dry:
Generally though, oceans tend to have low albedos. Clouds tend to have high albedos though, too...
If Gliese 581d is a world ocean, which could be probable, then it'd probably have quite a boring biosphere, unfortunately. :dry:
But what about all of the aqua life?
Eli13
Fish Dreamer
Who knows what there is though? Thats just up to us to discover for ourselves... that is if we can even get into LEO without failure. :lol:
Well, there are several problems my uneducated mind can sense in that regard:
1. In Earth's oceans, phytoplankton (basically the basis of the aquatic food chain) are fertilised by minerals that are fed into the oceans via rivers and dust storms. I'm not sure if volcanic action contributes to this, or if undersea volcanic action contributes to this, or if there's a cutoff point below a certain depth that doesn't inject sizable amounts of nutrients into the water.
2. When an organism, be it a phytoplankton or a aquamarinexenoshark dies, its carcass- and biomass- would fall into the abyss, never to be seen by the upper layers of the ocean again. If you have a substrate in these upper layers of ocean (the "euphotic zone"), then detrivores can recycle the biomass back into the ecosystem. On Earth, biomass that falls to the abyssal plain is eventually subducted back into the mantle, and potentially partially replenished into the ecosystem by volcanic eruptions. On an ocean world, the problem could be biomass continually sinking to the abyss.
3. A world-ocean could be so deep, that the seafloor would have enourmous pressures- potentially pressures high enough to create odd allotropes of ice. This might be problematic for organisms originating from or living on the deep seafloor, subsisting off of chemicals from hydrothermal vents, for example.
4. From our knowledge, a substrate (seafloor) in the euphotic zone played a large role in the evolution of complex life. It seems that the [ame="http://en.wikipedia.org/wiki/Ediacara_biota"]Ediacara biota[/ame] were (extremely odd and unclear in terms of relation to living animals) benthos, feeding off of abundant bacterial mats. Later in the [ame="http://en.wikipedia.org/wiki/Cambrian"]Cambrian period[/ame], where the early ancestors and relatives of modern animal phyla are recognisable, benthic animals clearly played an important role (though their abundance as fossils probably also has a lot to do with fossilisation bias).
Now, I am not trying to be all "Rare Earth", or saying that our history is the only possible history for complex life, but I think a planet like a prospective world-ocean Gliese 581d, would be a far less likely candidate for any complex organism, than a planet vaguely similar to Earth.
It's not impossible though, it's just that any complex organisms there, and their evolutionary history, would have to get around these problems.
Eli13
Fish Dreamer
Then again, there are those Extremophiles...
I don't really think being an extremophile in this situation would help much, especially when evolving as complex life. This isn't about surviving the inside of the Chernobyl site, or being dessicated for ten years, or sitting around at temperatures of over 80c... it's about living in a place that is environmentally poor.
Alternatively, a gigantic convection system could recycle nutrients from the ocean depths, though I'm not sure how effective this would be. And it still doesn't solve the substrate problem.
Alternatively, a gigantic convection system could recycle nutrients from the ocean depths, though I'm not sure how effective this would be. And it still doesn't solve the substrate problem.
Eli13
Fish Dreamer
Well, when we see a planet like this, we aren't exactly expecting complex life, are we?
No, but complex life is probably the single most interesting, exciting and inspiring phenomena that you can find on the surface of a celestial body.
After the two-week hype, people would probably get bored with some measly little microbe. But tripedal, massively jawed flying predators? Translucent trees 100 meters tall? Ecologies of land-clams with elaborate shells?
All of a sudden pretty much every 8 year old boy (and girl) is interested in science, and technology, and spaceflight. And thinking of the universe beyond our planet. I don't think it can be overstated how important the last bit is, and how it is especially important to that same planet of ours.
After the two-week hype, people would probably get bored with some measly little microbe. But tripedal, massively jawed flying predators? Translucent trees 100 meters tall? Ecologies of land-clams with elaborate shells?
All of a sudden pretty much every 8 year old boy (and girl) is interested in science, and technology, and spaceflight. And thinking of the universe beyond our planet. I don't think it can be overstated how important the last bit is, and how it is especially important to that same planet of ours.
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Eli13
Fish Dreamer
Of course. But since when has science been completely about the popularity contest?
But of course, people will become bored when they realize we can't get there. Trust me, the average person believes its a 'point-and-shoot' sort of deal and we're there in a moment or two.
Thanks Star Trek. :dry:
But of course, people will become bored when they realize we can't get there. Trust me, the average person believes its a 'point-and-shoot' sort of deal and we're there in a moment or two.
Thanks Star Trek. :dry:
Yeah, well, that isn't just ordinary people. I'm pretty sure that out of everyone, astronomers, astrobiologists, planetary scientists, are the ones who really, really yearn for an equivalent to the Starship Enterprise...
Science isn't about a popularity contest. But it helps if people are actually interested in it to the point that they support it and don't ignorantly see it as a waste of money. I'm pretty sure that the average person out there regards the scientific payload on Endeavour to be about as important as initiating a program of staring at toenails for $2 billion.
I can't get to Antarctica or the mid ocean ridges. Doesn't mean the organisms there aren't exciting.
Science isn't about a popularity contest. But it helps if people are actually interested in it to the point that they support it and don't ignorantly see it as a waste of money. I'm pretty sure that the average person out there regards the scientific payload on Endeavour to be about as important as initiating a program of staring at toenails for $2 billion.
I can't get to Antarctica or the mid ocean ridges. Doesn't mean the organisms there aren't exciting.
Eli13
Fish Dreamer
Apparently, my sarcasm didn't fall through.
You are entirely right T.Neo on all these points. However I'd also like to point out that Gliese 581d, with it's mass and probable range of densities and radius, even if it is covered with a surface ocean, probably will have active tectonics. Mars was too small and cooled early, Venus lost it's water and now undergoes massive resurfacing events instead of plate-tectonics dynamics. The usual theory is that Earth's oceans actually lubricates the subduction trenches and somewhat buffers ocean floor spreading at ridges... It might entirely be possible, even with an ocean planet to have such active ridges and trenches.
Also, the stronger gravity would increase buoyancy of light minerals versus heavier elements in the melt of magma chambers and thus differentiation of minerals in the mantle and the magma emanating from it. The stronger gravity would also enable much stronger "pull" on subducting slabs. Thus, oceanic ridges might be "enriched" in light, less dense, minerals with fast spreading rates which could support themselves to higher elevations on 581d than otherwise, hence sea mounts and plateaus could still either emerge from water or result in shallow seas. Let's also not forget back-arc basins and magmatic arcs resulting from the subduction process, which could be sped up by the stronger gravity.
All the carbonates and other detritus "snowing" on the abyssal ocean floors might therefore actually get an easier way back to the surface than on Earth, again because of the stronger gravity which would yield higher buoyancy to lighter melted minerals.
I don't have my notes from the volcanology and plate tectonics classes I had while I was in Iceland, but I'm pretty sure that's the outcome when you plug higher "gee" values in the equations. Less gravity = slower differentiation (rise and fall of light and heavy materials respectively in a fluid); more gravity = faster differentiation.
The problem stems from when you have an ocean that is many tens or even hundreds of kilometers deep. Earth's topographic/bathymetric variation is between around 19km and 4km (?), depending on whether you're measuring from the lowest to the highest point, or from the average abyssal plane to the average continental surface. I somehow doubt, even with convection assisted by higher gravity that a planet could have topographic variation on the order of hundreds of kilometers.
Of course, it all depends on how much water Gliese 581d has. Maybe it only has a relatively small amount of water, and oceans through which landmasses can break through. Or, if it arose in the outer system and spiraled inward, it could be largely comprised of water, in a manner similiar to the moons of Jupiter, with a world-ocean in excess of thousands of kilometers deep. Which would probably end up being pretty unfortunate.
Of course, it all depends on how much water Gliese 581d has. Maybe it only has a relatively small amount of water, and oceans through which landmasses can break through. Or, if it arose in the outer system and spiraled inward, it could be largely comprised of water, in a manner similiar to the moons of Jupiter, with a world-ocean in excess of thousands of kilometers deep. Which would probably end up being pretty unfortunate.
