Some Alien Worlds Could Have Too Much Water For Life To Exist

[Asbo Zaprudder]

You just made the orcas sad.

...he said, climbing out of the bathroom window...

 

[YellowSubmarine]

You just made the orcas sad.

I wholeheartedly apologize to all orcas. And to George and Gracie.

Three. I meant three.

 

[PurpleBuddha]

True. It takes long, it's unlikely and being under water makes it even more so. Trust me, I know – my crew constantly makes me go up for air and Ringo likes to put plot holes in my hull during lunch break. I have eight already.

But unless the obstacles are insurmountable (lack of limbs would qualify for insurmountable), the amount of stars and time out there takes care of the long and the unlikely. So long as there are enough intelligent aquatic life forms in the universe, some would find their way into space. There's no reason to believe there aren't many of them – we have one on our planet, so initial assumption should be roughly the same number of exodolphins and exoapes.

One path to technology could start at building rafts on the surface simply by lashing buoyant things together. It could get more complex and sophisticated one piece at a time. This produces a dry environment that is easily accessible from the water.

 

[psCargile]

You ain't be getting smart until you develop a comprehensive language to pass on those smarts.

 

[publiusr]

On a slightly different matter ... is it possible for a species that lives and survives in a liquid environment to develop into a technologically advanced civilization? I remember The Outer Limits episode "Trial by Fire"y.

No fire, no metallurgy?

 

[velour]

No fire, no metallurgy?

The Outer Limits episode that I referred to was, of course, fictional. The aquatic nature of those fictional aliens made me wonder if it is possible for an actual aquatic species to ever develop technologies, let alone, become a space faring species.

Another poster wrote about no fire, no metallurgy.

If that is the case, "no fire, no metallurgy", wouldn't that mean that there would be no bronze age, no iron age, ... , therefore no industrial revolution, no space age, etc.? An aquatic species would be stuck with a perpetual wet soggy age?

 

[PurpleBuddha]

Aquatic species could access dry areas. It takes no metallurgy to build a raft and use sticks to move things around on the raft. Even if the thing they were doing in the dry space was very basic to start with, it is not hard to imagine how it could incrementally improve over 100 generations or so. Clearly it is a disadvantage, but I think the problems could be worked out.

 

[publiusr]

I wonder about the advantages of--say--using volcanic vents for easily accessible heat. Aquatic balloons.

Maybe melting the nodules found on the sea floor that precipitate out. Uranium may be extracted for seawater.

I wonder if one could melt metal--and use vents to inflate metal bubbles....

 

[YellowSubmarine]

I still think we need to imagine things from their perspective before ruling it too difficult.

Imagine that up here on the surface, things couldn't catch fire, and you – a human – could just float in the air whenever you liked. It immediately starts looking plausible, and you start imagining ways to do it. Most of them would not be practical, but you come up with a great deal many of them.

First thing I imagine is how I'm digging in a nearly vertical ground at 3000 feet, inside which I find a strange bubble-making gas coming out of the wall. I contain it in an aquasheep bladder, and thinking the stink would chase predators away, I mix it with another such gas, only I got my tentacles badly burned.

In reality, I probably wouldn't find usable oxygen that way, but why stick to oxygen reactions at all? Many reactions release heat.
* Poison fish on my planet may produce high quantities of hydrogen peroxide. Liquid, deadly, pretty good oxidiser. Wouldn't trust water alone to protect me from getting burned.
* If I somehow get my tentacles on fluorine, and I don't immediately die, I'd immediately learn it causes water to combust. (Extract it from my toothpaste, maybe?)
* I may dig up alkali metal deposits from somewhere. They are neither rare, nor water-friendly.

Even with my B- in high-school Chemistry, I can still name a few more oxidisers, or alternative exothermic reactions that may work. I mean, high-schoolers love all about things that combust, explode, smoke or are just crazy. So long as your water aliens species have teenagers, they would find some.

And that's forgetting that volcanoes are now underneath you, and you can float away or lower/drop things into them from above. You'd have a hard time stopping your kids from dropping things on volcanoes.

 

[lpetrich]

There is a way for there to be too much water for life. If a planet has a deep-enough ocean, then the water at the bottom will freeze, even at high temperatures. Ice - Wikipedia has a nice phase diagram.

Let's see how deep an ocean would have to be to have a hot frozen bottom. I will use 1 Earth gravity, and that makes the pressure go up by 1 bar (10^5 pascal) every 10 meters of depth. The pressure at the bottom of the Mariana Trench, about 10 km below sea level, is thus 10^3 bar or 1 kilobar.

• 0 C: 6 kbar = 60 km (Ice VI)
  
• 25 C: 9 kbar = 90 km (Ice VI)
  
• 50 C: 13 kbar = 130 km (Ice VI)
• 100 C: 23 kbar = 220 km (Ice VII) -- maximum of known organisms is 122 C
  
• 200 C: 40 kbar = 400 km (Ice VII) -- likely upper limit for nucleic acids and proteins to keep their shape
  
• 300 C: 70 kbar = 700 km (Ice VII)

So hydrothermal vents will not operate beyond a few hundred kilometers of depth.

 

[lpetrich]

A big difficulty in extrapolating to other biochemistries is having only one example for all the Earth's known biota. But one can make handwaving arguments about what other biotas might have. Our biota uses these chemical elements in varying amounts:

H, C, N, O, P, S, Fe, various other metal ions

One can make arguments about the utility or superfluity of them, but I think that we'd need enough to do redox (reduction-oxidation) reactions. How did LUCA make a living? Chemiosmosis in the origin of life (Nick Lane, John F. Allen, and William Martin) argues (paper abstract):

Despite thermodynamic, bioenergetic and phylogenetic failings, the 81-year-old concept of primordial soup remains central to mainstream thinking on the origin of life. But soup is homogeneous in pH and redox potential, and so has no capacity for energy coupling by chemiosmosis. Thermodynamic constraints make chemiosmosis strictly necessary for carbon and energy metabolism in all free-living chemotrophs, and presumably the first free-living cells too. Proton gradients form naturally at alkaline hydrothermal vents and are viewed as central to the origin of life. Here we consider how the earliest cells might have harnessed a geochemically created proton-motive force and then learned to make their own, a transition that was necessary for their escape from the vents. Synthesis of ATP by chemiosmosis today involves generation of an ion gradient by means of vectorial electron transfer from a donor to an acceptor. We argue that the first donor was hydrogen and the first acceptor CO2.

Chemiosmosis: pumping ions to the outside of a cell membrane, and then making returning ones assemble ATP molecules, an important energy intermediate. ATP has structure (adenosine)-(phosphate)-(phosphate)-(phosphate), with the energy residing in the (phosphate)-(phosphate) groups and with the adenosine part, a RNA building block, acting as a handle.

A nice thing about this scenario is that it involves:

• Known or plausible geological environments
• Closely analogous chemistry
• Disequilibrium

So a very deep ocean is likely to be a biological desert, except for its bottom, where the hydrothermal vents are. Photosynthesis would be possible on top of it, but photosynthetic organisms would likely be starved for nutrients there.

If it is deep enough, then the water at its bottom would be frozen, precluding hydrothermal vents, and making the liquid part lifeless.