Hey all, just speculatin’ on a hypothesis…
Would a brown dwarf star be hot enough to sustain life on a planet, perhaps if close enough?
Is it possible for a world (say the one close to this brown dwarf) to have oceans of heavy water (D[sub]2[/sub]O)?
Brown dwarfs aren’t thought to very hot - maybe only a couple of thousand K at the surface tops, so they aren’t very luminous and it’s unlikely a planet would receive any significant heat from one at any possible stable orbit.
Deuterium is one part in 6500-ish of hydrogen so you’ll have to come up with some explanation of why your ocean has a different isotope ratio that the rest of the universe. But in principle why not. From the wiki article it seems that your ocean would be more viscous than ours. Anyway, the wiki article is an interesting read and seems to be replete with cites.
You could make sure that the conditions are logical to have produced an environment which encourages life; for plants you may need to change the chemical process for making food, a replacement for chlorphyll.
The Straight Dope on heavy water:
According to the article the oceans would be highly toxic to humans.
Thanks, I was trying to extract what I could from Wikipedia. I need a planet to have heavy water oceans… so I thought that since brown dwarves are thought to fuse deuterium, it might just be able to spit out a planet with such a mixture. Could there at least be enough heat from the dwarf to keep the oceans liquid? Any other ideas on how to produce a planet with such a high deuterium ratio?
Which would actually serve the purpose of my story. 
Although, I might need to have life in the oceans… that evolved there. Anyone lifeform from earth would perish quickly, but if life evolved in such an ocean, I can’t imagine it impossible. Otherwise, it’s okay for it to be devoid of life above sea-level.
The simplest solution would seem to be a binary star system. A brown dwarf locked to a more normal star. The normal star provides the energy, the dwarf provides the deuterium. You get the best of both worlds and egt to tinker with a fairly cool binary system with some awesome solar/solar eclipses.
Heavy water is made commercially by distilling liquified hydrogen and reacting the seperated deuterium with oxygen, so that may be adaptable within the bounds of the planetery system you’re creating. Otherwise, d20 likely has a slightly different boiling point than H20 so perhaps your planet had a gigantic ocean and found itself in a sweetspot where the h20 boiled off and the d20 didn’t, leaving 1/6500 of the water behind?
Heavy water is one of the three necessary fuel sources for COBRA’s teleportation beam, so Serpentor or Destro ought to show up halfway through the story with a ship. And then the Joes come in to save the day.
I’m not sure a planet could orbit a brown dwarf closely enough to have liquid water without breaking up due to tidal effects. (Roche limit, etc.)
Brown dwarfs by definition derive what energy they produce from deuterium fusion, but I don’t think that means they’re enriched in deuterium more than any other star. I can’t think of any plausible natural process that could leave a planet with oceans of D2O. Would it be too much of a deus ex machina to simply postulate that it was created artificially by now-long-gone aliens for unknown reasons?
Hey, I remember that episode.
From the Rules: “Please do not ask other members to do your homework”
Mmm. Hardly homework. I’ve been quite frank in my OP. More of a hobbie. And all the posts so far have been most helpful. I haven’t been in school since 1991.
Thanks everyone!
My immediate thought. Here’s a scenario :
Hundreds of millions of years ago, a powerful and patient alien race decides it needs a really large amount of deuterium. It seeds an icy planet orbiting a brown dwarf with self replicating machines designed to convert standard water ice into heavy water ( or ice once it freezes ). The fusion powered machines replicate, until they cover much of the surface. Over time, their own waste heat is enough to warm the planet up, until the ice melts and form oceans of progessively heavier water.
The aliens never come back, and in the ensuing millions of years some of the organic debris they left behind had the chance to defrost, and the microorganisms bred and spread and evolved, until a new ecosystem was formed. The result is a world covered in heavy water, in an eternal warm, dark night.
You know what? I may not go with exactly your idea here, but you’ve inspired a solution. I need to create a not necessarily evil race of aliens, but one that’s indifferent to our existence… that is, unless we get in their way. For reasons I won’t go into, they’re bent on turning whatever worlds they find with light liquid water into that of heavy water. So the planet discovered is one that’s already been converted… unbeknownst to the humans, to that will be a mystery to them. poifect.
Can’t thank you enough! And everyone else too… been trying to come up with a reason for several days.
One more question… what would it take to convert heavy water into light (regular) water?
You’d have to somehow remove the excess neutron from each deterium atom. Maybe put the atoms in a particle accelerator and collide them into a target at just the right speed to split the neutron off? Honestly I’m not sure why you’d want to; detertium is useful as a fusion fuel, and ordinary hydrogen is the most common element in the universe. It would probably be easier and more useful to simply remove the deterium and replace it with ordinary hydrogen.
Right! which is exactly why the humans dig the hell out of this planet, all the deuterium they can ask for. But what to drink? They can haul their own drinking/arrogation water there, but which would be easier? Converting heavy water to light, or shipping it in?
And, I suppose, also gives that nice un-dropped shoe to serve as a long-term plot development if you ever need one.
Any civilization capable of mounting interstellar voyages already knows how to recycle water. Especially a civilization which has interstellar travel sufficiently cheap enough to make traveling to another star system to harvest deterium. Deterium exists in limitless quantities on Earth, and extracting it from seawater is much easier than traveling between stars, at least with any reasonable near-future technology. Although a world with heavy-water oceans would be such an astonishing anomoly, it’s likely that the purpose of the mission would be scientific study and/or exoarcharology first, with harvesting deterium a secondary concern. But at any rate, if they can get there, recycling their own drinking water is unlikely to be a major concern.
For Q1, If you’re shopping for suitable planets a good resource would be solstation.com. That site gives good summaries of conditions for a wide range of star systems. It has many examples of red stars, and includes active visuals of the orbital set ups of binary and triple star systems. These orbital patterns are mostly not as many people imagine them to be.
A red star probably wouldn’t be the best choice. For a planet in such a system to be able to support life, the life zone would be so close to the star that its rotational period would probably become tidally locked, in a similar way to Mercury, Venus and, in the case of the Earth Moon system, the Moon. This might not rule out the possibility of life but it would probably rule out conditions suitable for high tech life forms to develop.
For Q2, I can’t answer that. I doubt that a tidally locked star could have much in the way of oceans but science fiction doesn’t have to be totally scientifically accurate.