Re: biological changes to make humans able to adapt to space

Robert J. Bradbury (
Sat, 4 Dec 1999 06:18:51 -0800 (PST)

On Fri, 3 Dec 1999, Zeb Haradon wrote:

> I was looking at some terraforming links today, and got the idea of
> adjusting humans to space, rather then space to humans.

Freeman Dyson has made this point in "Disturbing the Universe" and several of his other books.

> 1 - Try to figure out some way to incorporate the radiation-proofing
> strategies of Deinococcus radiodurans into our genome. This bacteria can
> survive massive dosages of radiation, strong enough to blast its DNA into
> peices - somehow it manages to put it all back together. I am not exactly
> sure how - they recently decoded its genome and I've been reading up on it.
> A protein called RecA seems to have a big part in it - if the resistance is
> as simple as the presence of a protein, it should be easy (by extropian
> standards) to introduce the proper sequence into my genome, through gene
> therapy, which would produce RecA.

I love it, we now have "Extropian standards" (what a concept)...

Actually D.r. has a host of defenses, beta carotene to absorb UV (that's why its red), free radical disposal proteins (catalase & SOD for example), all of the standard DNA repair proteins in more "muscular" forms (most bacteria have some form of RecA). It seems that the real trick that D.r. accomplishes is the repair of double strand breaks (usually caused by X/gamma radiation). It seems to do that by having enough copies of the genome around that it can always find a template that it can use to reassemble double strand breaks. (Eukaryotic cells normally do this by finding the homologous chromosome and doing a variant of recombination repair). This involves genes like rad52, rad 51, rad50, rad1 and rad10. Bacteria that don't have multiple chromosome copies (such as most bacteria unless they are replicating very rapidly) cannot do this type of repair.

The two classic books that you want to have to study this in more detail are:
DNA Replication by Arthur Kornberg and DNA Repair and Mutagenesis by Errol C. Friedberg et al. Kornberg and Friedberg are the experts in these respective areas.

To engineer radio-tolerant humans, you want to increase its DNA repair levels *and* replace most of our junk DNA with extra copies of essential genes. The strategies are clear, what we need is tools to implement them.

Trivia fact: I bought some D.r. from the ATCC back in 1991 and cultured it for a Microbiology project. Also delivered it to one of my associates in Russia when we were discussing sequencing the genome in 1994 (I'm sometimes, just a little bit ahead of the technology curve... :-\). One of the things they commented on was how slowly it grew (because you have to have time to reassemble a potentially sliced & diced genome).

> 2 - Lack of air could also be dealt with. The artificial blood cells
> proposed in Nanomedicine are basically miniature oxygen tanks.

The detailed discussion of these is in the Respirocytes paper at:

> A liter or
> two of these in place of blood could keep you alive for a couple days (I
> have read precise figure - I forgot them). It might even be possible to wire
> you up somehow so you wouldn't need to replentish yourself constantly with
> more artificial blood cells. CO2 could be exhaled via the lungs, as usual.

Actually if you have sufficient onboard energy (such as with say the gandolinium nuclear power source), you can recycle the CO2 back into O2 and carbon. I'll be seeing Robert next weekend and I'll ask him about the possibilities of "closed loop" survival in space.

> Intake of oxygen would depend on your planetary environment. On the moon,
> you could perhaps wear some kind of special shoe which sucks up regolith,
> breaks it down, and has tubes going into your feet to interface with the
> artificial blood cells. On Mars, basically the same thing, except sucking
> CO2 out of the air.

I believe (though I don't have hard numbers) that getting the oxygen out of regolith may be more expensive than getting it from CO2. It depends on the complexity of the various oxides. For example, getting O2 out Al2O3 is definately expensive. (The way to think about it is the inverse of the amount of energy you get from combining those materials such as burning carbon, e.g. charcoal or graphite or the thermite reaction).

> This would solve the radiation problem and the oxygen problem - there are
> still the issues of air pressure and temperature - any ideas?
I think you could solve the pressure problem with a nanobot grid just under the skin surface linked together with long velcro style hooks. They would have to have some process for delinking and relinking so that you could still allow dead skin cells to slough off.

Though this raises an interesting question -- do human bodies actually come apart in a vacuum? Or is the problem due to the difference in internal air pressure and external pressure? We don't have a problem when diving so long as the air pressure in the lungs and the external water pressure are equivalent. Do we have any problem in a vacuum if there is a vacuum in our lungs? Another way of looking at this is whether internal blood pressure would cause us to burst in a vacuum. If that is true, then you simply want to put a vacuum in the lungs and stop your heart (which is doable with the respirocytes) before you go out to walk around on the moon.

Then I think the problem becomes heat removal from your brain. So you have to put on a helmet with diamond conductors radiating out to sphere coated a high heat emissivity material (black copper oxide is quite good) of sufficient size to get rid of the 10-15 watts of heat your brain produces. There is an interesting problem that you have to keep high emissivity materials out of the sun (because the good emitters are also good absorbers).

Ideally temperature can be controlled locally by having nanobots throughout your skin that selectively flip micro-mirrors that have one reflective side and one aborbing side (white & black) depending on whether you want to absorb or release heat. If you had a series of diamond cable heat conductors or micro-pipes that could circulate high pressure cooling fluid from your brain to the rest of your body, you could probably do away with the heat radiator helmet.

I'll state for the record that this is going to be much easier to do with hard & dry nanotech than soft & wet biotech.