Expert: Mars Astronauts Would Lose Teeth

Ant wrote to us with a story on Discovery about the long term consequences of manned and "womanned" missions to Mars - lots of research about bone-weakening effects of zero G environments, with tooth loss high on the list.

Comments

Mars is not a zero G environment

[tinrobot]

The discovery page seems dead. But, going out on a limb -- from what I've read, it seems to take about 6 months to get to mars. There have been more than a few people who've lasted this long in space, and they seemed to have nice smiles when they returned.

Once on mars, the effects should be mitigated by the gravitational field - right? How much less is mars' gravity compared to earth?

ways to combat body atrophy

[tcyun]

As I recall, most astronauts who are in space for any extended period of time have a fairly rigorous workout routine to prevent muscle atrophy. Obviously, exercising with spring based machines (as it is fairly pointless to try to "lift" weights) helps to keep muscles in shape but also stresses the bones also helps maintain bone mass.

The Discovery article states "...in both older women and weightless astronauts, the bone-repair mechanisms in the body shut down." Are there any doctors out there that can explain (in detail) what happens to the body in low gravity that causes bones to atrophy?

Re:ways to combat body atrophy

[Anonymous Coward]

(IAAD, and used to be a bioengineer, but this is a gross simplification) Bones continually undergo remodeling, and are as such really dynamic structures. Osteoclast cells resorb bone, while osteoblasts lay down new bone. The clever part of this scheme is that in general, bone microstructure is aligned along stress planes. If you slice through the head of the femur for example, a bone subject to large forces, what you see is essentially scaffolding of bone along and perpendicular to the major lines of stress. This ensures that bone is always strongest along axes subject to the most force, and that bones remain able to bear loads as body geometry changes (with age, injury etc)

This gets you into trouble for example when you replace a joint. A common problem is that bone around the pin of an artificial femoral head seems to melt away. This results from distortion of the normal stresses -- the prosthesis carries most of the load, and the bone is not stimulated to maintain its usual architecture. This also explains why we recommend weight-bearing exercise to our patients.

Wrt the zero-g problem, as you might guess the big issue is that bones in 0-g aren't under load. Osteoclast activity dominates that of osteoblasts, and bone remodeling does not have gravity to orient it. I actually don't buy the argument about teeth in that regard--osteoporosis in zero-g isn't like that of "old age". I'm not convinced that the bone of the jaw melts away in zero-g like that of long bones, but then again it's not really my area.

(docdoc)

What about the Russians ?

[windi]

There are russians that have been in space for 6 month to a year and they have not lost their teath, and I have not heard of any problems with anyone spending time on Mir, and no one has said anything on this topic before (AFAIK, I can't read the article :-( ), so assume that the ISS astronauts are in no danger, and they are supposed to spend six month in orbit.

So, IMHO, the article was written by someone who is against a manned mission to mars or any other planet.

Re:What about the Russians ?

[Anonymous Coward]

So six months in space doesn't make your teeth drop out. Neither does staying underwater for 30 seconds make you die of asphyxia.

Now try six minutes underwater

Re:Artificial Gravity?

[Rinswind]

In another book of Arthur Clack he proposes an entirely different way to get artificial gravity.
The spacecraft can constantly accelerate with acceleratin equal to 1g. This means that the articicial gravity force will be directed about the spacecrafts axis (immagine a simple rocket here) and the experiance of being inside would be like in a several story building with the lower levels located right above the engine. When the spacecraft needs to stop there would be a short period of 0g during which the whole ship changes direction to 180 degrees.
The obvious drawback is that we don't have enough power (and reactive mass to throw backwards) to constantly accelerate a craft all the way yo Mars and beyond.
A possible solution would be to have a nuclear reactor and use superheated water or a gass of some sort as fuel. In this way we get very high acceleration with relatively little "reactive mass". (in the book they used a small black whole that could accelerate the hydrogen fuel to speeds close to the speed of light :)
All of this being just a theory though. I got no idea if it can realy work.

Gum anyone?

[M_T_Toaster]

Wouldn't chewing gum give some protection against this?
It would give them plenty of exercise to the teeth and jaw muscles, and might well be popular (most astronauts are American now and so presumably like chewing the cud).

OTOH the gum might also come in handy for fixing things in the ship and or holding things down in zero g

think of the sponsorship deals... the Wrigley's Orbiter etc

And what of MIR?

[OldCrasher]

I suppose the cosmonauts that rode MIR for more than a year were some how in a different form of Zero-G. I suppose that Russian Space being different to US Space, their research is useless... And assuming this means that some Dunderhead can still get Federal Tax Dollars to do research that someone else has already done.... better.

Re:Artificial Gravity?

[sean23007]

The Mars Society has already thought of this. You are correct when you assume that you need a ridiculously large vessel to make this feasible. But, the way the Mars Society theorists got around the issue is to separate the craft into two parts separated by a teflon tether, of a sort. The first part of the craft would be larger and contain everything the astronauts would need on the voyage to Mars. The second part would be considerably smaller but nearly equivalent in weight (space for living astronauts is considerable). The two parts would then be spun around each other with initial and occasional blasts from small, dedicated retro rockets.

The problem is, in order to simulate 1G of gravity (equal to that on Earth), you need a certain mixture of size and speed. For safety reasons, the tether can only be so long. So you would think they could just increase the speed. It works on paper, but when put into practice with such a small vessel, spinning at that speed would most likely just induce vertigo in the astronauts and the small size of the craft would allow small variations in the rotation to create noticeable rocking, much like a ship at sea. Luckily, there is an easy solution to this problem. Just simulate the gravity on Mars. Spinning at a reasonable speed, the craft would be able to simulate the necessary 0.38G safely and easily. And then there's less of a problem on both landings (Mars and Earth), because even if you were able to simulate full Earth gravity, would you really want to? When you land on Mars, some considerable amount of time would have to be devoted to getting acclimated to the gravity, during which time the astronauts would not be fully operational and not exactly able to do the required exploration work. With a gravity of 0.38G on the transporting spacecraft, that acclimation can be done over the 6 month travel period and the astronauts can hop out and get their work done immediately after landing.