Question about microgravity/ zero gravity adaptation

[ARS]

We all know that being in a microgravity environment on a planetary orbit (most people call it zero gravity, but it really isn't since the gravity is still in effect, but in a form of continuous freefall) weakens the human body since blood flows, skeletal and muscle tissue isn't counteracting against gravity like on a surface.

My question is, if for example, a person was born in that microgravity condition (like on earth orbit) and spend his/her life in that condition. What'll happen when one day, that person was brought to earth surface for the first time? How he/she will react? Astronauts does show a sign of weakness whenever they disembark from their capsule and had to be supported by other people just for walking. But how it turns out if the astronaut never experience earth's surface gravity before? If he/she becomes too weak, is there something to do to make that person able to adapt with earth gravity?

Also what happen if astronaut spend too long in microgravity condition? I know it does cause a weakening of a body, but does it cause death?

Let me know what you guys think

[Steel]

8 minutes ago, ARS said:

We all know that being in a microgravity environment on a planetary orbit (most people call it zero gravity, but it really isn't since the gravity is still in effect, but in a form of continuous freefall) weakens the human body since blood flows, skeletal and muscle tissue isn't counteracting against gravity like on a surface.

My question is, if for example, a person was born in that microgravity condition (like on earth orbit) and spend his/her life in that condition. What'll happen when one day, that person was brought to earth surface for the first time? How he/she will react? Astronauts does show a sign of weakness whenever they disembark from their capsule and had to be supported by other people just for walking. But how it turns out if the astronaut never experience earth's surface gravity before? If he/she becomes too weak, is there something to do to make that person able to adapt with earth gravity?

Also what happen if astronaut spend too long in microgravity condition? I know it does cause a weakening of a body, but does it cause death?

Let me know what you guys think

From what I've read, their bone density would be so low that they could break bones just by sitting down too quickly.

What's more their muscular system would likely be so weak (unless they'd been doing multiple hours a day of resistance training like astronauts on the ISS do) that they wouldn't be able to hold themselves upright. Their leg strength would probably be dismal (i.e not strong enough to support their body weight) because they would have never had much need to use their legs, unless they'd been doing the aforementioned resistance training.

Worst case is that their heart is too weak to pump blood around their body against gravity and so they die as soon as they get to the surface.

Edited July 29, 2017 by Steel

[Tex_NL]

Ask NASA, ESA, ROSCOSMOS and pretty much everybody else involved. This is one of those questions they are trying to answer with long term studies on the ISS.

Edit:
A more entertaining but less accurate/scientific answer can be found in the first season of The Expanse. Great TV series. highly recommendable.

Edited July 29, 2017 by Tex_NL

[YNM]

They'd become "weaker" under 1 g. But they can grow larger. Earth humans could be dwarfed.

[Bill Phil]

36 minutes ago, YNM said:

They'd become "weaker" under 1 g. But they can grow larger. Earth humans could be dwarfed.

Their hearts wouldn't have the strength if they returned to Earth.

This free fall issue is why most colony concepts that are in free fall are depicted as rotating, which simulates weight.

Edited July 29, 2017 by Bill Phil

[Nibb31]

For this to be an issue, you'll first have to be able to have children in microgravity and raise them for many years, which implies people living in microgravity for several years in a colonization scenario. Since we don't even know if a child can grow normally in microgravity, your question is moot.

And due to ethical issues, we probably won't know before it actually happens. Microgravity experiments on human embrios or on pregnant women, won't happen. If an astronaut was to suddenly become pregnant, they will probably be evacuated as soon as possible. Crews to Mars will probably have to be sterile or at least take contraceptives because they simply won't take the risk.

Edited July 29, 2017 by Nibb31

[YNM]

1 hour ago, Bill Phil said:

Their hearts wouldn't have the strength if they returned to Earth.

This free fall issue is why most colony concepts that are in free fall are depicted as rotating, which simulates weight.

Yes if you intend to be able to return "home". But what about the ones who don't ? Say, only adapted to 0.5 g ? 0.3 g ? 0.1 g ?

[Bill Phil]

1 hour ago, YNM said:

Yes if you intend to be able to return "home". But what about the ones who don't ? Say, only adapted to 0.5 g ? 0.3 g ? 0.1 g ?

Well then they won't ever get to experience Hawaiian vacations. Or visit family. Or climb Everest. Or visit historical landmarks.

1 hour ago, Nibb31 said:

For this to be an issue, you'll first have to be able to have children in microgravity and raise them for many years, which implies people living in microgravity for several years in a colonization scenario. Since we don't even know if a child can grow normally in microgravity, your question is moot.

And due to ethical issues, we probably won't know before it actually happens. Microgravity experiments on human embrios or on pregnant women, won't happen. If an astronaut was to suddenly become pregnant, they will probably be evacuated as soon as possible. Crews to Mars will probably have to be sterile or at least take contraceptives because they simply won't take the risk.

That's why we have mice. Although that could be unethical as well.

[YNM]

17 hours ago, Bill Phil said:

Well then they won't ever get to experience Hawaiian vacations. Or visit family. Or climb Everest. Or visit historical landmarks.

But they can properly climb the Olympus Mont.

[Bill Phil]

3 hours ago, YNM said:

But they can properly climb the Olympus Mont.

Not if they were born and raised in zero-g.

[ARS]

1 hour ago, Bill Phil said:

But they can properly climb the Olympus Mont.

Mars gravity is still too heavy for someone who's adapted to live in zero G

[YNM]

2 hours ago, Bill Phil said:

Not if they were born and raised in zero-g.

We're talking microgravity here, but I think it should be extended to partial gravity, if it turns out microgravity is lethal to fetal development or sonething.

[ARS]

1 hour ago, YNM said:

We're talking microgravity here, but I think it should be extended to partial gravity, if it turns out microgravity is lethal to fetal development or sonething.

Maybe it's because being born and raised in microgravity environment and never experiencing surface gravity makes the bones and muscles too weak. Somehow it reminds me of jellyfish...

[tater]

JAXA's mouse experiment watched 2 groups of mice for 38 days, one in a centrifuge at 1g, the other in microgravity. They have some data on radiation vs gravity as it affects things like bone loss now. They are flying up another one on the next SpaceX resupply. Each holds 12 mice, so they need to repeat it a few times, but apparently they observed differences in bone and muscle mass in even just 38 days. At some point they could obviously run the centrifuge and see where the knee in the gravity-dose curve is. Ie: at what point does gravity stop degrading mammals.