Would Laythe really be habitable, Redux

[czokletmuss]

Just a note about the radiation: if Laythe's atmosphere has roughly the same molecular weight as air, then the density at sea level is around 1 kg/m^3. If the scale height is 4km, then the mass shielding from the atmosphere is around 4,000 kg/m^2. That's equivalent to a few meters of water between life on the surface and the radiation, which would be a very effective shield, even against cosmic rays.

So what would be the radiation level on its surface then, assuming Jool's magnetosphere is as powerful as Jupiter's? I'll repeat my questions:

EDIT: I saw few people discussing the radiation problem and I believe (due to what they posted) that they have quite a lot of knowledge about this topic. So here's my question - what could be the scientifically probable level of radiation on the surface of Laythe with its own magnetosphere and without it? How much protection the atmosphere woudl provide assumig that Jool Van Allen belts are as strong as Jupiter's (scaled down to KSP universe)? I mean, could we reasonably except something like 1 Sv/h or should we count it in mSv rather than siverts?

[kiwi1960]

I only read page one.... BUT... I must say this...

Who cares if kerbals can survive there or not? Send them, MAKE them survive... if they die, then they die. Plenty of replacements...

This isn't real life... we are not NASA.... where, supposedly, life is sacred and we actually want them to stay alive...

I'm pretty sure that if there were volcanoes and radiation and green house gases... you would all be planning to build a base there.....

right?

As Jeb would say... "Feck it, lets do it... rockets are cheap, Kerbal's are cheap, what the feck do we have to lose?"

[Tommygun]

So what would be the radiation level on its surface then, assuming Jool's magnetosphere is as powerful as Jupiter's? I'll repeat my questions:

This might be helpful, it talks about radiation on Europa and colonization:

http://en.wikipedia.org/wiki/Colonization_of_Europa

[czokletmuss]

But Laythe is more or less when Io is IRL. And it has atmosphere, hence why I'm asking.

[Tommygun]

OK, but I personally think it would still be lethal over a few weeks at least, with or without it's own magnetic field or atmosphere.

I also wonder what all that radiation would do to oxygen molecules, that is, can it turn it into ozone like UV radiation does?

I actually would like to see Squad just switch Laythe and Minmus when they add the new planets.

[Trux]

I actually would like to see Squad just switch Laythe and Minmus when they add the new planets.

I like Laythe and Minmus where they are. The challenge of getting to Laythe makes half the reason of going there, plus it just wouldn't be the same without that huge green gas giant as your near constant companion.

[peadar1987]

-Laythe is not Europa. I don't buy into the hand-wavey, pseudo-scientific explanations for the tiny size and high density of the Kerbolar system's planets, I just take it to be that they've been scaled down for gameplay purposes, and imagine Kerbin to be the size of earth (not the size of Charon). With that scaling, Laythe would be almost earth-sized, far larger than Europa, and comparisons between the two aren't really relevant. Laythe would be able to hold onto a far thicker atmosphere, and with a substantial greenhouse effect caused by the right composition of atmosphere, could easily maintain a saltwater ocean near the equator, especially when combined with upwelling of warm water from tidal heating of the core. I doubt it would be habitable though, as most potent greenhouse gases are toxic at partial pressures needed for use as a buffer gas. Sulphur Hexafluoride maybe? And entire moon of people who sound like Barry White would be pretty awesome!

[Johnno]

Just a reminder, please stay on topic.

[Rokker]

OK, but I personally think it would still be lethal over a few weeks at least, with or without it's own magnetic field or atmosphere.

I also wonder what all that radiation would do to oxygen molecules, that is, can it turn it into ozone like UV radiation does?

Well the thing about this radiation is it isn't just one type of radiation, it is a combination of, assuming Jovian based conditions, EM radiation in the form of radio, near-IR, UV, and soft X-rays, and, to a much larger extent, particle radiation. The X-rays would simply be scattered to the point by the atmosphere itself. Ozone would likely form due to the UV radiation but the ozone formed could become an ozone layer behaving fairly similar to Earth's, however the particle radiation can break down ozone which could prevent the formation, however believe that the UV rays would not be too big of an issue as long as the proper minor UV shielding such as powerful sunscreen. Due to the particle radiation, there could be a decent amount of irradiated substances in the atmosphere and on the surface however the proposals of underground and underwater living would still likely be fairly feasible.

[Horn Brain]

So what would be the radiation level on its surface then, assuming Jool's magnetosphere is as powerful as Jupiter's? I'll repeat my questions:

With that level of shielding, you would receive dosages that would be safe for indefinite residence. You can basically ignore Jool's radiation belts because you would even be shielded from cosmic rays to nearly the same extent that you are on Earth. It would probably be comparable to flying around in an airplane all your life at worst. The dosages would almost certainly be less than certain places on Earth which have a high concentration of radioactive elements in the local bedrock. Order of 100 mSv/year at the VERY most.

Edited November 13, 2013 by Horn Brain

[czokletmuss]

Are you sure about this? According to this source, you would need something like 3,6m thick liquid water wall to lower the radiation level to 20mSv/year on Io. Is the Laythe atmosphere really dense enough to provide protection as good as 3,6m water wall? Plus there probably ain't much water vapor in it (if any), so I doubt there would be much hydrogen in it (maybe as NH3 or CH4 at best).

BTW I asked a question about radiation during AMA and I get the answer from the devs:

Radiation - will it be implemented? If so, how are you planning to do this? Will it be integrated into life support or science system?

Ted: Radiation would be a beneficial gameplay addition to more veteran players. But we try to avoid gameplay mechanics that will leave a player puzzled for too long or a mechanic that’s largely out of the player’s control. That doesn’t rule it out, just means that when it comes to it, it’ll take a bit of working out.

And I asked about Laythe

Laythe - is it habitable? There were countless threads about this, let's solve it once and for all

Ted: Habitable by whom?

Edited November 13, 2013 by czokletmuss

[LaydeeDem]

The only place where life could exist on Laythe is deep in it's oceans. And it's not just radiation from Jool that would render Laythe's surface uninhabitable, but the immense tidal effects mean that Laythe's surface is never constant or stable. Life on Laythe would probably only be as complex as the simple worms or arthropods that live at Earth's hydrothermal vents.

[Horn Brain]

Are you sure about this? According to this source, you would need something like 3,6m thick liquid water wall to lower the radiation level to 20mSv/year on Io. Is the Laythe atmosphere really dense enough to provide protection as good as 3,6m water wall? Plus there probably ain't much water vapor in it (if any), so I doubt there would be much hydrogen in it (maybe as NH3 or CH4 at best).

Here there is a table showing halving masses for gamma rays, which puts air at the same halving mass as water. The Laythe atmosphere (if it were air) would actually be slightly more than necessary to protect against Jupiter's radiation at Io. If Jool's is not so bad (presumably, since it's much smaller), then you should be fine.

Edited November 14, 2013 by Horn Brain

[czokletmuss]

Thank you for the link. Do you know by any chance where I can find halving masses for other gases? 'Cause I don't think that Laythe's atmosphere is really similiar to this on Kerbin.

[KerbMav]

Here there is a table showing halving masses for gamma rays, which puts air at the same halving mass as water. The Laythe atmosphere (if it were air) would actually be slightly more than necessary to protect against Jupiter's radiation at Io. If Jool's is not so bad (presumably, since it's much smaller), then you should be fine.

Halving mass - now stack 20.000m of air and 20.000m of water on a scale with eqally large pans - which side will tilt?

[magnemoe]

So what would be the radiation level on its surface then, assuming Jool's magnetosphere is as powerful as Jupiter's? I'll repeat my questions:

Why should Jool has a so strong magnetic field as Jupiter? Saturn's field is much weaker, as I understand its don't create more problems than Earths magnetic field and Saturn is not so much smaller.

[KerbMav]

As far as I understand from crossreading some wiki articles:

In very few words: Hydrogen under high pressure behaves like a liquid metallic conductor. This is what creates magnetic fields in our gas giants. In earth it is its core of molten iron.

Saturn's magnetic field's "strength at the equator – 0.2 gauss (20 µT) – is approximately one twentieth of that of the field around Jupiter and slightly weaker than Earth's magnetic field."

Saturns orbit contains more neutral particles, Jupiters and Earths more ions. The latter increasing the magnetic field.

http://en.wikipedia.org/wiki/Magnetosphere_of_Jupiter

http://en.wikipedia.org/wiki/Metallic_hydrogen#Astrophysics

http://en.wikipedia.org/wiki/Saturn#Magnetosphere

http://en.wikipedia.org/wiki/Magnetosphere_of_Saturn#Dynamics

[Monkeh]

So does it all boils down to how much 'metal' you have at your core and how fast it's spinning?

Edited November 14, 2013 by Monkeh

[KerbMav]

Technically not true, the atmosphere is not dense enough to deflect solar radiation. The majority of the solar radiation is deflected thanks to the earths magnetic field. In fact if the Earth did not have it's magnetic field, much of the atmosphere would simply blow off because of the solar winds and we would be more like Mars.

There is a theory that it is quite likely, that the solar wind itself would create a new magnetic field in a few hours, even after a sudden collapse of Earth's own.

[czokletmuss]

Halving mass - now stack 20.000m of air and 20.000m of water on a scale with eqally large pans - which side will tilt?

That's what I'm thinking about. I don't think so that if we, for example, put Titan with half its atmosphere where Io is there won't be any radiation at the surface. I mean, Laythe is in the middle of the Van Allen belt! There is a storm of radioactive particles hitting it all the time - and I don't think any gas (atmosphere) can offer protection as good as liquid or solid body. There's too much space between the particles in the atmosphere.

Or maybe I'm wrong - but my quastion stands. What is be the radiation level on the surface of Laythe in mSv?

[FITorion]

Why should Jool has a so strong magnetic field as Jupiter? Saturn's field is much weaker, as I understand its don't create more problems than Earths magnetic field and Saturn is not so much smaller.

Jupiter is larger than all other planets in the solar system combined including the other gas giants. It really is much larger than Saturn.

[Brotoro]

Halving mass - now stack 20.000m of air and 20.000m of water on a scale with eqally large pans - which side will tilt?

Why would you want to compare equal LENGTHS of the different materials? What matters is the mass of air or water between the radiation source and you, not the amount in an equal length. On Earth at sea level, the mass of atmosphere above you is equivalent to the mass of 10.4 meters of water. People underestimate the mass of air. The air in a cylinder that encloses the Eiffel Tower has a greater mass than the iron structure of Eiffel Tower itself.

[Brotoro]

Jupiter is larger than all other planets in the solar system combined including the other gas giants. It really is much larger than Saturn.

Jupiter is 447 times the mass of Jool.

[peadar1987]

That's what I'm thinking about. I don't think so that if we, for example, put Titan with half its atmosphere where Io is there won't be any radiation at the surface. I mean, Laythe is in the middle of the Van Allen belt! There is a storm of radioactive particles hitting it all the time - and I don't think any gas (atmosphere) can offer protection as good as liquid or solid body. There's too much space between the particles in the atmosphere.

Or maybe I'm wrong - but my quastion stands. What is be the radiation level on the surface of Laythe in mSv?

Well, 70km of atmosphere isn't going to block radiation as well as 70km of water or lead, but it will block it as well as a few metres of water or lead. It take surprisingly little to stop radiation. I've stood with 3 metres of water between me and more than 100 spent nuclear fuel rods, any one of which would give you a lethal dose in well under a second. My radiation meter showed only a minimal difference between standing there, and sitting in an office. Now, gas isn't nearly as good at stopping radiation as water (especially not when the water is boronated), but when you have 60km of the stuff, the gas only needs to be one two-hundreth of a percent as effective as the water. And that's assuming that the radiation outside is as severe as that coming from a nuclear fuel rod, which is wouldn't be, unless there's something very fishy going on at Jool!

And, (damn you), you made me interested, so I had a stab at working out what the radiation level would be. I used data from here: (http://en.wikipedia.org/wiki/Radiation_protection) for the halving thickness of air (150m at full pressure). I assumed that the halving thickness scaled linearly with density, and the density scaled linearly with pressure (not quite true, as the temperature will drop the higher in the atmosphere you get, and the density will actually be higher for a given pressure).

I whacked that into an excel spreadsheet, and starting from the top of Laythe's atmosphere (density, height, and scale height from the KSP wiki) for each 100m increment, I worked out the density of the atmosphere, and from that, the expected halving thickness. I then divided the 100m increment by the expected halving thickness as a rough linearisation to work out how much of the radiation would be absorbed, and fed that into the next 100m increment until I had reached the ground.

Long story short, the radiation dose rate at sea level on Laythe, assuming a dose rate at the top of the atmosphere of 5.4 Sv/day (Europa's environment), and an earth-like composition for Laythe's atmosphere, is 1.8uSv/hr. This corresponds to an annual dose of 15mSv/yr, which should pose no risk to human health (although Kerbal health is anyone's guess).

Careful though, the higher you climb, the greater the dose. If you get above about 600m, you're going to be getting a dose of 100mSv/yr, which is firmly linked to an increased chance of cancer.

It should be noted that those figures are likely an overestimation of the dose, as they underestimate the actual density of the atmosphere, and assume that all of the radiation is hard gamma radiation, which it isn't. Particles and softer electromagnetic radiation will be easier to stop.

Graphs here (everyone likes a graph!):

[czokletmuss]

And, (damn you), you made me interested

You're welcome

Fantastic work! I know that there is someone on this forum with the knowledge to calculate this So assuming Laythe gets as much radiation as Io, not Europa (which would be circa 36 Sv/day), the avarage dose on the sea level would be (more or less) 12.6 uSv/hr, right?