Why doesn't Tylo have an atmosphere?

[ThesaurusRex]

It has the mass of Kerbin, and far away enough from the sun to keep air from being blasted off, but no atmosphere.

How come it has no atmosphere yet Laythe does? And for that matter, how come Ganymede and all the other atmosphere-capable moons don't have atmospheres?

[Sky_walker]

Simple: It's a game. Not a logical physics simulation.

[Ralathon]

In the case of Tylo and Laythe, it's because its a game and it doesn't have to follow the rules of physics. Celestial bodies in KSP are made to pose unique challenges. For example, Tylo has no atmosphere so you can't use atmospheric drag to slow yourself down, making it hard to muster the dV budget for a landing.

As for ganymede and the other gallilean moons, I presume its simply too warm for them to retain an atmosphere. Then again I didn't do the math to check this and Im not an expert on this.

[NFUN]

So far as we can tell, it is sort of a crapshoot whether or not a moon will have an atmosphere, in that many factors and conditions can determine the viability of having an atmosphere. I will try to compare Ganymede and Titan the best I can, but I am not an expert or well-versed in these matters, and am mainly using Wikipedia as a crutch.

Ganymede and Titan are both about the same distance from their host, and have about the same escape velocity and mass. Titan is about 20 degrees Centigrade colder than Ganymede. Ganymede is largely composed of oxygen, hydrogen, sulfer and iron, while Titan has more nitrogen and silicon, with some hydrogen and oxygen.

Based on this data, a few explanations might be provided. A very thin atmosphere has been discovered on Ganymede, caused by radiation reacting with water on the planet, releasing oxygen and hydrogen gas. Because the tenuous atmosphere is generated by solar wind, and much of these particles are deflected by Ganymede's unusual magnetosphere, not many H20 molecules are ionized into O2 and H2. The hydrogen naturally escapes Ganymede, as the its gravity is not strong enough to retain the light gas, and the oxygen remains. Titan, on the other hand, has an abundance of relatively heavy organic compounds, that, unlike hydrogen, are retained by the body. Titan also spends about half of its time in orbit inside the magnetosphere of Saturn, shielding it from much of the energetic solar wind. The atmosphere it had accumulated, likely when the sun was cooler and spat out less ions, is also thick enough to create an ionosphere, which can slow gas loss due to solar wind by having charge (the ionosphere is an area of the atmosphere where energetic charged particles reside). Ganymede's initial oxygen atmosphere, if it had existed, probably would not have been thick enough to create an ionosphere capable of keeping the solar wind at bay while it got replenished by some form of volcanism. Ganymede has a very low orbital eccentricity, so it is doubtful whether or not its interior could have been warm enough to release gases in the first place to create any initial atmosphere. Titan appears to have a warm interior, mostly driven by radioactive decay, with tidal heating giving only 20% of the moon's interior warmth. Inherently, this radiation would have been stronger during Titan's early days, and could have served to instigate volcanism, creating the initial nitrogen atmosphere of Titan.

tl;dr Ganymede has its own magnetosphere, which repels solar wind, but its thin atmosphere is generated by the radiation. Titan is in Saturn's magnetosphere half the time, and has the potential for an ionosphere to further repel atmosphere-killing radiation. The potentially gaseous elements on Ganymede are H and O, with hydrogen freely leaving Ganymede. Titan has lots of N and organic molecules, which are far heavier than H2, needing more energy to escape. Titan also has a warmer interior that created gas during its early days.

In regards to Tylo and Laythe, it is a game. The Lords and Masters of Tylo decided it was not to be so, and lo! there was no atmosphere.

//holy crap, I love the autosaving of messages... after two more crashes of chrome on the iPad, I apologize to any ill feelings toward VBulletin I may have had and would like to have its babies.

Edited August 6, 2014 by NFUN
Edited for accuracy and clarity

[KerbMav]

Laythe is very close to Jool, so might be shielded from solar winds by its parent's magnetosphere.

Tylo seems to have no water and there is no visible volcanic activity, so there is no source that could produce an atmosphere in the first place.

Laythe only has a thin atmosphere and relatively low gravity - both might be an indication and reason respectively for Jool sucking up gas from Laythe - colonization might only be possible for a few million years then.

[NFUN]

Or, maybe Titan is lonely being the only big moon around Saturn and wants a hug, while Ganymede has 3 other friends, two of which he dances with.

[ThesaurusRex]

Ganymede spends much of its time outside of Jupiter's magnetic field, and because it does not have a magnetosphere of its own capable of repelling much of the solar wind (the wiki page for it is complex for a layman and I'm tired), oxygen can be stripped from the moon (solar wind can give enough energy to gas particles to speed them to escape velocity, heat=vibrations=velocity). The hydrogen naturally escapes Ganymede, as the its gravity is not strong enough to retain the light gas.

But Ganymede has a magnetosphere, and is also embedded in Jupiter's magnetosphere. And Titan is smaller than Ganymede and nitrogen (making up almost the complete dense stratosphere) has less mass than oxygen...O.o

Laythe is very close to Jool, so might be shielded from solar winds by its parent's magnetosphere.

Tylo seems to have no water and there is no visible volcanic activity, so there is no source that could produce an atmosphere in the first place.

Laythe only has a thin atmosphere and relatively low gravity - both might be an indication and reason respectively for Jool sucking up gas from Laythe - colonization might only be possible for a few million years then.

Laythe? A thin atmosphere? What?

[ZetaX]

Oxygen is no use by its own, it is way to reactive. An atmosphere of oxygen would in most cases either react with the planet's material or be blown away. Nitrogen is fine.

[Sky_walker]

There is no special law that makes oxygen be blown away and nitrogen stay on a planet.

[R0cketC0der]

There is no special law that makes oxygen be blown away and nitrogen stay on a planet.

Yes, but oxygen has a lower molecular mass and therefore it needs less energy to escape. Also an asteroid entering the atmosphere could heat it up enough to react with the planet/moon itself.

[Sky_walker]

Yes, but oxygen has a lower molecular mass and therefore it needs less energy to escape.

You mean: this nitrogen ant this oxygen?

The one N₂ that weights 28 g/mol and the one O₂ that weights 32 g/mol? How exactly 32 is less than 28?

Sorry, but my chemistry skills always sucked...

[ZetaX]

You don't need an asteroid, a lot of stuff slowly corrodes in oxygen. Also, no, it does not have lower molecular mass.

Edit: ninja'd.

[R0cketC0der]

You mean: this nitrogen ant this oxygen?

The one N₂ that weights 28 g/mol and the one O₂ that weights 32 g/mol? How exactly 32 is less than 28?

Sorry, but my chemistry skills always sucked...

Sorry, mixed something up there. My mistake.

[KerbMav]

Laythe? A thin atmosphere? What?

80% of Kerbin.

[JtPB]

Tylo is at the same size of Kerbin, and therefore it means it has to have the same mass, that means it has to have an atmosphere. but he doesnt have. why?

[Hannu]

There is not complete set of natural laws in the Kerbal world, from which you can derive answers to physical questions. Only real reason is, that developers had made as much variety in gaming as possible. Large body without atmosphere has its own unique requirements for spaceships, as everybody who have landed to and ascent from Tylo knows.

[Sirrobert]

Since when do all rocks of the same size automaticly have the same atmosphere?

[Pecan]

Size is not important - Tylo is not as dense as Kerbin so, although they are the same size they are not the same mass.

http://wiki.kerbalspaceprogram.com/wiki/Kerbin

http://wiki.kerbalspaceprogram.com/wiki/Tylo

The wiki just says "It is unknown why Tylo hasn't formed an atmosphere." but just making stuff up you could perhaps say somewhere in that different density is the reason. Different rocks that don't out-gass the same way? Hit by one more asteroid that stripped what atmosphere had formed?

[JtPB]

There is not complete set of natural laws in the Kerbal world, from which you can derive answers to physical questions. Only real reason is, that developers had made as much variety in gaming as possible. Large body without atmosphere has its own unique requirements for spaceships, as everybody who have landed to and ascent from Tylo knows.

yep, i know, but as for the current explanations our astronomers have, there's a reasonable one? for example, for the water on laythe despite that it so far from kerbol is probably the resonance of jool's moons' orbits. thats why europa, the moon of jupiter, might has an entire water ocean under its ice cover...

Since when do all rocks of the same size automaticly have the same atmosphere?

they roughly have the same mass, ok? not exactly the same...

Edited August 8, 2014 by JtPB

[MalfunctionM1Ke]

Tylo is at the same size of Kerbin, and therefore it means it has to have the same mass

That is not correct.

The mass of an object is defined by what it is made of.

On second thought, all bodies in KSP are utterly unrealistic by looking at their mass and gravity to serve a greater purpose: Fun and variety.

I.E.:

Uranus is way bigger than Earth but has about 1m/s less gravity than earth.

Venus is slightly smaler than Earth but has the almost the same gravity as uranus.

Sorry for the poor explanation but my intention is that you just cant take a game too serious becaus its sole purpose is to enlight and entertain our flawed human inteligence

Edited August 8, 2014 by MalfunctionM1Ke

[Frank_G]

Because it hasn't!

I find Tylo challenging and a nice addition to the variety of destination worlds. No need to make it more "real" as the rest of the kerbol system isnt too realistic too.

Edit: seems like i am not the only one standing at that point of view ... Good to know.

[Moss]

Could an atmosphere have been stripped away by all the nasty particles in Jool's magnetic field?

[Kasuha]

The real answer of course is: because developers didn't give it one.

But assuming we want to find a "realistic" explanation, the correct question is "how comes Kerbin has atmosphere" because these bodies are so small and light they wouldn't have one in Solar system.

Titan is ten times heavier than Kerbin and it is the lightest body in Solar system which still has some atmosphere.

For comparison, Titan has half the mass of Mercury, yet Titan has atmosphere ten times thicker than Mars and Mercury has none.

Also, of course, solar systems are not exactly stable and Tylo might have traveled as close to Sun as Moho in early phases of Kerbin system formation and might have lost its atmosphere in that phase.

Edited August 8, 2014 by Kasuha

[Wanderfound]

Siphoned off by gas-mining Vogons.

[Kerbart]

Size is not important - Tylo is not as dense as Kerbin so, although they are the same size they are not the same mass.

Tylo's even less dense?