Mutabilis Chapter Five

Jack_H · Post by **Jack_H** » Wed Jun 20, 2007 1:26 am

Looking at titan now. it is not understaood where the atmosphere came from and how it comes to have the composition it dose. They think it is losing it though, but also replenishing it.

Jack_H · Post by **Jack_H** » Wed Jun 20, 2007 1:37 am

Ok, I have kept looking (lunch braek almost over) and the titan atmosphere is likely a result of outgassing or comets, but likely outgassing. due to its low temperature, reactions are slower and there is less thermal energy to ionise the outer atmosphere and sent the molecules flying out. Cassini Hygens will hopefully figure it all out.

So with Venus, either water went out of control until it all evaporated into the atmosphere, or there wasn't any to begin with. either way with no liquid oxygen, there wa sno way to precipitate out the c02 in the air, so it kept on building up, increasing its partial pressure. c02 and water vapour work together to make a nice green house effect.

At least that is the best I can figure it. So gravity is needed to keep the molecules in place (lighter ones like hydrogen escape from venus all the time) and proximiti to the sun makes it easier for the atmosphere to ionise and escape, but the actual pressure one experience at ground level is directly related to the partial pressure of the gases, which doesn't seem to be affected by gravity (though gravity likely places an upper limit on what you can have)

Ok, back to work

Cmdr. Maegil · Post by **Cmdr. Maegil** » Wed Jun 20, 2007 5:09 pm

Then the question isn't about the atmosphere's pressure, but if its composition would still be breathable given that different molecules have different molar masses... Either way, some sort of breathing equipament would still be in order.

EDIT: With this post, I'm the 32nd forum user to become

---- E L I T E ----

I'll be waiting for whomever will introduce me to the hush-hush secret society and teach me the secret handshake.

drdenim · Post by **drdenim** » Wed Jun 20, 2007 6:02 pm

Jack_H wrote:
the actual pressure one experience at ground level is directly related to the partial pressure of the gases, which doesn't seem to be affected by gravity (though gravity likely places an upper limit on what you can have)

air pressure is related to how much of the atmosphere is pushing down on you. so basically how much the air above you weighs...so as a result I'd say that higher gravity would mean higher air pressure

on an interesting side note...moist air is lighter than dry air since water vapor is lighter than much of the molecules in the atmosphere...example oxygen gas is O_2...oxygen has a weight of 16 or so, so O_2 is 32...while water vapor, being composed of one part O [weight 16] and two parts Hydrogen [weight 1] so H2O has a weight of 18 or so...as a result...as strange as it sounds...soggy air is lighter than dry air while a soggy rag is heavier than a dry rag...(yea...I'm a meteorology student and have a tendency to go of on tangents...especially when weather is concerned...haha)

Jack_H · Post by **Jack_H** » Wed Jun 20, 2007 8:19 pm

Just because a planet has a lot of gravity doesn't mean it has to have a big atmosphere. a rocky planets atmosphere can come from within or without, so it has to actually get a big atmosphere before it can use gravity to retain it. ---Gravity is what keeps the air there, it doesn't actually make the air..but having an active planet, with tectonics and volcanoes etc can release 'atmosphere' from within the planet, so a big dead world would likely have little atmosphere, while a big, active planet would likey have more atmosphere, as you say, and have higher air pressure.

drdenim · Post by **drdenim** » Wed Jun 20, 2007 8:24 pm

Jack_H wrote:
Just because a planet has a lot of gravity doesn't mean it has to have a big atmosphere. a rocky planets atmosphere can come from within or without, so it has to actually get a big atmosphere before it can use gravity to retain it. ---Gravity is what keeps the air there, it doesn't actually make the air..but having an active planet, with tectonics and volcanoes etc can release 'atmosphere' from within the planet, so a big dead world would likely have little atmosphere, while a big, active planet would likey have more atmosphere, as you say, and have higher air pressure.

yea...I probably should have specified that that was for planets with atmospheres of similar density...

TGHC · Post by **TGHC** » Thu Jun 21, 2007 12:01 am

Aren't we going a bit OT.

Jack_H · Post by **Jack_H** » Thu Jun 21, 2007 12:33 am

Story of my life

drdenim · Post by **drdenim** » Thu Jun 21, 2007 12:38 am

what's OT stand for?
and by the sound of it...probably...

Cmdr. Maegil · Post by **Cmdr. Maegil** » Thu Jun 21, 2007 5:59 am

@drdenim: OT stands for "Off-Topic".

@TGHC: I don't think it's going OT, the subject of if the planet's atmosphere is breathable or not is an important(ish) realism point. Drew is writing science fiction, right?...

drew · Post by **drew** » Thu Jun 21, 2007 9:00 am

Interesting discussion though!

Yes, it's science fiction, and that is a bit distinct from fantasy. The scenario's should be believeable within the context of the elite/oolite universe and elite/oolite is based on Asimov et al and at least some vaguely plausible physics (weapons, drives, comms, antigravity, distance, witchspace etc)

I think it's a relevant question.

So... can I get away with a 20% o2 atmosphere on a small moon assuming something is replenishing it either by natural processes or artificial? (granted the atmosphere will evaporate off into space over time)

Having facemasks is a bit of a nuisance...

Cheers,

Drew.

Selezen · Post by **Selezen** » Thu Jun 21, 2007 12:10 pm

I just got round to reading it (at last).

Nice work. damn fine twist and a hell of a good way to use that poor, lonely, isolated planet. I also love the way you're using the OXP system in Oolite as part of the plot! That's some great thinking.

Raxxla's shaping up to be one powerful location.

drdenim · Post by **drdenim** » Thu Jun 21, 2007 12:57 pm

Cmdr. Maegil wrote:
@drdenim: OT stands for "Off-Topic".

@TGHC: I don't think it's going OT, the subject of if the planet's atmosphere is breathable or not is an important(ish) realism point. Drew is writing science fiction, right?...

ah...it all makes sense now...or at least the OT...I was trying to force something like Over the Top or something onto it...haha
thanks

drew · Post by **drew** » Thu Jun 21, 2007 1:38 pm

Selezen wrote:
I just got round to reading it (at last).

Nice work. damn fine twist and a hell of a good way to use that poor, lonely, isolated planet. I also love the way you're using the OXP system in Oolite as part of the plot! That's some great thinking.

Raxxla's shaping up to be one powerful location.

Thanks Selezen! I figured that the sudden influx of new ships and technologies needed some kind of 'real world' explanation...

I hope that 'Raxxla' is going to be rather 'non-obvious'. Everything I've seen so far seems to indicate that it is a hidden planet of some kind, which is a bit dull to my way of thinking. If it's somewhere you could travel to directly it would have been found, charted and exploited long ago IMHO...

Hopefully 'my' Raxxla will be a bit more subtle. We'll see!

Cheers,

Drew.

TGHC · Post by **TGHC** » Thu Jun 21, 2007 4:18 pm

According to the Dark Wheel it is a mysterious planet somewhere out there, I have been wondering how you are going to handle this.