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Magnetar
2009-Mar-29, 10:13 AM
Neon is more common than Nitrogen, which our atmosphere is chiefly composed of, yet none of the planets in our solar system have significant quantities of Neon in their atmosphere's.

Suppose a large terrestrial planet had an Earth-like atmosphere, but it's atmosphere was 78% Neon, with the remaining percentages being the same as Earth's.

Now, say we went to explore this planet, would we be able to breath in said atmosphere? And would the atmosphere look like Earth's or different?

chornedsnorkack
2009-Mar-29, 10:31 AM
Neon is more common than Nitrogen, which our atmosphere is chiefly composed of, yet none of the planets in our solar system have significant quantities of Neon in their atmosphere's.

Suppose a large terrestrial planet had an Earth-like atmosphere, but it's atmosphere was 78% Neon, with the remaining percentages being the same as Earth's.

Now, say we went to explore this planet, would we be able to breath in said atmosphere? And would the atmosphere look like Earth's or different?

Depends on what the other components are...

Neon has the property that it is very weakly narcotic. Something like 3,5 times less narcotic than nitrogen.

This means that a man could safely breathe 10 atm neon provided that there is enough oxygen for breathing, not too much oxygen for oxygen poisoning, and not too much other poisonous gases, like nitrogen or argon in amounts to cause narcosis.

As for looks, there is Rayleigh scattering. How would the amount of Rayleigh scattering compare between nitrogen and neon?

antoniseb
2009-Mar-29, 11:00 AM
It might be difficult for an inner planet to have a lot of Neon in its atmosphere, since it has a low boiling point, and wouldn't tend to combine with any of the particles that create the planet.

Magnetar
2009-Mar-29, 11:16 AM
Depends on what the other components are...

When I said:


Suppose a large terrestrial planet had an Earth-like atmosphere, but it's atmosphere was 78% Neon, with the remaining percentages being the same as Earth's.

I meant that I'm essentially taking an Earth atmosphere and replacing all the Nitrogen with Neon, the rest of the gases that make up Earth's atmosphere would be the same with the same percentages they have now.


Neon has the property that it is very weakly narcotic. Something like 3,5 times less narcotic than nitrogen.

This means that a man could safely breathe 10 atm neon provided that there is enough oxygen for breathing, not too much oxygen for oxygen poisoning, and not too much other poisonous gases, like nitrogen or argon in amounts to cause narcosis.

Ok, thanks, that is helpful information.


As for looks, there is Rayleigh scattering. How would the amount of Rayleigh scattering compare between nitrogen and neon?

I have no idea, hence me asking if the atmosphere would look the same.


It might be difficult for an inner planet to have a lot of Neon in its atmosphere, since it has a low boiling point, and wouldn't tend to combine with any of the particles that create the planet.

So, the planet would need to be far away from it's sun so that the Neon wouldn't boil away. Could it be at a distance that the Neon could realistically exist while still not being too far out to be too cold for human inhabitants? Perhaps if the planet formed far out and then migrated inward?

Also I'm curious what the planets escape velocity would need to be in order to retain a thick Neon atmosphere.

eburacum45
2009-Mar-29, 11:21 AM
Jupiter seems to have considerably less Neon than it might have. From
http://en.wikipedia.org/wiki/Neon#Occurrence

Mass abundance in the universe is about 1 part in 750 and in the Sun and presumably in the proto-solar system nebula, about 1 part in 600. The Galileo spacecraft atmospheric entry probe found that even in the upper atmosphere of Jupiter, neon is reduced by about a factor of 10, to 1 part in 6,000 by mass. This may indicate that even the ice-planetesmals which brought neon into Jupiter from the outer solar system, formed in a region which was too warm for them to have kept their neon (abundances of heavier inert gases on Jupiter are several times that found in the Sun).
But the helium content of Jupiter is not similarly depleted, so something odd is going on. It may be the case that gas giant planets in other systems do in fact have levels of neon content which are closer to the universal abundance. But a terrestrial planet would need to be significantly larger (or cooler) than the Earth to have a large neon component in its atmosphere. Someone with the right equations might be able to work out just how much bigger or cooler...

galacsi
2009-Mar-29, 04:49 PM
If such an atmosphere do exist , with high content of neon , there must be some spectacular shows during storms. And as neon is relatively easy to ionize we may have a conducting atmosphere with very strange results. Many small lightnings instead of big one like on earth. And very red ! I am not sure but I think on Earth there is an electric potential in the atmosphere so imagine all the sky glowing faintly red !!! (Too much imagination :D)

trinitree88
2009-Mar-29, 05:11 PM
Neon has a lot of yellow and orange in it's line spectrum, too. Ought to make great thunder & lightning shows. As it's mass is ~ 20 Daltons...and nitrogen is ~ 28, it's density would have it drifting up in the atmosphere a bit, but not beyond earth's gravitational grip. The density gradient would cause a distinct change in voices, and other sounds as the speed of sound would be faster, like it is in helium. Deion Sanders should like it. :shifty::lol: pete


see, spectrum: http://images.google.com/imgres?imgurl=http://hyperphysics.phy-astr.gsu.edu/hbase/quantum/modpic/neoncomp.jpg&imgrefurl=http://hyperphysics.phy-astr.gsu.edu/hbase/quantum/atspect2.html&usg=__VtZ3OkdmJwpo7amrWAyuya5CgUQ=&h=390&w=393&sz=42&hl=en&start=1&tbnid=nsUhrJ4XNkQWOM:&tbnh=123&tbnw=124&prev=/images%3Fq%3Dneon%2Bspectrum%26gbv%3D2%26ndsp%3D20 %26hl%3Den%26sa%3DN

chornedsnorkack
2009-Mar-29, 07:11 PM
As it's mass is ~ 20 Daltons...and nitrogen is ~ 28, it's density would have it drifting up in the atmosphere a bit, but not beyond earth's gravitational grip. The density gradient would cause a distinct change in voices, and other sounds as the speed of sound would be faster, like it is in helium. Deion Sanders should like it. :shifty::lol: pete

Another contribution to sound of speed would be the smaller heat capacity of neon, since it is monatomic.

Mind you, nitrogen might be dissociated into atoms by UV or collisions and escape the atmosphere in that form. Neon cannot.

grant hutchison
2009-Mar-29, 08:13 PM
The density gradient would cause a distinct change in voices, and other sounds as the speed of sound would be faster, like it is in helium.Not all sounds would be affected by a change in the speed of sound.
A resonant cavity (like the one responsible for picking out the dominant frequencies of the human voice) will change its characteristic resonant frequency if it is filled with a different gas mix, and so its pitch will change. But a vibrating string or tympanum will have the same resonant frequency, independent of the atmosphere; so our altered atmosphere will simply transmit the same frequency at a different speed of sound. The wavelength of the sound will therefore change, of course, but our ears respond to frequency, not wavelength.

Grant Hutchison

timb
2009-Mar-29, 09:22 PM
Neon is more common than Nitrogen,

Do you have a source for that claim?

Grashtel
2009-Mar-29, 10:30 PM
Do you have a source for that claim?
According to their Wikipedia pages Neon (http://en.wikipedia.org/wiki/Neon#Occurrence) is the 5th most abundant element and Nitrogen (http://en.wikipedia.org/wiki/Nitrogen#Occurrence) is the 7th.

ngc3314
2009-Mar-30, 02:45 AM
According to their Wikipedia pages Neon (http://en.wikipedia.org/wiki/Neon#Occurrence) is the 5th most abundant element and Nitrogen (http://en.wikipedia.org/wiki/Nitrogen#Occurrence) is the 7th.

Ahh, I get it. Astronomers think of abundance about as often by number as by mass - neon atoms are just about 1.5 times as massive as nitrogen, so there are slightly more nitrogen atoms in a generic galactic mix as neon. This fits with the usual pattern H, He, O, C, N, and Ne coming in just afterward. (The abundances by number enter more directly into interpreting spectra, for example).

Jens
2009-Mar-30, 03:26 AM
Neon has the property that it is very weakly narcotic. Something like 3,5 times less narcotic than nitrogen.


That's the first I've heard of that. Maybe it's best not to broadcast this fact too openly, otherwise politicians might enact laws banning it!

Nick Theodorakis
2009-Mar-30, 03:34 AM
That's the first I've heard of that. Maybe it's best not to broadcast this fact too openly, otherwise politicians might enact laws banning it!

You might have missed his point. It's less narcotic than nitrogen. At elevated pressures (such as those involved during deep sea scuba diving) breathing ordinary air can result in nitrogen narcosis (http://en.wikipedia.org/wiki/Nitrogen_narcosis). Neon would have less of this tendency, although divers doing extended work at great depths might actually use helium mixtures.

Nick

Jens
2009-Mar-30, 03:45 AM
You might have missed his point.

I was really just commenting on the reaction that some people might have to the word narcotic, in general, so didn't really mean anything about the neon/nitrogen comparison.

antoniseb
2009-Mar-30, 06:41 AM
Ahh, I get it. Astronomers think of abundance about as often by number as by mass - neon atoms are just about 1.5 times as massive as nitrogen, so there are slightly more nitrogen atoms in a generic galactic mix as neon. This fits with the usual pattern H, He, O, C, N, and Ne coming in just afterward. (The abundances by number enter more directly into interpreting spectra, for example).

C, O, and Ne are assembled (among other ways) by Helium 'burning'. They are the result of slamming alpha particles together. B, N, and F are a little harder to make in quantity, and the isotope/element abundances bear that out.

Magnetar
2009-Mar-30, 08:22 AM
Do you have a source for that claim?

As Grashtel says:


According to their Wikipedia pages Neon (http://en.wikipedia.org/wiki/Neon#Occurrence) is the 5th most abundant element and Nitrogen (http://en.wikipedia.org/wiki/Nitrogen#Occurrence) is the 7th.

Prior to looking there though, I actually read about it in a book called World Building by Stephen Gillett, and then I looked it up on wikipedia which confirmed what was said in the book.


Not all sounds would be affected by a change in the speed of sound.
A resonant cavity (like the one responsible for picking out the dominant frequencies of the human voice) will change its characteristic resonant frequency if it is filled with a different gas mix, and so its pitch will change. But a vibrating string or tympanum will have the same resonant frequency, independent of the atmosphere; so our altered atmosphere will simply transmit the same frequency at a different speed of sound. The wavelength of the sound will therefore change, of course, but our ears respond to frequency, not wavelength.

Grant Hutchison

Interesting.


The density gradient would cause a distinct change in voices, and other sounds as the speed of sound would be faster, like it is in helium.

What if the atmospheric pressure was higher than it is on Earth? Would that make a difference in terms of how things sound in a Neon atmosphere?

grant hutchison
2009-Mar-30, 08:54 AM
The density gradient would cause a distinct change in voices, and other sounds as the speed of sound would be faster, like it is in helium.What if the atmospheric pressure was higher than it is on Earth? Would that make a difference in terms of how things sound in a Neon atmosphere?The speed of sound is pretty insensitive to atmospheric pressure.
What trinitree88 is talking about (I think) is a difference in density at some standard pressure. That's a surrogate for the mean molecular mass, which bears an inverse relationship to mean molecular velocity, which correlates with speed of sound. So one standard atmosphere of neon will have a lower mass, higher molecular velocity, and therefore higher speed of sound compared to one standard atmosphere of nitrogen. Compressing the neon (at constant temperature) doesn't change its molecular velocity, so doesn't alter the speed of sound.

Grant Hutchison

eburacum45
2009-Mar-30, 09:12 AM
If such an atmosphere do exist , with high content of neon , there must be some spectacular shows during storms. And as neon is relatively easy to ionize we may have a conducting atmosphere with very strange results. Many small lightnings instead of big one like on earth. And very red ! I am not sure but I think on Earth there is an electric potential in the atmosphere so imagine all the sky glowing faintly red !!! (Too much imagination :D)

I would like to see the auroral displays on a planet with a neon atmosphere (with the added proviso that I survive to tell the tale...)

chornedsnorkack
2009-Mar-30, 09:28 AM
The speed of sound is pretty insensitive to atmospheric pressure.
What trinitree88 is talking about (I think) is a difference in density at some standard pressure. That's a surrogate for the mean molecular mass, which bears an inverse relationship to mean molecular velocity, which correlates with speed of sound.
Yes, but since sound propagates adiabatically, speed of sound depends on heat capacity even for a given molecular velocity!

Compressing the neon (at constant temperature) doesn't change its molecular velocity, so doesn't alter the speed of sound.


True.

But something that does depend on pressure is the acoustic impedance, and the contrast of acoustic impedance between air and flesh.

grant hutchison
2009-Mar-30, 09:41 AM
Yes, but since sound propagates adiabatically, speed of sound depends on heat capacity even for a given molecular velocity!Indeed, for the neon/nitrogen comparison, there's also a jigger factor arising from the difference in adiabatic index between monatomic and diatomic gases. That will increase the speed of sound over and above the effect of reducing the mean molecular mass.

Grant Hutchison

neilzero
2009-Mar-30, 10:18 AM
I will attempt a summary, but first a rant. ~20 daltons, boo-hiss. Please, let's do what we can to slow the proliferation of units named after people. Did any of us decide on a career in science in hopes of getting a unit named after us? = Very little motivation, but the thousands of units that need to be learned to get an engineering degree is definitely a deterrent and makes most people think egotistical nerds. The MKS system unit for density is kilograms per cubic meter. An other approach is the atomic weight, which works well for true gas, especially noble gas such as neon = 20 and helium = 4. So neon has 5 times the density of helium under the same pressure and temperature. The squeaky voice should be barely noticeable breathing neon with the optimum amount of oxygen.
We think the planets start to form before the proto sun gets very hot, but my guess is ambient temperature on the protoplanet surface is above the boiling point of neon = -246 c, so the low boiling point likely has little effect. In some simulations the surface is 1000 c = 1832 f due to bombarding accretion. The "does not combine with other elements" does not seem to have hindered Earth having almost 1% argon. Neil

grant hutchison
2009-Mar-30, 10:42 AM
I will attempt a summary, but first a rant. ~20 daltons, boo-hiss. Please, let's do what we can to slow the proliferation of units named after people. Did any of us decide on a career in science in hopes of getting a unit named after us? = Very little motivation, but the thousands of units that need to be learned to get an engineering degree is definitely a deterrent and makes most people think egotistical nerds. The MKS system unit for density is kilograms per cubic meter. An other approach is the atomic weight, which works well for true gas, especially noble gas such as neon = 20 and helium = 4.And what are the units for those atomic weights you've just quoted? :lol:

Grant Hutchison

antoniseb
2009-Mar-30, 10:42 AM
The "does not combine with other elements" does not seem to have hindered Earth having almost 1% argon. Neil

...Except that the Argon we have here is a decay product of a fairly long-lived isotope of Potassium, and not something that got here as a noble gas originally.

Magnetar
2009-Mar-30, 12:38 PM
Lots of interesting info, thanks for all the input everyone, feel free to continue to chime in with any other thoughts you have.

And if anyone knows what the planets escape velocity would need to be in order to retain a thick Neon atmosphere, I'm still interested in that as well.

antoniseb
2009-Mar-30, 01:04 PM
... if anyone knows what the planets escape velocity would need to be in order to retain a thick Neon atmosphere, I'm still interested in that as well.

That depends on the Temperature, but an Earth-sized planet at Earth's temperature, with a good magnetic field to protect it from solar wind, should be plenty.

chornedsnorkack
2009-Mar-30, 01:28 PM
That depends on the Temperature,
Not really...

How do you decide when a planet would retain a dense nitrogen atmosphere?

The energy of a molecule is proportional to temperature.

The solar constant is proportional to inverse square of distance to Sun. And black body radiation is proportional to fourth power of temperature. Therefore the temperature is proportional to inverse square root of distance to Sun, and so is energy of molecules.

Therefore the speed of molecules is proportional to inverse fourth root of distance to Sun.

Mars is roughly 6 times closer to Sun than Saturn. Therefore the nitrogen molecules in the atmosphere of Mars should be about 1,6 times faster than the molecules in the atmosphere of Titan.

Yet the escape speed of Mars is 1,9 times the escape speed of Titan.

Why then does Titan have a thick mass of nitrogen (1,6 bar) yet Mars has a very sparse nitrogen amount (200 microbars)?

Note that if a body is significantly smaller than Earth and less dense, with escape speed barely high enough to retain a massive neon atmosphere (like Titan), then the neon atmosphere would have large thickness for a given surface pressure (and therefore scatter a lot of light). Low gravity and dense atmosphere would also favour flying.

grant hutchison
2009-Mar-30, 01:39 PM
That depends on the Temperature, but an Earth-sized planet at Earth's temperature, with a good magnetic field to protect it from solar wind, should be plenty.Yes, neon seems to be heavy enough for the Earth to retain for geological timescales.
So I'm guess its rarity on Earth relates to its inertness and lightness relative to other chemical compounds that formed in the solar nebula: the Earth formed with very little neon, rather than losing it later.

Grant Hutchison

grant hutchison
2009-Mar-30, 01:44 PM
That depends on the Temperature,Not really...It really does. :)
But of course it also depends on other things (http://journals.cambridge.org/action/displayAbstract;jsessionid=D3A6CF745B9A677D1866603 F50C521FD.tomcat1?fromPage=online&aid=191609), too, as I'm sure antoniseb would agree.

Grant Hutchison

Magnetar
2009-Mar-30, 01:54 PM
Any thoughts on the atmospheric color? Would it be the same as with nitrogen or different?

antoniseb
2009-Mar-30, 01:57 PM
... it also depends on other things (http://journals.cambridge.org/action/displayAbstract;jsessionid=D3A6CF745B9A677D1866603 F50C521FD.tomcat1?fromPage=online&aid=191609), too, as I'm sure antoniseb would agree. ...
I certainly would!

grant hutchison
2009-Mar-30, 01:59 PM
Any thoughts on the atmospheric color? Would it be the same as with nitrogen or different?Neon itself is colourless, so the colour produced by neon gas will be from Rayleigh scattering. In an otherwise Earthlike atmosphere, that should produce something pretty similar to the blue shade of Earth's sky.

Grant Hutchison

chornedsnorkack
2009-Mar-30, 02:19 PM
Neon itself is colourless, so the colour produced by neon gas will be from Rayleigh scattering. In an otherwise Earthlike atmosphere, that should produce something pretty similar to the blue shade of Earth's sky.


But of course depending on thickness. Just as the colour of sky is different at horizon, and different again at sunset or sunrise.

How does the strength of Rayleigh scattering, in a given amount of neon, compare against nitrogen?

grant hutchison
2009-Mar-30, 04:00 PM
How does the strength of Rayleigh scattering, in a given amount of neon, compare against nitrogen?The Rayleigh scattering cross section for neon is about a 20th of that for nitrogen, so we can expect a similar change in optical thickness at one bar. So for an Earth-like scale height, we'd have a darker zenith and a bluer horizon.

Grant Hutchison

eburacum45
2009-Mar-30, 05:22 PM
That's useful to know. Thanks.
(a similar effect would apply to a hydrogen/helium atmosphere too, I presume).

grant hutchison
2009-Mar-30, 05:38 PM
That's useful to know. Thanks.Difficult information to track down. :)
I dug it out of an old NASA technical note (http://ntrs.nasa.gov/archive/nasa/casi.ntrs.nasa.gov/19770012747_1977012747.pdf) (1.5MB pdf) some time ago.

(a similar effect would apply to a hydrogen/helium atmosphere too, I presume).As you'll see from the tables in my reference, hydrogen is a better scatterer than neon, but helium has a very low Rayleigh scattering cross section.

Grant Hutchison

chornedsnorkack
2009-Mar-30, 06:09 PM
Very interesting. So, a neon atmosphere is clearer than hydrogen-helium one.

How much absorption would there be in a hydrogen-helium atmosphere that is thick and opaque to Rayleigh scattering?

What about helium/neon atmosphere?

eburacum45
2009-Mar-31, 06:15 AM
Helium-neon atmospheres seem unlikely, but from Grant's link the scattering values at 3638 angstroms are as follows
N2 33.4
O2 27.9
Ne 1.71
He 0.49
H2 6.62
CO2 7.82
etc

I was looking for, and signally failed to find, that same information, so well done, Grant.
Helium/neon atmospheres would scatter less than helium ones, which are low on the list anyway.
Hydrogen atmospheres scatter less than nitrogen ones, but the deeper you go in a gas giant's atmosphere the greater the density, so the whiter the sky.

Figure 5 in Craig Bohren's paper about the subject is very instructive in that regard, in my opinion;
http://homepages.wmich.edu/%7Ekorista/atmospheric_optics.pdf
.
.

antoniseb
2009-Mar-31, 06:50 AM
Another side effect would be that hot internal combustion engines would not produce Nitrogen-Oxides as pollutants in such an atmosphere.

eburacum45
2009-Mar-31, 07:00 AM
Nitrogen is a vital part of all CHON life; agriculture on such a world would require a lot of imported fertiliser.

chornedsnorkack
2009-Mar-31, 07:19 AM
Nitrogen is a vital part of all CHON life; agriculture on such a world would require a lot of imported fertiliser.

How do the terrestrial nitrogen fixers handle low but nonzero chemical potential of molecular nitrogen?

Mars has just 200 microbars nitrogen, 4000 times less than Earth. Suppose that you could terraform Mars by releasing carbon dioxide from polar caps and then photosyntesizing away the carbon so that Mars has an atmosphere of over 90 % oxygen (over 100 millibars) and still the same 200 microbars (under 0,2 %) of nitrogen. How would nitrogen fixers handle it?

eburacum45
2009-Mar-31, 07:22 AM
I'd import nitrogen in the form of ammonia ices from the Centaur belt to fertilise Mars. Titan has a lot of nitrogen too, but you have to dig it out of Titan's gravity well.

Magnetar
2009-Mar-31, 10:38 AM
Would a neon atmosphere pose any problems for a worldwide ocean?

Nick Theodorakis
2009-Mar-31, 01:32 PM
How do the terrestrial nitrogen fixers handle low but nonzero chemical potential of molecular nitrogen?
...

They pump a whole lot of energy into the reaction; nitrogenase (http://en.wikipedia.org/wiki/Nitrogenase) uses 16 ATPs to convert one molecule of nitrogen to ammonia.

Nick

chornedsnorkack
2009-Mar-31, 04:31 PM
Would a neon atmosphere pose any problems for a worldwide ocean?

Cannot see any.

Would it be nice if the ocean were rich in heavy water, compared to Earth´s?

Magnetar
2009-Mar-31, 06:11 PM
Cannot see any.

Would it be nice if the ocean were rich in heavy water, compared to Earth´s?

That might be interesting, why do you ask?

chornedsnorkack
2009-Mar-31, 06:18 PM
That might be interesting, why do you ask?

Because I thought that the formation of a neon atmosphere might produce heavy water...

Note that the sulphuric acid of Venus´ clouds is remarkably rich in deuterium. Where did it come from?

antoniseb
2009-Mar-31, 06:23 PM
Because I thought that the formation of a neon atmosphere might produce heavy water...

Note that the sulphuric acid of Venus´ clouds is remarkably rich in deuterium. Where did it come from?

Most likely because the light Hydrogen boiled off faster than the heavy Hydrogen. Venus is very deficient in that element.

chornedsnorkack
2009-Mar-31, 06:37 PM
Most likely because the light Hydrogen boiled off faster than the heavy Hydrogen. Venus is very deficient in that element.

I suspected it.

Now, imagine that there is an object which is a small gas giant in the early history - smaller than Uranus, but cold enough to accrete a massive hydrogen-helium atmosphere - and then it migrates inwards. Till it is hot enough that molecular hydrogen does escape.

If the hydrogen escapes then deuterium would escape slower. You could get an early atmosphere which is mostly helium (helium escapes slower than protium) and a secondary component of dideuterium. Which would react with diprotium monoxide vapour... the heavy water would rain back into ocean, and the protium would promptly escape.

The helium-neon atmosphere would also decay, leaving behind an atmosphere of neon, argon and other gases slightly too heavy to escape. Argon is less common in space than neon. And dioxygen but also dinitrogen are more readily absorbed by rock and iron.

Magnetar
2009-Apr-01, 02:15 PM
I suspected it.

Now, imagine that there is an object which is a small gas giant in the early history - smaller than Uranus, but cold enough to accrete a massive hydrogen-helium atmosphere - and then it migrates inwards. Till it is hot enough that molecular hydrogen does escape.

If the hydrogen escapes then deuterium would escape slower. You could get an early atmosphere which is mostly helium (helium escapes slower than protium) and a secondary component of dideuterium. Which would react with diprotium monoxide vapour... the heavy water would rain back into ocean, and the protium would promptly escape.

The helium-neon atmosphere would also decay, leaving behind an atmosphere of neon, argon and other gases slightly too heavy to escape. Argon is less common in space than neon. And dioxygen but also dinitrogen are more readily absorbed by rock and iron.

How large would the planet have to be for that to occur do you think? "Smaller than Uranus," is somewhat vague.

timb
2009-Apr-01, 02:27 PM
According to their Wikipedia pages Neon (http://en.wikipedia.org/wiki/Neon#Occurrence) is the 5th most abundant element and Nitrogen (http://en.wikipedia.org/wiki/Nitrogen#Occurrence) is the 7th.

I thought so. And their only reference is a popular science book. Has anyone seen this in a standard reference or refereed paper?

grant hutchison
2009-Apr-01, 02:30 PM
I thought so. And their only reference is a popular science book. Has anyone seen this in a standard reference or refereed paper?Will Allen's Astrophysical Quantities do? They list neon as marginally more abundant than nitrogen.

Grant Hutchison

timb
2009-Apr-01, 02:56 PM
Not really...

How do you decide when a planet would retain a dense nitrogen atmosphere?

The energy of a molecule is proportional to temperature.

... <snip ingenious calculation>

Why then does Titan have a thick mass of nitrogen (1,6 bar) yet Mars has a very sparse nitrogen amount (200 microbars)?


The dominant escape processes are generally not thermal. Absorbtion of solar EUV photons and collisions with particles in the solar wind are generally what give atoms in a planet's exosphere the kick they need to escape.



Note that if a body is significantly smaller than Earth and less dense, with escape speed barely high enough to retain a massive neon atmosphere (like Titan), then the neon atmosphere would have large thickness for a given surface pressure (and therefore scatter a lot of light). Low gravity and dense atmosphere would also favour flying.

That reads like something I might post from a dense atmosphere of herb vapor. Titan does not have a massive neon atmosphere and how does flying have anything to do with the thermal escape of neon? I don't think an extremely cold body like Titan with a massive inert atmosphere is a plausible habitat for flying animals.

chornedsnorkack
2009-Apr-01, 03:43 PM
That reads like something I might post from a dense atmosphere of herb vapor. Titan does not have a massive neon atmosphere
No, but Titan does have a massive nitrogen atmosphere compared to other bodies of similarly feeble gravity like Ganymede, Mars and Moon.


and how does flying have anything to do with the thermal escape of neon?
Flying is favoured by feeble gravity - so long as that feeble gravity does not lead to thermal escape of atmosphere

I don't think an extremely cold body like Titan with a massive inert atmosphere is a plausible habitat for flying animals.

An extremely cold body not. But a body which is somewhat bigger than Titan, and appreciably warmer - but still appreciably smaller than Earth - might be.

Magnetar
2009-Apr-01, 04:09 PM
I don't think an extremely cold body like Titan with a massive inert atmosphere is a plausible habitat for flying animals.

How is it you think Titan's atmosphere is inert? Titan has cryovolcanic eruptions, hydrocarbon rain, and even seasonal weather patterns.

If a human could survive on Titan they could take some fake wings and fly, under their own power, around the atmosphere easily due to it's thickness and the low gravity.

grant hutchison
2009-Apr-01, 04:49 PM
How is it you think Titan's atmosphere is inert? Titan has cryovolcanic eruptions, hydrocarbon rain, and even seasonal weather patterns.Chemically inert, I think. :)

Grant Hutchison

Magnetar
2009-Apr-01, 05:01 PM
Chemically inert, I think. :)

Grant Hutchison

Reference?

grant hutchison
2009-Apr-01, 05:02 PM
Will Allen's Astrophysical Quantities do? They list neon as marginally more abundant than nitrogen.More on this. AAQ uses Anders & Grevesse Abundance of the elements: Meteoritic and solar (http://adsabs.harvard.edu/abs/1989GeCoA..53..197A) (1989).
They in turn list a few other sources as well as their own estimates, all of which place Ne marginally ahead of N. The particular values quoted by AAQ are relative to a log abundance of H = 12. On that scale, N is given a log abundance of 8.05, while Ne scores 8.09.

Grant Hutchison

grant hutchison
2009-Apr-01, 05:22 PM
Reference?It's 98% nitrogen.

Grant Hutchison

timb
2009-Apr-01, 10:25 PM
How is it you think Titan's atmosphere is inert? Titan has cryovolcanic eruptions, hydrocarbon rain, and even seasonal weather patterns.


I don't think Titan's atmosphere is inert. Chorn hypothesized a planet like Titan with a massive neon atmosphere.

timb
2009-Apr-01, 11:12 PM
More on this. AAQ uses Anders & Grevesse Abundance of the elements: Meteoritic and solar (http://adsabs.harvard.edu/abs/1989GeCoA..53..197A) (1989).
They in turn list a few other sources as well as their own estimates, all of which place Ne marginally ahead of N. The particular values quoted by AAQ are relative to a log abundance of H = 1012. On that scale, N is given a log abundance of 8.05, while Ne scores 8.09.


Thanks for looking that up. My query was prompted by the fact that I have seen posted here several times statements that all the (solar) planets are deficient in Neon. This could be compensated for by a slight overabundance in the Sun though.

grant hutchison
2009-Apr-01, 11:22 PM
Thanks for looking that up.No worries. It was the first thing I did when I read the OP. :)
Isn't it interesting how mistakes show up better in quotes from one's original post than when one proofs the post itself? I only now notice that I should have written "relative to a log abundance of H = 12"; I've corrected the original.

Grant Hutchison

Magnetar
2009-Apr-02, 01:44 PM
I don't think Titan's atmosphere is inert. Chorn hypothesized a planet like Titan with a massive neon atmosphere.

Ah, so you meant if it had a neon atmosphere it would be, got it, your wording didn't really express that very well.


It's 98% nitrogen.

I'm aware of that. Surely there are chemical interactions taking place with the methane and such that make up the other 2% though. I've never seen, the entire atmosphere of, Titan listed as chemically inert so I was just curious.

grant hutchison
2009-Apr-02, 02:39 PM
It's 98% nitrogen.I'm aware of that.Ah. Your wording didn't really express that very well. ;)


Surely there are chemical interactions taking place with the methane and such that make up the other 2% though.Surely. But timb's remark was made in the context of suitable habitats for flying animals. Although I misunderstood his intention, I'd submit that a 98% nitrogen atmosphere is almost as poor a habitat for flying animals as a 100% neon atmosphere, and for the same reason: its gross thermodynamic stability.

Grant Hutchison

Magnetar
2009-Apr-02, 04:24 PM
Ah. Your wording didn't really express that very well. ;)

Surely. But timb's remark was made in the context of suitable habitats for flying animals. Although I misunderstood his intention, I'd submit that a 98% nitrogen atmosphere is almost as poor a habitat for flying animals as a 100% neon atmosphere, and for the same reason: its gross thermodynamic stability.

Grant Hutchison

You are funny. :-P Please elaborate on why thermodynamic stability in an atmosphere would make for a poor habitat for flying animals.

And my hypothetical atmosphere in this topic is not 100% Neon, it is 75% give or take a few percent, Neon with 25% oxygen, and other gases.

Another question, in regards to the lightning and auroral displays being interesting in a Neon atmosphere, would the lightning itself be red/orange, or would it still look white and have a sort of glow to it, or what? And would the auroral displays be completely red/orange or would those just be the most prominent colors?

grant hutchison
2009-Apr-02, 06:18 PM
Please elaborate on why thermodynamic stability in an atmosphere would make for a poor habitat for flying animals.Flying is energy-intensive, so flying animals on Earth are all strongly aerobic with high metabolic rates. They depend on chemical reactions, fired by oxygen, to release large quantities of energy continuously.
Unlike oxygen, nitrogen is at the bottom of a thermodynamic hole: getting it to react with other chemicals usually requires an input of energy.
With such an inert atmosphere, albeit containing a trickle of complicated carbon/nitrogen chemistry fueled by incoming solar photons and charged particles, where can our flying animals get their energy?

Grant Hutchison

chornedsnorkack
2009-Apr-02, 08:15 PM
Flying is energy-intensive, so flying animals on Earth are all strongly aerobic with high metabolic rates. They depend on chemical reactions, fired by oxygen, to release large quantities of energy continuously.
Unlike oxygen, nitrogen is at the bottom of a thermodynamic hole: getting it to react with other chemicals usually requires an input of energy.
With such an inert atmosphere, albeit containing a trickle of complicated carbon/nitrogen chemistry fueled by incoming solar photons and charged particles, where can our flying animals get their energy?


Why, from oxygen!

In 1 atmosphere of 21 % oxygen and the rest nitrogen, 1 l of air contains 210 ml (1 atm 100 %) oxygen, and weighs about 1,3 g total.

In equilibrium with 1 atm of 21 % oxygen, 1 l of fresh water at 25 Celsius contains 8 mg oxygen, which is about 6 ml 1 atm 100 % oxygen. 35 times less than the same volume of air - and it weight 770 times more. Water has 30 000 times more mass per unit amount of oxygen. Salt water holds even less oxygen.

I have a strong suspicion that an 10 atm atmosphere of 98 % neon and 2 % (0,2 atm) oxygen would be fairly comfortable for obligatory aerobes. And far easier to breathe than water, still.

grant hutchison
2009-Apr-02, 08:51 PM
Why, from oxygen!
...
I have a strong suspicion that an 10 atm atmosphere of 98 % neon and 2 % (0,2 atm) oxygen would be fairly comfortable for obligatory aerobes. And far easier to breathe than water, still.Ummm... I get the feeling you're not really tracking the conversation, here. :)
Magnetar and I were talking about Titan. Titan has a 1.5-bar atmosphere consisting almost entirely of nitrogen, with a little methane, less argon and hydrogen, and a host of very minor exotica from photodissociation. No oxygen.

The point is that an atmosphere which is at (or close to) chemical equilibrium doesn't provide a useful energy source for active animals. Saying "Why, from oxygen!" is just a way of saying, "I choose that my atmosphere is chemically active!"

Grant Hutchison

Magnetar
2009-Apr-02, 09:33 PM
Ummm... I get the feeling you're not really tracking the conversation, here. :)
Magnetar and I were talking about Titan. Titan has a 1.5-bar atmosphere consisting almost entirely of nitrogen, with a little methane, less argon and hydrogen, and a host of very minor exotica from photodissociation. No oxygen.

The point is that an atmosphere which is at (or close to) chemical equilibrium doesn't provide a useful energy source for active animals. Saying "Why, from oxygen!" is just a way of saying, "I choose that my atmosphere is chemically active!"

Grant Hutchison

I was actually talking about both Titan and about a hypothetical terrestrial planet that supported a neon/oxygen atmosphere.

Chornedsnorkack was addressing the latter. Which is mostly what I'm interested in, and only got on the subject of Titan due to timb.

Also, if we're talking hypothetical environments on alien worlds it is possible for the alien organisms to gain their energy from a different source then oxygen chemical interaction.

grant hutchison
2009-Apr-02, 09:55 PM
I was actually talking about both Titan and about a hypothetical terrestrial planet that supported a neon/oxygen atmosphere.You asked for clarification on a "thermodynamically stable" atmosphere. At that point I do believe you stopped talking about a neon/oxygen atmosphere. :)
But we seem to be galloping in ever-widening circles, here, and I'm not sure why.


Also, if we're talking hypothetical environments on alien worlds it is possible for the alien organisms to gain their energy from a different source then oxygen chemical interaction.For sure. Your flying creatures could come with batteries, in which case they could fly in 100% neon.
The point raised by timb was simply whether a cold, inert atmosphere was a plausible habitat for flying animals. And I'm certainly not the first to note that what keeps animals on Earth alive is a profound chemical disequilibrium in the atmosphere. Animal life as we understand it needs chemical disequilibrium, there are a limited number of places that can host such disequilibrium, and an inert atmosphere shuts down a very major option.

Why does that seem to have triggered such a mind-meltingly complicated conversation? :lol:

Grant Hutchison

Magnetar
2009-Apr-02, 11:43 PM
You asked for clarification on a "thermodynamically stable" atmosphere. At that point I do believe you stopped talking about a neon/oxygen atmosphere.
But we seem to be galloping in ever-widening circles, here, and I'm not sure why.

In the very same post where I asked about that I said:


And my hypothetical atmosphere in this topic is not 100% Neon, it is 75% give or take a few percent, Neon with 25% oxygen, and other gases.

So, as I said, I was talking about both Titan and my hypothetical planet with the Neon/Oxygen atmosphere.


For sure. Your flying creatures could come with batteries, in which case they could fly in 100% neon.
The point raised by timb was simply whether a cold, inert atmosphere was a plausible habitat for flying animals. And I'm certainly not the first to note that what keeps animals on Earth alive is a profound chemical disequilibrium in the atmosphere. Animal life as we understand it needs chemical disequilibrium, there are a limited number of places that can host such disequilibrium, and an inert atmosphere shuts down a very major option.

Why does that seem to have triggered such a mind-meltingly complicated conversation?

And my point is that we do not know everything there is to know about the universe. There could be alien organisms out there that get their energy in ways that we could never even imagine. So, saying that all life is going to need the set up you describe to function is not only unsupportable factually, but an assumption at best.

Also, repeating myself for about the 4th time now, the atmosphere I am concerned with would have 75% Neon and around 25% Oxygen.

I do appreciate your continued input by the way.

timb
2009-Apr-02, 11:44 PM
Maybe they could be like little furry rockets. A dense atmosphere makes flying easier, but that has nothing to do with whether it is composed of neon.

To try and hobble the galloping horse, no small body that we know of has a significant amount of neon in its atmosphere and there's probably a good reason for this. Whether neon is genuinely depleted in gas giants or has settled appears to be an open question.

Magnetar
2009-Apr-02, 11:51 PM
Maybe they could be like little furry rockets. A dense atmosphere makes flying easier, but that has nothing to do with whether it is composed of neon.

To try and hobble the galloping horse, no small body that we know of has a significant amount of neon in its atmosphere and there's probably a good reason for this. Whether neon is genuinely depleted in gas giants or has settled appears to be an open question.

That brings to mind a question. I'm sure there are a number of things we look at to determine the internal composition of the gas giants in our solar system, however...

Neon is heavier than Hydrogen and Helium, which is what most of the gas giants are chiefly composed of, from what we can tell. Could it not be possible that the Neon is simply closer to the core of the planets, since it is heavier, like our core is composed of the heavier elements of our planet?

Because, as far as I'm aware, we're not entirely sure what any of the cores of the gas giants are composed of, we have theories of course, but what is to say there isn't a good quantity of Neon down there?

Thoughts?

galacsi
2009-Apr-03, 11:02 AM
That brings to mind a question. I'm sure there are a number of things we look at to determine the internal composition of the gas giants in our solar system, however...

Neon is heavier than Hydrogen and Helium, which is what most of the gas giants are chiefly composed of, from what we can tell. Could it not be possible that the Neon is simply closer to the core of the planets, since it is heavier, like our core is composed of the heavier elements of our planet?

Because, as far as I'm aware, we're not entirely sure what any of the cores of the gas giants are composed of, we have theories of course, but what is to say there isn't a good quantity of Neon down there?

Thoughts?

You may be right . I remember a theory explaining the extra heat radiated by Jupiter by segregation of Helium from Hydrogen under the huge gravity of the planet. So what can be true for Helium must be truer for neon. You have a point.

grant hutchison
2009-Apr-03, 11:34 AM
And my point is that we do not know everything there is to know about the universe. There could be alien organisms out there that get their energy in ways that we could never even imagine. So, saying that all life is going to need the set up you describe to function is not only unsupportable factually, but an assumption at best.Well, since I seem to have found myself trying to explain something timb didn't actually say, I think I'll just not get into discussion on that one. :)

Grant Hutchison

timb
2009-Apr-03, 11:45 AM
That brings to mind a question. ...what is to say there isn't a good quantity of Neon down there?


I'm glad what I posted brought that to your mind, if not quite as directly as I intended. When I suggested that the neon might have "settled" I was suggesting that it had sunk into Jupiter's interior.

timb
2009-Apr-03, 11:46 AM
Well, since I seem to have found myself trying to explain something timb didn't actually say, I think I'll just not get into discussion on that one. :)


I for one agree with what it is you thought I said.

chornedsnorkack
2009-Apr-03, 12:08 PM
If a human could survive on Titan they could take some fake wings and fly, under their own power, around the atmosphere easily due to it's thickness and the low gravity.
Humans can take certain fake wings and fly under their own power here on Earth. But not easily.

Like MIT Daedalus, that escaped Crete. It weighed 32 kg empty - 104 kg with the human. Wingspan 34 m, wing area 30 square m.

This kind of long and slim wing, like that of a glider, is the one that provides least air drag. The plane flew slowly, so the actual power input required was affordable. I think bikers usually think they can sustain work output of 250 watts, or 1/3 horsepower.

What if the atmosphere were denser? Say, someone were to terraform Venus, get rid of that nasty carbon dioxide, and add the necessary amount of oxygen - leaving 3,2 atm nitrogen still there. (Well, it would be a bit much, and cause chronic mild nitrogen narcosis).

Venus has a bit smaller gravity than Earth et cetera. To get simpler numbers, let us assume a planet with exactly 1 g gravity and exactly 4 times denser atmosphere than Earth.

The selfsame MIT Daedalus would take off at half the speed it needed on Earth. Since the weight and drag would be the same, our biker could fly on a rather more leisurely stroll.

Alternatively, you might build a plane half the size of MIT Daedalus - 17 m wingspan, 7,5 square m wing area. It could take off at the same speed and effort as MIT Daedalus... but the effort of building it would be much less.

Now, suppose that you were to terraform Mars. That is, exactly 1 atm atmosphere, but, say, 0,36 g surface gravity.

In 0,36 g surface gravity, a plane will take off at 0,6 times the speed... and suffer 0,36 times the drag. So, the total power needed would be 0,216 times what was needed on Earth. Again, you could use it to take your flights in leisure - or manage to build and fly a more primitive and smaller plane. On Mars, you could fly faster, too.

Those physical scaling arguments apply to biological animals along with manmade structures.

timb
2009-Apr-03, 12:33 PM
Humans can take certain fake wings and fly under their own power here on Earth. But not easily.


Yes, but those devices were not even ornithopters, they had airscrews. The claim I've read regarding Titan is a man could fly like a bird there by flapping his arms, assuming he was magically protected from freezing solid.


....
Say, someone were to terraform Venus, get rid of that nasty carbon dioxide, and add the necessary amount of oxygen - leaving 3,2 atm nitrogen still there. (Well, it would be a bit much, and cause chronic mild nitrogen narcosis).


I'm sure that would be a party planet, but it is more plausible to genetically modify a human to fly on Earth than to terraform Mars or Venus. A more likely outlet for your speculations would be indoor arenas on the Moon. There the gravity would be one sixth g and the air density presumably atmospheric.

Interesting calculations, BTW.

grant hutchison
2009-Apr-03, 01:08 PM
Maybe they could be like little furry rockets.Yeah. :)
That'd get around the problem of an inert atmosphere, if there were some sort of exploitable disequilibrium at the surface. Eat your oxidant at one place, eat your fuel at another place. (Probably best to use different mouths for that.) Then mix them internally and blast off.
It's a more spectacular version of where I was going with my internal batteries suggestion.

Grant Hutchison

Magnetar
2009-Apr-03, 03:13 PM
You may be right . I remember a theory explaining the extra heat radiated by Jupiter by segregation of Helium from Hydrogen under the huge gravity of the planet. So what can be true for Helium must be truer for neon. You have a point.

Thanks. :-)


I'm glad what I posted brought that to your mind, if not quite as directly as I intended. When I suggested that the neon might have "settled" I was suggesting that it had sunk into Jupiter's interior.

Indeed, it is an interesting possibility to consider, maybe one day in the far future we'll know for sure.


Humans can take certain fake wings and fly under their own power here on Earth. But not easily.

Like MIT Daedalus, that escaped Crete. It weighed 32 kg empty - 104 kg with the human. Wingspan 34 m, wing area 30 square m.

This kind of long and slim wing, like that of a glider, is the one that provides least air drag. The plane flew slowly, so the actual power input required was affordable. I think bikers usually think they can sustain work output of 250 watts, or 1/3 horsepower.

What if the atmosphere were denser? Say, someone were to terraform Venus, get rid of that nasty carbon dioxide, and add the necessary amount of oxygen - leaving 3,2 atm nitrogen still there. (Well, it would be a bit much, and cause chronic mild nitrogen narcosis).

Venus has a bit smaller gravity than Earth et cetera. To get simpler numbers, let us assume a planet with exactly 1 g gravity and exactly 4 times denser atmosphere than Earth.

The selfsame MIT Daedalus would take off at half the speed it needed on Earth. Since the weight and drag would be the same, our biker could fly on a rather more leisurely stroll.

Alternatively, you might build a plane half the size of MIT Daedalus - 17 m wingspan, 7,5 square m wing area. It could take off at the same speed and effort as MIT Daedalus... but the effort of building it would be much less.

Now, suppose that you were to terraform Mars. That is, exactly 1 atm atmosphere, but, say, 0,36 g surface gravity.

In 0,36 g surface gravity, a plane will take off at 0,6 times the speed... and suffer 0,36 times the drag. So, the total power needed would be 0,216 times what was needed on Earth. Again, you could use it to take your flights in leisure - or manage to build and fly a more primitive and smaller plane. On Mars, you could fly faster, too.

Those physical scaling arguments apply to biological animals along with manmade structures.

Thanks for the calculations and exposition.

Nick Theodorakis
2009-Apr-03, 03:36 PM
Yeah. :)
That'd get around the problem of an inert atmosphere, if there were some sort of exploitable disequilibrium at the surface. Eat your oxidant at one place, eat your fuel at another place. (Probably best to use different mouths for that.) Then mix them internally and blast off.
It's a more spectacular version of where I was going with my internal batteries suggestion.

Grant Hutchison

Your almost describing a defense mechanism used by the bomardier beetle (http://en.wikipedia.org/wiki/Bombardier_beetle), which mixes peroxide and quinones to generate a violently exothermic reaction to spray at predators.

Nick

chornedsnorkack
2009-Apr-03, 04:24 PM
The claim I've read regarding Titan is a man could fly like a bird there by flapping his arms, assuming he was magically protected from freezing solid.


A more likely outlet for your speculations would be indoor arenas on the Moon. There the gravity would be one sixth g and the air density presumably atmospheric.


The air density is freely chosen by builders subject to constraints of human physiology and structural considerations.

Roughly how many g-s can an unaided human develop flying/swimming in air?

There are considerations why builders on Moon would do well to have more than atmospheric air density.

The pressure of atmosphere must match the weight of the roof. Otherwise the roof would need to bear its weight, which it can only do for small spans.

1 atm of air in Moon´s gravity will carry the weight of 65 m layer of water, or maybe 20 m of solid dense rock, or a few tens of m of porous regolith. But a layer of dense airtight rock floating on less dense air is inherently unstable against buckling which would cause it to crack and collapse. All that holds it against collapse is its strength and stiffness to bending.

By building deeper and holding higher pressures inside, the roof is made thicker and therefore more resistant to buckling failure. And human physiology indeed allows having higher pressures, especially if the inert gases are neon and helium rather than nitrogen. Plus, it would be nice to use organic materials. Wet flesh and hair are not awfully flammable in 20 % oxygen, but restricting oneself to asbestos and glassfiber clothes et cetera is inconvenient... see Apollo 1. If you can have oxygen concentrations of 10 % or 5 % and the rest inert diluents like nitrogen or helium to absorb and carry away heat from ignition sources, then sustaining fire will get that much harder.

grant hutchison
2009-Apr-03, 05:47 PM
Your almost describing a defense mechanism used by the bomardier beetle (http://en.wikipedia.org/wiki/Bombardier_beetle), which mixes peroxide and quinones to generate a violently exothermic reaction to spray at predators.Yes. :)
The significant difference being that the bombardiers are able to exploit a chemical disequilibrium in their environment (between atmospheric oxygen and their food) which allows them to generate enough energy to produce the internal chemical disequilibrium associated with their "rocket fuel" (hydroquinones and hydrogen peroxide).

Grant Hutchison