# How much neon would need to be in an Earth-like atmosphere to tint it considerably orange/red?

I'm creating a planet for a game I'm making that has orange-red skies. My explanation that I've currently come up with is that the atmosphere has a much higher neon content than Earth does. At the moment, I'm saying that the atmosphere of the planet consists of 72.9% molecular nitrogen, 18.75% molecular oxygen, 1.15% carbon dioxide, 1% argon, 0.05% trace gases, and finally 6.15% neon.

In essence, I'm wondering if this 6.15% would be enough to noticeably turn the sky an orange-red color or if the concentration would need to be higher than it already is. I haven't been able to find any concrete answers to a question like this, so I was hoping someone here could help! :)

If there's any other parts to this you need to know in order to answer it I'll do my best to provide!

EDIT: Thank you for your answers! I honestly don't know where I got that neon would create an orange-red sky just by being present? I had completely overlooked the fact that neon is colorless so thank you for reality checking me on that. I'm very new to literal worldbuilding (if it wasn't evident enough) so all of your input really helps!

• Why would inert Neon produce an orange-red sky ? Neon alone won't produce the orange-red color you may be think of in Neon signs. The martian atmosphere might be a better choice for inspiration, as dust in that absorbs blue wavelengths (AFAIK) and produces a reddish tint. Jun 5, 2020 at 3:54
• Neon is colorless. I have no idea why you believe that it is red. It glows reddish orange when it carries an electric current, but that's a different story; most of the time air does not carry any electric current. (For example, in a gas discarge lamp, nitrogen glows pink: and yet, our atmosphere is not pink.) Jun 5, 2020 at 6:14
• You're misunderstanding how Neon produces color here. Neon lights glow when you put electricity through it. If you turn off a neon light, it's transparent. Neon is colorless. If you want Neon gas to color your sky, you're gonna need a lot of lightning. Jun 5, 2020 at 8:41
• On the other hand, the auroras would be amazing Jun 5, 2020 at 23:23

As the direct anwer to your question is ‘absolutely no’, I will try to build up some ways leading to the skies you wanted, but there will be some points where persons with a deeper insight into physics then I have will have to fill up my ideas with hard facts.

First option: the mars-like dusty skies This is definitely the easier way and scientifically feasible. If your planet has a high part of dust or other ‘pollution’ in the air, you could get a reddish sky as we can see it on mars or even sometimes on earth if the sun has the right angle (sunrise and dawn). You just have to care about how this dust influences

Second option: high-atmosphere glowing neon This idea is a bit special and I don’t really know if it could work in reality. Your neon itself wouldn’t give you a sky coloured in any different colour as it is a colourless noble gas. Furthermore as a noble gas with an atomic weight of 0,9g/l it’s a bit lighter than air and not chemically bound so it would mainly rise up in the higher layers of the atmosphere and would get lost into space (as probably happened to our earth). So at first you would need a layer of any kind (like our ozone-layer but I don’t have a good idea at the moment and ozone is not sufficient) able to hold it in a high atmosphere layer. Second you need a star with a high radiance which is able to penetrate this ‘prison-layer’ without destroying it and get the neon (which should be highly concentrated in its layer) stimulated to higher energy levels. The discharging neon would give you a permanent orange/red glow in the higher atmosphere which could get you to the skies you wanted.

Third option: bromine You could get a reddish sky by adding a high level of bromine into your atmosphere as it is a red/brown gas by itself. But as bromine is toxic to earthly plants and animals this will be the option with the most difficult afterwork as it would lead to a totally different evolution, changing nearly everything.

• Another option would be to make the atmosphere thicker, but the thickness you'd need for red is a bit extreme (Venus's sky is apparently orange as seen from the surface, and even if Venus weren't so hot, the pressure would be a bit much). Jun 5, 2020 at 9:58

The earth's sky already turns orange..........every sunset and sunrise. Sunlight passes through more air at sunset and sunrise than during the day, when the sun is higher in the sky. More atmosphere means more molecules to scatter the violet and blue light away from your eyes. ... This is why sunsets are often yellow, orange, and red. Neon is only 0.0018% of the Earth's atmospheric composition. Neon is inert and colorless gas, thus obtaining a colored atmosphere requires a specific high energy input to interact with it. For a perpetual atmosphere of different colors are due to particulate matter.

Make your atmosphere thicker. The color of the sky can change from pale blue to white to pale yellow and finally orange. The atmosphere would be really thick and dense like on Venus. If you don't want that level of thickness you can alter the color light source itself, Its sun. Your planet with quite thick atmosphere orbit around a Red Dwarf can easily get orange sky. Oh, another easy option is dust or even orange-red skyplanktons (But you need A LOT).

About 12000 volts , is how much you need.

Neon, the gas, is virtually colorless. If you pile up many kilometers of it, it is supposed to be a soft straw yellow. Neon has less color in gas form than nitrogen has!

It is only orange/red when excited by an electric current, this excitation requires something on the order of 12000 volts per meter distance between electrodes.

Admittedly, even a very mild concentration (maybe 1-2% in the upper atmosphere), would make for much more visible and bloody Auroras.