# What is the color of Venusian sky 50km from surface

It is said that around 50km above the surface of Venus is the most earth like environment on the whole solar system (source here),

At an altitude of 50 kilometres (31 mi) above Venerian surface, the environment is the most Earth-like in the Solar System – a pressure of approximately 1000 hPa and temperatures in the 0 to 50 °C (273 to 323 K; 32 to 122 °F) range. Protection against cosmic radiation would be provided by the atmosphere above, with shielding mass equivalent to Earth's.

Therefore it is possible to build floating aerostat cities on the venusian cloud tops. Given sufficient time and technology humanity would be no doubt colonizing the venusian atmosphere in floating cities.

But only one problem remains, I can't find any good explanation or description of scientifically accurate depiction of how the sky looks like from a floating platform on Venus, 50 km from the surface.

There's an artist depiction of Venusian cloud tops on Wikipedia:

And from HAVOC,

Both depicting different coloration of sky and clouds of Venus.

The first shows orange-ish nuance of color (I think) and the second proposes Earth like coloration of sky and clouds.

While both looks beautiful enough, I am wondering on accurate depiction of sky and clouds coloration on Venus.

Therefore the question would be: What is the accurate depiction of how sky and clouds coloration 50-60 kilometers above venusian ground would be like as seen from a floating aerostat platform?

Someone has asked a similar questions here, but I have to make it clear that while the question is about the same general subject (venusian aerostat), I am asking about the accurate coloration of Venusian atmosphere 50-60km from surface, not about whether or not it is feasible.

• Usually a reason or a good explanation as of why to downvote is polite. – Hendrik Lie Dec 8 '16 at 18:59
• @kingledion It's not off topic here just because it could be on topic on another site. Otherwise nothing is on topic for Worldbuilding. This question is about building a fictional world (even if that fictional sci fi world is based in a world known about to us) and the answer could be useful for anyone else setting something on Venus or any other similar planet. – Tim B Dec 8 '16 at 20:05
• @Mołot after further thoughts, you're right. Mentioning what I don't need would save some time and answerers effort, especially if I know what answer I don't need. – Hendrik Lie Dec 8 '16 at 20:37
• IMHO, the world the OP is building is that of the inhabitants on these floating structures. Since we haven't done anything like that, it seems like a valid world to be building. Concern for sensory details shows interesting lines of thinking. – Catalyst Dec 8 '16 at 20:52
• I'm going to claim that Earth is the most Earth-like environment in the solar system. The upper atmosphere of Venus can only be the second most Earth-like. – Mike Scott Dec 8 '16 at 20:59

Common misconception is that Venus is a dirty yellow; this partly comes from false-colour images that are common used but also the association of Venus' sulfur content and how elemental sulfur looks. Venus is virtually pure white in true colour.

At 50km, an aerostat would be passing through cloudtops, that would be bright white, with hints of yellow at times due to the impurities that might be in the clouds at the time.

But in reality, the images displayed for the concepts are accurate.

• Thanks for the answer. I never thought of that before, that the commonly depicted coloration of Venus is just false color images. And thanks for noting that the artist renderings were quite accurate. – Hendrik Lie Dec 8 '16 at 20:17
• My answer is actually somewhat incomplete but I believe you answered your own question below and I think together completes the answer. – RomaH Dec 8 '16 at 21:01

Earth's sky is blue due to Rayleigh scattering. Rayleigh scattering redirects at an angle a percentage of incident light through a gas. The percentage of light reflected is proportion to $$1/\lambda^4$$, where lambda is the wavelength. That is, the shorter the wavelength, the more light is reflected. Violet light is most reflected, percentage-wise, but the purple section of the visible spectrum is small. So Blue light is the next most reflected, and since that portion of the visible spectrum is large, the sky is blue. Here is a graph from the above Wikipedia article of percent scattering vs. wavelength:

According to Shardanand and Prasad Rao, 1977, the Rayleigh scattering cross section for Carbon Dioxide is 3.5 times higher than that of Oxygen or Nitrogen (Table 1). Because the $$1/\lambda^4$$ term in the scattering cross-section is the same for all gasses (Eqn 12), the CO$$_2$$ scattering curve will have the same shape as the Oxygen-Nitrogen curve on Earth. Thus if we assume a similar molar density of gas particles, the sky of Venus would be even blue-er than our own.

I can't get any density measurements from 50km in Venus' sky, so I can't estimate molar density for calculation. But in the absence of any other color, I would expect the sky in Venus to be blue.

• According to a graph on wikipedia, @ 50km pressure on Venus is about one atmosphere. upload.wikimedia.org/wikipedia/commons/6/63/Venusatmosphere.svg – RomaH Dec 8 '16 at 21:04
• This information is accurate and concise but note that these cities will be passing through clouds - as mentioned by the other answer - so the true color of the sky will be replaced by the color of the clouds. – Zxyrra Dec 9 '16 at 4:15