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My understanding is that carbon dioxide makes up the majority of the Venusian atmosphere, and carbon dioxide is transparent. Even liquid CO2 is transparent!

Yet despite this Venus is enveloped in a thick all encompassing opaque atmosphere that conceals the surface, unlike Earth.

What is the primary cause for this? Why does Venus have an opaque atmosphere?

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  • $\begingroup$ This is a question from the category: "Why is the sky blue if the air is transparent?" $\endgroup$
    – A. Rumlin
    Sep 21, 2020 at 19:39
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    $\begingroup$ @A.Rumlin that question has an answer, I too would like an answer, but a Venusian answer. Don't forget, you can see large sections of earths surface from orbit in the visible spectrum, you can't see the surface of Venus though. I am not interested in the colour of Venus, but it's opacity $\endgroup$
    – Tom J Nowell
    Sep 21, 2020 at 22:21
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    $\begingroup$ about Raleigh scattering in Venus' atmosphere, there's @TomSpilker's authoritative answer $\endgroup$
    – uhoh
    Sep 21, 2020 at 23:30
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    $\begingroup$ re Raleigh scattering in Venus' atmosphere, there's @TomSpilker's authoritative answer. This is a good question, but there might be more than one answer depending on if you mean opaque as viewed from above (e.g. orbiter looking down) or near the surface (e.g. lander looking into the distance, trying to see the "horizon". Or maybe it will turn out to be the same answer. I put horizon in quotes because at a certain altitude, light parallel to the surface already bends around the planet. Can't find that answer right now but it's somewhere in SE... $\endgroup$
    – uhoh
    Sep 21, 2020 at 23:35
  • $\begingroup$ @TomJNowell Unfortunately, I have now not been able to find a Soviet publication on the properties of the lower layer of the atmosphere of Venus. As far as I remember, at these temperatures and pressures, carbon dioxide has amazing optical and physical properties. Something like a liquid. $\endgroup$
    – A. Rumlin
    Sep 22, 2020 at 6:30

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Venus is shrouded by an opaque layer of highly reflective clouds of sulfuric acid, preventing its surface from being seen from space in visible light.

Above the dense CO2 layer are thick clouds, consisting mainly of sulfuric acid, which is formed by sulfur dioxide and water through a chemical reaction resulting in sulfuric acid hydrate. Additionally, the atmosphere consists of approximately 1% ferric chloride.[80][81] Other possible constituents of the cloud particles are ferric sulfate, aluminium chloride and phosphoric anhydride. Clouds at different levels have different compositions and particle size distributions.[80] These clouds reflect and scatter about 90% of the sunlight that falls on them back into space, and prevent visual observation of Venus' surface.

Source: Venus Wikipedia

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  • $\begingroup$ This may be the answer to the OP's question (I'm not sure yet) but I'm really curious about the opacity near the surface, as in how far can one see. There's another Q&A somewhere that deals with the gradient of the refractive index of the dense atmosphere and how it bends light with a radius smaller than the planet's. So I'm curious which limits the visible horizon more, opacity or refraction. Maybe that needs a separate quesiton. $\endgroup$
    – uhoh
    Sep 22, 2020 at 19:25
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    $\begingroup$ I am pretty sure, this IS OPs questions answer ;-) ...You are right, yours question is interesting, too :-) $\endgroup$
    – CallMeTom
    Sep 23, 2020 at 4:45
  • $\begingroup$ great! fun = len(questions.on_topic()) I still have to find that invisible-horizon-due-to-refraction post, right now it's hiding beyond my local horizon. The question asked at what altitude would the radius of curvature of a ray bent by refraction result in a circle around the planet, and I think it was around 20 km, but right now local SE opacity is too high due to Me scattering off of other questions. (all puns intended) $\endgroup$
    – uhoh
    Sep 23, 2020 at 6:03
  • $\begingroup$ Found it! See "This notion is further discussed in Some Consequences of Critical Refraction in the Venus Atmosphere (Snyder, 1971) stating that critical refraction occurs at an elevation of 35km..". below the 2nd image in this answer. $\endgroup$
    – uhoh
    Sep 24, 2020 at 8:11

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