For complicated reasons our hero's blimp in the Venus atmosphere at an altitude of 50 km gets a tear in it and sunlight floods inside (there is no gondola, the blimp is a semi-ellipsoid of breathable air), and he is in an area of direct sunlight for half an hour. He doesn't have to worry about air for a while as the blimp is huge and there is little pressure difference between the exterior and interior at that altitude. Does venus's atmosphere above 50km have a similar UV blocking effect to the ozone layer? Will he get badly sunburnt?

  • $\begingroup$ I've added a couple of tags to show-up in the feeds of those with the appropriate interests. Feel free to roll-back the edit if you wish. $\endgroup$ Jan 14, 2020 at 23:37
  • $\begingroup$ "there is no gondola, the blimp is a semi-ellipsoid of breathable air". But there must be some internal structure for them to walk around in, attach walls and electric outlets and door, etc to. $\endgroup$
    – RonJohn
    Jan 15, 2020 at 22:14
  • $\begingroup$ @RonJohn its beyond the scope of the question, but the blimp is 1 km tall, 1 km long, and 1 km wide, the roof held stable by several carbon fiber beams, and the floor held up by a web of titanium and carbon fiber pylons that meet at the thorium reactor which hangs under the center of the blimp. $\endgroup$
    – qazwsx
    Jan 16, 2020 at 0:13
  • $\begingroup$ This blimp wouldn't be a pure blimp. Good Engineering Design says that -- if nothing else -- there will be baffles up there to slow down air movement or even isolate sections, like nylon "bulkheads". There will be shadow. But let's say there isn't. "NASA" would have recognized this possibility, and given the rooms... ceilings. Ergo, no sunburn. $\endgroup$
    – RonJohn
    Jan 16, 2020 at 0:21

2 Answers 2


No sunburn risk.

It's very dark at 50km.


this article tells us the opaque clouds extend up to 60km.

In addition:


The atmosphere of Venus absorbs UVs.

In addition, if it's important for your character to get a sunburn you'll need to raise your blimp up quite a bit.

  • 9
    $\begingroup$ One teacher of mine once explained that Venus is more like a pressure cooker than a microwave. It isn't the sun's direct radiation that cooks you, it is the very hot steamy gases on the planet surface. $\endgroup$
    – Mermaker
    Jan 15, 2020 at 12:38
  • 1
    $\begingroup$ @T.Sar-ReinstateMonica On the surface of Venus, the pressure is high enough they're not gasses anymore, they're super-critical fluids. $\endgroup$
    – nick012000
    Jan 16, 2020 at 5:44
  • $\begingroup$ I would consider wuwt an unreliable source, regardless of planet $\endgroup$
    – JollyJoker
    Jan 16, 2020 at 11:54
  • $\begingroup$ @jollyjoker What is "wuwt" ? $\endgroup$
    – kleer001
    Jan 16, 2020 at 21:00
  • $\begingroup$ @kleer wattsupwiththat.com $\endgroup$
    – JollyJoker
    Jan 17, 2020 at 6:37

Figure 4 in this paper would lead one to believe that the SO2 in the upper Venusian atmosphere does a poorer job of blocking the higher energy UV rays than Ozone on a per molecule basis. It's hard to say exactly how much SO2 there is compared to earth's Ozone layer though. But there is a thin ozone layer at Venus, and at 50 km, you're below the upper cloud deck so the would block most of the sunlight anyway. You would also need protection from the sulfuric acid droplets in any clouds you encounter, which is probably a bigger hazard than sun burn. So if you need a Tyvek suit anyway, it'll block the UV if you intended to be outside. Otherwise, your larger hazard may be hoping you don't drift into a cloud.


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