Gas giants put out a fair amount of heat from gravitational collapse, so there's bound to be quite a bit of upward moving winds. If Carl Sagan's idea about aerial ecologies pans out, could larger organisms soar endlessly on thermal updrafts? Are the updrafts outside storms thought to be strong, or like a mild breeze? Got to wondering about this because the mostly H-He atmosphere would make buoyancy-only methods of staying airborne kind of tricky. Small stuff is easy to imagine, but larger stuff may need a boost.

  • $\begingroup$ Choose a density for your creature. There is some height in the atmosphere of a gas giant planet at which the density is the same as that of the creature. The size is not a factor for floating, only its density is important. Mass makes a difference for flight but not for floating. Sagan imagined the creatures would have large bags filled with hydrogen to reduce the density. Also, larger wingspan can compensate for weaker updrafts. $\endgroup$ – eshaya Oct 23 '20 at 16:54
  • $\begingroup$ All of that is mentioned all the time in articles about this, except specifics on density. Hydrogen and helium are the lightest of gases and make meeting that low density a bit tricky. I'm also wondering if this would be even harder on warm Jovians with water clouds as their upper layer. The clement layers would he higher up than on Jupiter and Saturn, with a lower pressure and density, no? The only thing I'm left without a real inkling up is how strong and available updrafts would be. $\endgroup$ – Sam D. Jones Oct 23 '20 at 19:49

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