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Mars' average atmospheric pressure is 0.006 atm (0.088 psi). Is that enough to make fixed stars on Mars' night sky twinkle? Do we know an air pressure or density limit for that?

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    $\begingroup$ related but not necessary a duplicate: How would astronomical seeing on Mars differ from that on Earth? I can't prove it but I think the answer is "yes, but not much". Yes because it might be very small but non-zero, and "not much" because much of Earth's astronomical seeing is a problem from the ground, and observatories on the highest mountains (a few kilometers) see much less. $\endgroup$ – uhoh Dec 30 '20 at 14:31
  • $\begingroup$ Mars' atmosphere at the surface is like starting from roughly 40 kilometers altitude ($-\ln(0.006) \approx 5$ and $5 \times 8 \ km = 40 \ km$) (scale height) $\endgroup$ – uhoh Dec 30 '20 at 14:31
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Following howstuffworks and my own metereological intuition, the key effect for stars to twinkle seems less the pressure or size of the atmosphere but rather if different layers (usually of different temperature) exist, and if the gradiant between the layers is steep enough.

Light passing through zones of differently dense air on its way to the observer lead to small (time-dependent) distortions occuring for instance over warm asphalt of a road. Here, the light travels horizontally through the atmosphere, rather than vertically like in the case of twinkling stars. I like to imagine the parcles of hot, less dense air rising from the ground as the bubbles in a lava lamp. In the case of a hot road, a few dozends of meters (on Earth's surface) is enough to cause the flickering of e.g. cars at a distance. The visible image then becomes somewhat blurred, and since the air is constantly (and irregularly) moving upward over the hot street, it looks as if the air is flickering.

Applied to your question: I know that dust devils are likely occuring on Mars, which need atmospheric instabilities in order to exist, so I would assume that there are indeed atmospheric conditions where one could observe twinkling stars on Mars.

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    $\begingroup$ Well, the Martian atmosphere has several layers, but I thought there may be twinkling also because there's per se so much dust in Mars' atmosphere. $\endgroup$ – Greenhorn Dec 30 '20 at 8:42
  • $\begingroup$ Another influence to be considered: The twinkling of stars might be minimal for the naked eye at the site of ESO, but for the telescopes over there, the fixed stars twinkle significantly since the integrated air volume through which the light of a chosen star travels is larger. In other words: It depends whether you mean twinkling for the naked eye or for telescopes. $\endgroup$ – B--rian Dec 30 '20 at 8:50
  • $\begingroup$ I didn't even know that stars twinkle in telescopes too. $\endgroup$ – Greenhorn Dec 30 '20 at 9:57
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    $\begingroup$ @Greenhorn Concerning the twinkling stars in telescopes - it is usually not called like that, though: One uses artificial stars to correct the atmospheric distortion of light using adaptive optics. $\endgroup$ – B--rian Dec 30 '20 at 10:50

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