Astronomy

How would astronomical seeing on Mars differ from that on Earth?

How would astronomical seeing on Mars differ from that on Earth?


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Astronomical seeing is the limiting factor for the resolution of all but the smallest Earthbound telescopes.

Source

Stunning advances in adaptive optics (along with it's predecessor speckle interferometry and it's budget-minded cousin lucky imaging) get around this but only with substantial compromises in (some combination of) throughput, cost, complexity and wavelength range (see answers to Why aren't ground-based observatories using adaptive optics for visible wavelengths?)

If identical telescopes sat on the surface of Earth and Mars and looked at a distant and equi-distant body, how would the following differ between the Mars telescope and the Earth telescope?:


As far as I know, "seeing" (or rather the effects influencing optical wave propagation) is caused by turbulence in the atmosphere.

Using the Reynolds number Number $ Re = dfrac{ ho L v}{mu}$ as a measure for turbulence:

  • density $ ho$ drops due to the reduced pressure (about 1/100 earth pressure), additionally the gravity is smaller than on earth
  • characteristic length $L$ will stay similar
  • average wind speed $v$ is about 2 times higher than on earth
  • the dynamic viscosity $mu$ of an (ideal) gas is independent on the pressure, and the temperature dependency can be approximated with $sqrt{dfrac{T_{mars}}{T_{earth}}} approx 0.9$

So for an average martian day an atmospheric Reynolds number would be much smaller than on earth and I would expect a far better seeing due to less turbulence

Additonally, I would guess that the effects of a thinner and dryer atmosphere would help as well, since the index of refraction is dependent on the gas pressure as well.


Watch the video: What Astronomical Seeing Looks Like (November 2022).