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

<p>Using the <a href="https://en.wikipedia.org/wiki/Reynolds_number" rel="nofollow noreferrer">Reynolds number</a> Number <span class="math-container">$ Re = \dfrac{\rho L v}{\mu}$</span> as a measure for turbulence:</p>

<ul>
<li>density <span class="math-container">$\rho$</span> drops due to the reduced pressure (about 1/100 earth pressure), additionally the gravity is smaller than on earth</li>
<li>characteristic length <span class="math-container">$L$</span> will stay similar</li>
<li>average wind speed <span class="math-container">$v$</span> is about 2 times higher than on earth</li>
<li>the dynamic viscosity <span class="math-container">$\mu$</span> of an (ideal) gas is independent on the pressure, and the temperature dependency can be approximated with <span class="math-container">$\sqrt{\dfrac{T_{mars}}{T_{earth}}} \approx 0.9$</span></li>
</ul>

<p>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</p>

<p>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.</p>

CC BY-SA 4.0
2020-01-29T23:37:50.100Z
Thank you for your answer! The first link in the question is Wikipedia's [Astronomical seeing](https://en.wikipedia.org/wiki/Astronomical_seeing) and the first sentence there says that it is "...due to turbulent mixing in the atmosphere of Earth, causing variations of the optical refractive index." and later mentions "different temperature layers and different wind speeds" so a detailed analysis would require more information about Mars' atmosphere than we probably have today.
uhoh
CC BY-SA 4.0
2020-01-29T23:39:59.770Z
But I think your argument is mostly that since at any optically relevant altitude the density of Mars' atmosphere is lower than Earth's by roughly a factor of 100, seeing is likely to be far better from Mars' surface than from Earth's simply because theres far less gas and so far less opportunity for index of refraction variation.
uhoh
CC BY-SA 4.0
2020-01-29T15:24:42.313Z
2020-01-29T23:29:10.677Z
2020-01-29T23:29:10.677Z
Kalliope
<p><a href="https://en.wikipedia.org/wiki/Astronomical_seeing" rel="nofollow noreferrer">Astronomical seeing</a> is the limiting factor for the resolution of all but the smallest Earthbound telescopes. </p>

<p><img src="https://i.sstatic.net/e0NFD.gif" alt="Astronomical Seeing"> <a href="https://en.wikipedia.org/wiki/File:Seeing_Moon.gif" rel="nofollow noreferrer">Source</a></p>

<p>Stunning advances in <a href="https://en.wikipedia.org/wiki/Adaptive_optics" rel="nofollow noreferrer">adaptive optics</a> (along with it's predecessor <a href="https://en.wikipedia.org/wiki/Speckle_imaging" rel="nofollow noreferrer">speckle interferometry</a> and it's budget-minded cousin <a href="https://en.wikipedia.org/wiki/Lucky_imaging" rel="nofollow noreferrer">lucky imaging</a>) get around this but only with substantial compromises in (some combination of) throughput, cost, complexity and wavelength range (see answers to <a href="https://astronomy.stackexchange.com/q/14795/7982">Why aren't ground-based observatories using adaptive optics for visible wavelengths?</a>)</p>

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

CC BY-SA 4.0
2018-10-25T23:45:42.853Z
Lucky imaging is also mentioned in [this recent answer](https://astronomy.stackexchange.com/a/28156/7982) and many others: https://astronomy.stackexchange.com/search?q=lucky+imaging
uhoh
CC BY-SA 4.0
2018-10-26T04:21:12.693Z
FWIW, the atmospheric pressure on top of [Olympus Mons](https://en.m.wikipedia.org/wiki/Olympus_Mons#Description) is about 12% of the mean Martian atmospheric pressure; OTOH, Olympus Mons creates orographic clouds.
PM 2Ring
CC BY-SA 4.0
2018-10-26T05:15:02.750Z
@PM2Ring here's some closer to home, for some of us at least ;-) https://earthscience.stackexchange.com/q/10478/6031
uhoh
CC BY-SA 4.0
2018-10-26T13:14:06.507Z
@PM2Ring I'm still confused why you left your "Olympus Mons creates orographic clouds" comment here. Did you mean to leave it [here instead](https://earthscience.stackexchange.com/q/15436/6031), a question I asked at almost the same time, which *does reference clouds produced by Olympus Mons?*
uhoh
CC BY-SA 4.0
2018-10-26T14:09:19.743Z
Sure, the atmospheric pressure at the Mars datum level is already much lower than at Earth's sea level, and it's much more homogeneous, due to the low water content, but why not put your telescope as high as you can? The only problem is those pesky orographic clouds.
PM 2Ring
CC BY-SA 4.0
2018-10-26T14:25:40.890Z
@PM2Ring ah I understand now, thanks! For this question I just wanted an apples-to-apples comparison and low levels is where human (or robot) activity is mostl like start (if it ever does). I suppose an Olympus Mons to Atacama comparison would certainly be interesting as well.
uhoh
CC BY-SA 4.0
2018-10-26T17:03:54.020Z
Martian $r_0$ may not be large, but since the absolute value of the inhomogeneity is tiny compared with Earth, it doesn't matter much.
Carl Witthoft
CC BY-SA 4.0
2019-07-30T13:52:37.007Z
The Moon is nearer and maybe better: no atmosphere and the far side is well shielded from Earth interference.
badjohn
<observational-astronomy><mars><angular-resolution><atmospheric-effects><planetary-atmosphere>
How would astronomical seeing on Mars differ from that on Earth?
uhoh
# How would astronomical seeing on Mars differ from that on Earth?

(Asked by: username_0 on 2018-10-25)

[Astronomical seeing](https://en.wikipedia.org/wiki/Astronomical_seeing) is the limiting factor for the resolution of all but the smallest Earthbound telescopes.

![Astronomical Seeing](https://i.sstatic.net/e0NFD.gif) [Source](https://en.wikipedia.org/wiki/File:Seeing_Moon.gif)

Stunning advances in [adaptive optics](https://en.wikipedia.org/wiki/Adaptive_optics) (along with it's predecessor [speckle interferometry](https://en.wikipedia.org/wiki/Speckle_imaging) and it's budget-minded cousin [lucky imaging](https://en.wikipedia.org/wiki/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?](https://astronomy.stackexchange.com/q/14795/7982))

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?:

**Tags:** observational-astronomy, mars, angular-resolution, atmospheric-effects, planetary-atmosphere
> **Comments:**
> **username_0**: Lucky imaging is also mentioned in [this recent answer](https://astronomy.stackexchange.com/a/28156/7982) and many others: https://astronomy.stackexchange.com/search?q=lucky+imaging  
> **username_1**: FWIW, the atmospheric pressure on top of [Olympus Mons](https://en.m.wikipedia.org/wiki/Olympus_Mons#Description) is about 12% of the mean Martian atmospheric pressure; OTOH, Olympus Mons creates orographic clouds.  
> **username_0**: @PM2Ring here's some closer to home, for some of us at least ;-) https://earthscience.stackexchange.com/q/10478/6031  
> **username_0**: @PM2Ring I'm still confused why you left your "Olympus Mons creates orographic clouds" comment here. Did you mean to leave it [here instead](https://earthscience.stackexchange.com/q/15436/6031), a question I asked at almost the same time, which *does reference clouds produced by Olympus Mons?*  
> **username_1**: Sure, the atmospheric pressure at the Mars datum level is already much lower than at Earth's sea level, and it's much more homogeneous, due to the low water content, but why not put your telescope as high as you can? The only problem is those pesky orographic clouds.  
> **username_0**: @PM2Ring ah I understand now, thanks! For this question I just wanted an apples-to-apples comparison and low levels is where human (or robot) activity is mostl like start (if it ever does). I suppose an Olympus Mons to Atacama comparison would certainly be interesting as well.  
> **username_2**: Martian $r_0$ may not be large, but since the absolute value of the inhomogeneity is tiny compared with Earth, it doesn't matter much.  
> **username_3**: The Moon is nearer and maybe better: no atmosphere and the far side is well shielded from Earth interference.  

---

## 1 answers

### Answer by username_4 on 2020-01-29. Score: 6 | Accepted answer

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](https://en.wikipedia.org/wiki/Reynolds_number) Number $ Re = \dfrac{\rho L v}{\mu}$ as a measure for turbulence:

* density $\rho$ 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.

> **Comments:**
> **username_0**: Thank you for your answer! The first link in the question is Wikipedia's [Astronomical seeing](https://en.wikipedia.org/wiki/Astronomical_seeing) and the first sentence there says that it is "...due to turbulent mixing in the atmosphere of Earth, causing variations of the optical refractive index." and later mentions "different temperature layers and different wind speeds" so a detailed analysis would require more information about Mars' atmosphere than we probably have today.  
> **username_0**: But I think your argument is mostly that since at any optically relevant altitude the density of Mars' atmosphere is lower than Earth's by roughly a factor of 100, seeing is likely to be far better from Mars' surface than from Earth's simply because theres far less gas and so far less opportunity for index of refraction variation.  

---

