<p>Question 1:</p>
<p>From <a href="https://ui.adsabs.harvard.edu/abs/2000asqu.book..143T" rel="nofollow noreferrer">Tokunaga (2000):</a><strong>The major atmospheric absorbers</strong> [in the infrared] <strong>are H<sub>2</sub>O</strong> [and OH]<strong>, CO<sub>2</sub>, N<sub>2</sub>O, CH<sub>4</sub>, and O<sub>3</sub>.</strong></p>
<p>Question 2:</p>
<p><strong>X- and gamma rays:</strong> These would still be strongly attenuated even by a thin atmosphere. It would be better to go with one of @Darth Pseudonym's options in the comments.</p>
<p><strong>Ultraviolet:</strong> I did a back of the envelope calculation that the total column density of ozone above the Earth's surface is 100x more than at Mars. So there could generally be a 100x improvement in UV transparency at Mars, although this would vary with UV wavelength.</p>
<p><strong>Visible:</strong> Both atmospheres are transparent, but with Mars' lower surface temperature and lower pressure, there would be less distortion. Adaptive optics would not need to work as hard, and you could get sharper images.</p>
<p><strong>Infrared:</strong> <a href="https://doi.org/10.3390/rs15071811" rel="nofollow noreferrer">Roman (2023)</a> provided a nice plot of atmospheric tranmission, calculated for Cerro Paranal in Chile (high transmission is good, so it's the light-blue regions where the atmosphere is transparent enough for astronomy):</p>
<p><a href="https://i.sstatic.net/EDNz7n9Z.png" rel="nofollow noreferrer"><img src="https://i.sstatic.net/EDNz7n9Z.png" alt="Plot of atmospheric transmission as a function of wavelength from 5 to 30 micrometer wavelengths" /></a></p>
<p>So it looks like with low H<sub>2</sub>O, a window might open up around 7 µm, and the sky would be better at 18+ µm as well.</p>
<p>But the 15-µm region would not improve. Although Mars has a thinner atmosphere, that atmosphere is full of CO<sub>2</sub>, while the Earth has only about 420 ppm of CO<sub>2</sub>. That means the total column density of CO<sub>2</sub> is roughly 30x greater on Mars than on Earth.</p>
<p><strong>Submillimeter:</strong> Water vapor dominates in this region. This plot from <a href="https://ui.adsabs.harvard.edu/abs/2000asqu.book..143T" rel="nofollow noreferrer">Tokunaga (2000)</a> compares Kitt Peak (altitude 2 km) and Mauna Kea (altitude 4 km):</p>
<p><a href="https://i.sstatic.net/QsEyNbUn.png" rel="nofollow noreferrer"><img src="https://i.sstatic.net/QsEyNbUn.png" alt="Plot comparing atmospheric transmission as a function of wavelength from 250 to 5000 micrometer wavelengths at Kitt Peak and Mauna Kea" /></a></p>
<p>The &quot;<em>w</em>&quot; in the plot is the column density of water in the atmosphere in precipitable millimeters, that is, if you extracted all the water in the whole vertical column, it would make a 1-mm or 5-mm layer of liquid water. For Mars, that value is typically in the range of 10 precipitable µm, so 100x less than the Mauna Kea value in the plot (which is already 5x better than Kitt Peak). So there should be some nice far-IR/submillimeter windows opening up.</p>

CC BY-SA 4.0
2024-05-28T20:28:49.443Z
2024-05-28T20:28:49.443Z
giardia
<p>Earth’s atmosphere is composed of about 78 percent nitrogen, 21 percent oxygen, 0.9 percent argon, and 0.1 percent other gases. Trace amounts of carbon dioxide, methane, water vapor, and neon are some of the other gases that make up the remaining 0.1 percent.</p>
<p>Mars' atmosphere is 95% carbon dioxide, 3% nitrogen, 1.6% argon, and it has traces of oxygen, carbon monoxide, water, methane, and other gases, along with a lot of dust.</p>
<p>My QUESTIONS:</p>
<p><strong>1) But I am sure there is a lot of absortion of EM radiation in the atmosphere, due to water vapor, so is this absorption really caused by these trace amounts of water vapor?</strong></p>
<p><strong>2) If one were to make observations from the surface of Mars instead of that of the Earth, what radiation windows will (mostly) open ?</strong></p>
<p>I know that on the Earth execpt for the radio and visible spectrum which are open, the other EM windows of the spectrum are closed due to absorption, diffraction, Ionization and photodissociation whcih are the 4 main ways in which EM radiations interacts with the Earth 's atmosphere. I am basing this claim on the following picture:
<a href="https://i.sstatic.net/nD3Uz1PN.png" rel="nofollow noreferrer"><img src="https://i.sstatic.net/nD3Uz1PN.png" alt="enter image description here" /></a></p>
<p>My guess is that the gamma ray and UV should open, because there is no ozone, which is what blocks them right? I also thought about IF, becuase I though there was no water in Mars's atmosphere. But both Earth and Mars atmospheres contain traces of water so now I am not sure that the IR window would really open, maybe  just like in the Earth there s still absortion.</p>

CC BY-SA 4.0
2024-04-17T11:53:43.327Z
I’m voting to close this question because the user already asked it on Physics SE at https://physics.stackexchange.com/q/810722/6319
gerrit
CC BY-SA 4.0
2024-04-17T19:23:13.873Z
The fact that Mars's atmosphere is only about 1% as thick as Earth's probably has a much larger impact on observation than the composition does. The equivalent density  on Earth would be like building an observatory on a tower 28 miles tall.
Darth Pseudonym
CC BY-SA 4.0
2024-04-17T19:26:16.430Z
(or you could just put in an orbital observatory and skip the whole mars thing entirely, or build on Deimos or Ceres if you really want to glue it to a rock)
Darth Pseudonym
CC BY-SA 4.0
2024-04-18T04:53:59.650Z
[Atmospheric composition](https://en.wikipedia.org/wiki/Density_of_air#Composition) data usually omits the water content, because it's so variable. Warm moist air may have >2% water (by mass). See https://en.wikipedia.org/wiki/Humidity
PM 2Ring
<observational-astronomy><mars><planetary-atmosphere><planetary-science><atmospheric-effects>
Which of the blocked radiation windows will (mostly) open if one where to observe from the surface of Mars, instead of the Earth?
some_math_guy
# Which of the blocked radiation windows will (mostly) open if one where to observe from the surface of Mars, instead of the Earth?

(Asked by: username_0 on 2024-04-17)

Earth’s atmosphere is composed of about 78 percent nitrogen, 21 percent oxygen, 0.9 percent argon, and 0.1 percent other gases. Trace amounts of carbon dioxide, methane, water vapor, and neon are some of the other gases that make up the remaining 0.1 percent.

Mars' atmosphere is 95% carbon dioxide, 3% nitrogen, 1.6% argon, and it has traces of oxygen, carbon monoxide, water, methane, and other gases, along with a lot of dust.

My QUESTIONS:

**1) But I am sure there is a lot of absortion of EM radiation in the atmosphere, due to water vapor, so is this absorption really caused by these trace amounts of water vapor?**

**2) If one were to make observations from the surface of Mars instead of that of the Earth, what radiation windows will (mostly) open ?**

I know that on the Earth execpt for the radio and visible spectrum which are open, the other EM windows of the spectrum are closed due to absorption, diffraction, Ionization and photodissociation whcih are the 4 main ways in which EM radiations interacts with the Earth 's atmosphere. I am basing this claim on the following picture:
[![enter image description here](https://i.sstatic.net/nD3Uz1PN.png)](https://i.sstatic.net/nD3Uz1PN.png)

My guess is that the gamma ray and UV should open, because there is no ozone, which is what blocks them right? I also thought about IF, becuase I though there was no water in Mars's atmosphere. But both Earth and Mars atmospheres contain traces of water so now I am not sure that the IR window would really open, maybe just like in the Earth there s still absortion.

**Tags:** observational-astronomy, mars, planetary-atmosphere, planetary-science, atmospheric-effects
> **Comments:**
> **username_1**: I’m voting to close this question because the user already asked it on Physics SE at https://physics.stackexchange.com/q/810722/6319  
> **username_2**: The fact that Mars's atmosphere is only about 1% as thick as Earth's probably has a much larger impact on observation than the composition does. The equivalent density  on Earth would be like building an observatory on a tower 28 miles tall.  
> **username_2**: (or you could just put in an orbital observatory and skip the whole mars thing entirely, or build on Deimos or Ceres if you really want to glue it to a rock)  
> **username_3**: [Atmospheric composition](https://en.wikipedia.org/wiki/Density_of_air#Composition) data usually omits the water content, because it's so variable. Warm moist air may have >2% water (by mass). See https://en.wikipedia.org/wiki/Humidity  

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## 1 answers

### Answer by username_4 on 2024-05-28. Score: 1

Question 1:

From [Tokunaga (2000):](https://ui.adsabs.harvard.edu/abs/2000asqu.book..143T)**The major atmospheric absorbers** [in the infrared] **are H2O** [and OH]**, CO2, N2O, CH4, and O3.**

Question 2:

**X- and gamma rays:** These would still be strongly attenuated even by a thin atmosphere. It would be better to go with one of @Darth Pseudonym's options in the comments.

**Ultraviolet:** I did a back of the envelope calculation that the total column density of ozone above the Earth's surface is 100x more than at Mars. So there could generally be a 100x improvement in UV transparency at Mars, although this would vary with UV wavelength.

**Visible:** Both atmospheres are transparent, but with Mars' lower surface temperature and lower pressure, there would be less distortion. Adaptive optics would not need to work as hard, and you could get sharper images.

**Infrared:** [Roman (2023)](https://doi.org/10.3390/rs15071811) provided a nice plot of atmospheric tranmission, calculated for Cerro Paranal in Chile (high transmission is good, so it's the light-blue regions where the atmosphere is transparent enough for astronomy):

[![Plot of atmospheric transmission as a function of wavelength from 5 to 30 micrometer wavelengths](https://i.sstatic.net/EDNz7n9Z.png)](https://i.sstatic.net/EDNz7n9Z.png)

So it looks like with low H2O, a window might open up around 7 µm, and the sky would be better at 18+ µm as well.

But the 15-µm region would not improve. Although Mars has a thinner atmosphere, that atmosphere is full of CO2, while the Earth has only about 420 ppm of CO2. That means the total column density of CO2 is roughly 30x greater on Mars than on Earth.

**Submillimeter:** Water vapor dominates in this region. This plot from [Tokunaga (2000)](https://ui.adsabs.harvard.edu/abs/2000asqu.book..143T) compares Kitt Peak (altitude 2 km) and Mauna Kea (altitude 4 km):

[![Plot comparing atmospheric transmission as a function of wavelength from 250 to 5000 micrometer wavelengths at Kitt Peak and Mauna Kea](https://i.sstatic.net/QsEyNbUn.png)](https://i.sstatic.net/QsEyNbUn.png)

The "*w*" in the plot is the column density of water in the atmosphere in precipitable millimeters, that is, if you extracted all the water in the whole vertical column, it would make a 1-mm or 5-mm layer of liquid water. For Mars, that value is typically in the range of 10 precipitable µm, so 100x less than the Mauna Kea value in the plot (which is already 5x better than Kitt Peak). So there should be some nice far-IR/submillimeter windows opening up.


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