<p>astrosnapper@'s <a href="https://astronomy.stackexchange.com/a/31641/7982">thorough answer</a> to the question <em>What is precipitable water vapor in millimeter-wave radioastronomy and how is it measured?</em> links to the paper <a href="https://arxiv.org/abs/1107.5633" rel="nofollow noreferrer">Observing Conditions for Submillimeter Astronomy</a> which discusses spectral windows of atmospheric transmission in the 100 ~ 1500 GHz range. These windows are "delineated" or limited by strong absorption lines of molecular water vapor in the atmosphere. </p>

<p>Figure 2 is shown below. The caption reads</p>

<blockquote>
  <p>Fig. 2. Energy levels of the lowest rotational states of water with transitions labeled by the frequency in GHz. The lines at 557, 752, 988, 1113, and 1229 GHz delineate the principal submillimeter windows.</p>
</blockquote>

<p>and displays <em>ortho-</em> and <em>para-</em> water separately.</p>

<p>Curious to find out what those were, I went to <a href="http://www1.lsbu.ac.uk/water/martin_chaplin.html" rel="nofollow noreferrer">Martin Chapin</a>'s (also <a href="http://www.lsbu.ac.uk/about-us/people/people-finder/prof-martin-chaplin" rel="nofollow noreferrer">here</a>) site <a href="http://www1.lsbu.ac.uk/water/water_structure_science.html" rel="nofollow noreferrer">Water Structure and Science</a> which discusses the physics of <em>ortho-</em> and <em>para-</em> water, and describes experiments on single water molecules trapped and isolated in C60 fullerene "cages" (<a href="https://en.wikipedia.org/wiki/Endohedral_fullerene" rel="nofollow noreferrer">Endohedral fullerenes</a>): </p>

<ul>
<li><a href="http://www1.lsbu.ac.uk/water/ortho_para_water.html" rel="nofollow noreferrer">ortho-Water and para-Water</a></li>
</ul>

<p><strong>Question:</strong> Have caged molecules ever been observed in space?</p>

<p>These could be trapped in fullerenes (which I believe have been observed) or otherwise.</p>

<p><a href="https://i.sstatic.net/ijapj.gif" rel="nofollow noreferrer"><img src="https://i.sstatic.net/ijapj.gif" alt="ortho- or para- water trapped in a fullerene cage"></a></p>

<p><a href="http://www1.lsbu.ac.uk/water/ortho_para_water.html" rel="nofollow noreferrer"></a></p>

CC BY-SA 4.0
2019-04-27T07:22:30.117Z
Define "in space". Do you just mean extraterrestrial, or do you mean interstellar?
ProfRob
CC BY-SA 4.0
2019-04-27T07:27:41.480Z
@RobJeffries I'll stick with Von Karman's definition; anything higher than 100 km will do. If you suspected that I was originally thinking only of interstellar molecules, you are absolutely right, but that's because I didn't think it through. If there's a caged molecule "out there" somewhere, I'd love to hear about it!
uhoh
CC BY-SA 4.0
2019-04-28T00:01:36.840Z
Clathrates have been found I think.
ProfRob
CC BY-SA 4.0
2019-04-28T00:04:25.363Z
@RobJeffries I'd say those would count. See "...or otherwise" in last sentence.
uhoh
<radio-astronomy><astrochemistry>
Have caged molecules ever been observed in space?
uhoh
# Have caged molecules ever been observed in space?

(Asked by: username_0 on 2019-04-27)

astrosnapper@'s [thorough answer](https://astronomy.stackexchange.com/a/31641/7982) to the question *What is precipitable water vapor in millimeter-wave radioastronomy and how is it measured?* links to the paper [Observing Conditions for Submillimeter Astronomy](https://arxiv.org/abs/1107.5633) which discusses spectral windows of atmospheric transmission in the 100 ~ 1500 GHz range. These windows are "delineated" or limited by strong absorption lines of molecular water vapor in the atmosphere.

Figure 2 is shown below. The caption reads

> Fig. 2. Energy levels of the lowest rotational states of water with transitions labeled by the frequency in GHz. The lines at 557, 752, 988, 1113, and 1229 GHz delineate the principal submillimeter windows.

and displays *ortho-* and *para-* water separately.

Curious to find out what those were, I went to [Martin Chapin](http://www1.lsbu.ac.uk/water/martin_chaplin.html)'s (also [here](http://www.lsbu.ac.uk/about-us/people/people-finder/prof-martin-chaplin)) site [Water Structure and Science](http://www1.lsbu.ac.uk/water/water_structure_science.html) which discusses the physics of *ortho-* and *para-* water, and describes experiments on single water molecules trapped and isolated in C60 fullerene "cages" ([Endohedral fullerenes](https://en.wikipedia.org/wiki/Endohedral_fullerene)):

* [ortho-Water and para-Water](http://www1.lsbu.ac.uk/water/ortho_para_water.html)

**Question:** Have caged molecules ever been observed in space?

These could be trapped in fullerenes (which I believe have been observed) or otherwise.

[![ortho- or para- water trapped in a fullerene cage](https://i.sstatic.net/ijapj.gif)](https://i.sstatic.net/ijapj.gif)

**Tags:** radio-astronomy, astrochemistry

> **Comments:**
> **username_1**: Define "in space". Do you just mean extraterrestrial, or do you mean interstellar?  
> **username_0**: @RobJeffries I'll stick with Von Karman's definition; anything higher than 100 km will do. If you suspected that I was originally thinking only of interstellar molecules, you are absolutely right, but that's because I didn't think it through. If there's a caged molecule "out there" somewhere, I'd love to hear about it!  
> **username_1**: Clathrates have been found I think.  
> **username_0**: @RobJeffries I'd say those would count. See "...or otherwise" in last sentence.  

---

## 0 answers

