<p><strong>The denser rings are actually very comparable <em>in mass density</em> to that of air</strong>.  Because of their larger particle/particulate sizes, the number density is much much smaller.</p>

<p>e.g.<br>
<strong>Ring A</strong>: Radius ~ 137,000km, thickness ~ 10m, surface density ~ 20 g/cm^2<br>
so a density of about 0.02 g/cm^3, which is about 10 times more than air, and 100 times less than water.</p>

<p>Much, much more info here:<br>
<a href="http://nssdc.gsfc.nasa.gov/planetary/factsheet/satringfact.html">http://nssdc.gsfc.nasa.gov/planetary/factsheet/satringfact.html</a></p>

CC BY-SA 3.0
2014-11-04T03:31:34.620Z
2014-11-04T03:31:34.620Z
DilithiumMatrix
<p><strong>Elements of answer</strong>:</p>
<p>It is not an easy question, as we lack of data to constrain strongly the density and mass of Saturn's rings.</p>
<p>However, a first clue of their density is their <strong>optical depth</strong> (that is a measure of the transparency of a medium). The densest rings are the one of the <em>main ring system</em> (rings A, Cassini Division, B and C) plus ring F; they are characterized by optical depth larger than 0.1 (up to about 5 for the densest part of ring B). Rings in the <em>faint ring system</em> (E and G) have very small optical depth (lower than <span class="math-container">$10^{-5}$</span>).</p>
<p>With this regard, B is indeed the densest ring of Saturn's rings. <strong>(edit)</strong> Looking around (<a href="http://caps.gsfc.nasa.gov/simpson/kingswood/rings/" rel="nofollow noreferrer">[1]</a> and <a href="https://nssdc.gsfc.nasa.gov/planetary/factsheet/satringfact.html" rel="nofollow noreferrer">[2]</a>) you can find numbers that help to figure out the density of this ring. Knowing its mass (about <span class="math-container">$2.8\times10^19$</span> kg) and its extend (from 1.527 to 1.951 Saturn radii, with a typical thickness of 100 m), you can deduce a mean density of about 10 kg.m<span class="math-container">$^{-3}$</span> (about 10 times denser than the terrestrial atmosphere at sea level).</p>
<p><strong>Just for fun:</strong></p>
<p>This gives you an idea of what means the optical depth. In the densest parts of ring B, optical depth is between 2.5 and 5, so you'll definitely notice you're in the ring. It is probably more complicated than that (with ring particles ranging from dust size to house size), but you get the idea.
<img src="https://i.sstatic.net/qkFXO.png" alt="enter image description here" /></p>
<p><strong>Side note:</strong></p>
<p>Optical depth is a measure of transparency of one medium; it measures how radiation is neither scattered nor absorbed by the medium. It expression is given by</p>
<p><span class="math-container">$$\frac{I}{I_0} = {\rm e}^{-\tau}$$</span></p>
<p>where <span class="math-container">$I_0$</span> is the source intensity, <span class="math-container">$I$</span> the observed intensity, and <span class="math-container">$\tau$</span> the optical depth.</p>
<p><strong>Sources:</strong></p>
<ul>
<li><a href="http://arxiv.org/abs/0912.3017" rel="nofollow noreferrer">Charnoz 2009</a></li>
</ul>

CC BY-SA 4.0
2023-01-27T23:20:01.177Z
Since your answer is still above DilithiumMatrix's: I think you are off by many orders of magnitude.  [The typical mass of the rings of Saturn is 10^19 kg](https://www.science.org/doi/10.1126/science.aat2965), *not* 10^9 kg.  For rings 10^7 km wide and 100m thick, this gives a density of 10 kg/m^3, 10 times air and 1/100th of water. As the rings are mostly ice, this means 1% by volume.  There's at least an order of magnitude uncertainty there, but the dense parts of the rings are *way* denser than the value you give (0.00167 g/m^3).
Jess Riedel
CC BY-SA 4.0
2023-02-20T13:27:56.103Z
There was indeed a typo in my answer that lead to wrong results. The optical depth still hold (I rechecked the numbers than can be found [here](https://nssdc.gsfc.nasa.gov/planetary/factsheet/satringfact.html). I edited my answer accordingly.
MBR
CC BY-SA 4.0
2013-10-22T16:54:11.917Z
2023-02-20T13:31:08.817Z
2023-02-20T13:31:08.817Z
MBR
<p>I assume that the A ring is the densest, but I might be wrong. Nevertheless, I failed to find any explicit information over the net about the minimum and maximum of densities for the different rings. As a less practical question: what would one see upon entering one of the denser rings? Would it be obvious that it is a dense but thin (few metres - 1 km) cloud of particles, continuously bombarding the spacecraft irregardless whether it orbits along within the ring, or one would not see more than just a distant haze (if lit by the Sun) that spans over the horizon?</p>

CC BY-SA 3.0
2016-07-11T14:30:51.637Z
holy crap - Saturn's rings are only ***a few meters thick?!?***.  WTF
Fattie
CC BY-SA 3.0
2016-07-11T14:32:03.700Z
@IstvánZachar - it seems the rings are only ***one or two meters thick***, up to a few meters.  You couldn't really "enter" one.  It would be more a case of "sticking your head in" you know??  Wow.
Fattie
CC BY-SA 3.0
2014-11-04T16:05:50.003Z
@RoryAlsop Would a 'what would this look like' include images, or something else?
HDE 226868
CC BY-SA 3.0
2014-11-04T16:19:11.857Z
I was thinking images or a description, and to be honest, MBR's update looks like it could fit the bill, so unless a better answer comes along, he'll probably get the bonus. For some reason I wasn't expecting it to look like fog...
Rory Alsop
CC BY-SA 3.0
2014-11-04T19:14:30.707Z
@RoryAlsop Hadn't seen MBR's edit. Yep, that should be good.
HDE 226868
CC BY-SA 3.0
2014-11-06T14:59:29.557Z
Thanks @Rory for raising the visibility of my Q! I'm not familiar with the bounty system, is it awarded when I accept an answer (and that answerer is awarded the bounty), or the bounty is independent of my decision?
István Zachar
<saturn><planetary-ring>
How dense are Saturn's rings?
István Zachar
# How dense are Saturn's rings?

(Asked by: username_0 on 2013-10-21)

I assume that the A ring is the densest, but I might be wrong. Nevertheless, I failed to find any explicit information over the net about the minimum and maximum of densities for the different rings. As a less practical question: what would one see upon entering one of the denser rings? Would it be obvious that it is a dense but thin (few metres - 1 km) cloud of particles, continuously bombarding the spacecraft irregardless whether it orbits along within the ring, or one would not see more than just a distant haze (if lit by the Sun) that spans over the horizon?

**Tags:** saturn, planetary-ring

> **Comments:**
> **username_2**: @RoryAlsop Would a 'what would this look like' include images, or something else?  
> **username_3**: I was thinking images or a description, and to be honest, username_5's update looks like it could fit the bill, so unless a better answer comes along, he'll probably get the bonus. For some reason I wasn't expecting it to look like fog...  
> **username_2**: @RoryAlsop Hadn't seen username_5's edit. Yep, that should be good.  
> **username_0**: Thanks @Rory for raising the visibility of my Q! I'm not familiar with the bounty system, is it awarded when I accept an answer (and that answerer is awarded the bounty), or the bounty is independent of my decision?  
> **username_1**: holy crap - Saturn's rings are only ***a few meters thick?!?***.  WTF  
> **username_1**: @IstvánZachar - it seems the rings are only ***one or two meters thick***, up to a few meters.  You couldn't really "enter" one.  It would be more a case of "sticking your head in" you know??  Wow.  

---

## 2 answers

### Answer by username_5 on 2013-10-22. Score: 20 | Accepted answer

**Elements of answer**:

It is not an easy question, as we lack of data to constrain strongly the density and mass of Saturn's rings.

However, a first clue of their density is their **optical depth** (that is a measure of the transparency of a medium). The densest rings are the one of the *main ring system* (rings A, Cassini Division, B and C) plus ring F; they are characterized by optical depth larger than 0.1 (up to about 5 for the densest part of ring B). Rings in the *faint ring system* (E and G) have very small optical depth (lower than $10^{-5}$).

With this regard, B is indeed the densest ring of Saturn's rings. **(edit)** Looking around ([[1]](http://caps.gsfc.nasa.gov/simpson/kingswood/rings/) and [[2]](https://nssdc.gsfc.nasa.gov/planetary/factsheet/satringfact.html)) you can find numbers that help to figure out the density of this ring. Knowing its mass (about $2.8\times10^19$ kg) and its extend (from 1.527 to 1.951 Saturn radii, with a typical thickness of 100 m), you can deduce a mean density of about 10 kg.m$^{-3}$ (about 10 times denser than the terrestrial atmosphere at sea level).

**Just for fun:**

This gives you an idea of what means the optical depth. In the densest parts of ring B, optical depth is between 2.5 and 5, so you'll definitely notice you're in the ring. It is probably more complicated than that (with ring particles ranging from dust size to house size), but you get the idea.
![enter image description here](https://i.sstatic.net/qkFXO.png)

**Side note:**

Optical depth is a measure of transparency of one medium; it measures how radiation is neither scattered nor absorbed by the medium. It expression is given by

$$\frac{I}{I\_0} = {\rm e}^{-\tau}$$

where $I\_0$ is the source intensity, $I$ the observed intensity, and $\tau$ the optical depth.

**Sources:**

* [Charnoz 2009](http://arxiv.org/abs/0912.3017)

> **Comments:**
> **username_6**: Since your answer is still above username_4's: I think you are off by many orders of magnitude.  [The typical mass of the rings of Saturn is 10^19 kg](https://www.science.org/doi/10.1126/science.aat2965), *not* 10^9 kg.  For rings 10^7 km wide and 100m thick, this gives a density of 10 kg/m^3, 10 times air and 1/100th of water. As the rings are mostly ice, this means 1% by volume.  There's at least an order of magnitude uncertainty there, but the dense parts of the rings are *way* denser than the value you give (0.00167 g/m^3).  
> **username_5**: There was indeed a typo in my answer that lead to wrong results. The optical depth still hold (I rechecked the numbers than can be found [here](https://nssdc.gsfc.nasa.gov/planetary/factsheet/satringfact.html). I edited my answer accordingly.  

---

### Answer by username_4 on 2014-11-04. Score: 9

**The denser rings are actually very comparable *in mass density* to that of air**. Because of their larger particle/particulate sizes, the number density is much much smaller.

e.g.  
**Ring A**: Radius ~ 137,000km, thickness ~ 10m, surface density ~ 20 g/cm^2  
so a density of about 0.02 g/cm^3, which is about 10 times more than air, and 100 times less than water.

Much, much more info here:  
<http://nssdc.gsfc.nasa.gov/planetary/factsheet/satringfact.html>


---

