<p>For a liquid, hydrostatic pressure is <span class="math-container">$\rho g h$</span> where <span class="math-container">$\rho$</span> is density (this is always the same for all water) g is gravitational acceleration and h is depth.</p>

<p>The gravitational acceleration on Europa is 1.3 <span class="math-container">$\text{m/s}{}^2$</span> (compared with 9.8 <span class="math-container">$\text{m/s}{}^2$</span> on Earth). But on Europa there is 20km of ice floating on the water. </p>

<p>As a rough estimate, the gravity in Europa is 1/10 that on Earth, so the pressure at the bottom of the ice/top of the water would be comparable to the pressure at 2km in the Earth's Oceans. </p>

<p>Since we can build submarines that can operate at 10km, we could reasonably suppose that we could operate submarines down to about 100km on Europa, which takes us to the rocky surface. However we have no way to pass through 20km of ice crust to reach the water layer. Building the submarine may be the easy part!</p>

CC BY-SA 4.0
2018-11-29T00:03:53.327Z
A *hot* submarine could melt its way through, a bit like a dark stone on a glacier ;-)
Chappo Hasn't Forgotten
CC BY-SA 4.0
2018-11-29T01:28:32.657Z
Nice answer.   Is 20 km of ice a pretty good estimate?   I thought it was a lot less certain.
userLTK
CC BY-SA 4.0
2018-11-29T04:50:33.543Z
@Chappo Yup.  Put a nuclear reactor (not merely a RTG) on board, melt your way down.
Loren Pechtel
CC BY-SA 4.0
2018-11-29T07:46:11.303Z
To be fair, the density *does* change due to pressure and impurities - the difference is small, but whether it's negligible depends on what you're trying to calculate. In this case, it's definitely dwarfed by the difference in gravity and the ice layer, though (unless there's something *very* weird about Europa's oceans, which is a distant possibility).
Luaan
CC BY-SA 4.0
2018-12-01T18:08:28.457Z
what kind of radio or other communication device is needed to transmit through 20km of water ice?
Alonda
CC BY-SA 4.0
2018-12-01T20:27:56.523Z
@Alonda a magical one (or a long piece of wire)
James K
CC BY-SA 4.0
2018-12-01T23:30:14.900Z
naive proposal; x-ray laser?
Alonda
CC BY-SA 4.0
2018-12-02T10:11:01.247Z
https://physics.stackexchange.com/questions/150546/why-dont-x-rays-travel-through-water x-rays will penetrate through several meters of water. Not several km.
James K
CC BY-SA 4.0
2018-11-28T21:44:32.433Z
2018-12-01T07:28:03.117Z
2018-12-01T07:28:03.117Z
James K
<p>How different would being under water in Europa differ from being under water on Earth? Would it be possible to dive deeper on Europa with a submarine than on Earth and by how much?</p>

<p><a href="https://i.sstatic.net/mLYOy.jpg" rel="nofollow noreferrer"><img src="https://i.sstatic.net/mLYOy.jpg" alt="enter image description here"></a></p>

CC BY-SA 4.0
2018-11-28T21:39:51.927Z
In order to answer this you'd need to know the density of Europa's oceans, which I don't believe anyone knows. Water pressure is created by the weight of the column of water above the depth in question, and this is directly related to its density. But if one assumes the density to be about equal to Earth's oceans, then the diving depth would simply be the ratio of Earth's and Europa's gravity (Earth = 9.78, Europa = 1.314).
BillDOe
CC BY-SA 4.0
2018-11-28T22:17:02.487Z
@BillDOe How compressible do you think water is?
ProfRob
CC BY-SA 4.0
2018-11-29T04:49:28.190Z
@BillDOe Why do you think there would be a meaningful difference in density?  (Obviously, if you get deep enough you'll start seeing effects but long before you get appreciable compression you'll get phase changes.)
Loren Pechtel
CC BY-SA 4.0
2018-11-29T20:15:59.170Z
I was thinking about dissolved solids in Europa's oceans possibly increasing the water's density and therefore weight, not the compressibility of water. Ocean water on Earth, for instance, is more dense that fresh water.
BillDOe
<gravity><astrophysics><planetary-atmosphere><europa>
How does gravity affect pressure under water?
Muze
# How does gravity affect pressure under water?

(Asked by: username_0 on 2018-11-28)

How different would being under water in Europa differ from being under water on Earth? Would it be possible to dive deeper on Europa with a submarine than on Earth and by how much?

[![enter image description here](https://i.sstatic.net/mLYOy.jpg)](https://i.sstatic.net/mLYOy.jpg)

**Tags:** gravity, astrophysics, planetary-atmosphere, europa
> **Comments:**
> **username_1**: In order to answer this you'd need to know the density of Europa's oceans, which I don't believe anyone knows. Water pressure is created by the weight of the column of water above the depth in question, and this is directly related to its density. But if one assumes the density to be about equal to Earth's oceans, then the diving depth would simply be the ratio of Earth's and Europa's gravity (Earth = 9.78, Europa = 1.314).  
> **username_2**: @BillDOe How compressible do you think water is?  
> **username_3**: @BillDOe Why do you think there would be a meaningful difference in density?  (Obviously, if you get deep enough you'll start seeing effects but long before you get appreciable compression you'll get phase changes.)  
> **username_1**: I was thinking about dissolved solids in Europa's oceans possibly increasing the water's density and therefore weight, not the compressibility of water. Ocean water on Earth, for instance, is more dense that fresh water.  

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## 1 answers

### Answer by username_4 on 2018-11-28. Score: 11 | Accepted answer

For a liquid, hydrostatic pressure is $\rho g h$ where $\rho$ is density (this is always the same for all water) g is gravitational acceleration and h is depth.

The gravitational acceleration on Europa is 1.3 $\text{m/s}{}^2$ (compared with 9.8 $\text{m/s}{}^2$ on Earth). But on Europa there is 20km of ice floating on the water.

As a rough estimate, the gravity in Europa is 1/10 that on Earth, so the pressure at the bottom of the ice/top of the water would be comparable to the pressure at 2km in the Earth's Oceans.

Since we can build submarines that can operate at 10km, we could reasonably suppose that we could operate submarines down to about 100km on Europa, which takes us to the rocky surface. However we have no way to pass through 20km of ice crust to reach the water layer. Building the submarine may be the easy part!

> **Comments:**
> **username_5**: A *hot* submarine could melt its way through, a bit like a dark stone on a glacier ;-)  
> **username_6**: Nice answer.   Is 20 km of ice a pretty good estimate?   I thought it was a lot less certain.  
> **username_3**: @Chappo Yup.  Put a nuclear reactor (not merely a RTG) on board, melt your way down.  
> **username_7**: To be fair, the density *does* change due to pressure and impurities - the difference is small, but whether it's negligible depends on what you're trying to calculate. In this case, it's definitely dwarfed by the difference in gravity and the ice layer, though (unless there's something *very* weird about Europa's oceans, which is a distant possibility).  
> **username_8**: what kind of radio or other communication device is needed to transmit through 20km of water ice?  
> **username_4**: @Alonda a magical one (or a long piece of wire)  
> **username_8**: naive proposal; x-ray laser?  
> **username_4**: https://physics.stackexchange.com/questions/150546/why-dont-x-rays-travel-through-water x-rays will penetrate through several meters of water. Not several km.  

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