<p>North and south are defined according to the planet's rotation about its axis. A "right hand" rule is used: If you make a fist with your right hand, and orient your curled fingers in the direction the planet rotates, your thumb points north. Alternatively: Standing on the equator, facing the direction the planet rotates, North is to your left.</p>

<p><a href="http://en.wikipedia.org/wiki/Axial_tilt" rel="nofollow">Axial Tilt</a> on wikipedia has this information (and more.)</p>

<p><strong>update</strong></p>

<p>hey! Don't up vote this answer; It's wrong... see the comments where the OP has actually researched and discovered the real answer. (I don't want to delete this answer because we'll lose the comments too!)</p>

CC BY-SA 3.0
2014-07-16T18:12:15.667Z
That's interesting; I wouldn't have thought to look for that information under "Axial Tilt". Thanks for sharing!
called2voyage
CC BY-SA 3.0
2014-07-16T18:15:50.513Z
I also tried to find a better link on the [IAU](http://www.iau.org/) web site, but didn't find anything better. There's probably an official document that says exactly how they do it.
Craig Constantine
CC BY-SA 3.0
2014-07-16T18:18:30.403Z
It appears the IAU actually defines north differently: http://download.springer.com/static/pdf/49/art%253A10.1007%252Fs10569-007-9072-y.pdf?auth66=1405707429_bc7c5277c4389320d62d623be73d0bf0&ext=.pdf
called2voyage
CC BY-SA 3.0
2014-07-16T18:21:19.107Z
Relevant portion: "The north pole is that pole of rotation that lies on the north side of the invariable
plane of the solar system." The north of the invariable plane is the side that Earth's North pole points to.
called2voyage
CC BY-SA 3.0
2014-07-16T18:21:43.530Z
Now I've found it on Wikipedia as well: http://en.wikipedia.org/wiki/Poles_of_astronomical_bodies
called2voyage
CC BY-SA 3.0
2014-07-16T18:24:48.290Z
Dwarf planets, minor planets, their satellites, and comets *do* follow the right-hand rule, though.
called2voyage
CC BY-SA 3.0
2014-07-16T20:43:00.457Z
The North Pole of any system being the pole on the same side as earth's north is indeed the correct definition. This applies to the Milky Way galaxy as well, in which case the North Galactic Pole is the pole towards the hemisphere of the galactic sphere which also contains the celestial north pole.
Takku
CC BY-SA 3.0
2014-07-16T20:53:47.193Z
...then my answer is *completely* wrong. Write your comments up as an answer so I can delete my answer.
Craig Constantine
CC BY-SA 3.0
2014-07-17T03:32:49.070Z
@CraigConstantine You're free to steal my info. Besides, the right-hand rule *is* right for planetoids.
called2voyage
CC BY-SA 3.0
2014-07-17T12:50:20.323Z
...but your actual question is about Mars. I won't steal your answer/reasearch, but thanks. :)
Craig Constantine
CC BY-SA 3.0
2014-07-17T13:35:03.250Z
@CraigConstantine Since you insisted, I have posted my own answer. I can accept it tomorrow.
called2voyage
CC BY-SA 3.0
2014-07-17T14:01:28.350Z
@TracyCramer I know that you deleted your comment, so you may have realized that your question isn't valid. Earth's geographic pole does not swap. It's magnetic poles can swap, but that does not affect which side of Earth we consider North or South, magnetically or geographically.
called2voyage
CC BY-SA 3.0
2014-07-16T18:00:50.863Z
2014-07-17T12:51:17.130Z
2014-07-17T12:51:17.130Z
Craig Constantine
<p>The research in other answers helped me come across the actual International Astronomical Union (IAU) standard:</p>

<blockquote>
  <p>The north pole is that pole of rotation that lies on the north side of the invariable plane of the solar system.</p>
</blockquote>

<p>The north of the invariable plane is the side that Earth's North pole points to. In fact, one of our other users has observed:</p>

<blockquote>
  <p>The North Pole of any system being the pole on the same side as earth's north is indeed the correct definition. This applies to the Milky Way galaxy as well, in which case the North Galactic Pole is the pole towards the hemisphere of the galactic sphere which also contains the celestial north pole.</p>
</blockquote>

<p>Dwarf planets, minor planets, their satellites, and comets do follow the right-hand rule mentioned in other answers (see <a href="http://en.wikipedia.org/wiki/Axial_tilt">Axial tilt</a> on Wikipedia).</p>

<p><strong>Sources:</strong></p>

<ul>
<li><a href="http://download.springer.com/static/pdf/49/art%253A10.1007%252Fs10569-007-9072-y.pdf?auth66=1405707429_bc7c5277c4389320d62d623be73d0bf0&amp;ext=.pdf">Report of the IAU/IAG Working Group on cartographic
coordinates and rotational elements: 2006 - P. Kenneth Seidelmann, B. A. Archinal,
M. F. A’hearn, et al.</a></li>
<li><a href="http://en.wikipedia.org/wiki/Poles_of_astronomical_bodies">Poles of astronomical bodies - Wikipedia</a></li>
</ul>

CC BY-SA 3.0
2014-07-17T13:34:34.707Z
2014-07-17T13:34:34.707Z
called2voyage
<p>How was it decided which hemisphere was North and which hemisphere was South on Mars? Clearly, the designations "North" and "South" apply only to the hemispheres which contain the axis of rotation at their center, but what determined whether a hemisphere received "North" or "South" as its designation?</p>

<mars><naming>
How were the designations of "North" and "South" applied to the hemispheres of Mars?
called2voyage
# How were the designations of "North" and "South" applied to the hemispheres of Mars?

(Asked by: username_0 on 2014-07-16)

How was it decided which hemisphere was North and which hemisphere was South on Mars? Clearly, the designations "North" and "South" apply only to the hemispheres which contain the axis of rotation at their center, but what determined whether a hemisphere received "North" or "South" as its designation?

**Tags:** mars, naming

---

## 2 answers

### Answer by username_0 on 2014-07-17. Score: 7 | Accepted answer

The research in other answers helped me come across the actual International Astronomical Union (IAU) standard:

> The north pole is that pole of rotation that lies on the north side of the invariable plane of the solar system.

The north of the invariable plane is the side that Earth's North pole points to. In fact, one of our other users has observed:

> The North Pole of any system being the pole on the same side as earth's north is indeed the correct definition. This applies to the Milky Way galaxy as well, in which case the North Galactic Pole is the pole towards the hemisphere of the galactic sphere which also contains the celestial north pole.

Dwarf planets, minor planets, their satellites, and comets do follow the right-hand rule mentioned in other answers (see [Axial tilt](http://en.wikipedia.org/wiki/Axial_tilt) on Wikipedia).

**Sources:**

* [Report of the IAU/IAG Working Group on cartographic
  coordinates and rotational elements: 2006 - P. Kenneth Seidelmann, B. A. Archinal,
  M. F. A’hearn, et al.](http://download.springer.com/static/pdf/49/art%253A10.1007%252Fs10569-007-9072-y.pdf?auth66=1405707429_bc7c5277c4389320d62d623be73d0bf0&ext=.pdf)
* [Poles of astronomical bodies - Wikipedia](http://en.wikipedia.org/wiki/Poles_of_astronomical_bodies)


---

### Answer by username_1 on 2014-07-16. Score: 2

North and south are defined according to the planet's rotation about its axis. A "right hand" rule is used: If you make a fist with your right hand, and orient your curled fingers in the direction the planet rotates, your thumb points north. Alternatively: Standing on the equator, facing the direction the planet rotates, North is to your left.

[Axial Tilt](http://en.wikipedia.org/wiki/Axial_tilt) on wikipedia has this information (and more.)

**update**

hey! Don't up vote this answer; It's wrong... see the comments where the OP has actually researched and discovered the real answer. (I don't want to delete this answer because we'll lose the comments too!)

> **Comments:**
> **username_0**: That's interesting; I wouldn't have thought to look for that information under "Axial Tilt". Thanks for sharing!  
> **username_1**: I also tried to find a better link on the [IAU](http://www.iau.org/) web site, but didn't find anything better. There's probably an official document that says exactly how they do it.  
> **username_0**: It appears the IAU actually defines north differently: http://download.springer.com/static/pdf/49/art%253A10.1007%252Fs10569-007-9072-y.pdf?auth66=1405707429_bc7c5277c4389320d62d623be73d0bf0&ext=.pdf  
> **username_0**: Relevant portion: "The north pole is that pole of rotation that lies on the north side of the invariable plane of the solar system." The north of the invariable plane is the side that Earth's North pole points to.  
> **username_0**: Now I've found it on Wikipedia as well: http://en.wikipedia.org/wiki/Poles_of_astronomical_bodies  
> **username_0**: Dwarf planets, minor planets, their satellites, and comets *do* follow the right-hand rule, though.  
> **username_2**: The North Pole of any system being the pole on the same side as earth's north is indeed the correct definition. This applies to the Milky Way galaxy as well, in which case the North Galactic Pole is the pole towards the hemisphere of the galactic sphere which also contains the celestial north pole.  
> **username_1**: ...then my answer is *completely* wrong. Write your comments up as an answer so I can delete my answer.  
> **username_0**: @CraigConstantine You're free to steal my info. Besides, the right-hand rule *is* right for planetoids.  
> **username_1**: ...but your actual question is about Mars. I won't steal your answer/reasearch, but thanks. :)  
> **username_0**: @CraigConstantine Since you insisted, I have posted my own answer. I can accept it tomorrow.  
> **username_0**: @TracyCramer I know that you deleted your comment, so you may have realized that your question isn't valid. Earth's geographic pole does not swap. It's magnetic poles can swap, but that does not affect which side of Earth we consider North or South, magnetically or geographically.  

---

