<p>If I understood it correctly, the important point is the temperature difference between mars and earth. On earth increasing obliquity, as you wrote, leads to increased melting of ice, ie. you increase the amount of liquid water on earth.</p>

<p>On mars average temperatures even during summer are too low to allow for liquid water. Higher obliquity doesn't really lead to a melting of ice. It mainly increases sublimation thereby increasing the water content of the atmosphere also on lower latitudes. The water vapour freezes out and leads to ice shields extended to lower latitudes.</p>

<p>So in short, since temperatures on mars are too low to allow for liquid water, the extend of the ice cover is larger, when the ice receives increased insolation. 
Whereas on earth the ice cover is larger when insolation is low, since it gains mass from the pool of liquid water.    </p>

CC BY-SA 3.0
2014-06-23T18:13:39.850Z
So Martian ice ages are actually *warm* periods?
gerrit
CC BY-SA 3.0
2014-06-23T18:49:09.987Z
Hmm, no, I wouldn't conclude that. You have more insolation at the poles and therefore more humidity in higher latitudes. That doesn't mean it's warmer on average. In fact you get increased ice shields so the albedo will go up. I would expect ice ages on mars to be cooler on average than interglacials. It's similar on earth, ice ages are not cold because the poles receive less insolation but because this drop in insolation leads to extended ice shields and thereby to a higher albedo. It's the change in albedo that is important, not the amount of insolation on the poles.
taupunkt
CC BY-SA 3.0
2014-06-23T19:54:15.427Z
Still, two conflicting effects: more water vapour (warmer) and more ice (lower albedo -> colder).  The limiting factor for the formation of ice on Earth is temperature (in most places); the limiting factor on Mars would be humidity.  So the physics are quite different.  Interesting.
gerrit
CC BY-SA 3.0
2014-06-23T20:28:15.293Z
Ya, I guess one can put it that way. On earth you have water everywhere but in most places it's too warm for it to freeze. On Mars it's cold enough almost everywhere but you don't necessarily have water that could freeze.
taupunkt
CC BY-SA 3.0
2014-06-22T17:02:24.170Z
2014-06-22T17:02:24.170Z
taupunkt
<p><a href="http://www.nature.com/nature/journal/v426/n6968/full/nature02114.html#B7">This paper</a> here goes into some detail about how Mars' experiences its own form of 'ice ages' on a quasi periodic basis driven by the wobbling of its axis. The main mechanism outlined is that the stability of water ice on the surface increases with increased obliquity. This is in contrast to Earth when at high obliquity there is increased polar summer insolation leading to metling. What is the difference? </p>

<p>On a more discussion based addition to the question, could factors such as ice albedo and other feedback loops play a similar role in Mars' ice ages that they do in Earth's ice ages?</p>

<p><em>I have also asked this at the Astronomy stack exchange <a href="https://astronomy.stackexchange.com/questions/3711/why-does-mars-experience-an-ice-age-at-high-axis-obliquity-when-earth-experi">here</a></em></p>

<climate><planetary-science><ice-age><mars>
Why does Mars' experience an 'ice age' at high axis obliquity, when Earth experiences an ice age at low axis obliquity
AlexLipp
# Why does Mars' experience an 'ice age' at high axis obliquity, when Earth experiences an ice age at low axis obliquity

(Asked by: username_0 on 2014-06-20)

[This paper](http://www.nature.com/nature/journal/v426/n6968/full/nature02114.html#B7) here goes into some detail about how Mars' experiences its own form of 'ice ages' on a quasi periodic basis driven by the wobbling of its axis. The main mechanism outlined is that the stability of water ice on the surface increases with increased obliquity. This is in contrast to Earth when at high obliquity there is increased polar summer insolation leading to metling. What is the difference?

On a more discussion based addition to the question, could factors such as ice albedo and other feedback loops play a similar role in Mars' ice ages that they do in Earth's ice ages?

*I have also asked this at the Astronomy stack exchange [here](https://astronomy.stackexchange.com/questions/3711/why-does-mars-experience-an-ice-age-at-high-axis-obliquity-when-earth-experi)*

**Tags:** climate, planetary-science, ice-age, mars


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## 1 answers

### Answer by username_1 on 2014-06-22. Score: 11 | Accepted answer

If I understood it correctly, the important point is the temperature difference between mars and earth. On earth increasing obliquity, as you wrote, leads to increased melting of ice, ie. you increase the amount of liquid water on earth.

On mars average temperatures even during summer are too low to allow for liquid water. Higher obliquity doesn't really lead to a melting of ice. It mainly increases sublimation thereby increasing the water content of the atmosphere also on lower latitudes. The water vapour freezes out and leads to ice shields extended to lower latitudes.

So in short, since temperatures on mars are too low to allow for liquid water, the extend of the ice cover is larger, when the ice receives increased insolation.
Whereas on earth the ice cover is larger when insolation is low, since it gains mass from the pool of liquid water.

> **Comments:**
> **username_2**: So Martian ice ages are actually *warm* periods?  
> **username_1**: Hmm, no, I wouldn't conclude that. You have more insolation at the poles and therefore more humidity in higher latitudes. That doesn't mean it's warmer on average. In fact you get increased ice shields so the albedo will go up. I would expect ice ages on mars to be cooler on average than interglacials. It's similar on earth, ice ages are not cold because the poles receive less insolation but because this drop in insolation leads to extended ice shields and thereby to a higher albedo. It's the change in albedo that is important, not the amount of insolation on the poles.  
> **username_2**: Still, two conflicting effects: more water vapour (warmer) and more ice (lower albedo -> colder).  The limiting factor for the formation of ice on Earth is temperature (in most places); the limiting factor on Mars would be humidity.  So the physics are quite different.  Interesting.  
> **username_1**: Ya, I guess one can put it that way. On earth you have water everywhere but in most places it's too warm for it to freeze. On Mars it's cold enough almost everywhere but you don't necessarily have water that could freeze.  

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