View Full Version : Carbon dioxide atmosphere on Mars

2004-Jan-30, 04:50 PM
Carbon dioxide in our atmosphere has been declared a "greenhouse gas" that prevents earths heat from dissipating into space. Mars atmosphere is 95 percent carbon diodide and has a concentration some 30 times greater than that in the earths atmosphere. My question is why does'nt the carbon dioxide atmosphere on Mars create a "greenhouse effect " and keep the planet warmer?

2004-Jan-30, 05:35 PM
Mars do have some atmospheric carbon dioxide, but almost no atmosphere! The existing atmosphere is so thin that it can't retain energy from the Sun. Therefore extreme temperature contrasts between day and night and sun or shade ro whatever that calls.

The Red Planet displays hardly any greenhouse effect. However, most scientists agree that Mars was much warmer in the past and even had oceans, which means that the atmosphere was also very different. About 3600 million years ago, something happened and the planet evolved towards its current state.

Hope this help


2004-Jan-31, 10:01 PM
I guess you are saying that carbon dioxide is ineffective as a "Greenhouse" gas.


2004-Feb-01, 12:23 AM
Carbon dioxide would be particularly good in suitable quantities, but I believe the martian atmosphere is 1000 times thinner than earths and receives about a quarter of the sun's energy as earth does...maybe there is a Martian greenhouse effect already occurrring, but considering the conditions, it may not amount to much by earth standards.

2004-Feb-01, 05:48 PM
I thought this was an excellent question to pose to Dr. Wood, a planetary scientist. He thought it was a good question too. We are ever appreciative of his timely responses. His answer:

Good question!

The answer lies in the total mass of the atmosphere. Venus and Mars both have the same relative amount of carbon dioxide in their atmospheres, but Venus’ atmosphere is 100 times thicker than Earth’s atmosphere and Mars’ is about 100 times thinner than Earth’s. Mars is also more than 2.5 times farther from the Sun than Venus is, so it receives only about 1/7 of the total sunlight that Venus does at the top of the atmosphere.

Venus’s atmosphere acts like a very thick and heavy blanket, while Mars’ atmosphere is not much more than a very light sheet. Combined with the amount of incident solar radiation, you can begin to understand why Mars’s greenhouse effect is so small.

Dr. Wood

2004-Feb-02, 09:22 AM
I want Dr. Wood's autograph!!

Is it therefore possible to generate a sustained greemhouse on Mars, artificially?

2004-Feb-02, 04:12 PM

Here is a few ideas that they have for Terraforming mars which of course would have to start with the thickening of the atmosphere.


2004-Feb-02, 05:20 PM
I would like to thank Dr. Wood for his responce to my question. It was very helpful, but it leads to several other questions. On earth, where our atmospheric blanket is controlled primarily by a greehouse gas (water vapor), why is so much attention being given to the control of carbon dioxide under the quise of protecting our climate? Woudn't the added impact of carbon dioxide be insignificant in comparison to the effect of water vapor? As carbon dioxide is the raw material for photosynthesis, isn't there be a bigger threat in the possibility of run away algae blooms?

2004-Feb-02, 10:35 PM
I think you've hit on part of the big debate on global warming. I believe the ability to KEEP an atmosphere depends the the mass of the planet too. Not enough mass, not enough gravity to keep the atmosphere from escaping into space.

2004-Feb-03, 05:20 PM
What you must remember with Earth's "greenhouse" is that both water vapour and carbon dioxide in the atmosphere are intimately tied into homoeostatic processes on a huge scale. It is a BIOLOGICAL system, not a purely physical one. The problem with anthropogenic CO2 in the atmosphere is that it originates outisde the current biological processes and swamps the homoeostatic capacity, leading eventually to the runaway greenhouse which would be our worst case scenario.....

The problem (for us as a species) is that these systems are like elastic bands - they'll stretch a long, long way, but will probably fail catastrophically in the end (eg ocean conveyor system).

But why are we SO different to Mars and Venus - Earth is a living planet. That's the whole point behind the Gaia theory (life is complex, creates feedback loops with different lag times, and it dominates its surroundings). Mars and Venus are dead - their atmosphere is determined by chemical equilibirum and physical forces alone. A planet with healthy life has an atmosphere far from chemical equilibrium.

As to getting off this planet, I'm torn. We're gonna need a new one soon, but should we have it before we learn how this one works??

2004-Feb-04, 01:38 AM
Another difference between earth & mars also relates to the difference in mass between the two planets. As mars is only 1/3 as large as the earth, water vapour that gets into the atmosphere and reaches the cloud tops and is broken down by sunlight into O2, ozone & H, escapes. This is because these gasses' escape velocity is low enough to escape from mars, whereas O2 & ozone are held by earths gravity.

Because O2 "bleeds" out of mars' atmosphere, it is unable to recombine with hydrogen that may be released by volcanic activity. Therefore there is no opportunity for mars to develope the greenhouse effect that water vapour provides on earth.

This is partly why the martian atmosphere is so thin.

Methane also plays a large role on earth--and this is mostly the result of biospheric activity.

2004-Feb-04, 01:34 PM
"We find that we live on an insignificant planet of a humdrum star .... " - surely, until and unless we find other life, our planet is the MOST significant and least humdrum that we know of ?