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Lack of CO2...A Curse or a Blessing?


 
written by Alex Moore on February 13, 2003 | author profile | forum profile | contact me
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Southern Polar Cap
Southern Polar Cap
Credit: NASA/JPL/MSSS
This week, two scientists announced the stunning discovery that Marsí southern polar cap is made primarily of water and not carbon dioxide. There was an initial reaction from the press that terraforming, however unlikely it once was, is now impossible. If the cap were solid CO2, then once it was heated a few degrees a runaway greenhouse effect would ensue, heating the entire planet to habitability. But now, with a greatly reduced CO2 count, isnít this the end of terraforming?

To understand the extent of this new discovery, we must first understand Earth. The Earth is made up of 0.035% of carbon dioxide, or about 1/2850ths of the total atmospheric composition. With an average atmospheric pressure of 1000 millibars, 0.35 millibars of CO2 exist in their gaseous state. Oxygen is much more plentiful: about 21% or 209 millibars.

The amount of water on Earth is about 1.36 billion cubic kilometers, or 1,260,000,000,000,000,000,000 (1.26 billion trillion) liters. About 2% of the atmosphere is water vapor. 1.6% is frozen in polar caps and glaciers, and 0.36% is underground in aquifers.

On Mars, the pressure is about 8 millibars. Thatís the equivalent pressure of 35,000 meters (115,000 feet) above Earth. At around 3000 meters on Earth, Acute Mountain Sickness kicks inÖ thatís 675 millibars. Since the planet is so far away from the sun, we have to raise the pressure even more. So as you can see, for terraforming to work, we have a long way to go.

According to Global Surveyor, there is 95.23% CO2 in the Martian atmosphere and 0.021% water vapor.

Letís imagine that we begin terraforming and raise the pressure (with PFCs and oxygen from plants) to 675 millibars. Without adding any CO2 or H2O to the system, we find that there would be 1.128% CO2 in the atmosphere, far under the fatal level of 10% and far above Earthís level of 0.035%. 675 millibars would also yield 0.00025% water vapor on Mars, somewhat dryer than Earthís hospitable 2% (See Also: PFCs).

Marsí southern cap contains 6 to 9 million cubic kilometers of solid something-or-other. Once thought to be CO2, it was theorized that if the planet were warmed slightly, the subliming cap would fill the planet with carbon dioxide. According to Robert Zubrin and Christopher McKay, if all that CO2 went into the atmosphere, the atmospheric pressure would rise between 50 and 100 millibars. Thatís a total between 8.5 and 15.9 percent CO2 at 675 millibars. And with only a little water vapor, the northern polar cap and aquifers underground, weíd be lucky to reach Earth proportions.

But now that we find the cap is made up of ice water, everything changes. At 675 millibars, instead of a fatal 11% carbon dioxide weíll have a little more than 1% CO2. We (some of us anyway) could run marathons on the surface. The really good news is that, instead of 6 to 9 million cubic kilometers of CO2, weíll have 6 to 9 million cubic kilometers of ice water. Thatís great for biologists, and it lends more support to the hunt for ancient or present-day life. Itís a perfect combination of carbon dioxide and water for a growing biomass.

An entirely other matter however, is the 450 to 900 millibars of CO2 hidden deep in the regolith. If it all came to the surface at once, a huge percent of the atmosphere would be carbon dioxide. But Zubrin and McKay donít expect all the CO2 in the regolith to surface for thousands of years. By that time, the CO2 gradually leaking into the atmosphere would be absorbed by the planetís biomass. A similar phenomenon occurs on Earth. The planetís CO2 cycle is refreshed with every volcanic eruption. Most of Earthís carbon dioxide is absorbed in sea algae!

Losing all this carbon dioxide is certainly not harmful to terraforming; itís actually helpful! We now realize Mars has an abundance of water, water that will someday form immense oceans. Carbon dioxide will no longer have to be ďscrubbedĒ from the atmosphere. Today, a perfect combination of gasses exists so that, when the pressure is raised, Mars will support life. It would be a wonder if we didnít find signs of ancient life.

Works Cited:

1) Yahoo News
2) Supporting Material for Science Paper
3) http://observe.arc.nasa.gov/nasa/exhibits/mars/voyage/atmos.html
4) http://www.galactic-guide.com/articles/2R34.html
5) http://space.com/scienceastronomy/mars_ice_030213.html
6) http://www.lpi.usra.edu/meetings/geomars2001/pdf/7031.pdf
7) http://humbabe.arc.nasa.gov/mgcm/faq/thin_atm.html
8) http://www.met.fsu.edu/explores/atmcomp.html
9) http://www.marsacademy.com/intro/intro1_2.htm
10) http://ftp.seds.org/pub/info/mars/Weather.txt
11) http://ga.water.usgs.gov/edu/earthhowmuch.html
12) http://www.thecookinginn.com/equiv.html
13) http://www.howstuffworks.com/question157.htm
14) http://cmex-www.arc.nasa.gov/CMEX/data/catalog/PolarCaps/SouthernCap.html
15) http://www.geocities.com/Pipeline/Shore/4331/articles/breathing.htm
16) The Case for Mars - Robert Zubrin (page 257)

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