Lecture 25

Conceptual illustration of nine stages of terraforming Mars.

Terraforming is the process by which an uninhabitable environment is altered into an Earth-like environment that terrestrial plants and even humans could survive i.e., planetary engineering.

Mars and Venus have both been considered as candidates for terraforming.

The possibility of terraforming has become part of the common psyche.  It has been used so frequently in science fiction plots (like Star Trek: Wrath of Khan, a particularly unrealistic example) that most of us know what it is (or at least think we do!) and believe it can be done.

However, to actually take a planet and alter its natural environment to create a more terrestrial friendly one is a complicated process, one that is not in our near future.

Timescale: To terraform a planet like Mars would mean the initial stages might take decades or centuries and to transform the entire planet into an Earth-like habitat would take several millennia.

Nevertheless, scientists have considered the possibilities: 

Present-day Mars  

MARS--Could we terraform and then colonize Mars?

  Red Mars cover Green Mars cover Blue Mars cover

Mars seems to be the most likely candidate for terraforming because it is most Earth-like to begin with - the temperature range overlaps that of Earth, H2O is present, and the length of the day is similar enough that organisms adapted to a 24-hour day/night cycle could adapt.  (This is a fortunate coincidence -- the day on Venus is more than 200 Earth days long!)

We have already determined that liquid water needs to stay liquid on the surface of a planet for it to be habitable----->surface temp needs to be greater than 0 C for at least part of the year for the kind of life we think of as typical to form and thrive.

Recall: the temp on Mars rises above 0°C at the equator. BUT the average temp at the surface is 50-60 C below freezing.  Even when the temperature on Mars does rise above freezing, the very thin atmosphere means the water does not remain liquid, but quickly evaporates and refreezes.

So---->to terraform Mars would mean we would need to raise the daytime surface temp to at or above freezing for at least part of the year on at least part of the planet. We also would need to give Mars a thicker atmosphere, both to give plants enough CO2  to use and to give animals oxygen to breathe.

How do we do this?


1.  CFCs or PFCs have been suggested as a possible alternative but they would need to be manufactured constantly and the amounts needed to use these gases exclusively, without carbon dioxide or water as an additional greenhouse gas, would not be easy to achieve.  Nevertheless, they would be possible, though expensive, with existing technology.

2.  One alternative gases to CO2 to raise the atmospheric temp is NH3.  Ammonia is a very efficient greenhouse gas but to obtain it we would need to convert nitrogen in the atmosphere and we don't possess that technology yet.  An alternative would be to deliberately crash ammonia-rich asteroids or comets into Mars (deliberately crashing things into Mars comes up again and again in terraforming studies!)    

3.  Another possible greenhouse gas is water vapor -- it is actually responsible for the majority of the greenhouse effect on Earth!   Like CO2 , water is present on Mars, though the exact amounts are unknown.  Once again, melting the ice caps could release greenhouse gases into the atmosphere, or deliberately crashing comets into Mars could provide a supply of water.  Once again this can be done at least partly with materials already present on Mars, and without creating an atmosphere hostile to human or other animal life.

mirror radius plot Artist's depiction of orbiting mirrors

While terraforming Mars is an exciting idea, the short-term feasibility is questtionable.  Depending on the amount of CO2 in the polar caps will determine if it is at all possible in the long-term, and the process would take thousands of years in even the best-case scenario.  Robert Zubrin and Christopher McKay, scientists who extensively studied the possibility of terraforming Mars, have concluded that

"a drastic modification of Martian conditions can be achieved using 21st century technology. The Mars so produced will closely resemble the conditions existing on the primitive Mars. Humans operating on the surface of such a Mars would require breathing gear, but pressure suits would be unnecessary. With outside atmospheric pressures raised, it will be possible to create large dwelling areas by means of very large inflatable structures. Average temperatures could be above the freezing point of water for significant regions during portions of the year, enabling the growth of plant life in the open. The spread of plants could produce enough oxygen to make Mars habitable for animals in several millennia. More rapid oxygenation would require engineering efforts supported by multi-terrawatt power sources. It is speculated that the desire to speed the terraforming of Mars will be a driver for developing such technologies, which in turn will define a leap in human power over nature as dramatic as that which accompanied the creation of post-Renaissance industrial civilization. "  --from http://www.users.globalnet.co.uk/~mfogg/zubrin.htm

A final option is "partial terraforming".  Perhaps Valles Marineris could be covered over with some type of roof (for which the technology does not yet exist).  The area within it is lower than the overall surface of Mars, giving it a higher atmospheric pressure, and since it is equatorial it is relatively warm.   It would be easier to raise the temperature and adjust the atmosphere within this "greenhouse" than it would be to do so for the entire planet, and it would still provide a large living area for humans.

Terraformed Mars
An artist's rendering of a fully terraformed Mars


The terraforming of Venus has also been considered, though it would be even more difficult than terraforming Mars:

How could the temp of Venus be brought down to a more clement level?

BUT there are not enough large asteroids in the solar system to do the job.  In addition this method would require the devastation of a large fraction of the Venus surface.

The Ethical Implications

Is it right to terraform?  Should we alter a natural environment?  

These questions are philosophically interesting but they also bear on reality.  

Some of the tricky issues are:

Does Mars as a planet have any intrinsic value in and of itself?

Is there less intrinsic worth in a planet that is devoid of life than in one with an active biosphere?  

Is Mars more valuable as a unique planet than as an "imitation Earth"?

Some of these arguments have analogs here on Earth.   Imagine you could make it possible for twice as many people to live in Arizona, by flooding the Grand Canyon.  
Would the additional living space for humans outweigh the loss of a unique geological formation?

Should we access and use the resources that are available there or should we leave them as they are?

1) Even a thick (nonbreathable) CO2 atmosphere would allow people walk on mars with just simple breathing apparatus rather than full space suits.

2) Local biomass would be critical for colonists

3) Would provide a uniting project for all of the Earth.

4) Would allow life to survive on Mars if something really bad happened to Earth

5) New technologies would be developed

6) These technologies would likely also help Earth's environment as well.

7) Planets with life on them are more important than those that do not.

8) Better use of funds than building up military stockpiles.

1) The time scales are longer than the world economic order needed to support the effort.

2) The economic benefits would be less than than the costs for a very long time.

3) Such an effort would take away Earth's "best and brightest" from important terrestrial projects and problems

4) It is not possible to prove today that Mars is devoid of life. Therefore, such a terraforming project would possibly wipe-out indigenous martian biota.

5) It is better to leave Mars as it is for scientific and aesthetic reasons.

6) We might fail and make Mars less hospitable than it is today.

7) We have done poorly here on Earth, why would we be able to make Mars into a new "earth".

8) Political or legal roadblocks might exist.

9) Who gets to live on Mars? Who owns it? Who controls it Earth or Mars?

10) The future of the Mars biosphere cannot be predicted or controlled possibly leading to failure.

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