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"There is nothing more difficult to take in hand, more perilous to conduct, or more uncertain in its success than to take the lead in the introduction of a new order of things."

-Jean-Jacques Rousseau, 1712-78

Could people live freely on Mars one day? Today, Mars is a frozen desert with a carbon dioxide atmosphere that is too thin for liquid water to exist. Water may however, exist deep underground in subsurface aquifers.  Spacecraft images show what appear to be flood channels and valley networks which may be billions of years old, originating in a time when liquid water flowed across the surface of Mars.

In that time, Mars would have possessed a thicker atmosphere and its climate and environment were more like Earth's. So, where did the atmosphere and all the water go? What caused the environment to change? Could we change it back again? Could we make Mars a warm, wet, habitable planet like Earth? This process is called terraforming (terra = Earth).

The first task would be to thicken the Martian atmosphere. Much of the ancient Martian atmosphere and water are believed to have been frozen into the Martian polar caps as the planet cooled off over time. The ice caps are composed of dry ice (frozen carbon dioxide) and water ice. Some of the atmosphere may be in permafrost below the surface. How could we evaporate the ice caps into the atmosphere and begin to increase the temperature? Both water and carbon dioxide are greenhouse gases. That is, they trap heat from sunlight, which would increase the surface temperature. This would begin a cycle that would melt more ice, warm the planet, and increase both air pressure and temperature. The process could become self-sustaining and could lead to a runaway greenhouse effect. Even though it would increase the amount of carbon dioxide in the atmosphere, this is a mandatory step towards increasing atmospheric pressure and density. See a series of images showing the greening of Mars from the IMAX film, Destiny in Space.

The sunlight that hits a planet's surface arrives primarily as visible and ultraviolet light. The planet absorbs this solar energy, and then radiates warming infrared energy back out into the atmosphere. Greenhouse gases in the atmosphere work as a global layer of insulation, trapping that infrared radiation and preventing it from escaping into space.

But, how could we accomplish this? In the 1970's, astronomer Carl Sagan suggested covering the polar caps with dark material - such as carbon black from a pulverized asteroid - to a depth of 1 millimeter. Sagan estimated that over 100 million tons (or a 600-meter asteroid) would be necessary to cover the ice caps. This cover would have to be replaced each year due to frequent dust storms. Since this would be a very arduous task, Sagan also proposed using plants that are capable of growing on ice. 

watermar.jpgIn the 1980's, Planetary scientist Chris McKay suggested that we could seed the Martian polar caps with green plants or genetically engineered microbes that extract the liquid water they need from ice. These organisms would be dark and, thus, would absorb more sunlight that would warm up the ice and increase the overall rate of evaporation. If the surface temperature was high enough, more carbon dioxide might be released from the Martian soil, permafrost, and polar ice and would flood the lowlands. This process could take from 100 to 10,000 years.

The benefit of using plants or microbes is that they are self-reproducing. Research has shown that some microbes can survive in a simulated Martian environment, similar to Earth's polar regions. Such organisms could spread out over the ice caps in a relatively short time. This process would take a few hundred years to free the ancient atmosphere of Mars. The increased surface pressure and temperature would then allow liquid water to condense on Mars. There would be rain, rivers, and perhaps even oceans. Other green plants would grow on Mars, getting nutrients from the soil and carbon dioxide from the air just as they do here on the Earth.

marsglob.gifIn 1989, scientist Martyn Fogg suggested carbon dioxide might be located in its carbonate rocks. He suggested using 10 million fusion bombs to vaporize the rocks and free the carbon dioxide.  In 1992, scientist Paul Birch suggested building large mirrors and lenses in space to reflect sunlight onto the Martian ice caps melting them. 

Releasing large amounts of chlorofluorocarbons (greenhouse gases) by the use of factories on the surface of Mars is another possibility. Some scientists suggest this process could take 100,000 years. 

The introduction of green plants would remove some of the carbon dioxide and they would give off oxygen, but it would take many thousands of years to build up enough oxygen to make the atmosphere on Mars breathable for humans and animals. The oxygen would produce an ozone layer protecting the surface from solar ultraviolet rays.  Animals and insects could then be introduced to the environment. 


Once most of the atmosphere of Mars was restored, the air pressure would be high enough to allow people to walk around without space suits. We still might need oxygen tanks and respirators (similar to scuba gear), however, because we can't breathe carbon dioxide. The thick atmosphere would shield the surface from cosmic radiation. We also would still need to protect our skin and eyes against ultraviolet rays from the Sun because the atmosphere would not have any ozone layer to shield us such as ours on Earth does.

To find out if terraforming is even possible, we need to learn a lot more about Mars. Is there enough atmosphere frozen on Mars? If so, can it be freed? If we find that Mars has life, would we want to leave the planet as it is and not interfere with it? If Mars turns out to be lifeless, we might decide to terraform it and become not only Earthlings but also Martians.

For more on terraforming Mars, check out some of these links:

Images of a terraformed Mars

Terraforming Home Page

What about life on Mars?

On August 7, 1996, a team of scientists lead by David McKay at NASA's Johnson Space Center in Houston, Texas, announced their discovery of microscopic evidence of possible Martian fossil life in a meteorite recovered from Antarctica. How might this affect future Mars exploration and settlement? What are the practical and ethical issues of the discovery of life on Mars? What should our course of action be toward possible Mars life? How much time and effort should we make towards searching for life before we declare Mars to be lifeless? Martian life could be almost anywhere.

We will need to decide, as a planet, how long we should spend searching Mars for evidence of life. What about contamination if life does exist on Mars? Humans on Mars will be exposed eventually to any Martian life that exists. Returning spacecraft and astronauts could also introduce alien organisms to Earth. Many scientists think it is unlikely that independently evolved Mars life would have enough in common with life on Earth to cause harm; but it is impossible to know for certain. 

What about our contamination of Mars? People and unsterilized robots will contaminate Mars with terrestrial organisms. Even if we are willing to risk our own lives, what about the rights of the Martians? If we did contaminate Mars with terrestrial microbes, that could complicate studies of any life that was found later on Mars.

The author Mark Lupisella, in 1997, wrote in an issue of Space Policy, "Could we forgive ourselves if we caused the extinction of the first extraterrestrial species we came into contact with?". 

Questions to think about:

  • Which method of terraforming do you think is most viable? Why? 
  • Do you think we should consider changing the environment of Mars at all? Why or why not? 
  • What do you think a plan for determining whether there is life on Mars should be?
  • If microbial life was discovered on Mars, do you think that humans should not colonize the planet? Why or why not? 

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