Many scientists believe that billions of years ago, Mars was a warm, wet place. Such conditions may have been more hospitable to life. Scientists also believe that the red planet can be transformed to support life again, including human colonies.
The process of transforming a planet to make it hospitable for humans is known as terraforming. NASA scientists, groups such as the Mars Society, and Internet-based communities such as Red Colony continually discuss how to colonize and terraform Mars.
While no single method or process is considered best, Rothschild said the common goal is breathable air and drinkable water. "If you get oxygen and liquid water, you can do a whole lot," she said.
Rothschild's major concern about human exploration of Mars is that the mere presence of humans will contaminate the planet and potentially compromise any life that may be there.
"If you're trying to look for indigenous life and you contaminate the area, it will be difficult to prove it's not just something you brought along with you," she said.
Zubrin said not to worry. Modern biological techniques allow scientists to determine the genetic identity of any microorganism.
By way of example, Zubrin pointed to the anthrax attacks in Washington, D.C., and New York City in the fall of 2001. "Scientists were able to determine that the microbes in question were not only anthrax, but that the anthrax stock in question originated from a lab in Ames, Iowa and, furthermore, that the [anthrax] had been taken from the Ames lab in 1987," he said.
Zubrin said scientists, using similar techniques, could determine if microbes potentially found on Mars are from a space-launch site on Earth, from material ejected during an asteroid impact millions of years ago, or truly Martian life-forms.
Rothschild, meanwhile, pointed out the potential political risks of endorsing Mars colonization. She said human lives may be lost during trips to Mars and few politicians have the will to allow astronauts to die under their watch.
"But there are plenty of people who are willing to take that risk," she said. "There are people who will take a one-way ticket to Mars. There are plenty of volunteers."
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