In August, NASA’s unmanned Phoenix Mars Mission blasted off from the Kennedy Space Center as the first mission of NASA’s Mars Scout Program. Phoenix will reach the Red planet in May 2008, and is part of NASA’s strategy to ”follow the water” on Mars. This will pave the way for manned Martian missions, which President George W. Bush made a NASA priority in 2004. No date has been set for the crewed mission to Mars, but NASA is drawing up plans. The ultimate goal: making Mars a human outpost.
The renewed focus on Mars has rejuvenated the idea of terraforming Mars, which once belonged to the realm of science fiction, but is becoming increasingly possible today. Terraforming—or earthforming—is a Herculean feat of planetwide engineering that will change the Martian atmosphere and allow humans to make uninhabitable Mars into a planet fit for natural life. Space suits will still be necessary for human habitation, but food will available from plants that grow on a more temperate Mars.
”Now we have fairly accurate maps of the Red Planet, and can imagine how it might be modified—terraformed—to make it nearer to our heart’s desire,” said space visionary Arthur C. Clarke recently. A little more than a decade ago, Clarke wrote a book, The Snows of Olympus: A Garden on Mars (W.W. Norton & Co., 1994) that dealt with how to create a biosphere on Mars. He envisioned a huge garden on the slopes of Olympus Mons, the giant Martian volcano.
Mars, the only likely candidate for terraforming in the solar system, has numerous features in common with Earth. Like Earth, it has a rocky composition and marked seasons. Clearly, an environment different from the cold, dry world we see today once existed on Mars, as has been clear from recent NASA missions. Liquid water flowed on the Martian surface in the past: there are vast dry gorges and canyons etched by water and ice. The reddish color of the soil indicates hydration of the surface rocks, and is evidence of the role of water in the evolution of the planet.
Earlier this year the NASA rover Spirit confirmed that Mars was once a wet place. Spirit was exploring an area called Gusev Crater, when it found a piece of nearly pure silica. Silica is a component of window glass, and it is often a main ingredient in sand. The sort of silica found on Mars is usually formed in the presence of a significant amount of water. And if water flowed once on this frigid planet, will it not be possible to make it flow again?
Given that most astronomers and space scientists believe that humans have been responsible for global warming on Earth, some scientists think so.
”Humans are effectively warming the Earth,” says NASA’s Christopher McKay, who says we ”can, and should, do the same on Mars.” McKay has written extensively about terraforming Mars, which he terms ”planetary ecosynthesis.” McKay is one of a handful of NASA scientists who have begun to think about creating a permanent outpost on Mars even though many years may pass before a human sets foot there.
The first step to terraforming Mars would be to warm up the planet. It has a lot of frozen carbon dioxide (dry ice) at its poles. Increasing the temperature from its current 60 °C to just above 0 °C would turn the dry ice into gas. The ensuing thick atmosphere of carbon dioxide would create a greenhouse effect and would allow water to flow on Mars; in principle, plants could then grow slowly.
The first Martian plants would probably be lichens. In a few decades, there would be a seasonally ice-free lake on the summit of Olympus, Mars’s largest volcano. Soon thereafter, a terraformed Mars would witness a veritable green revolution characterized by pines and oaks, allowing it to become our second home.
Of course, questions remain as to what is the best way to warm up Mars. One possibility, espoused by James Oberg in his book New Earths in 1981, is to use giant mirrors in orbit around the planet to increase the temperature by reflecting sunlight onto the poles. NASA researchers are currently investigating large solar sails in an effort to provide spacecraft with solar power. Such solar sails could be adapted for this purpose.
Another warming idea, as proffered by McKay, is to generate gases known as halocarbons that would create a greenhouse atmosphere. They would exclude gases like bromine and fluorine, which can damage an ozone layer. It would involve building a factory on Mars to make halocarbons through chemical reactions. The raw materials would be the Martian soil and the Martian atmosphere. Mars has a thin atmosphere, and many light gases such as hydrogen aren’t trapped by Martian gravity. However, the heavier halocarbon molecules would be trapped, and they would contribute to a greenhouse effect. McKay says that real chemical studies have yet to be done, but he favors this method because we already have ”produced halocarbons on Earth that have contributed to global warming.”
In addition, there are more speculative ideas, such as using nuclear-powered rockets to divert asteroids to crash on Mars. This would create a catastrophe that would release a lot of heat into the atmosphere, which would increase the planet’s temperature dramatically.
Most ideas put forward by scientists such as McKay budget about five to 10 decades for the temperature increase. Most space scientists agree that we now have the technological capability to attempt some of these schemes; of course, the execution of any particular one on a planetary scale will be quite challenging, according to McKay.
Scientists also say that carbon dioxide and water alone will not be enough to sustain life. ”A biosphere requires large amounts of carbon dioxide and water but also nitrogen,” says McKay. ”Nitrogen gas is essential for a breathable atmosphere and nitrogen is needed by life as an essential macronutrient.”
As far as scientists know, there is very little nitrogen in the Martian atmosphere and there is no data on the amount of nitrates in the Martian soil that could be converted to nitrogen. Theoretical arguments suggest lightning and meteorites should have produced nitrates on Mars that could be adequate, says McKay.
”The question of the nitrogen supply is probably the key question in terms of the feasibility of ecosynthesis on Mars,” he stresses.
Ethical questions also abound. As Clarke pointed out recently, ”Whether we should embark on such a venture should be decided very carefully, and future Martian inhabitants must be allowed to have their say.”
Many who have thought about the topic view it from an anthropocentric view. Anthropocentrism puts human interests foremost.
In a 2002 article in Environmental Law Reporter on the ethics of terraforming, Robert D. Pinson wrote, ”The most applicable environmental ethic to terraforming Mars is anthropocentrism. It puts our interests at the forefront while still ensuring the existence of all life. It seems obvious that we should give ourselves the highest level of intrinsic worth since we are the ones placing the value. Life, of course, has the ultimate intrinsic worth, but we are a part of that life. It is in our best interest to preserve and expand life. What better way than by changing a planet that is currently unable to sustain life into one that can.”
And of course there is the business of getting to Mars and back safely, while sustaining the crew through the long multiyear trip. Unmanned missions like Phoenix are technologically possible today because we do not need to worry about transporting a big payload. There are ideas for manned missions that involve getting to Mars with the aid of nuclear rockets, but a lot of work remains to be done before we can send humans there.
”We cannot, of course, begin terraforming today, but we can research and plan the future,” Pinson had said in 2002. That sentiment, if anything, has gotten stronger.
”Given the situation here on Earth, I think it prudent that we try to colonize Mars,” Pinson told IEEE Spectrum recently. ”Since the evidence for water on Mars is becoming stronger and stronger, I really believe we should make an effort to get over there and investigate further.”
About the Author
SASWATO R. DAS is a New York Citybased writer.
To Probe Further
NASA maintains a Web site devoted to Martian terraforming: http://nssdc.gsfc.nasa.gov/planetary/mars/mars_colonize_terraform.html.
In July 1997, NASA did a pioneering study on the human exploration of Mars. The full report is available at ftp://nssdcftp.gsfc.nasa.gov/miscellaneous/planetary/mars_future/mars_ref_mission_sp6107.pdf.