A Colony In The Sky

ONE DAY EARLY IN THE NEXT CENTURY, SEVERAL PEO-ple will land on Mars. They will put on spacesuits and leave their vehicle, bounding over red rocks under a pink sky. After this exhilarating day, seen on Earth by billions, they will move into a cluster of habitats already on site. They will spend a year living there making scientific studies, and then they will return to Earth. Another team will cycle in. Back at home we will start to take the base for granted. Nevertheless, something very big will have begun.

The initial crossing to Mars will be made for a great number of reasons, some of them solid (to see if there really are fossil bacteria there), some of them not (to look for Elvis). Most of the reasons will be scientific and practical: the more we know about the solar system's other planets, the better we will understand Earth, and the safer we will be. It's not heroic but it makes sense, and it is important. Even if these were the only reasons, they would be good enough to send us.

But Mars will never remain just a research site to sharpen Earth management skills. We've been fascinated by the red wanderer ever since our days on the savannah, and even if life at the research station proves to be quite ordinary, the videos they send back will show us a magnificent world of volcanoes and canyons, icecaps and sand dunes, wind and weather. These wild new landscapes will also look somewhat familiar, especially in comparison to the bone-white moon. This familiar quality is not just superficial, for Mars does resemble Earth in several important ways--general size, presence of water, length of day, range of temperatures--so many similarities, in fact, that some people are beginning to ask if it might be possible to make Mars even more like Earth than it is now. And that's the question that will shift us to the next level of our fascination with the place: the idea that we could live there, that Mars could be ""terraformed.''

To terraform means to alter a planet's surface until Earth's life forms can survive there. It's a hypothetical discipline at this point, born in science-fiction stories. But in the last 30 years a number of scientists have taken up the concept. Their studies make it clear that the process would be somewhat slower than the cork-popping transformations seen in some recent sci-fi movies; in reality, it would take centuries. But it is an idea that operates within physical reality as we know it. It's possible to do it.

The recipe is simple. Add nitrogen and oxygen to the atmosphere; pump water to the surface; cook for decades, spicing first with cyanobacteria, then with all the rest of Earth's plants and animals, adding them in the order they evolved here. Mars is blessed with all the ingredients called for in the recipe; indeed, Mars turns out to be perfect for terraforming. So, because we have all the life forms here at hand, we can try replaying evolution at extreme fast forward.

Of course it will be more complex than the recipe--it always is. And the process will certainly spiral out of our control. Eventually, however, if all goes well, we will have helped to start a new biosphere. Think of that! It's hard to know how even to characterize such an activity. It would be something like growing a garden, or creating a wilderness, or building a cathedral, or flying seeds over an ocean to drop them on a new island. It would be unlike anything else, a new thing in history.

Some people may believe that such a project is too large or slow or presumptuous for humanity to undertake. But consider our current situation on Earth. There are nearly 6 billion of us now, and the number may double, though we have no good idea how many of us the Earth can support. Many larger species are in danger of extinction unless we protect them from us. We have rearranged much of the land, and we have altered the atmosphere to the point where the global climate in the future will be a matter of legislation and industrial practice. In other words, we are already starting to terraform Earth by necessity to keep it livable. Given this situation, the attempt to terraform Mars does not look so outlandish. Doing it could be regarded as a valuable experiment, with Mars as a giant lab or university, in which we learn how to steward a planet's biosphere for long-term sustainability.

Long term indeed! Terraforming Mars would take 300 years at least. It's not a time scale we often think about, and it does seem unlikely that any society could persist in anything for so long. Luckily, the process will not depend on our consistent backing, but on the people who settle there and pursue it as their own closest interest.

As for us, here on Earth in the age of the quarterly statement, it is probably a good thing occasionally to contemplate a really long-term project. Humanity's existence on this Earth is a long-term project, after all, and it's important to remember what that means. People will be living here 500 years from now, and they will all be our relatives. These distant children of ours deserve to be given a livable planet to care for in their turn. For their sake we need to work out a sustainable way of life on Earth. Going to Mars will be part of that larger environmental project, and terraforming it will be an education that we will apply at home as we learn it--pausing, from time to time, to look up at our wilderness garden in the sky.