Terraforming Mars - grafting an Earth-like atmosphere and ecology onto that rocky and poisonous planet - remains a great idea that is likely to become one of the supreme engineering projects of humankind. But due to some problems that have recently become apparent, the process will take longer to get started than I thought. First, finances. This is a venture that will cost many billions of dollars. Only governments can afford that, but Washington seems to care solely about terrorism and tax cuts. When will there be the political will to make that kind of financial commitment?
Second, if we do find life when we get to Mars, the discovery will raise a tricky ethical question - even if we just find bacteria living under the surface, as is likely. Terraforming a dead planet is like gardening a rock, but if Mars is alive, we're invading a biosphere. If DNA testing proves that the Martian natives originated on Earth and hitched a ride through the solar system on some ancient meteor, maybe we will decide to proceed with inhabitation, figuring we can coexist with these cousins. But if the Martians prove to be truly alien, do we have a right to remodel their planet? We may decide to stay away.
Yet whatever we decide is ultimately going to be moot. Early Martian explorers will take matters into their own hands sooner or later. Living on Mars in small stations similar to beached submarines, it will be obvious to these scientists that life on Mars would be a lot safer and easier if the atmosphere were thicker. Sooner or later someone is sure to release bacteria to get things going, no matter what people on Earth think. Over time, microbial life will create an oxygen-rich atmosphere.
Or the terraformers might choose to go the mechanical-engineering route. Comets or even small asteroids might be guided into aerobraking orbits that would make them burn up in the Martian atmosphere, thickening it with gases. In order to warm the planet's surface, orbiting mirrors and lenses could redirect and concentrate sunlight that would ordinarily miss Mars. Nuclear explosions underground could quickly melt the deep permafrost. Digging holes to the mantle would release the necessary heat. Nitrogen could be imported from Saturn's moon Titan, and so on.
Slow start, fast finish. Estimates as to how long it might take before people could walk around on Mars in shirtsleeves (and maybe a respirator) vary from 500 to 100,000 years. That's a very big range, but it depends on how we go about it. If we use all the high-impact methods - "planetary engineering" - it may take only a few hundred years. If we introduce a bacterial ecology, add some heat, and then let nature take its course - "ecopoeisis" - it would take many thousands of years. But it's better to think of the process as never-ending, like history itself. People will just keep working, and eventually we will inhabit both planets, one whose ecology we will have grown like a garden. It will be a beautiful journey, and it doesn't matter if it's slow. It's the doing that's the fun part.
Kim Stanley Robinson is the author of the epic trilogy Red Mars, Blue Mars, *and *Green Mars.
