An explosion in our ability to detect planets in other solar systems has made astronomers increasingly confident that it’s only a matter of time until we discover life on other planets. Astronomers just discovered methane on a planet 63 light-years from Earth — a sign that life just might exist. Here’s what Carl B. Pilcher, director of the NASA Astrobiology Institute, said following the discovery in this fascinating Washington Post article by Marc Kaufman.

There are a hundred billion stars in our galaxy and probably a hundred billion other galaxies with as many stars as ours, so it seems highly unlikely that there are not Earth-like planets orbiting some of them out there, waiting to be discovered.

I find the idea of life on other planets enormously uplifting: life is a miracle. But the idea of our civilization finding life on other planets fills me with apprehension. After all, civilization “discovering” new worlds teeming with life is nothing new to us: we’ve been doing it since agricultural civilization started expanding from Mesopotamia millennia ago.

But for as long as we’ve been discovering these new worlds, we’ve been destroying them, whether it was the Clovis people slaughtering the woolly mammoths, mastodons, and giant beavers that used to make North America home, the Sumerians turning wetlands and forests into wheat fields, or our own civilization slaughtering everything from the dodo to the bison to (just last year) the Baiji dolphin formerly of China’s Yangtze River. And now we’re turning our attention to the world’s remaining tropical forests.

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Of course, it’s not only natural worlds we’re destroying; it’s also indigenous people, from the Native North Americans felled by massacre and disease to the Tibetans now being made a minority in their own homeland.

So what will happen when we contact another planet as full of life as our own but as defenseless to the onslaught of agricultural civilization as Earth? Will the oil companies tout it as the solution to high gas prices? Will palm oil producers turn their attention away from destroying the tropical forests of Southeast Asia towards destroying the forests of some distant planet? Will we double or triple or quadruple our home planet population by turning some far-off wetland into a big feeder lot for our livestock?

If we have any capacity to learn from the ongoing destruction of our planet, in the tradition of Star Trek, we must establish our own Prime Directive for the future. You never know — first contact could come far sooner than we think:

Observe, but do not contact.

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It’s very human to think we’ll be able to walk the hills and sail the seas of some distant new Earth. But who knows what diseases we’ll bring — or what diseases we’ll become infected with. How will our civilization be able to resist colonizing some distant planet when we can’t even resists colonizing the last pristine bits of our own?