Pale Blue Dot - Carl Sagan [32]
You look more closely at the center of the South American continent, which—as you know by now—is a vast rain forest. Every night you see thousands of fires. In the daytime, you find the region covered with smoke. Over the years, all over the planet, you find less and less forest and more and more scrub desert.
You look down on the large island of Madagascar. The rivers are colored brown, generating a vast stain in the surrounding ocean. This is topsoil being washed out to sea at a rate so high that in another few decades there will be none left. The same thing is happening, you note, at the mouths of rivers all over the planet.
But no topsoil means no agriculture. In another century, what will they eat? What will they breathe? How will they cope with a changing and more dangerous environment?
From your orbital perspective, you can see that something has unmistakably gone wrong. The dominant organisms, whoever they are—who have gone to so much trouble to rework the surface—are simultaneously destroying their ozone layer and their forests, eroding their topsoil, and performing massive, uncontrolled experiments on their planet’s climate. Haven’t they noticed what’s happening? Are they oblivious to their fate? Are they unable to work together on behalf of the environment that sustains them all?
Perhaps, you think, it’s time to reassess the conjecture that there’s intelligent life on Earth.
LOOKING FOR LIFE ELSEWHERE: A CALIBRATION
Spacecraft from the Earth have now flown by dozens of planets, moons, comets, and asteroids—equipped with cameras, instruments for measuring heat and radio waves, spectrometers to determine composition, and a host of other devices. We have found not a hint of life anywhere else in the Solar System. But you might be skeptical about our ability to detect life elsewhere, especially life different from the kind we know. Until recently we had never performed the obvious calibration test: to fly a modern interplanetary spacecraft by the Earth and see whether we could detect ourselves. This all changed on December 8, 1990.
Galileo is a NASA spacecraft designed to explore the giant planet Jupiter, its moons, and its rings. It’s named after the heroic Italian scientist who played so central a role in toppling the geocentric pretension. It is he who first saw Jupiter as a world, and who discovered its four big moons. To get to Jupiter, the spacecraft had to fly close by Venus (once) and the Earth (twice) and be accelerated by the gravities of these planets—otherwise there wasn’t enough oomph to get it where it was going. This necessity of trajectory design permitted us, for the first time, to look systematically at the Earth from an alien perspective.
Galileo passed only 960 kilometers (about 600 miles) above the Earth’s surface. With some exceptions—including pictures showing features finer than 1 kilometer across, and the images of the Earth at night—much of the spacecraft data described in this chapter were actually obtained by Galileo. With Galileo we were able to deduce an oxygen atmosphere, water, clouds, oceans, polar ice, life, and intelligence. The use of instruments and protocols developed to explore the planets to monitor the environmental health of our own—something NASA is now doing in earnest—was described by the astronaut Sally Ride as “Mission to Planet Earth.”
Other members of the NASA scientific team who worked with me on Galileo’s detection of life on Earth were Drs. W. Reid Thompson, Cornell University; Robert Carlson, JPL; Donald Gurnett, University of Iowa; and Charles Hord, University of Colorado.
Our success in detecting life on Earth with Galileo, without making any assumptions beforehand about what kind of life it must be, increases our confidence that when we fail to find