Pale Blue Dot - Carl Sagan [109]
Some humans (all from the former Soviet Union) have already been in space for periods longer than the entire round-trip time to Nereus. The rocket technology to get there already exists. It’s a much smaller step than going to Mars or even, in several respects, than returning to the Moon. If something went wrong, though, we would be unable to run home to safety in only a few days. In this respect, its level of difficulty lies somewhere between a voyage to Mars and one to the Moon.
Of many possible future missions to Nereus, there’s one that takes 10 months to get there from Earth, spends 30 days there, and then requires only 3 weeks to return to home. We could visit Nereus with robots, or—if we’re up to it—with humans. We could examine this little world’s shape, constitution, interior, past history, organic chemistry, cosmic evolution, and possible tie to comets. We could bring samples back for examination at leisure in Earth-bound laboratories. We could investigate whether there really are commercially valuable resources—metals or minerals—there. If we are ever going to send humans to Mars, near-Earth asteroids provide a convenient and appropriate intermediate goal—to test out the equipment and exploratory protocols while studying an almost wholly unknown little world. Here’s a way to get our feet wet again when we’re ready to re-enter the cosmic ocean.
*If it had not, perhaps there would today be another planet, a little nearer to or farther from the Sun, on which other, quite different beings would be trying to reconstruct their origins.
*Asteroid 1991JW has an orbit very much like the Earth’s and is even easier to get to than 4660 Nereus. But its orbit seems too similar to the Earth’s for it to be a natural object. Perhaps it’s some lost upper stage of the Saturn V Apollo Moon rocket.
CHAPTER 18
THE MARSH OF CAMARINA
[I]t’s too late to make any improvements now. The universe is finished;
the copestone is on, and the chips were carted off a million years ago.
—HERMAN MELVILLE, MOBY DICK, CHAPTER 2 (1851)
Camarina was a city in southern Sicily, founded by colonists from Syracuse in 598 B.C. A generation or two later, it was threatened by a pestilence—festering, some said, in the adjacent marsh. (While the germ theory of disease was certainly not widely accepted in the ancient world, there were hints—for example, Marcus Varro in the first century B.C. advised explicitly against building cities near swamps “because there are bred certain minute creatures which cannot be seen by the eyes, which float in the air and enter the body through the mouth and nose and there cause serious disease.”) The danger to Camarina was great. Plans were drawn to drain the marsh. When the oracle was consulted, though, it forbade such a course of action, counseling patience instead. But lives were at stake, the oracle was ignored, and the marsh was drained. The pestilence was promptly halted. Too late, it was recognized that the marsh had protected the city from its enemies—among whom there had now to be counted their cousins the Syracusans. As in America 2,300 years later, the colonists had quarreled with the mother country. In 552 B.C., a Syracusan force crossed over the dry land where the marsh had been, slaughtered every man, woman, and child, and razed the city. The marsh of Camarina became proverbial for eliminating a danger in such a way as to usher in another, much worse.
THE CRETACEOUS-TERTIARY COLLISION (or collisions—there may have been more than one) illuminates the peril from asteroids and comets. In sequence, a world-immolating fire burned vegetation to a