THE FOUR-POUND ROCK CAME TO US free of charge, a gift from the heavens, hurtling through the atmosphere and plummeting to Earth without the aid of astronauts, space stations, or the National Aeronautics and Space Administration. Before that time it had existed placidly for more than four billion years as part of the surface of the planet Mars, oblivious as the climate shifted from balmy to harsh, as the water that once flowed freely mysteriously vanished, as meteorites bombarded the planet and fractured the ground. At some point, a signal event occurred: A particularly violent meteorite collision launched the rock into space, where it floated, ignored and unimpeded, for 16 million years. Then came another signal event: The rock succumbed to the inescapable pull of Earth’s gravity. Glowing from the heat of its descent, the rock formed a thin shell around its inner core, protecting its history within.
It landed in what is for meteorites the neighborhood of choice: Antarctica, the pristine, sterile, keep-to-yourself continent. There the rock lay for 13,000 quiet years. Having missed the era of dinosaurs, it now remained profoundly anonymous during the creation of cave paintings and the construction of the pyramids, during the rise and fall of the Roman Empire, the French Revolution, the two world wars, and Elvis. And then, with the crunching of snow boots on a jagged ice field in 1984, the rock had its first contact with humanity.
It was picked up on a routine meteorite-gathering expedition by a NASA scientist who was drawn to its luminous green cast, an attraction that owed everything to her green-tinted sun goggles. It was flown back to the agency’s Johnson Space Center in Houston, where it was wrongly identified as a diogenite—an asteroid fragment—and sequestered in a nitrogen-enhanced cabinet when it wasn’t being examined. No one except a few NASA planetary scientists (scholars who devote their lives to the study of planets) paid the rock much mind until 1993, when an old NASA hand who happened to be one of the world’s experts on diogenites found it troubling. He ran a few tests, scratched his head, and ran a few more. The rock was similar to a diogenite, but it wasn’t a diogenite. In fact, its chemical characteristics resembled those of only eleven other rocks on Earth, all of which, science had determined, came from the same place: Mars.
As word of