“What did they find?” whispered Joe.
“Well, the model found that, depending on the angle of entry, the impact can produce a massive corridor of incineration ahead of the impact site. In that area, just about all life ends in minutes. But the model predicted other changes that destroyed nearly all life on Earth within a few years.”
“Like what?” Zip’s voice was dusky.
“I’m sounding like a textbook,” complained Mark.
“Go on,” insisted Zip.
Mark closed his eyes and tilted his head back. “A few hours after the impact, clouds of noxious gases billow up and block out the sun for months. Temperatures drop drastically all over the Earth and corrosive acid snow and rain fall. These short-term effects alone—intense cold, darkness, and acid rain and snow—kill the plants and photosynthetic plankton, the base of most food chains. Herbivores starve, and then the carnivores that feed on the herbivores starve. This is enough to kill most of the remaining human life on the planet. After the clouds clear, the atmosphere is thick with carbon dioxide from fires and decaying matter. Then the carbon dioxide contributes to global warming that lasts for ages.”
Tears slowly escaped from Zip’s closed eyes and made tracks down his cheeks. He remembered that when he was small his aunt and uncle had taken him on a two-hour flight in their small plane to the place closest to their home where there was a field of nuclear devastation. His first view of the terrain beyond the boundary had been indelibly burned into his seven-year-old mind. The cities and towns surrounded by fields, orchards, streams, ponds, and woods had rapidly tapered off below a slight rise into a land of gray, utterly lifeless, gasping dust thatreached as far southeastward as the eye could see. The center of the field had been the nation’s capital, the third of the great American cities to be destroyed in the holocaust of 2048.
“How big was the asteroid they modeled?” asked Joe.
“About six to ten miles across,” said Mark.
“And the one Zimbardo has aimed at Earth is forty miles long?”