April 5, 2031
Earth Departure Minus Four Years
14:40 Universal Time
The Rock
The rock was tiny, barely a foot in diameter, with a mass of less than thirty pounds. It had been orbiting the Sun for nearly fifteen million years in an elliptical path that took it roughly from the distance of Mars to a little closer to the Sun than the heat-blistered planet Mercury.
It had been blasted off the surface of Mars by the impact of a much bigger meteoroid, the one that sent the famous Allen Hills Meteorite wandering through space until it crashed into the ice sheets of Earth’s Antarctica some 15,000 years ago.
If the rock had reached Earth it would have never made it to the ground, but would have streaked across the night sky to burn up high in the atmosphere—a “falling star” to anyone who happened to notice its demise.
But that didn’t happen. Instead, the rock continued on its long, looping trajectory, swinging through the vast, dark, silent emptiness.
Interplanetary space is not completely empty, of course. There were thousands of other meteoroids created by that single Mars impact so long ago. And millions more engendered by other impacts with different planets and the smaller bodies of the main Asteroid Belt, out beyond the orbit of Mars. They all quietly orbited the Sun, but they were very far apart, most of them too small to be seen even by the finest scientific instruments of humankind.
Looping around the Sun for millennia at an average velocity of 40,000 miles per hour, this rock was in a fairly stable orbit that would not bring it near Earth or any other planet for another ten million years. The chances of it hitting anything smaller than a planet were, well, astronomically small.
But astronomically small is not the same as zero. And humans were already planning to send explorers across the gulf of space to the planet Mars.