Worlds Beyond Earth

The human presence in outer space continues to expand, whether in person or through our robotic emissaries. Coming decades are expected to see permanently inhabited outposts on the Moon and Mars, while machines may mine asteroids for precious metals. With this, too, may come anthropogenic contamination of the lunar and planetary surfaces, fouling of resources such as water ice thought to exist near the Moon’s poles, and contamination of other worlds with terrestrial biota.