The terraforming of Mars had begun in the earliest days of the golden age of man's expansion to the stars, bringing new life and hope, but in the end, this was a remission, not a cure. Within the span of a few centuries, the planet had died its second death, choking on the fumes of volcanic forge complexes, continent-sized refineries and the effluent of a million weapons shops.
—Horus Heresy: Mechanicum
