Mars is the fourth planet from the Sun in our solar system, located in the Milky Way galaxy.
Herman Cromwell was doing research on a Mars meteorite, that was found in the Antarctic in 1996. Fossils in the meteorite convinced him that there might have been life on Mars. But these fossils weren't anything organic to the planet. He found Carbon-based elements in the fossils, which exist only in the Magellanic galaxy, 100-million light years away from Earth. Cromwell speculated, that Mars was visited by an Unnamed Alien Species approximately one-billion years ago. The species was like a plague, a cancer. It turned a thriving planet with rivers, oceans and rudimentary plant life into a useless hunk of rock. Cromwell thought that the alien DNA might remain on the planet to this day, and would contaminate any human (or other species) that would attempt to violate the planet.
Despite Cromwell's warnings, the Excursion team was sent to Mars in 1998. Patrick Ross landed on the Planet and extracted soil ore samples, which indeed were contaminated with the alien DNA, and it infected the whole Excursion crew, excluding Dennis Gamble.