The Martian Ship is a scout ship belonging to the Martians.
At some point, as part of a long-planned invasion of Earth, a Martian scout ship lay in wait just past the Moon collecting Earth transmissions. The crew was tasked with translating them and cataloging crucial intelligence. After the crew intercepted the 1938 broadcast of "War of the Worlds," they took the ship to Elmo's Hill to investigate. They concluded the broadcast was a trap and tried to leave for their home world. The ship was critically hit by a meteor and crashed back into Elmo's Hill. The crew attempted to activate a self-destruct mechanism but it failed. The impact led the ship to be buried underground.
Many decades later, a cable company unearthed the ship and caused the manifestation of Martian Phantasms. The Ghostbusters were called in to capture the ghosts. The last ghost returned to the ship and managed to get it into the air. Surprisingly, the navigation was still functional. However, the self-destruct finally activated and the ship was blown up.