A line of automated defences based at Mars that makes a brief and hopeless attempt to stop the Borg cube on its way to Earth after the Battle of Wolf 359.
The Mars Defence Perimeter is part of the Sol system's protection in the twenty-fourth century, seen in the Next Generation episode The Best of Both Worlds, Part II. With the fleet shattered at Wolf 359, it is among the last obstacles between the Borg cube and Earth.
As the Enterprise-D pursues the cube into Sector 001, Jupiter Outpost 92 reports visual contact with the intruder. Three small defensive craft then rise from the perimeter to meet it, and the cube destroys all of them within moments without slowing down.
The cube goes on to take up orbit of Earth, where Data's use of Locutus's link to put the drones to sleep finally ends the invasion. The scene is one of the few on-screen glimpses of the home system's fixed defences, and of how little they could do against the Borg.