The Tothian Minefield is a magnetic minefield suspended in space covered in dust made to look like a giant cloud. It is the remnants of a battle from the great war of 12185.
The Protector II unfortunately flew into the minefield in an attempt to escape Sarris's ship, resulting in high damage to the ship and the injuries of Tommy Weber. Once the crew regained control, Jason Nesmith ordered to fly back into the minefield and Tommy, now a skilled pilot, avoided the mines. They flew as close to the mines as possible to attract as many as possible but avoid damage. Once out, they flew to confront Sarris who failed to realize the mines in time turn. The mines hit the core and the whole ship exploded. It's unclear if the minefield was put onto the show's reboot, but it's assumed otherwise.