Off-line mud circulation during lithosphere drilling

During the drilling of a bore hole in the litosphere, mud is fed to a drill string (2) via a mud circulation structure and canalized through the drill string (2) to a distal end of the drill string (2). Each time the drill string (2) has progressed into the litosphere over a predetermined distance, the drill string (2) is disconnected from the mud circulation structure so that the feeding of mud to the drill string (2) is interrupted. A buffer quantity of mud is stored in the drill string (2) during the feeding of mud to the drill string and at least a portion of the buffer quantity of mud is fed in the direction of the distal end of the drill string (2) during the interruption of the feeding of mud to the drill string (2). Thus, the interruption of the supply of mud at the distal end of the drill string can be reduced or eliminated.