In a written statement, the certified flight instructor (CFI) reported that the student pilot had accomplished five dual instructional flights earlier that day. The CFI then cleared the student pilot for a solo flight. The glider was attached to a tow airplane, and the takeoff and tow were normal. The student released the glider at 2,000 feet above ground level (agl). The student used the airbrakes to descend to pattern altitude (1,000 feet agl). The CFI reported that the student forgot to close the airbrakes upon reaching traffic pattern altitude and the glider continued to descend rapidly. The student pilot maintained a 45-degree entry to the downwind leg of the runway and the glider impacted Joshua trees about 500 feet short of the airport, substantially damaging the wings, fuselage, and right horizontal stabilizer drag spar. When the CFI arrived on-scene, the airbrakes were in the open position. There was no report of a mechanical failure or malfunction with the glider at the time of the accident.