The student pilot reported that he was conducting a solo instructional flight in the airport traffic pattern at the time of the accident. He stated that it was a "soft landing on [the] main wheels." However, once the nose landing gear touched down the airplane "darted" to the left. His attempts to maintain control were unsuccessful and the airplane departed the runway pavement. A postaccident examination did not reveal any anomalies related to the nose wheel steering or main wheel brakes. The recorded wind was calm about the time of the accident.