This was the Soviet Union's first attempt at a planetary probe. The Mars probe had a mass of about 640 kg and carried a magnetometer, cosmic ray counter, plasma-ion trap, and micrometeorite detector. A fourth stage was added, the Molniya or 8K78, the new launcher was designated SL-6/A-2-e. After launch, the third stage pumps were unable to develop enough thrust to commence ignition, so Earth parking orbit was not achieved. The spacecraft reached an altitude of 120 km before reentry.