Two identical Soviet probes launched in spring 1969 and intended to orbit the planet Mars. Both were lost following launch failures and not officially announced. Each spacecraft carried three television cameras designed to image the Martian surface, a radiometer, a water vapor detector, ultraviolet and infrared spectrometers, a radiation detector, a gamma spectrometer, a hydrogen/helium mass spectrometer, a solar plasma spectrometer, and a low-energy ion spectrometer.
