The Mars 2 descent module was mounted on the bus/orbiter opposite the propulsion system. It consisted of a spherical 1.2 m diameter landing capsule, a 2.9 m diameter conical aerodynamic braking shield, a parachute system and retro-rockets. The entire descent module had a fueled mass of 1210 kg, the spherical landing capsule accounted for 358 kg of this. An automatic control system consisting of gas micro-engines and pressurized nitrogen containers provided attitude control. Four "gunpowder" engines were mounted to the outer edge of the cone to control pitch and yaw. The main and auxiliary parachutes, the engine to initiate the landing, and the radar altimeter were mounted on the top section of the lander. Foam was used to absorb shock within the descent module. The landing capsule had four triangular petals which would open after landing, righting the spacecraft and exposing the instrumentation.
The lander was equipped with two television cameras with a 360 degree view of the surface as well as a mass spectrometer to study atmospheric composition; temperature, pressure, and wind sensors; and devices to measure mechanical and chemical properties of the surface, including a mechanical scoop to search for organic materials and signs of life. It also contained a pennant with the Soviet coat of arms. Four aerials protruded from the top of the sphere to provide communications with the orbiter via an onboard radio system. The equipment was powered by batteries which were charged by the orbiter prior to separation. Temperature control was maintained through thermal insulation and a system of radiators. The landing capsule was sterilized before launch to prevent contamination of the martian environment.
The Mars 2 and 3 landers carried a small walking robot called PROP-M. The robot had a mass of 4.5 kg and was tethered to the lander by a cable for direct communication. The rover was designed to "walk" on a pair of skis to the limit of the 15 m cable length. The rover carried a dynamic penetrometer and a radiation densitometer. The main PROP-M frame was a squat box with a small protrusion at the center. The frame was supported on two wide flat skis, one extending down from each side elevating the frame slightly above the surface. At the front of the box were obstacle detection bars. The rover was planned to be placed on the surface after landing by a manipulator arm and to move in the field of view of the television cameras and stop to make measurements every 1.5 meters. The traces of movement in the martian soil would also be recorded to determine material properties.
The descent module was separated from the orbiter on 27 November 1971 about 4.5 hours before reaching Mars. After entering the atmosphere at approximately 6 km/sec, the descent system on the module malfunctioned for unknown reasons and the descent sequence did not operate as planned. The lander impacted the Mars at high velocity near 45 S, 313 W. The cause of the failure may have been related to the extremely powerful martian dust storm taking place at the time. Mars 2 was the first manmade object to reach the surface of Mars.
