First spacecraft to land on Mars

The first spacecraft to land on the surface of Mars was the Soviet Union's Mars 3 lander, which touched down on the Martian surface at 13:50:35 UTC on 2 December 1971. Although the descent and landing was a success, something went wrong with the lander just 20 seconds after it deployed its instruments, and all transmissions abruptly cut off.

The Soviet Mars exploration programme was highly ambitious, with a pair of lander/orbiters (Mars 2 and Mars 3) dispatched to the planet for the 1971 launch window. The programme was also, however, plagued with technical problems and bad luck. On the approach to the planet, the probe carrying the Mars 3 lander suffered a fuel leak. As a result, instead of a circular 25-hour orbit, it only had enough fuel to get into a highly elliptical 12-day orbit.

Mars 2 fared better, but the first pictures the probe broadcast back to Moscow were not encouraging. Instead of the crater-pocked, mountainous landscape they'd been expecting, Soviet engineers saw only an orange ball of haze. The same thing had been seen a few weeks earlier when the American Mariner 10 orbiter reached the planet. Mars was enveloped in a planet-wide dust storm, meaning that the probe's sophisticated cameras had nothing to photograph.

To make things worse, neither probe was designed to allow the mission sequence to be reprogrammed after launch, so the landers were going to be dropped into the middle of this dust storm. Mars 2 went first, releasing its lander on 27 November 1971, but lost contact almost immediately. It is now thought that the lander's parachute failed, sending it crashing to the ground.

Mars 3 released its lander the following week, on 2 December. This time the descent went according to plan. The module entered the Martian atmosphere at 13:47 UTC, aerobraking through the upper atmosphere using its conical heat shield. The parachutes opened on schedule and, when the lander was about 20 metres (65 ft) above the ground, the retrorockets fired to bring it down as gently as possible. The probe touched down at about 74 km/h (46 mph), with a heavy foam pad taking the brunt of the impact.

What happened after this is still not clear. The four petal shaped covers must have opened up to deploy the antenna and instruments, but it's possible that they were partially obstructed or caught in some way. At 13:52:05, 90 seconds after touchdown, the lander began transmitting data (which it could not have done if the deployment had failed) but then at 13:52:25, just 20 seconds later, the transmissions suddenly stopped.

All Soviet mission control received was a burst of largely incomprehensible data. It is generally believed that this was supposed to be the first few lines of a panoramic image of the landing site, but whether the data is a fragment of an image or just random noise is unknown. The lander's small tethered rover, Prop-M, would not have had time to be deployed.

What caused the failure is still a mystery. It could be that a component was broken by the hard landing, but the leading theory is that the dust storm was the culprit. Martian dust storms carry a static charge that could have scrambled the lander's systems, and the strong winds may have been enough to topple the lander if it had settled at an already unstable angle.

In 2013, a group of Russian amateur researchers found what appears to be the landing side of Mars 3 while looking through images taken by the HiRISE camera on the NASA's Mars Reconnaissance Orbiter. They've identified the discarded heat shield and parachute as well as what appears to be the intact lander.