The Salyut 4 space station, designated DOS-4, marked the second phase of the Soviet Union’s civilian space station program. It was an improved version of the failed Salyut 2 station, with several notable enhancements.

The crew of Soyuz 17 embarked on a historic 29-day mission, surpassing the previous Soviet mission-duration record of 23 days set by the Soyuz 11 crew aboard Salyut 1 in 1971.

Upon impact, the spacecraft sank into the soft snow but continued forward, rolling down the slope and gaining speed. As it neared a five hundred-foot cliff, the cosmonauts felt their hearts pound and adrenaline surge.