Before man became brave enough to conquer space himself, canine cosmonauts were sent in our place.
It was a perilous job, with almost half of all dogs destined not to come home.
But two female strays employed in the Soviet space programme, Comet and Shutka, proved to be remarkable survivors.
During a mission, the pair plummeted 125 miles to Earth after their rocket malfunctioned and remained trapped inside for four days in -40C temperatures in the Siberian wilderness.
Their incredible story has only just emerged after being kept secret for more than 50 years.
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On Christmas morning, rescuer Armen Gyurdzhian began to open the capsule and could hear quiet barking.
'They were alive despite the most pessimistic forecasts,' he said.
Gyurdzhian wrapped the frozen and exhausted animals in his coat and went back to Tura by helicopter.
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The fate of Shutka after returning to Moscow is not known.
But Comet was adopted by academic Oleg Gazenko, a specialist in aviation medicine, with whom she lived for 14 years. After her Siberian adventure, she went on to have puppies.
'She was such a cute, fluffy, fair-haired dog with a sharp nose,' he said.
'She was a hero, flying as many as three times - twice in rockets, and a third on board the satellite, the forerunner of the ship which was used for Yuri Gagarin's flight'.
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