In 1951, two female stray dogs named Dezik and Tsygan became the first mammals to successfully cross the border of space and return alive

In 1951, two female stray dogs named Dezik and Tsygan became the first mammals to successfully cross the border of space and return alive. Their July 22 flight reached 110 kilometers above Earth. The mission tested how living organisms responded to launch forces, weightlessness and reentry. The data later supported Soviet research into animal and human spaceflight.