- Dogs, cats, fish, and monkeys are among the animals that humans have sent into space.
- Most have been sent to study how weightlessness affects humans, and were originally sent before humans ever left Earth to test how such a journey could be done safely.
- But some - like Russia's famous space dog Laika - were sent as part of the space race, and were never intended to return.
- NASA said that early animal astronauts prevented "great losses of human life."
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NASA and other space agencies put animals in space long before humans, using monkeys, dogs, and cats to figure out how humans could survive leaving Earth.
Countries including the US, the USSR, France, and China sent insects, mammals, fish, and reptiles into space from the 1940s as part of their studies, and some continue to send animals into orbit today.
Some animals were sent up to test the impact of space on living beings, and scientists tried to ensure that they would come back safely so they could be studied - though many were killed during or after their journeys.
Others were sent as countries scrambled to make progress in the space race, and were sent into orbit never to return.
According to NASA: "Despite losses, these animals have taught the scientists a tremendous amount more than could have been learned without them."
"Without animal testing in the early days of the human space program, the Soviet and American programs could have suffered great losses of human life."
Here are some of the most famous, significant, and bizarre: