In 1968, two Afghan tortoises who beat humans to the Moon lost 10% of their weight - They flew around the moon on Soviet Zond 5 and returned alive 3 months before Apollo 8

In 1968, two tortoises made spaceflight history by becoming the first animals to circle the Moon and return safely to Earth. The animals, identified as Central Asian tortoises, also known as Afghan tortoises or the steppe tortoises, traveled aboard the Soviet Union’s Zond 5 spacecraft in September 1968. The mission lasted about a week and carried the tortoises around the Moon before bringing them back alive. During the journey, they lost roughly 10% of their body weight but survived the demanding flight. Their mission came about three months before NASA’s Apollo 8, which became the first crewed spacecraft to orbit the Moon. The remarkable Zond 5 mission demonstrated that living organisms could survive a journey around the Moon and helped pave the way for future human spaceflight.

The Soviet Union’s Zond 5 mission carried more than just a spacecraft around the Moon. Launched on September 15, 1968, the uncrewed vehicle traveled around the Moon, passed behind its far side and returned to Earth, splashing down in the Indian Ocean on September 21. The tortoises became the first vertebrates known to travel around the Moon and return alive - a more precise description than simply calling them the first animals to make the journey. Along with the tortoises, the spacecraft carried fruit flies, worms, plants, algae, bacteria and a variety of other biological samples.

The tortoises also lost about 10% of their body weight during the experiment. However, that figure should not be interpreted as weight lost solely during their week in space. Researchers had stopped feeding them before launch as part of the biological experiment, meaning their fasting began before Zond 5 left Earth. The mission was ultimately much more than an unusual animal experiment. Zond 5 served as a critical test of spacecraft systems, reentry procedures and the effects of deep-space travel on living organisms. Its successful return came just months before Apollo 8 carried humans around the Moon, making the Soviet mission an important chapter in the race toward crewed lunar exploration.


According to Space Daily, the two tortoises selected for the mission weighed between 340 and 400 grams each. NASA’s historical account, 'Challenge to Apollo', notes that Soviet scientists chose tortoises because they could survive without complicated life-support systems and could be securely restrained inside the spacecraft. Their biology also allowed them to endure extended periods without food.

The flight tortoises were placed aboard the spacecraft on September 2, 1968, nearly two weeks before launch, and their feeding was stopped at that point. Researchers also maintained two other tortoises on Earth under the same fasting conditions as a control group, while four additional tortoises were not subjected to the experiment. This setup allowed scientists to look beyond the simple question of whether spaceflight affected the animals. By comparing different groups, they could better determine whether changes in the flight tortoises were caused by the journey itself or by the prolonged period without food.

The reported 10% weight loss should not be interpreted as the direct effect of spending six days traveling around the Moon, reported the Space Daily. The tortoises had already been deprived of food for nearly two weeks before launch, and the spacecraft did not return to Moscow for examination until October 7.

The return journey did not unfold exactly as Soviets had planned. A guidance-system malfunction on September 21 prevented Zond 5 from making the intended soft landing on Soviet territory, forcing the spacecraft to splash down in the Indian Ocean instead, reported the outlet. American naval vessels photographed the capsule after it landed, while Soviet sailors aboard the Golovnin later recovered the spacecraft. Zond 5 was then transported to Bombay, where it was loaded onto an aircraft and flown back to Moscow for further examination.

As a result, the animals experienced several conditions during the broader experiment, including prolonged fasting, confinement, microgravity, radiation exposure, a rough splashdown and a delay before scientists could conduct detailed examinations. Their weight change therefore reflected a combination of factors rather than a single effect caused by the lunar journey itself.