The descent module of the Bion-M No. 2 biological satellite successfully landed on September 19, 2025, at 11:00 Moscow time in the Orenburg region after 30 days of flight in orbit. On board were 75 mice, more than 1,500 fruit flies, plants, microorganisms, and other biological objects. The Director of the Institute of Biomedical Problems (IBMP) of the Russian Academy of Sciences, Oleg Orlov, reported that 10 out of 75 mice died.
The causes of the death of the mice, which were males, are related to intragroup conflicts and other factors. Scientists plan to establish the exact stages and circumstances of the losses based on the collected data. The overall result of the flight is considered satisfactory for further analysis.
Out of 75 mice, we were short ten. With this result, we are all satisfied, and first of all, the scientists and organizers of the flight. The cause of death of these animals is different. Because these are male mice, aggressive animals, with complex intragroup conflicts. Of course, the data has not been lost, we will find out at what stages and for what reason they died.
The spacecraft was launched from the Baikonur Cosmodrome on August 20, 2025. The flight was conducted in a polar orbit to study the influence of space factors on living organisms. The mice were divided into groups: one with a modified genetic apparatus to assess sensitivity to radiation, the second group received pharmacological preparations to increase resistance to such effects. Different methods of feeding and keeping animals were also tested, including dry food and special water.
The landing took place as normal, although there was a fire of dry grass at the landing site. The local administration, search and rescue services of Rosaviatsia, and the Ministry of Defense promptly extinguished the fire. All biological objects were delivered to Earth in a condition that allows for planned research. Some experiments were started in the field at the landing site, the remaining samples will be transported to laboratories in Moscow.
Biosputnik "Bion-M" No. 2 is the second spacecraft in this series, designed for fundamental research in the field of space biology. The results of the experiments will be transferred to Roscosmos and the Russian Academy of Sciences.