Hugh Pickens writes "Studies of reproduction in space have previously been carried out with sea urchins, fish, amphibians and birds, but Brandon Keim writes in Wired that Japanese biologists have discovered that although mammalian fertilization may take place normally in space, as mouse embryos develop in microgravity their cells have trouble dividing and maturing. The researchers artificially fertilized mouse eggs with sperm that had been stored inside a three-dimensional clinostat, a machine that mimics weightlessness by rotating objects in such a way that the effects of gravity are spread in every direction. Some embryos were ultimately implanted in female mice and survived to a healthy birth, but at lower numbers than a regular-gravity control group. Part of the difference could be the result of performing tricky procedures on sensitive cells, but the researchers suspect they also reflect the effect of a low-gravity environment on cellular processes that evolved for Earth-specific physics. '"These results suggest for the first time that fertilization can occur normally under G environment in a mammal, but normal preimplantation embryo development might require 1G," concludes the report. "Sustaining life beyond Earth either on space stations or on other planets will require a clear understanding of how the space environment affects key phases of mammalian reproduction."'"