Radiation and microgravity present challenges to life forms in subtle ways that may only become evident through carefully planned experimentation. In May 1997, silkworm eggs were flown on the Shuttle Atlantis during STS-84, a nine-day mission. The study involved investigating how the space environment influences embryonic development. It is documented by JAXA that the results revealed abnormalities in the development of the flight samples, such as mottling and restricted body segmentation, occurring at higher frequencies than those in the control ground eggs. A published study by Toshiharu Furusawa and colleagues, titled “Effects of space flight on the development of silkworm eggs,” also reported a roughly twofold higher frequency of incomplete embryonic reversal in one group of flight eggs, along with increased frequencies of abnormalities such as segment fusion and abnormal crescent markings.
The 1997 experiment was an early step in a longer line of research rather than the beginning of the later ISS experiment itself. More than a decade later, JAXA's separate Rad Silk investigation placed silkworm eggs aboard the International Space Station's Kibo laboratory in 2009 to examine the biological effects of longer-term cosmic radiation exposure. The ISS experiment built on findings from the earlier shuttle work and from ground-based radiation studies.
