Twins in Space: Review and Perspectives

Abstract

Monozygotic (MZ) twins subjected to different environmental exposures offer an informative, naturally occurring, co-twin control design. Given their genetic identity, differences in physical, medical and behavioral outcomes between them can be associated with their experiential differences. In space research, a wide range of ethological studies has been conducted on the effects of microgravity on sensorimotor activity and on social group behavior during orbital flights, in a large array of isolated and confined environments and for short-term, mid-term and long-term missions. The study of MZ twin astronaut, Scott Kelly (SK), who spent nearly one-year at the International Space Station (ISS) while his co-twin, Mark Kelly, stayed on earth, is a unique opportunity to identify factors affecting astronauts' health and the extent to which a space mission modifies different adaptive systems at the genetic and epigenetic levels.