Astronauts can suffer sleeping problems in space just as on Earth. Stress, heavy workloads, anxiety, background noise, light and air quality can all upset their body clocks. Minimizing sleep disturbances for astronauts is just one of the goals of the European Astronaut Centre's medical team.
Twins are always interesting (at least to those of us who are not a twin ourselves) and probably one of the few things more interesting than twins on Earth is twins in space! Mark and Scott Kelly, astronaut twins that have inhabited the ISS at the same time, are once more going to be contributing to NASA's science mission, but this time, one twin will be headed up to the ISS for a year and one will be left here on Earth!