Write a letter to inform a potential astronaut, or the family members of an astronaut, about what to expect during a year long mission to space. In your letter explain to them how their body (or their family member's body) will react to being in zero-gravity. Compare the normal functions of the immune system and the lungs and the respiratory system with how they would be altered during space travel, describing what they should expect so that they can prepare for their yearlong mission.