Orbital by Samantha Harvey
Four astronauts and two cosmonauts are on a nine-month mission aboard a space station orbiting Earth. Besides daily meetings with ground crew, regular exercise, cabin cleaning, and sleep, they are tasked with performing experiments on plant and animal life, monitoring their own biomedical conditions, and, crucially, reporting on atmospheric changes observed from space… Their conversations range from the trivial (favorite childhood candy) to the profound (human evolution and the meaning of life).