The Mars500 crew is only two months from their 'arrival' back on Earth and they can't wait to see the sunlight. To prepare for that and to understand more about how the human brain reacts to variations of day and night and adjusts the sleep-wake cycle, the marsonauts are wearing red glasses andilluminating their modules with blue light. Diego explains about the photopigments in our eyes and and shows how the experiment is done.
After all, life inside the Mars500 'spacecraft' is all about the science!