Sclera the sclera can make it appear slightly yellow. Many people with dark skin have naturally darkened sclerae, the result of melanin pigmentation. The human eye is relatively rare for having an iris that is small enough for its position to be plainly visible against the sclera. This makes it easier for one individual to infer where another individual is looking, and the cooperative eye hypothesis suggests this has evolved as a method of nonverbal communication. The sclera forms the posterior five-sixths of the connective tissue coat of the globe. It is continuous with the dura mater and the cornea, and
Effect of spaceflight on the human body 2015, the NASA Office of Inspector General issued a health hazards report related to space exploration, including a human mission to Mars. Many of the environmental conditions experienced by humans during spaceflight are very different from those in which humans evolved; however, technology such as that offered by a spaceship or spacesuit is able to shield people from the harshest conditions. The immediate needs for breathable air and drinkable water are addressed by a life support system, a group of devices that allow human beings to survive in outer space. The life support system supplies air, water and food. It