The atmosphere is quite dusty, giving the Martian sky a light brown or orange-red color when seen from the surface; data from the Mars Exploration Rovers indicate that suspended dust particles of roughly 1.5 micrometres diameter.
Glutamate is a powerful excitatory neurotransmitter that is released by nerve cells in the brain. It is responsible for sending signals between nerve cells, and under normal conditions it plays an important role in learning and memory.
Contrary to Deb A's posting, glutamic acid (glutamate) is one of the 20 amino acids making up proteins/enzymes in nature. It is also the most common neurotransmitter in the brain. While glutamate is in MSG, glutamate does not equal MSG. I am a vegetarian and to Carol H I say that I eat nutritional yeast (yum!) yet I do not make the claim that humans are not meant to eat meat, quite the contrary.