Signs and symptoms are both signals of injury, illness, disease â signals that something is not right in the body. A sign is a signal that can be seen by someone else â maybe a loved one, or a doctor, nurse, or other health care professional.
Besides silicon and oxygen, the most abundant elements in the Martian crust are iron, magnesium, aluminum, calcium, and potassium. Oxidation of the iron dust is what gives the surface its reddish hue. Composite image showing the size difference between Earth and Mars. Credit: NASA/Mars Exploration.
The atmosphere of Mars is enriched considerably with the noble gas argon, in comparison to the atmosphere of the other planets within the Solar System. Unlike carbon dioxide, the argon content of the atmosphere does not condense, and hence the total amount of argon in the Mars atmosphere is constant.