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.
Mars' atmosphere is made mostly of carbon dioxide, with some nitrogen and argon. It has a very small amount of oxygen and carbon monoxide and tiny amounts of noble gases and other compounds. Earth's atmosphere is 100 times thicker than the atmosphere of Mars. Continue Reading.