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 center of Mars likely has a solid core composed of iron, nickel, and sulfur. It is estimated to be between 1,800 and 2,400 miles (3,000 and 4,000 kilometers) in diameter. The core does not move, and therefore Mars has no magnetic field.he center of Mars likely has a solid core composed of iron, nickel, and sulfur. It is estimated to be between 1,800 and 2,400 miles (3,000 and 4,000 kilometers) in diameter. The core does not move, and therefore Mars has no magnetic field.