Mars was named by the ancient Romans for their god of war because its reddish color was reminiscent of blood. Other civilizations also named the planet for this attribute - for example, the Egyptians called it 'Her Desher,' meaning 'the red one.' Even today, it is frequently called the 'Red Planet' because iron minerals in the Martian dirt oxidize, or rust, causing the surface to look red.
With a radius of 2,106 miles (3,390 kilometers), Mars is about half the size of Earth. If Earth were the size of a nickel, Mars would be about as big as a raspberry. From an average distance of 142 million miles (228 million kilometers), Mars is 1.5 astronomical units away from the Sun. One astronomical unit (abbreviated as AU), is the distance from the Sun to Earth. From this distance, it takes sunlight 13 minutes to travel from the Sun to Mars.
Why is Mars called the Red Planet?
The word oxidize appears in the chunk above. The text says iron minerals 'oxidize, or rust.' What does 'oxidize' mean based on the context clue 'or rust'?
Ancient Romans named Mars after their god of war. Can you think of other things named after gods or mythological figures?
As Mars orbits the Sun, it completes one rotation every 24.6 hours, which is very similar to one day on Earth (23.9 hours). Martian days are called sols - short for 'solar day.' A year on Mars lasts 669.6 sols, which is the same as 687 Earth days. Mars' axis of rotation is tilted 25 degrees with respect to the plane of its orbit around the Sun. This is another similarity with Earth, which has an axial tilt of 23.4 degrees. Like Earth, Mars has distinct seasons, but they last longer than seasons here on Earth since Mars takes longer to orbit the Sun.
Mars has two small moons, Phobos and Deimos, that may be captured asteroids. They're potato-shaped because they have too little mass for gravity to make them spherical. The moons get their names from the horses that pulled the chariot of the Greek god of war, Ares (whose Roman counterpart is Mars). Phobos, the innermost and larger moon, is heavily cratered, with deep grooves on its surface. It is slowly moving towards Mars and will crash into the planet or break apart in about 50 million years.
Why are Phobos and Deimos potato-shaped instead of round?
Why do Mars's seasons last longer than Earth's seasons?
A day on Mars is very close to an Earth day. If you lived on Mars, what would you do with the slightly longer day?
Mars has a thin atmosphere made up mostly of carbon dioxide, nitrogen, and argon gases. To our eyes, the sky would be hazy and red because of suspended dust instead of the familiar blue tint we see on Earth. Mars' sparse atmosphere doesn't offer much protection from impacts by such objects as meteorites, asteroids, and comets. The temperature on Mars can be as high as 70 degrees Fahrenheit (20 degrees Celsius) or as low as about -225 degrees Fahrenheit (-153 degrees Celsius). And because the atmosphere is so thin, heat from the Sun easily escapes this planet.
Mars appears to have had a watery past, with ancient river valley networks, deltas, and lakebeds, as well as rocks and minerals on the surface that could only have formed in liquid water. There is water on Mars today, but the Martian atmosphere is too thin for liquid water to exist for long on the surface. Today, water on Mars is found in the form of water-ice just under the surface in the polar regions as well as in briny (salty) water, which seasonally flows down some hillsides and crater walls.
Why can't liquid water exist for long on Mars's surface today?
The word briny appears in the chunk above. The text mentions 'briny (salty) water, which seasonally flows down some hillsides.' What does 'briny' mean based on the context clue in parentheses?
Scientists look for signs of ancient water on Mars to understand if life could have existed there. Why do you think water is so important for life?