The Changing Face of Mars
En Español
Long ago, Mars was alive with action. Wind blew hot ash around. Hot rocks blasted into the sky. Huge rocks fell from space. Water rushed down rivers.
For a long time, people thought that Mars had grown quiet. Then astronomers took a closer look. Astronomers are scientists who study space.
It turns out that Mars is still pretty active. Clouds float across the sky. Rocks fall down hills. As the seasons change, ice melts and freezes again. The face of Mars, we now know, is always changing.
The Red Planet
Mars is the fourth planet from the sun. Red rocks and sand cover Mars. That is one reason why it is called the red planet.
The red planet is smaller than Earth. Yet Mars has the largest volcano ever found. It is called Olympus Mons. Mars also has a valley as long as the United States.
Rocky Rain
Thousands of huge holes dot the face of Mars. They are called impact craters. Most of the craters formed long ago. The holes appeared when space rocks crashed into the planet.
Rocks of all sizes fly through space. The largest ones are called asteroids. You can usually find them between Mars and Jupiter. Smaller rocks are known as meteoroids.
The largest impact crater on Mars is the Hellas Impact Basin. It is half the size of the United States. The rock that made this hole must have been huge. Another hole is called the Happy Face Crater. Rocks inside the crater look like eyes and a smile.
Space rocks still hit Mars today. Twenty small craters have formed in the past seven years.
Running Water
Holes aren't the only marks on the face of Mars. There are lines too. These are gullies, or deep ditches.
Astronomers think running water made the gullies. It rose up from underground. Then it raced across the planet. As it moved, the water carved some 10,000 gullies.
Two gullies look different from all the rest. They are white. The water that carved them carried bits of white dirt. It stayed behind when the water dried up.
Heating Up
Mars keeps changing today. The planet is heating up. This is called global warming.
Wind is one reason Mars is turning hotter. Wind blows sand around. That uncovers dark rocks.
The dark rocks take in lots of heat from the sun. The heat rises, stirring the winds. The winds then blow more sand and uncover more rocks.
As Mars heats up, ice at the south pole melts. That changes Mars too. What will it look like next?
Article by Fran Downey. Top-of-page photo by Kees Veenenbos. "The Changing Face of Mars" appears on pages 18-23 of the October 2007 issue.
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