Category: Planetary science

How the planetary systems were born

How the planetary systems were born

Our solar system began to form about 4.6 billion years ago. Astronomers think small rocky and icy grains within the solar nebula began sticking together, growing into even larger objects. Although the process remains poorly understood, solid objects miles or more across eventually populated the disk. Astronomers call these bodies planetesimals. Within a million years…

Mars, the red planet: Facts and information

Mars, the red planet: Facts and information

Once upon a time, though, wind and water flowed across the red planet. Robotic rovers have found clear evidence that billions of years ago, lakes and rivers of liquid water coursed across the red...