Billions of years ago, the fourth planet from the sun could ... With a radius of 2,106 miles, Mars is the seventh largest planet in our solar system and about half the diameter of Earth.

Mars, the fourth planet from the sun ... it is one of the most explored places in the solar system, with many rovers and orbiters searching the planet for evidence of past or present life.

Watch this video to find out more about the Earth, planets in our Solar System and other planets far off in outer space. From up here on the International Space Station I get a great view of Earth.

Everyone knows about the Solar System, and the planets that make it up. They’re in space, orbiting the Sun, in an order we all at least used to be able to recite. But it was not always so.

Aurora, commonly known as the Northern Lights in the northern hemisphere, occur when charged particles from the Sun collide ...