Mars is the seventh largest planet in our solar system and about half the diameter of Earth. Its surface gravity is 37.5 percent of Earth’s. Mars rotates on its axis every 24.6 Earth hours ...

but Neptune orbits once every 165 Earth years For a planet to form, its own gravity must be strong enough to make it round or spherical in shape. Its gravitational field must also be strong enough ...

Every other solar system planet was named for a Greek ... Getty Images We also enjoy protection from Earth's magnetic field, generated by our planet's rotation and its iron-nickel core.

A new model has been developed to simulate interstellar activity within our solar system and the nearby Alpha Centauri system ...