Slide 32 of 49

Another fortuitous result of the collision of the Mars-sized planet with the Earth is the presence of the Earth's large and heavy metallic core. In fact, the Earth has the highest density of any of the planets in our Solar System. This large nickel-iron core is responsible for our large magnetic field. This magnetic field produces the Van-Allen radiation shield, which protects the Earth from radiation bombardment. If this shield were not present, life would not be possible on the Earth. The only other rocky planet to have any substantial magnetic field is Mercury - but its field strength is 100 times less than the Earth's. The magnetic field of Mars is at least 1,000 times less than that of the Earth. Even Venus, our sister planet, has no magnetic field. The Van-Allen radiation shield is a design unique to the Earth.