The period of rotation for any of the Jovian planets is               than Earth’s period of rotation.

(a)  

The formation of the solar system from a rotating disk of dust and gases is described by the                                   theory.

(a)  

Planets were originally formed when bits of matter collided and clumped together to form                                   .

(a)  

Because of its many similarities to Earth          , has been referred to as “Earth’s twin.”

(a)  

Some scientists believe that on             , a thick, water-laden atmosphere once surrounded the planet, producing torrential downpours.

(a)  

       (a)   satellite system resembles a miniature solar system with at least 63 moons.

     (a)    is the smallest planet in the solar system.

Pluto’s orbit is very      .

(a)  

The orbits of most         lie between Mars andJupiter.

(a)  

The total mass of all the asteroids is estimated to be only 1/1000 that of                                   .

(a)  

             are pieces of rocky and metallic materials held together by frozen gases.

(a)  

Comets with long orbital periods form a spherical shell around the solar system called the                                  .

(a)  

A few                                          are thought to be fragments of the moon, or possibly Mars, that were ejected when an asteroid impacted these bodies.

(a)  

A meteoroid that reaches Earth’s surface is called a(n)                                   .

(a)