HINTS： 

Dozens of

asteroids 

comets

Earth 

Neptune

Triton

outskirts 

we humans

Pluto

Charon

Uranus 

Saturn 

Dozens of moons, thousands of asteroids and billions of comets, the family of the sun. Only four light hours from Earth is the planet Neptune, and its giant satellite, Triton. Even in the outskirts of our own solar system, we humans have barely begun our explorations. Only a century ago we were ignorant even of the existence of the planet Pluto. Its moon Charon, remained undiscovered till 1978. The rings of Uranus were first detected in 1977. There are new worlds to chart even this close to home. Saturn is a giant gas world. If it has a solid surface it must lie far below the clouds we see. Saturn's majestic rings are made of trillions of orbiting snowballs.

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