探索频道英语听力 Cosmos 宇宙的边疆07

…… dozens of moons, thousands of asteroids and billions of comets—the family of the sun.

Only 4 light hours from Earth is the planet Neptune, and its giant satellite, Triton.

Even in the outskirt 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 until 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.

We’re now only 80 light minutes from home, a mere one and a half billion kilometers.

The largest planet in our solar system is Jupiter. On its dark side, super bolts of lightning illuminate the clouds as first revealed by the Voyager spacecraft in 1979.

Inside the orbit of Jupiter are countless shattered and broken worldlets----the asteroids. These reefs and shoals mark the border of the realm of giant planets. We are now entering the shallows of the solar system. Here there are worlds with thin atmospheres and solid surfaces, earth-like planets with landscapes crying out for careful exploration. This world is Mars.

In 1976, after a year’s voyage, two robot explorers from Earth landed on this alien shore. On Mars, there is a volcano as wide as Arizona and almost 3 times the height of Mount Everest. We've named it Mount Olympus. This is a world of wonders. Mars is a planet with ancient river valleys and violent sandstorms driven by winds that half the speed of sound. There is a giant rift in its surface 5,000 Kilometers long. It’s called Vallis Marinaris -- the valley of the Mariner spacecraft that came to explore Mars from a nearby world.