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They orbit between our planet and our star. Mercury and Venus make up half of our terrestrial planets, but we still know very little about them. As we take a closer look at our companions, we find more questions than answers.
The moon is our closest celestial companion. It lights our night sky and gently tugs at our shores. Few have walked on her surface, but her allure remains strong.
Mars has fired our imagination for thousands of years. The tantilizing possibility of life has made it the most inviting planet in our solar system. It is the only other place that man may one day call home.
Our modern-day itch to find out what lies out beyond our atmosphere is rising again. The frontiers of space exploration are expanding as scientists debate a range of future missions: a return to the Moon, manned flights to Mars, robotic missions to Titan and Europa, or mining asteroids. This expansive series shows that this grand quest is driven as much by technology as our attitudes toward Earth.