I was 15 years old when the United States first landed on the moon in July 1969, and I remember it like it was yesterday. I was out with friends that night, and we listened to the moonwalk of Neil Armstrong and Buzz Aldrin on the car radio. Like millions of others, I was both excited and proud of this accomplishment — the first time in history in which humans set foot on another celestial body. I followed the rest of the Apollo missions, and realized only later how much we had lost when the lunar landings ended with Apollo 17 in December 1972.