UNSPECIFIED - JANUARY 17:  American astronomer Clyde Tombaugh discovered Pluto, the ninth planet in our solar system, on 18 February 1930. Many key questions about Pluto, its moon Charon, and the outer fringes of our solar system await close-up observations. A proposed NASA mission called New Horizons, depicted in this artist's concept, would use miniature cameras, radio science experiments, ultraviolet and infrared spectrometers and space plasma experiments to study Pluto and Charon, map their surface compositions and temperatures, and examine Pluto's atmosphere in detail.  (Photo by SSPL/Getty Images)