Gerard Kuiper

Explanation: Gerard Peter Kuiper (born December 7, 1905) was a Netherlands-born American astronomer after whom the Kuiper belt was named. Kuiper spent most of his career at the University of Chicago, but moved to Tucson, Arizona, in 1960 to found the Lunar and Planetary Laboratory at the University of Arizona. Kuiper discovered Uranus's satellite Miranda and Neptune's satellite Nereid. In addition, he discovered carbon dioxide in the atmosphere of Mars and the existence of Titan's methane atmosphere in 1944.

Pluto

Image credit: Lunar and Planetary Laboratory, University of Arizona.