Pluto: Dwarf Planet - Images over time (1992-2015)

This is an animation showing the history of knowledge of Pluto's surface over the last few decades. In the 1990s the best images were available were from a combination of the Hubble Space Telescope and studies of eclipses of transits between Pluto and its largest moon Charon. As we can see in the animation, at such a great distance from Earth, even the Hubble Space Telescope has difficulty viewing Pluto in any real detail. During 2015 several stages of approach by the New Horizons spacecraft are shown with a great wealth of detail being visible for the first time. However, even in the most recent frame, New Horizons spacecraft made its closest approach to Pluto, flying by so quickly that there wasn't any time for all of Pluto to rotate into view. Thus some longitudes are seen only at lower resolution from a greater distance. Also, much of the southern latitudes are in winter darkness, and it will take a century or so for them to be well seen.

Pluto is the brightest dwarf planet that is located in the Kuiper belt, a ring of small icy bodies outside the orbit of Neptune. It was discovered by Clyde Tombaugh in 1930 at the Lowell Observatory in Flagstaff, Arizona. Pluto was "classically" known as the ninth planet until 2006 when the International Astronomical Union set up new guidelines for qualifications of a planet. Pluto didn't meet all the qualifications and is now considered a dwarf planet. Pluto averages an astounding distance of 3,670,050,000 miles from the Sun. It is very small 1500 miles in diameter, placing it even smaller than seven of the moons found in the solar system. It has been determined that Pluto has a bright layer of methane, nitrogen and carbon monoxide ice near the surface with 70% rock and 30% water ice mostly underneath in its bulk composition. Some of the detail that is visible on Pluto is the presence of polar ice caps as well as large dark spots near the equator. The surface temperature of Pluto varies between -391°F and -346°F. The "warmer" temperatures loosely correspond to the darker areas. Pluto has five known satellites, the largest of which is Charon. Charon's diameter is over half the diameter of Pluto, making Charon the biggest moon with respect to the planet it orbits. Because of this, Pluto is often referred to as a double planet. A new mission called New Horizons was launched in 2006 and flew by Pluto in July 2015, and is providing a spectacular increase in knowledge about Pluto with ongoing images and data being transmitted back to Earth expected through 2016.

This view is constructed mostly from New Horizons images. Some of the southern hemisphere is filled in by previous imagery taken by the Hubble Space Telescope. With the very cold temperatures present, ices of substances such as nitrogen, methane, carbon monoxide, and water ice cover the surface. When Pluto is closest to the sun some of the frozen gases sublimate and create a very thin atmosphere. A deep but tenuous haze layer extends up to 60-100 miles above the surface. Some of the mountainous areas may be made of water ice, and the white heart-shaped region called Tombaugh Regio has areas of carbon monoxide ice and some of the flattest terrain seen. This has a provisional name of Sputnik Planum and shows evidence of flowing ices. A dark "Whale" shaped feature (provisionally called Cthulu Regio) wraps around Pluto to the lower left (southwest) of the "Heart".