11. Pluto
The surface of the dwarf planet Pluto constructed from NASA Hubble Space Telescope images
Pluto movie
Photo montages of Pluto from images taken by the Hubble Telescope
Photo montages of Pluto from images taken by the Hubble Telescope

Photo montages of Pluto from images taken by the Hubble Telescope

Courtesy of NASA, ESA, and M. Buie/Southwest Research Institute

http://www.nasa.gov/mission_pages/hubble/science/pluto-20100204.html


The Hubble pictures underscore that Pluto is not simply a ball of ice and rock but a dynamic world that undergoes dramatic atmospheric changes. These are driven by seasonal changes that are as much propelled by the planet's 248-year elliptical orbit as its axial tilt, unlike Earth where the tilt alone drives seasons. The seasons are very asymmetric because of Pluto's elliptical orbit. Spring transitions to polar summer quickly in the northern hemisphere because Pluto is moving faster along its orbit when it is closer to the sun. Ground-based observations, taken in 1988 and 2002, show that the mass of the atmosphere doubled over that time. This may be due to warming and sublimating nitrogen ice. The new Hubble images from 2002 to 2003 are giving astronomers essential clues about how the seasons on Pluto work and about the fate of its atmosphere.