The Importance of Being Pluto
Pluto will not go away.
The puzzle? What causes the redness of objects within the solar system? The inner solar system has red colored objects (think Mars), and scientists assume it's carbon-related. But at the same time, if it is carbon-related, why aren't the objects black, like charcoal? Other objects in the Kuiper Belt, where Pluto resides in the outer solar system, also are red.
The Hubble Space Telescope photographed the planet from 2000 to 2003, and with the data it imaged, Buie and his colleagues found that the planet was redder. 20% redder. As Buie admits, this scared him, "It was so hard to believe-- I wondered many times, did I screw up the data?"
Buie was assured that his data were accurate when he noticed Pluto's moon, Charon, had the same color throughout the images.
Pluto is a planet of extremes because its orbit is very severe. Pluto takes 248 years to circle to the sun-- moving dramatically closer to and farther from the Sun. This causes temperatures to fluctuate greatly. Some color change (the increased brightness captured by Hubble) was expected due to nitrogen ice melting as it gets warmer. But some of the color change (regions getting darker, or redder) was not expected.
So, planet or dwarf, don't count Pluto out! As Mike Brown stated when asked about Pluto's status, "There's nothing wrong with being an ice ball-- I affectionately call it an ice ball."
As the New Horizons spacecraft approaches Pluto in 2015, we will discover more about this beloved ice ball.