Here is some more in depth info on their observations and the physics properties that may be responsible for this mystery:

Carly Howett, a senior research scientist at the Southwest Research Institute, is one of the scientists studying the mystery of what is causing this color difference and why it shows up at Charon’s north pole.

“Looking at Charon, it’s very clear that the northern polar region is much redder than the rest of the moon,” said Howett in a post on the New Horizons website. “Surfaces vary in color when something about them changes.”

So what is this red material? The leading theory right now is that material from Pluto’s atmosphere is falling to Charon and being ensnared in the polar region by what is known as “cold-trapping.”

Ok what does that mean exactly?  Here is some info from wikipedia:

In vacuum applications, a cold trap is a device that condenses all vapors except the permanent gases into a liquid or solid.^[2] The most common objective is to prevent vapors being evacuated from an experiment from entering a vacuum pump where they would condense and contaminate it. Particularly large cold traps are necessary when removing large amounts of liquid as in freeze drying.

Well this sounds reasonable and we’re looking forward to more data as it comes in from this latest mission!

thanks to universetoday.com for the great info

thanks to NASA for the great pic