"Wow, I don't think anyone expected Charon to reveal a mystery like dark terrains at its pole. Who ordered that?" said Alan Stern, principal investigator for the mission at the Southwest Research Institute in Boulder, Colo., in a statement.
New Horizons is scheduled to make a close flyby of Pluto and its moons on July 14.
Stern said the science team is "ecstatic" that during its flyby the spacecraft will face the side of Pluto that includes "every terrain type," both the brightest and darkest areas on the dwarf planet's surface.
Late last week, video of Pluto and Charon captured by New Horizons revealed that they are completely different colours — Pluto is beige-orange and Charon is grey.
That was a surprise. Lisa Hardaway, a manager with Ball Aerospace, the company that built the camera that shot the colour images, told Discovery News that scientists were expecting Pluto and Charon to be made of the same material, "but they're obviously not."
As of noon ET today, New Horizons was about 24 million kilometres away from Pluto. That's about a sixth of the distance between the Earth and the sun.
Last week, the National Space Society, a non-profit organization "dedicated to the creation of a spacefaring civilization," released a beautiful video offering a preview of what we might see when New Horizons makes its flyby in less than a month. It has been viewed over a million times on YouTube.