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July 7, 2015

ALAN STERN: Our knowledge of Pluto is quite meager....We know very, very little about this world....It’s very much like our knowledge of Mars was before the first mission to Mars.

Alan Stern heads the first mission to Pluto, known as New Horizons. If everything is on track, it’ll pass less than 8,000 miles from Pluto a week from today — on the 50th anniversary of the first encounter with Mars.

Until now, Pluto has been seen as little more than a pinpoint of light in even the biggest telescopes. Even so, scientists have managed to piece together a basic outline about the little world.

For one thing, they’ve found that it’s only about two-thirds the diameter of the Moon. It has at least five moons, including one that’s half as big as Pluto itself; we’ll have more about that tomorrow. And its surface is coated with frozen nitrogen mixed with a smattering of methane and carbon monoxide.

Computer-processed images from Hubble Space Telescope, along with long-range pictures from New Horizons, have shown a wide variation in the brightness of Pluto’s surface. Some regions are almost black, while others are slightly orange and others are almost white.

When Pluto is closest to the Sun, some of the ice at its surface vaporizes and forms a thin atmosphere. Right now, Pluto is moving away from the Sun, so scientists expect the atmosphere to eventually freeze out and coat the surface with a fresh layer of frost — a major change for this little world.

Script by Damond Benningfield, Copyright 2015

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