Strange Worlds At The Edge Of Our Solar System Finally Come Into Focus

Scientists have unveiled the best photos of Pluto and its moons that humanity is likely to see for at least a generation. These images were taken Tuesday by NASA's New Horizons space probe as it hurtled past Pluto at more than 30,000 miles per hour.

Since its discovery in 1930, Pluto has revealed itself to be an oddball world. It's smaller than our own moon, and it orbits at an angle relative to the plane of the solar system. Because of its size and distance, even the Hubble Space Telescope could only make it out as a brown smudge, billions of miles away.

With New Horizons, all that has changed. Scientists can now see craters and regions of dark-reddish ground. A large, white, heart-shaped feature on the equator is made of ice, though Pluto is so cold it's probably an ice of nitrogen or methane, rather than water. A new close-up of a small region on Pluto's surface also reveals towering ice mountains, up to 11,000 feet high.

Pluto's largest moon, Charon, has also been brought into focus. It is believed to have formed when a large object struck Pluto sometime in the past. Today, the moon is "locked" with Pluto in a tight orbit.

Scientists on the mission were elated when they finally got a look. After all, these images are the culmination of decades of work. And the fun is only beginning. Many more images will come in the next few months, as the spacecraft beams back its data over the vast chasm of space.

But it's also bittersweet moment, says Jim Greene, NASA's head of planetary sciences. "The team constantly since launch thought, 'Every day we're closer to Pluto, every day we're closer to Pluto,' " he says. Now, suddenly, Pluto is in the rear-view mirror and New Horizons is plunging deeper into the darkness of space.

"Time marches on," Green says.

In the mood for more? Check out this poetic tribute to Pluto by NPR's Skunk Bear.