Pluto Explored at Last!

85 years after it was discovered, Pluto and its moons have been explored at last. On July 14, the New Horizons spacecraft sped through the Pluto system, taking images with three different types of cameras, studying the atmosphere and solar wind interactions, measuring temperature and pressure, measuring the dust in the Pluto system and beyond, and detecting the plasma and energetic particles resulting from Pluto's escaping atmosphere. 

Just before the closest approach on July 14 at 6:49 AM CDT, NASA released this image of Pluto, better than we had ever seen before: 

This true-color image of Pluto shows off its most noticeable feature, a bright heart shape. The smooth surface of the heart is a big clue to planetary geologists that Pluto may be geologically active. The smoothest part of the heart is likely carbon monoxide ice. Credit: NASA/Johns Hopkins University Applied Physics Laboratory/Southwest Research Institute

Mission team members' reaction to seeing the above image. Lovely. Photo Credit: (NASA/Bill Ingalls)

After 9.5 years of flying, New Horizons was speeding through the Pluto system. People were pretty excited, including everyone at the planetarium. The people who had worked on it for so long were the most excited, and rightly so.

 Credit: NASA/Bill Ingalls

During the critical time of the close fly through of the Pluto system, the mission scientists didn't want to take the time to turn the spacecraft around to send data and pictures back to Earth - it was too busy doing science! However, around midday, New Horizons was programmed to send a short burst of telemetry back to Earth, with information that basically would say "Hello! I'm here! Nothing hit me and I am still working!". Then it would get back to the science. The "phone home" signal took 4.5 hours to get back to Earth (moving at the speed of light), so we had to wait until about 8 PM CDT to know for sure that the spacecraft survived the flyby. 

It made it. 

Flight controllers celebrate as the "phone home" signal is received. I was jumping up and down in my kitchen, so I can't imagine how much more excited these people felt. Image Credit: NASA/Bill Ingalls

After all the excitement of Tuesday, we had to wait until the afternoon of the next day for new images to be released. Because the signals take 4.5 hours to get to Earth, and the downlink is slow, new data will be released from the flyby for another 16 months! 

Here was the first new image released, showing Pluto's small moon, Hydra. This image was taken when New Horizons was still very far away from Pluto, so better images are coming. 

Although this image is obviously low resolution, it does tell scientists new things about the moon. We now know it is irregularly shaped, and measures about 27 x 20 miles. It is also very reflective, and so probably covered in water ice. Water is abundant in our Solar System! Image Credit: NASA-JHUAPL-SwRI

Preliminary science from New Horizons indicates that Pluto is covered in methane ice, but the thickness varies greatly. Read more at:

Credit: NASA/Johns Hopkins University Applied Physics Laboratory/Southwest Research Institute

The most exciting images revealed from the flyby were of Charon, Pluto's largest moon, and a high resolution image of a portion of Pluto. 

This image of Charon was taken while New Horizons was still almost 300,000 miles away, but it is by far the best detail we have ever seen of the large moon. Image Credit: NASA/Johns Hopkins University Applied Physics Laboratory/Southwest Research Institute

The dark patch on the north pole is informally referred to as Mordor. There is a series of troughs and cliffs that extend from northeast to southwest, which could be due to activity inside the moon. The area just below the troughs is smoother, which could mean that there was recent resurfacing (geologic activity!). At about 2:00, you can see a long canyon that is about 2 to 3 miles deep! You can actually see through the canyon to space on the other side. New Horizons will release higher resolution images of Charon soon, but this first look is incredible. 

The zoomed in image of Pluto was very exciting. It is in black and white because they don't have data from the color camera for this image yet. 

This is a close up image of Pluto's surface, in the bright portion of the "heart" feature. Credit: NASA/Johns Hopkins University Applied Physics Laboratory/Southwest Research Institute

There are a number of exciting things about this image. Firstly, those mountains are 11,000 feet tall! (For reference, Gemini South is on a 9,000 foot tall mountain). Also, scientists can tell that they must be young compared to Pluto, and may still be in the process of building. Scientists estimate their age to be only 100 million years old, based on the lack of craters in this scene. Because Pluto is in the Kuiper Belt, full of thousands of asteroids and debris, it's surface should be heavily cratered - unless recent geologic activity has erased the scars left behind by impacts. Pluto is too far away from any large body to be heated by gravitational interactions, as Io and Titan are, for example. Some other process must be heating this tiny world.

Also, the mountains are probably composed of Pluto's water-ice "bedrock". Although most of Pluto is covered in exotic methane and nitrogen ices, those materials are not strong enough to build mountains. As cold as Pluto is, water-ice behaves like rock. 

Structures less than a mile across are resolved in the above image. I can't wait to see the next photos released! 

Our views of Pluto, from its discovery to today. See complete list of credits here.

As far as we have been told, the New Horizons team is not expecting to release any new images today, but say tuned. We will have delightful discoveries for months to come. Stop by the Dome Planetarium for our 3 PM Dynamic Planets show to learn about Pluto all summer.