This Is What a Day on Pluto and Charon Looks Like
Although the NASA New Horizons mission's close encounter with the Pluto system lasted a matter of hours, the probe was still able to image a full 'day' on Pluto and largest moon Charon.
Although the NASA New Horizons mission's close encounter with the Pluto system lasted a matter of hours, the probe was still able to image a full "day" on Pluto and largest moon Charon.
Both Pluto and Charon are a tidally locked system - i.e. the same hemisphere of Charon always faces the same hemisphere of Pluto - so their days span the same amount of time. One rotation of the Pluto-Charon system is 6.4 Earth-days long, so as New Horizons began its approach, it was already taking photos.
The flyby would only reveal one side of Pluto and Charon, but as shown in these sequences, the probe started taking observations long before point of closest approach, allowing us a glimpse - albeit a blurry glimpse - of the "binary planet's" far side.
New Horizons used its Long Range Reconnaissance Imager (LORRI) and Ralph/Multispectral Visible Imaging Camera to capture observations from 5 million miles (8 million kilometers) distant on July 7 to 400,000 miles (645,000 kilometers) on July 13. Closest approach occurred on July 14, when the mission came within 7,800 miles (12,500 kilometers) of the dwarf planet's surface. But in the lead-up to close approach, New Horizons was able to see an entire day in the Pluto-Charon system.
Most striking are the peculiar cluster of (what appear to be) impact craters on the "far side" of Pluto (the images shown at the 10 o'clock to 2 o'clock positions). These features were quickly sighted as New Horizons began its dive into the Pluto system, but mission scientists knew that this would be the best view they'd get of the small world's far side.
The rest of the mission's imagery would be filled with the vast dynamic plains and frozen mountain ranges we are becoming intimately familiar with in the months since flyby. The observation in the 6 o'clock position is what is known as the mission's "encounter hemisphere", showcasing Pluto's now-famous "heart" - informally known as Tombaugh Regio.
As for Charon, its surface contrasts greatly with the variations visible on Pluto's surface. In this sequence of images, Charon's "encounter hemisphere" is showcased at the 12 o'clock position. The most distant image of the moon's far side is at the 9 o'clock position.
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On approach in July 2015, the cameras on NASA’s New Horizons spacecraft captured Pluto rotating over the course of a full “Pluto day.” The best available images of each side of Pluto taken during approach have been combined to create this view of a full rotation.
New images of Pluto taken during New Horizons' flyby paint a picture of surprising complexity and variety.