NASA released images of the dwarf planet Pluto and its main moon Charon showing most of their surface. They’re formed by compositions of various photographs taken by two cameras of the New Horizons space probe: the Long Range Reconnaissance Imager (LORRI) and the Ralph/Multispectral Visible Imaging Camera. The photographs were taken between July 7 and 13, during the approach that led to the extraordinary July 14, 2015 flyby.
The images were created based on observations of a Pluto’s day, equivalent to 6.4 Earth days. Charon is tidally locked to Pluto so it always shows it the same face, like the Moon to the Earth, which means that its rotation period and its revolution one are equal. Put simply, its day is 6.4 Earth days long as well.
In the course of almost a week, the New Horizons space probe went from a distance of about 8 million kilometers (about 5 million miles) from Pluto at about 645,000 km (about 400,000 miles). The consequence is that the quality of the photos taken varied greatly during those days and remained lower than that of the high-resolution images taken during the flyby that NASA published in recent months.
The flyby lasted too little to capture details of large parts of Pluto and Charon’s surface so the lower-resolution photographs taken in the previous days are very useful to get an idea of the characteristics of the areas not photographed on July 14, 2015. In Pluto’s composite image, the area photographed during the flyby is at 6 o’clock. In Charon’s composite image, its instead at 12 o’clock.
This operation of the photographs’ graphic composition isn’t perfect. There are dimples in the bottom showing the south of Pluto and Charon formed by artifacts produced by the way in which the images taken by the New Horizons space probe were combined.
They still allow to understand that the diversity on Pluto’s surface is even greater than we saw because the hemisphere photographed at high resolution appears different from the other. On Charon instead the two hemispheres look very similar but you can see the borders of the huge canyon which runs through the area photographed during the flyby. Even low-resolution images are really interesting.
