If you paid attention to the data sent back by New Horizons when it zipped by Pluto and Charon, you know that Pluto has a heart-shaped region, which is known as the Tombaugh Regio. The western lobe of the heart-shaped regio was originally named Sputnik Planum but is now known as Sputnik Planitia. It lies mostly in the northern hemisphere, but does extend southward beyond the equator.
The surface of the Sputnik Planitia consists mostly of irregular polygons separated by troughs. The polygons average about 21 miles (33 km) across. The surface also has what appear to be wind streaks, with evidence of sublimation, which is the rapid change from solid to vapor form. Sublimation also appears to be the cause of pits found in the planitia. No craters were detectable by New Horizons, implying the surface is less than 10 million years old.
Most of the ice in this basin is thought to be primarily nitrogen ice, with small fractions of carbon monoxide and methane ices. At Pluto's ambient temperature of 38°K, nitrogen and carbon monoxide ices are much less rigid than water ice, making glacial-like flows possible.
This basin likely originated when something about 125 miles across hit the area. The subsequent hole would have subsequently collected volatile ices. The nature of Pluto's atmosphere means that a topographic depression becomes a cold trap.
Nitrogen ice is denser than water ice, and the accumulation of this much dense nitrogen ice has created a higher level of gravity associated with this area. This gravity anomal may have caused Pluto to reorient itself to put the planitia near the Pluto-Charon tidal axis. Currently, Pluto and Charon always keep their same faces towards each other, and Sputnik Planitia is presently close to the anti-Charon point on Pluto, which has a less than 5% probability of happening by chance.
Contrary to popular belief, Charon does not orbit Pluto. Both Charon and Pluto orbit the same point, which is located between the two of them. Some scientists believe Charon and Pluto are a binary dwarf planet. That's what I think.
I also think there is a case to call Earth and its moon a binary planet, but that's a little harder to convince people, because the point being orbited is within Earth's diameter. What do you think on the subject?
Astronomy, March 2017, Page 13, "Pluto's Slusky
Heart Contains a Large Ocean.
https://en.wikipedia.org/wiki/Sputnik_Planitia
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