Pluto's Heart

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

Twins

I consider Pluto and Charon twins. They run around the sun, constantly together, and pretty much ignoring all their other siblings. Pluto was discovered in 1930, and was considered a planet until fairly recently, when it was demoted to dwarf planet.

Charon wasn’t discovered until 1978, and is usually considered Pluto’s closest and largest moon. However, there are scientists who (like me) think Pluto and Charon should be classified as a binary dwarf planet unit. For one thing, Charon’s diameter is slightly more than half of Pluto’s, which is very large for a moon. The relative sizes of a moon to its planet rarely approach that, from what we’ve been able to observe so far. Charon’s size is so large, compared to Pluto’s, that - strictly speaking - it doesn’t actually revolve around Pluto. Both of these twins revolve around a point somewhere between them. Kind of like 2 kids on a playground, holding each other’s hands and spinning around, laughing as they get dizzy and the world around them starts to look silly. And like those 2 kids, they don’t allow the 4 remaining ‘moons’ to join them. The tiny moons revolve around the pair, wishing they were part of the game.

Pluto’s diameter is 2,372 km[1,474 miles], making it the largest dwarf planet we know of. My quick research didn’t find Charon’s exact diameter, but it’s slightly more than 1,186 km[737 miles], which certainly makes it larger than Ceres (950 km)[590 miles].

While NASA’s probe thoroughly studied Pluto, it didn’t neglect Charon. Since it was there, why waste the opportunity? And aside from size, they do rather resemble each other.

Both Pluto and Charon are believed to have a rocky core surrounded by water ice, with other ices covering that. And at the temperatures experienced that far out, water ice is as hard as stone. I find that a little hard to fathom, but not impossible to accept.

Pluto and Charon are tidally locked, meaning each keeps the same side facing the other at all times. Rather like the 2 kids mentioned earlier. But they must have gotten so dizzy they fell over, because they travel around the sun on their sides - still revolving around each other. Maybe the twins got the idea of laying down from Uranus.

And like Uranus and Venus, Pluto rotates backwards, so that sun rises in the west and sets in the east. I found no mention of Charon doing that.

Both of the twins have some interesting features, like Pluto’s ‘heart’, which is a huge glacier made of Nitrogen ice, and Charon’s huge chasm that crosses its entire face. The ‘southern’ half of Charon is smoother and has less craters than the ‘northern’ half. The current thought is that when Charon’s internal water froze (and therefore increased in volume), the pressure forced some partially frozen water out as a type of lava. Remember Ceres’ cryovolcano?

For at least part of its year, Pluto has an atmosphere, or maybe it should be called ‘layers of haze’. And some of it is escaping into space, but not as much as scientists expected, and mostly methane, not the nitrogen they expected would be leaving. I thought I had heard that Charon also had some haze, possibly borrowed from Pluto, but I couldn’t find anything like that during my research, so I may have mis-heard or misunderstood what was said.

And now, I’m going to give a self-satisfied raspberry to those who decided Pluto was ‘just’ a dwarf planet. It (and Charon) were full of surprises and brain-twisting facts for the entire New Horizons team that studied the incoming data. Way to go, Twins!

More on Pluto & Charon

Last week, I made a prediction to a friend that, alas, has come true. My prediction was that by this week, NASA’s look at Pluto and Charon would have fallen out of the news as being too old, and the ‘news’ programs will have returned to dissecting and analyzing some politician’s speech or statement made last week... or even earlier. As exciting as the Pluto/Charon photos and info are, the people analyzing that information are scientists who want to be sure they understand what they have before making any big announcements like “Life found on Pluto!” or “Charon a huge alien generation ship!”

I find Pluto and Charon far more interesting than all this way-too-early political jibber-jabber we’ve been getting for what seems like the past decade. So I’ll take this opportunity to go through my reasons why I feel Pluto (& Charon) should go through yet another reclassification.

In my research reading the past couple of days, it seems there is no upper size limit to ‘dwarf planet’. One article actually said that if an object larger than Mercury were found in the Keiper Belt, it would be classified as a dwarf planet, because it has not substantially cleared out its neighborhood of debris. Can you imagine? If Earth were located in the asteroid belt, it would be a ‘dwarf planet’! 

The lower size limit of ‘dwarf planet’ is pretty fuzzy, too, but from what I gathered, the lower size for a rocky planet is about a radius of 372 miles.

Pluto’s radius is 1,430 miles, about half the size of Mercury, and definitely bigger than that lower limit. NASA’s new photos show it as round and rocky/icy. But look at this; Charon’s radius is 751 miles (about half Pluto’s size), also bigger than that lower limit, and it is also round and rocky/icy. So, why is it still considered by most to be a moon and not a dwarf planet?

Technically, Charon does not revolve around Pluto. Both Charon and Pluto revolve around a common point that is located outside Pluto’s body. If Earth and Mars were in the same orbit and both revolving around a common point, they would be a binary planet. Why not just jump in and classify Pluto/Charon a binary dwarf planet?

I have to imagine that Pluto’s ‘other’ 4 moons probably revolve around that same point, or run the risk of slamming into Charon. If they’re small enough, they could zip around Pluto inside Charon’s ‘orbit’, but from what I understand, Pluto and Charon are pretty close.

The European Space Agency referred to Earth/Moon as a binary planet, and the moon is 1/4 the size of Earth. Another website said that unequivocally, Earth/Moon is not a binary planet, because the moon does not orbit the sun, as set forth in the current definition of planet. Really? How does the moon orbit Earth and not go around the sun at the same time? By that reasoning, binary planets are impossible, because their primary orbit would not be around their star. So, what would they be?

To be fair, I did glimpse some websites that indicate there are others who - like me - think Pluto and Charon are a binary dwarf planet. I hope the idea spreads. Pluto deserves to be somewhat special, in my mind.

What do you think?