Wild New Theory Suggests Pluto Formed From A Billion Comets

Pluto may not be a planet, but it remains one of the most intriguing objects in the outer Solar System. Its unexpected chemical composition has confounded scientists for years, but a new theory may finally hold the answer. Pluto, according to a pair of Southwest Research Institute scientists, is basically an overgrown comet.

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Normal accretion
Cometary accretion.
Any others?

Would there be more comets during solar system accretion?

We discussed this in chat.

• media has blown importance of paper out of all proportion.
• all the paper is saying is that Pluto’s nitrogen originated in the form of N2 rather than NH3. That’s hardly news because Earth’s nitrogen came here the same way.
• Pluto formed in a completely different part of the solar system to the comets.

Tau.Neutrino said:

Normal accretion
Cometary accretion.
Any others?

The formation of Pluto is not a mystery (apart from its smoothness). By way of contrast, the formation of Neptune is a mystery – it’s too big. But if you take the formation mechanism for Earth and move it out to the location of Pluto then you get Pluto. Everything in the outer solar system moves slower over longer distances, so Pluto formed more slowly so is still in the process of formation, so is smaller.

The Earth formed by the collision of planetessinals, which in turn formed by the collision of asteroids, which in turn formed by the collision of chondrules. With the occasional comet thrown into the mix. All this happened initially within a disk and cloud of hydrogen and helium gas. Eventually the UV light from the Sun and the solar wind pushed the gas out of the solar system.

Pluto’s formation is just the same, but with lots of ices among the chondrules.

> Would there be more comets during solar system accretion?

Yes, but I have no idea what percentage of the initial number of comets are still hanging around. It could be anywhere between 0.00000001% and 100% for all I know. Some crashed into planets, some were ejected in hyperbolic orbits, and some were thrown out as passing stars ploughed through the Oort Cloud.

The origin of the Oort Cloud is still a great mystery to me.