Formation of Rocky & Metal Meteors

[Airbrush]

Correct me if I am wrong, but I think these rocky and metallic meteors are the results of collisions between massive asteroids. They are the fragments that explode outward. So these heavy meteors were originally inside giant asteroids that collided and broke up into pieces, and metallic meteors came from the cores of these giant exploded asteroids. Otherwise, small meteors would be puff balls that easily break up into dust. The puff ball first generation meteors accumulate to form giant asteroids. They never are hard like rock or metal until after they are melted inside giant asteroids. This means the asteroid belt is most composed of broken fragments of ancient giant asteroids. Right?

[Enthalpy]

This is more or less the standard theory. Whether the whole asteroid belt is composed of dense bodies, I'm not so sure.

[JohnStu]

Correct me if I am wrong, but I think these rocky and metallic meteors are the results of collisions between massive asteroids. They are the fragments that explode outward. So these heavy meteors were originally inside giant asteroids that collided and broke up into pieces, and metallic meteors came from the cores of these giant exploded asteroids. Otherwise, small meteors would be puff balls that easily break up into dust. The puff ball first generation meteors accumulate to form giant asteroids. They never are hard like rock or metal until after they are melted inside giant asteroids. This means the asteroid belt is most composed of broken fragments of ancient giant asteroids. Right?

 

Hmm, not mostly, just few of them were once part of a bigger asteroid. Most of them are just chunks of rocks that never fell into a nearby big object such as a planet

[Airbrush]

Hmm, not mostly, just few of them were once part of a bigger asteroid. Most of them are just chunks of rocks that never fell into a nearby big object such as a planet

 

That is what I thought before, but think about it. In order to be made of rock or metal it had to be in a molten state, and that only happens inside of giant asteroids that have a molten interior. So when you see meteorite hunters using a metal detector, they are searching for metal pieces that were once in the core of giant asteroids that crashing into other giant asteroids so that Billions of rock and metal fragments went flying off in every direction.

Edited September 18, 2012 by Airbrush

[Enthalpy]

It still doesn't imply that most or all asteroids are made of compact and differentiated matter. Only that some are, and parts of these can be searched on Earth with a metal detector.

 

By the way, I estimated once that a body must have only D=500km to be differentiated, a value consistent with what a recent spacecraft observed. This would be less than a giant asteroid: rather a big one.

[Airbrush]

It still doesn't imply that most or all asteroids are made of compact and differentiated matter. Only that some are, and parts of these can be searched on Earth with a metal detector.

 

By the way, I estimated once that a body must have only D=500km to be differentiated, a value consistent with what a recent spacecraft observed. This would be less than a giant asteroid: rather a big one.

 

I heard that all asteroids are composed of dust as fine as smoke particles that stick together electrostatically. How can that fine dust become solid rock or metal? It must become molten and that requires a great mass, maybe not "giant" but at least "rather big". Also the molten metals will fall to the center of the molten rock of rather big asteroids. So initially asteroids and meteors are very fragile dust piles that will easily fragment when they crash into each other. The solid ones, that we are most familiar with, must be pieces of "rather big" ones that smashed into other rather big ones and fragmented. The molten fragments cool into solid rock and metallic chunks (the metals originating in the very centers of large asteroids). The ones that reach Earth must be rather robust fragments of "rather big" ones, because a fragile dust pile will not go very far before getting blasted back into fine dust by the solid objects around it. That dust will have to start accretion again painfully slowly.

Edited September 18, 2012 by Airbrush

[Ophiolite]

That is what I thought before, but think about it. In order to be made of rock or metal it had to be in a molten state, and that only happens inside of giant asteroids that have a molten interior.

This turns out to be incorrect as far as the rocky asteroids are concerned. The temperature of the accretion disk that formed duirng the formation of the proto-sun. These formed the chondrites and achondrite meteors many of which coalesced to form chondritic asteroids. (Caveat: there is some recent research that suggests that at least one chondritic parent body did manage to partially differentiate. This is based upon the ratios of certain siderophile and lithophile elements when compared with the solar norm.)

[Airbrush]

This turns out to be incorrect as far as the rocky asteroids are concerned. The temperature of the accretion disk that formed duirng the formation of the proto-sun. These formed the chondrites and achondrite meteors many of which coalesced to form chondritic asteroids. (Caveat: there is some recent research that suggests that at least one chondritic parent body did manage to partially differentiate. This is based upon the ratios of certain siderophile and lithophile elements when compared with the solar norm.)

 

I don't understand this process. Could you elaborate in simpler language? Are you saying that the accretion disk that formed around our Sun reached high enough temperatures to melt the space dust without them collecting into large bodies that (thru their gravitational pressure) developed a molten interior?

Edited September 24, 2012 by Airbrush

[Ophiolite]

Yes, broadly. Temperatures in the disc were high. This was a consequence both of kinetic energy from infalling particles being converted to heat and radiation from the protosun.

 

An earlier understanding of the formation process saw the differences between the terrestrial planets and the gas and ice giants as being due to this. Planetologists refer to snow line, beyond which temperatures were low enought to allow ices to condense.

 

The dust that formed at this time gradually coagulated into larger particles then into kilometres sized bodies and then onto planetesimals. There were dozens of Mars sized objects flying around. Anything over about 100km in diameter was big enough to remelt itself and differentiate into mantle and core.

 

Does that help? It's way more complex than this, but that captures the highlights.

[Airbrush]

Does that help? It's way more complex than this, but that captures the highlights.

 

That helps a great deal. Thank you.