Origin of asteroids

[Moontanman]

Asteroids are often thought of as solid objects but the truth be told many are just piles of rubble. Vast piles of gravel and this is what you would expect if tiny rocks clumped together, or maybe what I would expect given the small size of asteroids. How would a pile of gravel coming together generate enough heat to solidify the object? 

This begs the question of where did the solid asteroids come from, I think the source has to be larger asteroids, dwarf planet sized at least that had small chunks broken off in collisions. 

Is this valid or does science say different?  

[Vmedvil]

On 4/5/2024 at 7:15 PM, Moontanman said:

Asteroids are often thought of as solid objects but the truth be told many are just piles of rubble. Vast piles of gravel and this is what you would expect if tiny rocks clumped together, or maybe what I would expect given the small size of asteroids. How would a pile of gravel coming together generate enough heat to solidify the object? 

This begs the question of where did the solid asteroids come from, I think the source has to be larger asteroids, dwarf planet sized at least that had small chunks broken off in collisions. 

Is this valid or does science say different?  

I am uncertain as to why the asteroids are solid, this is a subject I do not know the answer to, personally. It must be that gravity pushes them together with enough force to fuse into a solid object when they were molten at some point, I would think.

"Aside from composition, there are other important differences in the internal structure of the asteroids. Most are solid, indicating that they must have been molten at some point in their existence. Others are 'rubble piles'."

Link = https://www.esa.int/Science_Exploration/Space_Science/Asteroids_Structure_and_composition_of_asteroids

Edited April 11 by Vmedvil

[oldpaddoboy]

On 4/6/2024 at 10:15 AM, Moontanman said:

Asteroids are often thought of as solid objects but the truth be told many are just piles of rubble. Vast piles of gravel and this is what you would expect if tiny rocks clumped together, or maybe what I would expect given the small size of asteroids. How would a pile of gravel coming together generate enough heat to solidify the object? 

This begs the question of where did the solid asteroids come from, I think the source has to be larger asteroids, dwarf planet sized at least that had small chunks broken off in collisions. 

Is this valid or does science say different?  

Pretty valid I would suggest, plus also moons that have drifted inside their Roche limit, and of course, left over debris from the original formation of the solar system. 

[Halc]

Rubble piles would seem to disperse at even a minor hit from some meteor. How are they stable? Do they simply not get hit due to being such a small target?

 

On 4/14/2024 at 5:46 AM, oldpaddoboy said:

plus also moons that have drifted inside their Roche limit

Things that drift inside the Roche limit of some larger object tend to fall into that larger object in due time. They don't end up escaping the gravity well that created them.

[Moontanman]

1 hour ago, Halc said:

Rubble piles would seem to disperse at even a minor hit from some meteor. How are they stable? Do they simply not get hit due to being such a small target?

Gravity holds them together... barely. I am sure that electrostatic and chemical bonds have some effect but the fact remains that many asteroids are just rubble piles.

[oldpaddoboy]

5 hours ago, Halc said:

Rubble piles would seem to disperse at even a minor hit from some meteor. How are they stable? Do they simply not get hit due to being such a small target?

 

Things that drift inside the Roche limit of some larger object tend to fall into that larger object in due time. They don't end up escaping the gravity well that created them.

Essentially Correct, but if that planetary body was inhabited, (like Earth for example) we would see that fragment as a meteorite once it hit that planet. And if other collisions occurred between the fragments of that moon, it is within the realms of possibility that it may be ejected from that system anyway and be seen elsewhere as a meteoroid. 

5 hours ago, Halc said:

Rubble piles would seem to disperse at even a minor hit from some meteor. How are they stable? Do they simply not get hit due to being such a small target?

Asteroids are essentially larger then meteors or meteoroids. Asteroids are also sometimes classed as minor planets, so can be pretty big in fact. In fact  Ceres, (from the asteroid belt) a former asteroid, around a 1000kms in diameter,  and poor old "demoted" Pluto are classed as  dwarf planets.  

Edited April 16 by oldpaddoboy

[Halc]

5 hours ago, Moontanman said:

Gravity holds them together... barely.

Well OK. Some high speed rock hits it, and instead of it all dispersing like a triangle of completely elastic pool balls, it absorbs the energy more like a ball pit, a far more inelastic situation. The rubble pile expands from the new KE, but gravity slowly pulls it all back together and only some little bits might escape.  I can buy that. 

 

2 hours ago, oldpaddoboy said:

Ceres, (from the asteroid belt) a former asteroid, around a 1000kms in diameter,  and poor old "demoted" Pluto are classed as  dwarf planets.

Neither of those objects are rubble piles, although Ceres has quite a bit of ice that holds together at least the outer layers.  They both have similar constitution, like that of a typical Kuiper object.

I also did not call any asteroid a meteor, but I did suggest that they can be hit by one, just as can any other celestial object.

 

2 hours ago, oldpaddoboy said:

And if other collisions occurred between the fragments of that moon, it is within the realms of possibility that it may be ejected from that system anyway and be seen elsewhere as a meteoroid. 

Only way the fragments get ejected is if some other higher-speed object comes in and smacks out a few of them now and then. All the rubble from an object torn apart by Roche forces end up going the same local speed. You don't see Saturn ejecting material of the rings without outside help. Every bit of it is moving pretty much with zero velocity relative to its nearest neighbors.

Mars will have some nice rings soon. I wonder how long the whole process takes?

[oldpaddoboy]

10 hours ago, Halc said:

Well OK. Some high speed rock hits it, and instead of it all dispersing like a triangle of completely elastic pool balls, it absorbs the energy more like a ball pit, a far more inelastic situation. The rubble pile expands from the new KE, but gravity slowly pulls it all back together and only some little bits might escape.  I can buy that. 

 

Neither of those objects are rubble piles, although Ceres has quite a bit of ice that holds together at least the outer layers.  They both have similar constitution, like that of a typical Kuiper object.

I also did not call any asteroid a meteor, but I did suggest that they can be hit by one, just as can any other celestial object.

 

I'm simply making the observation that it is a matter of classification. Ceres while once being an asteroid, is now a dwarf planet. Plenty of other objects in the asteroid belt, some little more then rubble. And if one happens to be ejected, it becomes a meteoroid. If it doesn't, over time, it will probably grow due to gravitational attraction and become a more sizable asteroid.  Pluto while once a planet, is now also a dwarf planet.

10 hours ago, Halc said:

Only way the fragments get ejected is if some other higher-speed object comes in and smacks out a few of them now and then. All the rubble from an object torn apart by Roche forces end up going the same local speed. You don't see Saturn ejecting material of the rings without outside help. Every bit of it is moving pretty much with zero velocity relative to its nearest neighbors.

Mars will have some nice rings soon. I wonder how long the whole process takes?

The possibility of ejection is still there, and yes, the time frame  with regards to Phobos falling inside the Roche limit is an unknown time frame. The same applies to Saturn's rings and many moons. There is also a Saturn moon called PAN, that is called a shepard moon, as in its orbit, it actually clears other particles from the ring system and ejects them. https://en.wikipedia.org/wiki/Shepherd_moon  Saturn also has a couple of moons that swap orbital parameters, Epimetheus and Janus... more details of those moons can be found here.... https://www.planetary.org/articles/janus-epimetheus-swap

[oldpaddoboy]

Another point has just come to mind...There is evidence of planetary migration, at least in extra solar systems, and the observational data of Hot Jupiters.  And of course our own satellite Moon, is thought to have formed after a catastrophic collision with a Mars size body. https://en.wikipedia.org/wiki/Planetary_migration    https://en.wikipedia.org/wiki/Origin_of_the_Moon