APOD: Tagging Bennu (2023 Sep 21)

[johnnydeep]

It is easily distinguished. Presolar grains, which make up a fraction of a percent of carbonaceous material, are largely unaltered grains of the molecular dust cloud from which the Solar System formed. They are very refractory dust particles. Everything else is highly altered- melted, shocked, subjected to aqueous reactions. Material that formed here and no longer resembles the original dust except in gross elemental percentages. These things are readily determined by looking at isotope ratios.

Are those "unaltered grains" composed of a small number of types of molecules/minerals/etc., or is there wide variation?

Quite a few mineral species have been identified- diamond, silicon carbide (and a number of others that you might recognize from applications like drill bits and sandpaper), olivine. They range in size from a few thousand atoms to micron scale. They are found embedded in the matrix of altered material that makes up many asteroids (primarily observed from carbonaceous meteorites).

Thanks. And just to stick a pin in this point, those particular minerals are such that they couldn't possibly have been formed by any of the known processes going on in the still-forming solar system (high speed collisions, heating/cooling, etc.) ?

[Chris Peterson]

Are those "unaltered grains" composed of a small number of types of molecules/minerals/etc., or is there wide variation?

Quite a few mineral species have been identified- diamond, silicon carbide (and a number of others that you might recognize from applications like drill bits and sandpaper), olivine. They range in size from a few thousand atoms to micron scale. They are found embedded in the matrix of altered material that makes up many asteroids (primarily observed from carbonaceous meteorites).

Thanks. And just to stick a pin in this point, those particular minerals are such that they couldn't possibly have been formed by any of the known processes going on in the still-forming solar system (high speed collisions, heating/cooling, etc.) ?

It's not that there might not be processes that could create them, but these are objectively observed to have isotope ratios that would require a different elemental soup than found in the bulk molecular cloud. They are older than the Solar System and must have originated in a different environment (in a supernova).

[johnnydeep]

Quite a few mineral species have been identified- diamond, silicon carbide (and a number of others that you might recognize from applications like drill bits and sandpaper), olivine. They range in size from a few thousand atoms to micron scale. They are found embedded in the matrix of altered material that makes up many asteroids (primarily observed from carbonaceous meteorites).

Thanks. And just to stick a pin in this point, those particular minerals are such that they couldn't possibly have been formed by any of the known processes going on in the still-forming solar system (high speed collisions, heating/cooling, etc.) ?

It's not that there might not be processes that could create them, but these are objectively observed to have isotope ratios that would require a different elemental soup than found in the bulk molecular cloud. They are older than the Solar System and must have originated in a different environment (in a supernova).

Ah, right - thanks. You did mention the usefulness of isotopes before.

[Ann]

I didn't comment on this picture before because, well, it's not my kind of picture. But the mission itself is certainly impressive.

Now the sample return capsule carrying rocks and gravel from Bennu has returned to the Earth! And the rest of the spacecraft is on its way to another asteroid to continue its mission to find out more about asteroids in the Earth's vicinity. I must applaud NASA!

Ann

[Galaxian]

This is a C-type asteroid, so we know that it is made up of the primitive earliest material forming the Solar System. The selection of a carbonaceous asteroid was based on obtaining good samples of such material unaltered by passage through the atmosphere in the form of meteorites.

Yeah, but now we have a pure, uncontaminated blob of Original Stuff that hasn't been cooked by passage through our air nor slimed by all of the bugs our air and ground are full of.

That is an amazing achievement.

FWIW, there is no evidence that any planets were ever shattered and formed debris in the Solar System. The largest bodies that collided and created asteroids were at most a few hundred kilometers in diameter.

I find that problematic.

Earth is supposed to have been smacked by A Giant Impactor a while back and the result is supposed to be our lovely little Moon. One Moon. No others. Not even tiny, littly bits. The odds of absolutely everything falling back to the Earth or merging into Luna don't seem very high.

But that's only intuition. I don't have a supercomputer to model this on so maybe I'm being simplistic and wrong?

However: yet another Giant Impactor is sometimes blamed for "tipping" Uranus and her satellites. This one, too, left nothing behind. That, too, seems unlikely.

Venus rotating "backwards"? Oh, yes, yet another Giant Impactor. Why Venus has nothing even resembling a Phobos as a moon after the Giant Impact is a mild mystery.

My tea getting cold? That, too, must be a Giant Impactor.

Still, at least we now have good Science telling us that only Little Impactors such as Bennu are likely to hit us any time soon and even Bennu isn't very likely.

Unless Osiris tapped it hard enough to alter its orbit a bit?

After DART, that would be rather ironic.

[Galaxian]

I didn't comment on this picture before because, well, it's not my kind of picture. But the mission itself is certainly impressive.

Now the sample return capsule carrying rocks and gravel from Bennu has returned to the Earth! And the rest of the spacecraft is on its way to another asteroid to continue its mission to find out more about asteroids in the Earth's vicinity. I must applaud NASA!

Ann

Definitely!

It's an achievement the entire species should be proud of!

And something I never thought would ever happen. But then, I never expected to get close-ups of Pluto and Charon, nor images of planets not in our Solar System, nor evidence of thousands of exoworlds.

Astro-stuff certainly has progressed a bit since I was reading Hugh Walters oh so many years ago.

Those people are amazing!

[Chris Peterson]

This is a C-type asteroid, so we know that it is made up of the primitive earliest material forming the Solar System. The selection of a carbonaceous asteroid was based on obtaining good samples of such material unaltered by passage through the atmosphere in the form of meteorites.

Yeah, but now we have a pure, uncontaminated blob of Original Stuff that hasn't been cooked by passage through our air nor slimed by all of the bugs our air and ground are full of.

That is an amazing achievement.

FWIW, there is no evidence that any planets were ever shattered and formed debris in the Solar System. The largest bodies that collided and created asteroids were at most a few hundred kilometers in diameter.

I find that problematic.

Earth is supposed to have been smacked by A Giant Impactor a while back and the result is supposed to be our lovely little Moon. One Moon. No others. Not even tiny, littly bits. The odds of absolutely everything falling back to the Earth or merging into Luna don't seem very high.

But that's only intuition. I don't have a supercomputer to model this on so maybe I'm being simplistic and wrong?

However: yet another Giant Impactor is sometimes blamed for "tipping" Uranus and her satellites. This one, too, left nothing behind. That, too, seems unlikely.

Venus rotating "backwards"? Oh, yes, yet another Giant Impactor. Why Venus has nothing even resembling a Phobos as a moon after the Giant Impact is a mild mystery.

My tea getting cold? That, too, must be a Giant Impactor.

Still, at least we now have good Science telling us that only Little Impactors such as Bennu are likely to hit us any time soon and even Bennu isn't very likely.

Unless Osiris tapped it hard enough to alter its orbit a bit?

After DART, that would be rather ironic. :)

To the extent that giant impacts occurred, they were very, very early in the formation of the Solar System. And giant impacts are most likely to produce gravitationally bound debris (as with the Earth/Moon), meaning that material doesn't escape to other parts of the Solar System. And residual material would not be in stable orbits, so it would have long since vanished into the Sun.

So no... we have no reason to think that any significant amount of debris in the Solar System is the product of planet-scale collisions.