Is asteroid Psyche actually a planetary core? James Webb Space Telescope results cast doubt

[Admin]

The presence of hydrated minerals, including possibly water-ice, might indicate an unexpected origin for Psyche, far from the sun.

Is asteroid Psyche actually a planetary core? James Webb Space Telescope results cast doubt : Read more

 

[Deleted member 1146189]

What is to stop Psyche forming in a metal rich gaseous zone of the disc (and sweeping up/ absorbing water elements) as temperatures cool, to be left as an entity in its own right?

 

[Torbjorn Larsson]

What is to stop Psyche forming in a metal rich gaseous zone of the disc (and sweeping up/ absorbing water elements) as temperatures cool, to be left as an entity in its own right?

Nothing, but such an element sorting in the disk is less likely,

Gravitational sorting in rocky planets with metal cores is ubiquitous, and we expect many protoplanets in the early system. C,f. how the Venus massed Tellus and Mars massed Theia collided to form Earth and Moon, and how Uranus may have gotten its tilt from an Earth massed impactor.

But the question of what Psyche is is still open.

 

[Unclear Engineer]

Given the mass of Psyche and the local environment, it would not surprise me if an exposed planetary core would accumulate some surface materials that were not from the core, but rather from other debris from its own collision and/or other collisions in the asteroid belts.

The density is the main indicator. How well do we really know the density value for Psyche?

 

[Deleted member 1146189]

Nothing, but such an element sorting in the disk is less likely,

Gravitational sorting in rocky planets with metal cores is ubiquitous, and we expect many protoplanets in the early system. C,f. how the Venus massed Tellus and Mars massed Theia collided to form Earth and Moon, and how Uranus may have gotten its tilt from an Earth massed impactor.

But the question of what Psyche is is still open.

With respect - why would sorting of metals within the disk be less likely than something that might have occurred later. The article posits sorting wrt water elements in the disk.

" The solar system formed out of a protoplanetary disk, or a frisbee shaped disk around the young sun filled with dust, gas and ice. The snow line is a certain distance from the sun in this disk where temperatures would have been low enough for volatile gases, such as water and carbon dioxide, to freeze out as ice and become incorporated into the structure of any small bodies that formed out there."

At higher and cooling temperatures would there not have been a "snow line" for eg iron, resulting from gas to liquid to solid?

 

[billslugg]

It is possible to do some amount of sorting of elemental iron in the solar nebula. The freeze line of iron would be very close to the Sun. The amount of volume available for sorting purposes is very small. There is not enough volume to do enough separation to explain the amount of separated out iron in the Solar System.

 

[Deleted member 1146189]

It is possible to do some amount of sorting of elemental iron in the solar nebula. The freeze line of iron would be very close to the Sun. The amount of volume available for sorting purposes is very small. There is not enough volume to do enough separation to explain the amount of separated out iron in the Solar System.

Thanks. Can you support those statements?

 

[Unclear Engineer]

When theorists calculate temperatures in the various locations of the protoplanetary disk, how do they account for shadowing of disk material from solar energy by intervening disk material, and heat transfer by radiation out of the disk, more or less perpendicular to the plane of the disk? Doesn't that depend strongly on the thickness and density of the disk, and how that changes over time as planets form? And is the transfer of kinematic energy to heat energy of particles and protoplanets in the disk accounted for? This seems like it would need to be quite complicated, and have some substantial levels of uncertainty.

And, with the models showing that the major planets may have migrated towards and away from the Sun as the planets evolved, why would that not have scattered the asteroids that we seen in a belt inside Jupiter now, unless they formed after Jupiter went through the current asteroid belt for the last time?

I wonder if the asteroids formed "late" in the process, with Jupiter effectively demolishing some protoplanets whose debris eventually coalesced into the various asteroid belt objects we see now. Perhaps much of the debris ended up in Jupiter, and what we see is a fraction of what was initially in that distance from the Sun.

 

[billslugg]

Thanks. Can you support those statements?

No, I can't cite where I read it. I've seen the explanation twice in the last couple of weeks though. Just ignore me.

 

[Unclear Engineer]

These 2 links provide some better discussion of formation locations and migrations:

Frost line (astrophysics) - Wikipedia

en.wikipedia.org

The Building Blocks of Earth Could Have Come From Farther out in the Solar System

Part of Earth's bulk came from asteroids that formed well beyond the Solar System's frost line, according to a new study.

www.universetoday.com

And iron in the planets' formations is discussed here:

https://www.ncbi.nlm.nih.gov/pmc/articles/PMC8713747/

Iron in the protoplanetary disk seems to have been present in molecules of various sorts, rather than in reduced form. So, its volatility is not what you would expect by looking at the properties of the pure metal. It is probably best thought of as non-volatile dust until it gets into a very hot accreting protoplanet.

 

[Deleted member 1146189]

No, I can't cite where I read it. I've seen the explanation twice in the last couple of weeks though. Just ignore me.

No worries billslugg, you might well be right - I'm just imagining different scenarios so they can be scrutinised here.

 

[Deleted member 1146189]

These 2 links provide some better discussion of formation locations and migrations:

Frost line (astrophysics) - Wikipedia

en.wikipedia.org

The Building Blocks of Earth Could Have Come From Farther out in the Solar System

Part of Earth's bulk came from asteroids that formed well beyond the Solar System's frost line, according to a new study.

www.universetoday.com

And iron in the planets' formations is discussed here:

https://www.ncbi.nlm.nih.gov/pmc/articles/PMC8713747/

Iron in the protoplanetary disk seems to have been present in molecules of various sorts, rather than in reduced form. So, its volatility is not what you would expect by looking at the properties of the pure metal. It is probably best thought of as non-volatile dust until it gets into a very hot accreting protoplanet.

Thanks. There is plenty in those links that I need to spend time over. What I don't get is why the liquid metal elements would Not coalesce within a spiralling disk in the liquid phase - Maybe Psyche is an example of this having happened, staring at us in the face, and remnant iron meteorites maybe also. Extrapolating back from left over debris which formed later would not represent this.

 

[Unclear Engineer]

I doubt there is much in the way of "liquid metal" in any of the protoplanetary disk material until it has coalesced into a big enough planet to get some significant temperature level and have some chemical reactions to reduce the iron from some oxidized states.

But, the third link has a lot of discussion about how the conditions in the protoplanetary disk ranged from reducing to oxidizing due to the "volatiles" such as water being dissociated by sunlight and the oxygen being swept outward by the solar wind. with measurements of iron on the surfaces of Mercury, Earth and Mars used to support the theory.

But to get strata differentiation of a body to form a core and a mantle of different densities, this paper says it requires about a 10 km diameter to be able to retain enough heat from the impacts and decay of radioactive materials to melt the iron so that it will "sink" to the center.

 

[Deleted member 1146189]

I doubt there is much in the way of "liquid metal" in any of the protoplanetary disk material until it has coalesced into a big enough planet to get some significant temperature level and have some chemical reactions to reduce the iron from some oxidized states.

But, the third link has a lot of discussion about how the conditions in the protoplanetary disk ranged from reducing to oxidizing due to the "volatiles" such as water being dissociated by sunlight and the oxygen being swept outward by the solar wind. with measurements of iron on the surfaces of Mercury, Earth and Mars used to support the theory.

But to get strata differentiation of a body to form a core and a mantle of different densities, this paper says it requires about a 10 km diameter to be able to retain enough heat from the impacts and decay of radioactive materials to melt the iron so that it will "sink" to the center.

On Earth iron precipitates at 2861 degrees C. Accepting that pressures and allowing for impurities might change that temperature , what would stop All of the iron in, essence, becoming liquid across the whole of the disk at certain temperatures/pressures etc, if that disk had a hot start and was cooling?

In addition, the disk did not start off as a disk - how much of that associated sorting is taken into consideration?

 

[billslugg]

This make sense. As the nebula cooled, iron would be the first to rain out. For awhile there would be nothing there but hot gas and tiny droplets of iron. They might coalesce into large droplets. They might cool too quickly to coalesce, in that case the iron would be in the form of dust.

 

[Unclear Engineer]

I don't think that is a likely scenario.

The elements in the nebula were blasted into space by a supernova explosion, which resulted in very hot ionized plasma, free electrons and atomic nuclei with few if any bound electrons.

That plasma had to cool enough to allow it to be re collapsed by gravity to form a star with a protoplanetary disk. In the cooling process electrons became bound to nuclei, creating atoms. Those atoms might still not have electrons bound to their lowest energy shells, so would still be "ionized" for some extended period during the cooling process.

So, I would expect the atoms in a supernova nebula to be highly reactive. Even if two iron atoms found each other and clung together, they would be split apart if they encountered an oxygen atom, either alone or as part of a water molecule, for instance. And water is not the only thing that will react with iron.

So, long before the center of a condensing cloud of gas gets dense enough to create a star in its center, I expect the atoms of iron to be bound into molecules of rust or other iron-bearing molecules. Thus, iron should not be able to condense into a metallic planetary core directly from metallic dust floating in space.

This is consistent with what we observe on Mars, Earth, etc, today. Iron is in the form of rust on planetary surfaces. It requires high heat and gravitational differentiation in collapsed solid planetary bodies to create metallic planetary cores.

So, my thinking is that metallic meteorites and asteroids are remnants of demolished protoplanets.

 

[Unclear Engineer]

https://www.space.com/planet-growth-rapid-secret-recipe is a new Space.com article that addresses some of the issues raised in the comments to this thread.

 

[Catastrophe]

Are we getting rather confusing generally in terminology?

In August 2022, I posted:

It is worth pointing out that Ceres is by far the largest 'asteroid' in the asteroid belt, witness the fact that it has been designated as a dwarf planet. Ceres is more akin to objects found beyond Neptune such as Pluto and Eris.

Strange dwarf planet Ceres may have formed at the icy edges ...
https://www.space.com › News › Science & Astronomy

18 Mar 2022 — The dwarf planet Ceres is located in the asteroid belt but looks nothing like its neighbors. In a new paper, scientists propose an ...

Now we have Psyche being considered as a possible planetary core.

It was only the 16th asteroid known, but we now know it's among the 12 largest minor planets orbiting the Sun between Mars and Jupiter. With an average diameter of some 220 kilometres, asteroid 16 Psyche contains about 1% the total mass of the entire asteroid belt.5 Oct 2023

Are Ceres and Psyche going to remain asteroids, or are we going to have multiple classifications such as asteroid, minor planet, planetary core . . . . . . . . .

We still retain the classification "planet" for the inner rocky terrestrial planets, and for gas or ice giants for the outer planets. Can't we just allow the variations within these? For our Solar System we could just settle for Inner and Outer planets?

Obviously wider classification is required for exoplanets.

We can add this to the confusion over universes:

Universe and universes - some conformity please.

Many of us are familiar on when it is appropriate to use a capital U or small u. Korzybski (Science and Sanity) clearly teaches that "the map is not the territory". Some find it easier to understand "the menu is not the meal". The words are not the reality they may purport to describe. :)...

forums.space.com

Cat

 

[Unclear Engineer]

Meanings keep changing as we learn more.

Back when I was a child, the asteroids were thought to be fragments of a large planet that was shattered in some way by its proximity to Jupiter's enormous mass. It was roughly where a planet should be along the series of increasing distances from the Sun exhibited by the other planets. Others thought it was just material that never formed into a single planet because of disruption by the proximity to Jupiter.

But, as we learned more, we found that some large ones were like small planets, having become roughly spherical and probably stratified differentially by core melting, while others were just groups of rock and dust loosely bound together by gravity.

And, then there is Psyche, which looks like the core of a small planet that was shattered, probably by a collision with another small planet, rather then tidal forces from Jupiter.

The theories of our solar system formation have gone from dust coagulating into planets in roughly the positions they now occupy to a much more chaotic process with the major planets moving in towards the Sun and back away from the Sun, along with a much larger number of smaller planets than now exist crashing into each other, plus asteroids (whatever they are) and comets crashing through the solar system adding mass and maybe returning water to the inner planets.

So, I don't really see a problem with calling differentiated spherical bodies "planets" of some types (e.g., small, minor, rocky, gas giants, ice giants, etc. etc.) if those are the best descriptions of what they seem to be. I just think we need to dispense with the idea that planets need to have cleared their orbits of other objects in order to achieve the title.

And, now that we know there are "dark comets" that look like asteroids because they are not giving of gas and blowing off dust, we will probably need to start subdividing "asteroids" into rubble piles, icy somethings, etc., but still distinguish them from "comets" that seem to be mostly ices.

Then what about 1I/ʻOumuamua, that doesn't really seem to fit any of those descriptions? It seemed to change velocity like a comet, but without any visible plume of exhausting gases. Just calling it "interstellar object" doesn't seem satisfactory, because that could fit anything that is coming by at more than escape velocity from the Sun, no matter what it was like.

 

[Catastrophe]

Unclear Engineer,

I am certainly in favour of differentiating different types of SS bodies.

The point I was trying to make was that I would like to see some simple hierarchical system.

Major Planets easily subdivide into Inner and Outer.
Outer subdivide into Gas and Ice Giants,
Too few to bother further differentiation, other than individual names.

Next step could do with a single group embodying Dwarf Planets down to smallest bodies worth designating. This includes Dwarf Planets, Asteroids, Trojans, Trans Neptunian Objects and so on.

Not many may know that:

As of April 2022, the catalog of minor planets contains 901 numbered TNOs. In addition, there are more than 3,000 unnumbered TNOs, which have been observed since 1993.

Such (as well as some other objects) might be divided by composition or location.
Some names are ambiguous. Trojans, for example, began as objects co-orbiting with Jupiter at 60o ahead and behind that planet. Now it seems to refer to such bodies co-orbiting any planet.

In astronomy, a trojan is a small celestial body (mostly asteroids) that shares the orbit of a larger body, remaining in a stable orbit approximately 60° ahead of or behind the main body near one of its Lagrangian points L4 and L5. Trojans can share the orbits of planets or of large moons.

Trojans are one type of co-orbital object. (Wiki)

There are also Near Earth Asteroids, and asteroids in the region of the outer planets (Jupiter to Neptune) and TNOs beyond Neptune.

BTW, to keep Belt Asteroids in perspective:

Ceres makes up 40% of the estimated (2394±5)×1018 kg mass of the asteroid belt, and it has 3+1⁄2 times the mass of the next asteroid, Vesta, but it is only 1.3% the mass of the Moon.

The four largest asteroids in the belt are called Ceres, Vesta, Pallas, and Hygiea. These large asteroids make up about half of the mass of the entire asteroid belt. Scientists like to say that if you combined all of these rocky asteroids together, it would make a planet a bit smaller than Earth's moon.

Cat


See also:

https://scienceandtechnology.jpl.nasa.gov/research/research-topics-list/planetary-sciences/small-bodies-solar-system#:~:text=The%20small%20bodies%20of%20the,of%20our%20Solar%20System%27s%20formation.