Hayabusa 2 on its way back to earth

[Green Baron]

We have a classification for asteroids, based on their spectra. Let us use it until there is new data.

I mean, nobody has the idea of using terms like convertible, suv, semitruck, station wagon for ships on the ocean :-)

[YNM]

11 minutes ago, kerbiloid said:

But "entirely different"...

Say, Pluto or UT will be entirely different.

Spoiler

4 minutes ago, Green Baron said:

nobody has the idea of using terms like convertible, suv, semitruck, station wagon for ships on the ocean :-)

Unless...

 

 

[MinimumSky5]

35 minutes ago, Green Baron said:

We have a classification for asteroids, based on their spectra. Let us use it until there is new data.

I mean, nobody has the idea of using terms like convertible, suv, semitruck, station wagon for ships on the ocean :-)

True, but the question @kerbiloidraised is still a very valid one. At what size do we start using the sed/ig/meta system, rather than spectra? Spectra also aren't massively useful for hand samples. 

[Green Baron]

It is like asking "at what distance from the beach do we switch from car to ship classification ?". We don't because the distance is irrelevant, as is the size.

The classification of rocks on earth is tied to the dynamic processes that form them, to physics (gravity, chemistry, heat, pressure, elements, ...), not to the size of a celestial object. But the size does influence the processes because a small object has other dynamics (if at all) as a big one. But there is no generalization. "It is here like this, so it must be there the same" does not work because "there" is different(*). And MANY other processes one can find on earth, partly early Mars, but NOT on Ryugu. When we find a mineral that apparently has undergone similar processes as we observe on earth we can use similar expressions to describe them. Until then we live with the classifications we have and do not mic apples and eggs (tastes awful, maybe with sugar and cream ?).

If you need simple terms then here you go:

Rocky asteroids are made from material similar to earths mantle (olivine, pyroxene, ..).

Metallic 'roids are made from material similar to earth's core: iron, nickel. Mixed pickle.

Comets (and KBOs) are rather dirty snowballs, with a lot of other stuff like hydrogen, oxygen, carbon, nitrogen, ...

Some 'roids have a cover of these volatiles plus carbon, aka organics (and maybe other elements). The spectral classification gives more in- and onsight.

You will not find a sandstone on Ryugu.

You will not find a carbonate platform on Mars.

There is no braided river on Pluto.

No continental shelf with a mud cover does exist on Titan.

 

No asteroid or dwarf planet shows the processes that form sediments as those on earth. That is why this classification does not apply. Until we find evidence for plate tectonics, orogenies, rivers, glaciers, atmospheres, etc. pp. These things are in discussion and will be more so as new data comes in. Until then, live with the classifications we have.

 

(*)Edit: i must say though that according to a certain principle ("Uniformitarianism", handle with care !) we can assume that the similar conditions will likely produce similar results just because physics are assumed to be the same on earth than on other bodies. That is how we judge the valleys on Mars. But conditions ARE NOT the same elsewhere, so this principle should only be used by experts and with as little guessing as possible :-)

Edited January 8, 2019 by Green Baron

[YNM]

30 minutes ago, MinimumSky5 said:

At what size do we start using the sed/ig/meta system, rather than spectra?

I suppose where they're possible :

- "Igneous rock" is only possible if there exist a liquid form of the rock in the body.

- "Metamorphed rock" is only possible if there's enough heat and an active tectonic/volcanic process.

- "Sedimentary rock" is only possible where the rocks can be eroded.

So, for instance, on Enceladus it's only possible to have "igneous" and "sedimentary" "rock" (ice, really); on Io there may be all three rocks; on 67P/C-G probably only "sedimentary", but in truth it's not rocks.

Now the difficult question : Should we consider rocks that formed from / went through a collision (which is the main way that planetary bodies grow, namely "accretion") be classified as Igneous, Metamorphed or Sedimentary ?

[kerbiloid]

16 minutes ago, YNM said:

"Igneous rock" is only possible if there exist a liquid form of the rock in the body.

Or in the parental body.

22 minutes ago, Green Baron said:

No asteroid or dwarf planet shows the processes that form sediments as those on earth.

Ceres and a 10 m rock are both asteroids. Are you sure, Ceres doesn't have glaciers (if you prefer ice over flakes)?

22 minutes ago, Green Baron said:

Rocky asteroids are made from material similar to earths mantle (olivine, pyroxene, ..).

Quote

Olivine occurs in both mafic and ultramafic igneous rocks and as a primary mineral in certain metamorphic rocks.

Unless they can create a non-metamorphic olivine

Edited January 8, 2019 by kerbiloid

[Green Baron]

6 minutes ago, kerbiloid said:

Ceres and a 10 m rock are both asteroids. Are you sure, Ceres doesn't have glaciers (if you prefer ice over flakes)?

Nonsense. Where did i say that ?

Edited January 8, 2019 by Green Baron

[kerbiloid]

2 minutes ago, Green Baron said:

Nonsense. Where did i say that ?

So, Ceres may have sedimentaries?

 

(My update was ninja'd, so a repeat.)

24 minutes ago, Green Baron said:

Rocky asteroids are made from material similar to earths mantle (olivine, pyroxene, ..).

Quote

Olivine occurs in both mafic and ultramafic igneous rocks and as a primary mineral in certain metamorphic rocks.

Unless they can create a non-metamorphic olivine

Edited January 8, 2019 by kerbiloid

[Green Baron]

3 minutes ago, kerbiloid said:

So, Ceres may have sedimentaries?

You tell me. How did the ice form ? How long is it there ? Are there processes that change its composition, its forming ? Any dynamics like thawing and new buildup ? Transport ? Atmosphere ? Weathering ? What is the ground like ? Is the chemism changing ? How does it affect or alter the ground ? Is Ceres covered with the products of something ?

--------------

Olivine is a mineral.

Metamorphosis is a process.

I could say this 3 times :-)

[kerbiloid]

1 minute ago, Green Baron said:

Olivine is a mineral.

Metamorphosis is a process.

I could say this 3 times :-)

Metamorphosis (process) is the way of a mineral creation. 

 

https://en.wikipedia.org/wiki/Metamorphic_rock#Metamorphic_minerals

Quote

Metamorphic minerals are those that form only at the high temperatures and pressures associated with the process of metamorphism. These minerals, known as index minerals, include sillimanite, kyanite, staurolite, andalusite, and some garnet.

Other minerals, such as olivines, pyroxenes, amphiboles, micas, feldspars, and quartz, may be found in metamorphic rocks, but are not necessarily the result of the process of metamorphism. These minerals formed during the crystallization of igneous rocks

Would you prefer metamorphic or igneous olivine in your asteroid, sir?

 

4 minutes ago, Green Baron said:

You tell me. How did the ice form ? How long is it there ? Are there processes that change its composition, its forming ? Any dynamics like thawing and new buildup ? Transport ? Atmosphere ? Weathering ? What is the ground like ? Is the chemism changing ? How does it affect or alter the ground ? Is Ceres covered with the products of something ?

With pleasure, once you list the cases found on Earth.

[Green Baron]

Sorry, this is becoming childish nitpicking. You do not understand. Olivine is not a metamorphic mineral, but may be the result of igneous crystallisation. It is also a main component of earth's upper mantle and in silicate asteroids. Read the wikipedia link you posted, it is not that bad as i can tell from a short overfly. And stop bothering me with nitpicking.

-------------

The question was how do we classify Ryugu rocks geologically.

Geology as on earth does not apply. We give it a spectral classification based on surface properties. This and orbital parameters leads us to an estimation of the main "ingredients". Which, in analogy with meteorites found on earth, leads us to a proposed mineral composition.

More when we have moar data.

 

Edited January 8, 2019 by Green Baron

[kerbiloid]

12 minutes ago, Green Baron said:

Olivine is not a metamorphic mineral, but may be the result of igneous crystallisation.

Yes, it's a mineral of a metamorphic or an igneous origin, It doesn't appear just on its own.

Metamorphic minerals are the minerals which appear from the metamorphic process, igneous - from ... igneous ones. This term describes the way of the mineral creation, and the minerals are usually named "metamorphic" or "igneous" or "sedimentary" depending on their way. Some of them (see above: olivine) have several ways.
Obviously, no mineral has a label M/I/S on it.

So, if you find the olivine in a 'roid, it's of one of these two origins.

12 minutes ago, Green Baron said:

Geology as on earth does not apply.

Chemistry and physics are the same.

12 minutes ago, Green Baron said:

We give it a spectral classification based on surface properties.

Just because not enough data to give informative answers based on their geological properties.
We use spectral classification for stars. This doesn't mean their metals differ from the solar ones.

Edited January 8, 2019 by kerbiloid

[Green Baron]

16 minutes ago, kerbiloid said:

Yes, it's a mineral of a metamorphic or an igneous origin, It doesn't appear just on its own.

I repeat, olivine is not a metamorphic mineral, and yes, it appears on its own, even in crystalline gem form; or on the moon, and was found in asteroid samples (Itokawa).

Wikipedia says this not all that wrong: "Other minerals, such as olivines, pyroxenes, amphiboles, micas, feldspars, and quartz, may be found in metamorphic rocks, but are not necessarily the result of the process of metamorphism."

Edited January 8, 2019 by Green Baron

[kerbiloid]

4 minutes ago, Green Baron said:

I repeat, olivine is not a metamorphic mineral

Yes, it can be not only a metamorphic (by origin) mineral, it can be a crystallized igneous mineral, that's what I'm repeating.

4 minutes ago, Green Baron said:

it appears on its own

Transfiguration spell?

I thought any chemical compound, including minerals, appears as a result of some chemical and physical processes. Even in Itokawa.
The olivine has two, unless you know a third.

Edited January 8, 2019 by kerbiloid

[YNM]

1 hour ago, kerbiloid said:

Or in the parental body.

A bit difficult when your parental body is a gas giant !

[kerbiloid]

4 minutes ago, YNM said:

A bit difficult when your parental body is a gas giant !

OK, instead of "parental body" please substitute "the former celestial body whose destruction has created this asteroid".

[Green Baron]

2 hours ago, kerbiloid said:

Yes, it can be not only a metamorphic (by origin) mineral, it can be a crystallized igneous mineral, that's what I'm repeating.

It goes deeper (haha): the concept of metamorphic (m.) minerals is a bit misleading. A schist is metamorphic, a gneiss, a marble may be (contact metamorphosis). These rocks are composed of minerals, but most of these minerals can exist elsewhere. Some minerals otoh can be transformed through (regional) metamorphosis and form new minerals, even as indicators. But an indicator of a pressure of 60km depth on earth and 900° would be impossible to find on an asteroid (gravity is missing, one does not have that combination). For metamorphosis to take place one needs rocks to be transformed, like an intrusion of a pluton into a package of sediments, or subduction of an ocean plate with sediments on top. Plate tectonics play the main role here. M. in its various forms is in itself not an origin, but part of a process. The oldest rocks on earth are m., the original rocks are gone. This is where the process and the state must not be confused, or these misunderstandings happen.

Quote

Transfiguration spell?

Almost. Peridot ;-)

Quote

The olivine has two, unless you know a third.

I do. Olivine is a natural silicate mineral with Mg, Fe, Mn, some configurations are stable, others will weather away more quickly when exposed to surface conditions on earth. Olivine has pressure modifications typical for earth's upper mantel(*). But it also occurs freely, in cometary dust, etc. Astronomical style processes that father it aren't all that difficult to imagine ;-)

(*) Wikipedia has an article on Fosterite that may serve as a further reading.

Edited January 8, 2019 by Green Baron

[kerbiloid]

12 hours ago, Green Baron said:

It goes deeper (haha): the concept of metamorphic (m.) minerals is a bit misleading. A schist is metamorphic, a gneiss, a marble may be (contact metamorphosis). These rocks are composed of minerals, but most of these minerals can exist elsewhere. Some minerals otoh can be transformed through (regional) metamorphosis and form new minerals, even as indicators. But an indicator of a pressure of 60km depth on earth and 900° would be impossible to find on an asteroid (gravity is missing, one does not have that combination). For metamorphosis to take place one needs rocks to be transformed, like an intrusion of a pluton into a package of sediments, or subduction of an ocean plate with sediments on top. Plate tectonics play the main role here. M. in its various forms is in itself not an origin, but part of a process. The oldest rocks on earth are m., the original rocks are gone. This is where the process and the state must not be confused, or these misunderstandings happen.

How does this wordplaying reject existence in asteroids of the minerals of (especially for those who dislikes the widely used "metamorphic" and "igneous" mineral term) any of metamorphic and igneous origin, appeared in a bigger celestial body whose destruction had given a particular asteroid?

12 hours ago, Green Baron said:

I do. Olivine is a natural silicate mineral with Mg, Fe, Mn, some configurations are stable, others will weather away more quickly when exposed to surface conditions on earth. Olivine has pressure modifications typical for earth's upper mantel(*).

The magic word "natural" doesn't mean it's "without GMO"
It means that the olivine appears without human efforts as a product of any of metamorphic and igneous origin, appears in a bigger celestial body whose destruction had given a particular asteroid.

Edited January 9, 2019 by kerbiloid

[Green Baron]

 

Quote

It means that the olivine appears without human efforts as a product of any of metamorphic and igneous origin, appears in a bigger celestial body whose destruction had given a particular asteroid.

It is (probably like almost anything else) bread in Supernovae and flies through space. It does not appear in all of those m. and i. rocks, in fact its origin has little to do with these processes, as much as for example a feldspar.

It exists independently of the process, just accept it, though it and its modifications are abundant on earth and in space. After all, it is Iron/Magnesium and Silicon dioxide. You have probably stepped on it today several times, in more or less high concentrations.

 

Edited January 9, 2019 by Green Baron

[MinimumSky5]

I suppose that the main reason I'm wanting a fourth catagory for rocks is that the very first thing I've been told to do with a rock, throughout college and university, is to determine if a rock is sedimentary, metamorphic, or igneous, saying none of the above was never an option. Actually thinking about it, though, there is no reason that that is not a valid answer! 

[Green Baron]

Because people don't understand the difference between an element, a mineral and a rock, and an asteroid and a planet like earth. Why is it so difficult to grasp that an asteroid is not earth with its dynamics ?

Yes. That is the classic most fundamental address to a piece of stone on earth. In many cases it can be done on site with very basic equipment. Because we have abundant examples and rocks here are the outcome of geological processes, of the dynamics of the earth from the core to the edge of space. Rocks are composed of minerals, in many different forms (there are thousands), and minerals are composed of chemical elements. Rocks are the outcome of tectonic processes, weathering, transport, etc.

You will find the same elements on celestial bodies as on earth, and in many cases the same minerals (though by far not in that variety as on earth), but you will not find the same rocks there because the processes that form them do not exist. Why is that so difficult to grasp i ask myself ?

Of course, you are allowed to use whatever designation you want, but you will not find a classification of rocks for asteroids that resembles the classification on earth because these rocks do not exist there. Some of them or similar ones may exist on other planets, as on outcome of the processes that are at work there. But there are no sediments on an asteroid because there is no weathering and transport as on earth. There is no metamorphosis because no hot magma climbs from a core boundary, and no subduction brings surface material into a GPa and 2.000K regime.

But there is a classification for roids. Use it. Or leave it. I don't care (any more).

Edited January 9, 2019 by Green Baron

[YNM]

57 minutes ago, Green Baron said:

But there is a classification for roids.

Maybe we'll need a different one when we find large icy stuff like Pluto.

[James Kerman]

Division F (Planetary Systems and Bioastronomy) of the International Astronomical Union (IAU) Working Group for Planetary System Nomenclature (hereafter IAU WG) has begun naming features on Ryugu:
 

Quote

The surface of celestial bodies has a range of different topologies. We applied to give names to four different topology types on the Ryugu surface. The first type is “dorsum” which originates from the Latin for peak or ridge. The second type is “crater” which are familiar structures on the Moon and asteroids. Then “fossa” meaning grooves or trenches and finally the Latin word “saxum” for the rocks and boulders that are a main characteristic of the Ryugu terrain. Saxum is actually a new classification of terrain type that we applied to introduce due to the nature of Ryugu.

Numerous boulders are distributed on the surface of Ryugu. Regardless of where you look, there are rocks, rocks and more rocks. This is a major characteristic of Ryugu and continues to make plans for the touchdown operation of the spacecraft difficult. Additionally, spectroscopic observations revealed that the giant boulder (Otohime saxum) at the south pole has not only a substantial size, but also a distinct visible light spectrum that reveals materials and surface conditions that are different from the surrounding areas. Since this boulder is the most important topographical feature for understanding the formation history of Ryugu, the Project strongly hoped to name it. However, there was no precedent for boulder nomenclature and even the name type did not exist (during the exploration of the first Hayabusa mission, naming the huge boulder protruding from asteroid Itokawa was not allowed). We therefore proposed the type name for boulders at the same time as applying for the place names. Since terrain type names are usually Latin, we proposed “saxum” (meaning rocks and stones in Latin) as the type name for boulders. The IAU accepted this nomenclature for boulders with a few conditions (such as the boulder must be 1% or more of the diameter of the celestial body) and the type name that we suggested was adopted (!). This is how the new terrain type “saxum” was born.

http://www.hayabusa2.jaxa.jp/en/topics/20190121e_Nomenclature/

 

[Green Baron]

Phew, the list can get long in the future, with new features on other bodies. But so it is ... different worlds, different features.

[tater]