As we migrate further away from the Sun temperature drops and volatile gasses and ices tend to dominate the solar system in comet, moon and planet bodies. Solar system bodies called comets and asteroids are the two which are given distinct names due to their content or lack, thereof, of ices/gasses. |
The distance from the Sun to the Earth equals one Astronomical Unit (AU). Near the Sun, less than 2 AU, where the terrestrial rocky planets reside, most of the volatile gasses (ices) are evaporated away into space, hence, we are left with an abundance of the harder metals and minerals in bodies called asteroids planets or moons.
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Earth Rocks come in three flavors
Melting points of Rock and metal
If you melt sand or silica dioxide (SiO2) and cool it rapidly such that it does not have time to form a crystal lattice structure, it becomes an amorphous glass such as obsidian or olivine. Olivine is a green SiO2 rock/glass but some silica sands are reddish, yellow or brown. Obsidian is typically a black silica glass mixed with magnesium and/or iron. |
>>>>>>>>>>>>>>>>>>>>> In this image take note of how the asthenosphere is referred to as "plastic" (flexible, pliable), whereas, the mantle below is "stiffer" Felsic or Feldspar rocks are constructed primarily of lighter materials such as silica, sodium and potassium (sandy quartz) and are less dense (2.56 g/cm^3) than rocks that are more magnesium and iron rich. Granite is a felsic rock. Felsic rock makes up about 41% of the stuff you walk on, on Earth. Wiki Quote Feldspars (KAlSi3O8 – NaAlSi3O8 – CaAl2Si2O8) are a group of rock-forming tectosilicate minerals that make up about 41% of the Earth's continental crust by weight. Feldspars crystallize from magma as veins in both intrusive and extrusive igneous rocks and are also present in many types of metamorphic rock. As we migrate deeper into the Earth's core;
While this pattern may exists on rocky bodies like asteroids and dwarf rocky planets, it does not necessarily hold true for ice dominant bodies like comet 67P. Water has a density of 1 g/cm^3, ice has a density of 0.916, hence, ice floats on water. Comet 67P has a density of only 0.533, it's core has been compared to cotton candy. It has a harder outer shell with a fluffier less dense porous interior similar to a chicken egg. |
Here is a commonly expressed unreasonable explanation describing the Earth's core where crustal rigid rock migrates down through the mantle, heats then rises again in a process called convection.
>>>>>>> Since colder fluids are more dense than warmer fluids it is depicted that the upper crystallized crust subducts down through the mantle dropping as a cold slab of rock falling through lava. The problem with this scenario is that the less dense felsic rock is a brittle crystalline (conductive) material that resides at the upper crust boundary of the lithosphere and is less dense than the material below. Less dense crystallized conductive material does not sink down into more dense material just because the dense material is in a more fluid state. Density increases toward the core. Density defines the layers and because of pressure the mantle is stiffer than the plastic asthenosphere |
This concept of convection currents apply to liquids of similar densities since temperature dictates density in fluids, it doesn't apply to solids as they are rigid and conductive in nature (they don't easily transfer heat).
A less dense solid rigid crust might possibly get pushed down via subduction to a small degree, however, it would quickly fracture and break at some point and remain at its upper less dense zone. This less dense iron anvil (7.874 g/cm^3) getting pushed down into a bath of more dense liquid mercury (13.534 g/cm^3) serves as an example. >>>>>>>>>>> |
Meteorite types & ratios found on Earth
Stone 94% (silicate/magnesium oxide minerals).
Metal 5% (Iron/nickel) melted metals must have formed under heat and pressure inside a large bodied asteroid or proto-planet which was sometime later broken apart by an impact. |
Two hundred and forty one meteorites were studied to understand the average ratio of each compound found inside. Knowing this gives a rough sense of what ratios of matter are floating around the solar system and subsequently the general ratios and compositions of larger potentially planetary bodies.
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The suffix meaning of pallasite, meteorite, granite or chondrite in French is ite or Latin ita or Greek ites
"connected with or belonging to" = ite When two or more basic elements are combined or bonded together, they are a compound. |
Above images show meteorites constructed of
To the right you can see a breccia fault zone inside a terrestrial rock (picture by Carly Lee @_Sackung) |
Meteorite Composition ratios
The most abundant compounds inside meteorites are
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This is a rare Pallasite meteorite (1%) named Fukang (once an asteroid) and it's one big Fukang meteorite Boundary Conditions: We observed multiple (olivine) inclusions hundreds of microns in length in Fukang. These inclusions contain a Cr-rich silicate (Cr=chromium), silica crystals, and k-rich (k=potassium) orthoclase-normative glass. We identified the silica crystals as monoclinic tridymite. The presence of tridymite provides a constraint on the size of the pallasite parent body since tridymite is a SiO2 polymorph that only crystallizes in a narrow range of pressures (<0.40 GPa) and temperatures (870–1470 °C). The pressure stability for tridymite varies in the literature (0.15 – 0.40 GPa) due to the presence of impurities that catalyze its formation. Pallasite is a metal/rock meteorite with olivine crystals encased in melted iron which means these types of meteorites formed between temperatures of 1,127 °C (greater than iron’s melting point) & 1,900 °C (less than olivine’s melting point), most likely 1,250 °C. The presence of tridymite in Fukang further narrows the melting temperature and pressure under which it developed. The temperature of normal mafic (magnesium – ferric (iron)) or surface ejected basaltic lava on Earth is 700 to 1,200 °C (too cool to melt iron and form a pallasite meteorite), however, interior temps and pressure could achieve this. Jupiter’s moon Io, on the other hand, expels ultramafic lava which is 1,700 to 2,000 °C at the surface. Pallasite meteorites could potentially exist at Io surface conditions but for inclusions of tridymite to form, a pallasite meteorite needs specific temperature AND pressure conditions, hence, a meteorite like Fukang had to form deep inside its parent body. The temperature and pressure range for producing pallasite meteorites with tridymites presents a somewhat singular scenario for its development. Most scientists for the past 30 years have felt the asteroid belt is leftover material from the solar system's formation which never successfully came together as one planet. |
Wiki says
HED meteorites are all thought to have originated from the crust of the asteroid Vesta, their differences being due to different geologic histories of the parent rock. Their crystallization ages have been determined to be between 4.43 and 4.55 billion years from radioisotope ratios. HED meteorites are differentiated meteorites, which were created by igneous processes in the crust of their parent asteroid. HED meteorites are a subgroup of achondrite meteorites. Sixty percent of achondrite meteorites are HED. They were formed under igneous (magma or lava) conditions HED is an acronym of Howardite, Eucrite and Diogenite type meteorites
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Riedite
Quote Hypervelocity impact processes are uniquely capable of generating shock metamorphism, which causes mineralogical transformations and deformation that register pressure and temperature conditions far beyond even the most extreme conditions created by terrestrial tectonics. The mineral zircon (ZrSiO4) responds to shock deformation in various ways, including crystal-plasticity, twinning, polymorphism (e.g., transformation to the isochemical mineral reidite) Reidite is a very rare altered zircon mineral formed under extreme pressure and temperature induced by impact shock waves, the same kind of impact shock waves that form Howardite. |
Japan sent a probe named Hyabusa2 to asteroid Ryugu to gently touch down and collect a sample which will be returned to Earth in late 2020. NASA is preparing to do the same thing on asteroid Bennu. Close up images show how amazing these objects are but to give a sense of scale, I've added this below image of Vesta with other asteroids and their relative sizes. |
Mars' is about 1.5 AU from the Sun. Apollo asteroids are a group of Near Earth Objects (NEO) that orbit closer to the Sun than Mars (less than 1.1 AU) and could potentially impact with Earth some day but not anytime soon (hopefully). Ryugu is a NEO Apollo asteroid. Apollo asteroids cross the orbital path of Earth. Asteroids in the main asteroid belt are beyond Mars' orbital path (2-3.5 AU). Within the asteroid belt, there is a zone where objects transition from rocky silicate magnesium oxide dominant bodies to organic carbon based water ice rich bodies. This zone is called the frost line because the Sun's radiative energy is too weak to evaporate water ices as the temperature drops. Beyond the frost line, bodies tend to be more ice rich, at least from a volume standpoint. |
The asteroid belt, long purported to be just a jumbled hodge podge of rocks orbiting between Mars and Jupiter is now known to be a family of 5, 6 or even 7 previously larger bodies.
In other words, there used to be basically 6 large bodies smaller than Mars which were driven (most likely by Jupiter) to collision and/or self-destruction. We partially know this because meteorites like Fukang could only develop inside a body with specific pressure and heat conditions. It is also known by their spectrographic similarity and orbital resonance, inclination and eccentricity that these groups of objects once belonged together. |
I wonder if Jupiter and Saturn's early orbital migration outward with their combined resonant pulse might have created a Roche limit radius zone that broke these 6 planetesimals apart because it seems unlikely that all of them including the last two just happened to collided and mutually self destruct.
The Roche radius is the point at which the external forces from a planet exerted on a moon or body are greater than the internal forces that hold it together. The Roche limit is about 2.4 times the radius of a planet, think comet shoemaker-Levy 9 breakup as it approached Jupiter. |
Back to Bennu and Ryugu
The biggest difference between Bennu and Ryugu has to do with water. Even though scientists believe them to be portions of the same parent body, which broke apart between 800 million and one billion years ago, Bennu appears to be water rich, while Ryugu is much less so. The same holds true for the near Earth Apollo objects Encke (a comet) and 2004 TG10 (an asteroid) which are part of the Taurid meteor shower which occurs twice per year (June & Nov). Encke is considered a comet while 2004 TG10 is an asteroid yet both come from the same astronomical object which is thought to have begun breaking up 20,000 years ago as it was perturbed toward the inner solar system. Larger bodies differentiated (separated into density layers) into their ice vs rock vs metal components, upon breakup these components clustered into orbital groups. |
There are three types of asteroids, C, S & M.
C-type 75% = (Carbon based water ice rich) occur most frequently at the outer edge of the asteroid belt, 3.5 astronomical units (AU) from the Sun, where 80% of the asteroids are of this type, whereas only 40% of asteroids at 2 AU from the Sun are C-type with Albedos in the 0.03 to 0.10 range (Extremely dark similar to a charcoal briquette). Any asteroid containing carbon (carbonaceous) is considered organic because all organic material is built from carbon. S-type 17% = (Silica stony, (SiO2) aka quartz or sand, water poor) with albedos typically around 0.20 (moderately bright) consists mainly of iron and magnesium-silicates. They are dominant in the inner part of the asteroid belt within 2.2 AU, common in the central belt around 3 AU, but become rare further out. M-type 8% = (Metal mixed with stone) moderately bright (albedo 0.1–0.2). |
Determining the size of an object in space requires understanding its brightness or its albedo. |
Albedo is the amount of light hitting a surface relative to the amount reflected off a surface. It’s a ratio of emitted vs absorbed/scattered light. A hundred percent of light reflected off a surface equals a bond albedo of 1.
Bond albedo is the ratio of the total flux (fluctuating inflowing light) reflected and scattered in all directions, to that incident (angle). Incident light is the available light from a source while the reflected light is the incident minus the absorbed/scattered light. For example, Saturn's moon Enceladus' bond albedo = 0.81. Out of 100 photons hitting Enceladus, only 81 reflect so 81/100 = 0.81 albedo. Geometric albedo differs from bond albedo in that it is the ratio of the flux (fluctuating light) reflected head-on to that incident (available light). Enceladus' geometric albedo is 1.4. How can Enceladus reflect more than 100% light received? It doesn’t. |
In this table >>>>>>>>>>
Plutinos = objects in 3:2 resonance with Neptune. Comets = ice dominant bodies beyond 3 AU Centaurs = exist between 5 AU and 30 AU SDO's = Neptune Scattered Disk Objects Cubewanos = Kuiper Belt Objects 30-50 AU Trojans = objects in 60° lead/lag L4,L5 Lagrange zone |
Lagrange points or zones are low pressure or resonance zones created by the gravity of a planet or orbital body. Lagrange points L4 & L5 lead and lag a body like Jupiter where objects cluster into groups similar to what Neptune does to bodies called Plutinos. These 60 degree lead/lag objects around Jupiter are called Trojans. Centaurs are objects that orbit between Jupiter and Neptune and are often considered asteroids (rocky bodies) but since they are icy bodies could be considered comets that are not currently out-gassing. Centaurs don't have comas like other comets because they don't get close enough to the Sun to sublimate (evaporate) their gasses, nevertheless, they are icy comet like bodies. |
To easily remember the difference between a Trojan object and a Centaur. Trojan's (like a horse) run 60° ahead of and behind planets |
Centaurs are a mix of asteroid/comets (mythical half man, half horse) scattered randomly among the outer gas giants. |
Pluto is reddish brown while Charon is more blueish gray suggesting they are most likely from different zones in the solar system mixed together by Neptune in the same way Scattered Disk Objects are multicolored and scattered by Neptune. Neptune's orbital path is thought to have migrated outward, as it did, it scrambled up the objects that got too close. This then created the scattered disk objects SDO, the mixed colors of objects around the gas planets. Neptune's migration also put a lot of objects into resonant pulses with it and probably caused Haumea to collide with something creating the blueish Haumea family of objects. The bright albedo of the Haumea collisional family indicates this collision occurred within the last billion years. Neptune's migration outward is also credited with creating the late heavy bombardment some 4byr ago. Neptune's migration outward wreaked havoc in our solar system. |
This image was derived from File:TheTransneptunians Color Distribution.svg to show the neutral (non-red) colors of the Haumea family of TNOs.
The + marks the location of the reddest member of the Haumea family: 2005 RR43 This is pretty clear evidence that the reflected surfaces of the Haumea family is younger than the other transneptunian objects due to a collision. Regardless of size all members of the Haumea family are bluish. |
There are long pass, wide, medium & narrow spectra filters identifying electromagnetic waves from 2,000-10,000 angstroms (aka 200-1,000 nm, or 0.2-1.0 microns).
Dips in the observed light spectrum, also known as, lines of absorption occur as gasses absorb energy from light at specific points along the light spectrum. These dips or darkened zones (lines of absorption) leave a finger print which identify elements and compounds. In this image the dark absorption bands appear as lines of emission which occur as the result of emitted not reflected (absorbed) light. |
Scientists analyzed 4.4 billion year old zircon mineral grains from the Jack Hills of Western Australia and concluded early Earth was a water world half a billion years prior to the LHB. Additionally, the water on Earth does not match deuterium ratios found in comet 67P and so was not primarily delivered by comets or asteroids. I'm saying,
Earth was basically a comet (water ice rich body) prior to the Sun's ignition and it had a magnetosphere just like Jupiter's moon Ganymede which helped preserve its low deuterium ratio water once the Sun ignited. Sure some impactors delivered water to the Earth during the late LHB but Earth was constructed of material that was water rich long before the LHB. I’m pleased to see, Wiki has done some updating on this subject Study of zircons has found that liquid water must have existed as long ago as 4.404 ± 0.008 Ga, very soon after the formation of Earth.[10][11][12][13] This requires the presence of an atmosphere. The cool early Earth theory covers a range from about 4.4 to 4.0 Ga. In fact, recent studies of zircons (in the fall of 2008) found in Australian Hadean rock hold minerals that point to the existence of plate tectonics as early as 4 billion years ago. If this holds true, the previous beliefs about the Hadean period are far from correct. That is, rather than a hot, molten surface and atmosphere full of carbon dioxide, Earth's surface would be very much like it is today. The action of plate tectonics traps vast amounts of carbon dioxide, thereby reducing greenhouse effects, and leading to a much cooler surface temperature, and the formation of solid rock, and possibly even life.[14] |
In October 2014, Adam Sarafian of the Woods Hole Oceanographic Institution released a study suggesting that water was on earth as the planet was forming.
This conclusion was drawn after establishing a link between the oldest known carbonaceous chondrite meteorites and meteorites believed to be from Vesta (which formed in the same region as earth during the birth of the solar system), and noticing how their composition are similar, and both contained a lot of water.[15] |
Comet 67P is thought to have come from the Kuiper Belt (50 AU).
Comet 67P has a hard outer shell with at least 8 inches of dust with a very porous core similar in ways to an egg. The unusually high porosity of the interior of the nucleus provides the first indication cometary growth could not have been from violent collisions, as these would have compacted the fragile internal material. Comet 67P is also a bylobed object constructed of two roughly same sized and compositionally similar objects which grew individually then conjoined gently enough not to rupture their outer crusts' (egg shell). At least thirty five percent of transneptunian binary pairs (TNB) are similar in size and composition page 66. |
It appears, similar sized comets/asteroids with similar compositions that are mutually captured into a binary pair is relatively common in the Kuiper Belt. I suspect the reason has to do with the similarity in size/mass.
If one object is much larger than the other, the larger object will either eject or gravitationally attract the smaller object. similarly sized objects have similar mass with a similar centrifugal gravity breaking effect as they drift closer and closer. As two bodies get closer in an orbital dance, their collective spin speed increases to preserve their angular momentum. As they get closer to colliding and their spin velocity increases their centrifugal force (outward flinging) grows which in turn slows their impact speed. Basically their closely related gravitational pull (escape velocity) causes a somewhat balanced centrifugal orbital velocity that cancels against each other nullifying the (collision velocity) effect of their individual gravitational pull. |
This, I suspect, is how an object like comet 67P constructed of two cotton candy like interiors and a brittle outer shell could survive the merge between these similarly sized objects.
Meteorites on average are 94% stone, of that stone 86% is chondritic (round pebbles and space dust), 8% of the stone is achondritic (cooled lava from a differentiated core body).
This chart shows the relative amount of potasium (K) and uranium (U) on various solar system bodies. Chondrites contain less Uranium (1/100 gram per ton of rock) than Potasium (10^2.7 grams about one pound/ton of rock) than any other type of listed body while basaltic achondrites contain more U than K. In other words 86% of meteorite material contains larger quantities of K than U as a radiogenic heat source. Potassium gives off less radiation heat energy than uranium. From this paper The K/U ratio of the silicate Earth: Insights into mantle composition, structure and thermal evolution I pulled the below chart showing the relative contribution of U, K and Th radiogenic heating of our Earth's core.
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Potassium's contribution to Earth's heat has been decreasing steadily. Today it is contributing less than 20% of the heat provided by radioactivity. Eighty six percent of the material in meteorites (chondrites) which contain a higher ratio of potassium relative to uranium is only contributing 20% of the heat from radiation. If these values can be extrapolated to Pluto and if Pluto has a differentiated core then potassium would be the most abundant radioactive material in its core providing the least amount of heat energy to that core. The dominant available quantity of radiogenic material (K) inside Pluto is currently providing the least amount of heat. |
This is what F. Nimmo was saying prior to the flyby, however, today with no additionally supportive data he supports the hypothesis that there is a subsurface ocean created by a radioactively hot core.
The only thing added since these statements by Nimmo and McKinnon are models bent and twisted, messaged and caressed to create single minded outcomes while ignoring some basic fundamental observational facts. Objects in a Neptune orbital resonance with radius larger than 600-700 km tend to be brighter (higher albedo) than non resonant objects suggesting resonance is the engine driving their resurfacing not radioactivity.
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There are exceptions to every rule but the trend exists.
Objects with bright albedos suggest their surfaces are renewed and there is a correlation with the renewed surfaces and their orbital interaction with Neptune. Pluto is in a 3:2 resonance with Neptune. Pluto has the most eccentric orbit of all the planets creating Milankovitch warming weather cycles. Pluto wobbles 20° dragging Charon and the smaller satellites in a lead lag flex stress scenario. All of these are energy sources for Pluto. The monkey speaks his mind. |
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