Extraordinary claims (of an alternative solar-system-formation model) require extraordinary evidence (here in the form of siderophile-depleted igneous comet crust).

Abstract:

¶    ‘Comet-crust meteorites’ are suggested here to be a new class of outer solar system meteorites, composed of the igneous crust of Kuiper belt objects (KBOs).  Since former KBOs are presumably uncommon in the inner solar system, compared to asteroids and chondrites, comet crust meteorites should be proportionately uncommon in present-day meteorite falls.  But 12,800 years ago, a ‘YD impact hypothesis’ suggests that the Laurentide ice sheet was impacted with a fragment of a former KBO comet in the vicinity of the Great Lakes, causing the extinction of 90 genera of megafauna from the Americas.  And that KBO comet fragment is suggested here to have had an igneous comet crust that was distributed across North America and beyond, imbedded large fragments of the Laurentide ice sheet, launched into ballistic trajectories as part of the ejecta curtain of the primary impact.

¶    Inner solar system asteroids and chondrites are well characterized, but no meteorite finds on Earth have been specifically attributed to the Kuiper belt.  This omission is suggested here to be due to the similarity of KBO core rock to terrestrial continental basement rock.  Indeed, the metamorphic rock of the continental tectonic plates on Earth are suggested here to be authigenic sedimentary cores of hot-classical KBOs acquired during the late heavy bombardment of the inner solar system, circa 4.1–3.8 Ga.  The hot-classical KBOs are suggested here to have condensed from a siderophile-depleted ’trifurcation debris disk’ > 4,567 Ma that lay on the 3-oxygen-isotope terrestrial fractionation line.
¶    Large KBOs underwent spontaneous ’aqueous differentiation’ at formation by streaming instability (gravitational collapse), internally melting water ice, which precipitated authigenic sedimentary cores with a gneissic composition.  The liquid water refroze to form icy mantles surrounding sedimentary gneissic cores, with the icy mantles depleted in gneissic silicates.
¶    A trifurcation debris disk requires a former binary-Sun whose binary components spiraled in to merge in a luminous red nova (LRN) at 4,567 Ma.  The solar-merger LRN briefly enveloped the solar system out to and including the Kuiper belt with solar plasma, melting the KBO regolith into an igneous ‘comet crust’.  This comet crust is composed of the solutes and suspended mineral grains of the frozen salt-water ocean of aqueously-differentiated KBOs.  Thus comet-crust meteorites of KBO origin should be depleted in siderophile elements and also depleted in bulk gneissic silicates, and hence silicate depleted as well.
¶    LRN solar plasma partially reduced iron oxides in the molten crust to metallic iron, with comet crust inheriting millimeter- to centimeter-scale metallic iron inclusions that remained suspended in the lower-density rocky matrix under the KBO microgravity conditions.  Additionally some comet-crust meteorites exhibit fusion crust and occasionally flow lines in the fusion crust as well.
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Introduction:

¶    Sedimentary cores dated to the onset of the Younger Dryas, 12,800 BP, from the Americas, Europe, and Asia exhibit iron-rich spherules, glass-like carbon, glass spherules, nanodiamonds, and platinum enrichments.  Additionally, closely-dated glacial cores exhibit platinum enrichments and numerous markers for extreme biomass burning.  Some sedimentary horizons from this time period are so enriched in black carbon/soot deposits as to engender the term ‘black mat’ for their distinctive appearance.  Significantly, 90 genera of megafauna went extinct in the Americas by 12,700 BP.  A thousand year period of glacial conditions known as the Younger Dryas followed the brief warming of the Late Glacial Interstadial at the end of the Last Glacial Maximum.
¶    A group of 63 scientists from 55 universities in 16 countries have created the Comet Research Group to pursue the likelihood that a comet impact on or over the Laurentide ice sheet 12,800 BP was the cause for this unusual combination of anomalies.

¶    Petaev et al., 2013 analyzed Greenland ice sheet cores from the Greenland Ice Sheet Project 2 and discovered a large platinum anomaly at the onset of the Younger Dryas,  not accompanied by an iridium anomaly, with the Pt/Ir ratios at the Pt peak exceeding those in known terrestrial sediments.  The Pt concentrations rise by at least 100 fold over ~ 14 years before dropping back during the subsequent ~ 7 years.  “The Pt anomaly precedes the ammonium and nitrate spike in the GISP2 ice core (2) by ∼30 y and, thus, this event is unlikely to have triggered the biomass burning and destruction thought to be responsible for ammonium increase in the atmosphere and the Greenland ice (11).”
¶    Subsequently, a platinum anomaly was documented in bulk sedimentary sequences from 11 widely-separated sites across the continental United States.  (Moore, West et al., 2017)  This article constrains the Greenland ice core Pt anomaly, from Petaev et al. 2013, to ~12,836–12,815 cal BP.

¶    In a recent study measuring biomass burning proxies, 23 sites with previous YD impact markers were examined across North America and northern Europe, including one site in northern South America and one site in the Middle East.  The study revealed a major peak in biomass burning at the YD onset that appears to be the highest during the latest Quaternary.  (Wolbach et al.,2., 2018)

¶    In a related article, biomass-burning aerosols were discovered in 4 ice-core sequences from Greenland, Antarctica, and Russia.  The perturbations on CO2 records from Taylor Glacier, Antarctic suggest the combustion of ~9% of Earth’s terrestrial biomass.  (Wolbach et al.,1., 2018)
¶    This 2018 paper, which includes 24 scientists from the Comet Research Group, states that the “cosmic-impact hypothesis is based on considerable evidence that Earth collided with fragments of a disintegrating ≥100 km-diameter comet, the remnants of which persist within the inner solar system ~12,800 y later”.  (Wolbach et al.,1., 2018)  Elsewhere Comet Encke and the Taurid meteor stream are suggested as the possible debris stream of a former KBO that fragmented in the inner solar system in the last 20,000 to 30,000 years, whose debris stream once included the former YD comet.
¶    No crater has been positively identified for the one or more posited Younger Dryas (YD) impacts on the Laurentide ice sheet in the Great Lakes Region, circa 12,800 BP.  This absence of a primary impact crater reduces the likelihood of recognizing primary bolide material, particularly if it belongs to a new class of outer solar system meteorites that is radically different from inner solar system asteroids and chondrites.
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YD impact comet-crust overview:

¶    The former YD impact bolide is suggested to have possessed an igneous crust that constitutes a new class of siderophile-depleted (low nickel, < 2 ppb iridium) meteorites on Earth.  This suggested comet crust contains frequent millimeter-to-centimeter-scale metallic-iron inclusions that appear to have solidified in a microgravity environment, and thus extraterrestrial.
¶    The primary impact was presumably on the Laurentide ice sheet, with comet crust ferried into SE PA and elsewhere as bolide contamination within a secondary ejecta curtain of Laurentide ice sheet fragments.  Indeed, a chunk of apparent comet crust was found in California.

¶    Comet crust was fortuitously preserved on Earth impact by the cushioning effect of the relatively-compressible ice of the Laurentide ice sheet.  The relative compressibility of water ice compared to bedrock silicates presumably clamped the impact shock wave pressure below the melting point of silicates, preserving bolide material from melting on impact, with the relative endothermic compressibility of water absorbing the lion’s share of the impact energy.  The target ice sheet absorbed the lion’s share of the energy in the form of PdV compressive heating, raising the temperature of the resulting supercritical water to thousand of Kelvins, which scorched much of the comet crust, imparting fusion crust at impact onto the surfaces of many comet-crust meteorites.

¶    As many as 500,000 elliptically-shaped Carolina bays, located along the Atlantic Seaboard and Gulf Coast of the US, have been suggested by the Comet Research Group to have been caused by secondary impacts from an ejecta curtain of Laurentide ice sheet fragments from a primary impact on the ice sheet, circa 12,800 BP.  Many ice sheet fragments traveled over 1000 km in ballistic trajectories above Earth’s atmosphere at 3 km/s, and impacted with 1% of the specific kinetic energy of the primary YD comet traveling at 30 km/s.

¶    Presumably a similar density of secondary ice-sheet-fragment impacts occurred inland from the coastal Carolina bays, which blanket North America and beyond.  But secondary ice-fragment impacts on harder terrain inland of the swampy coastline caused less target damage, which has been visually erased by subsequent weathering during the intervening millennia.
¶    The impulse of secondary ballistic impacts of ice-sheet fragments on thin soil is suggested here to have fractured target bedrock, occasionally forming discrete boulder fields by way of dynamic rock slides/debris flows when ice-sheet fragments hit the leeward side of mountains and slopes, where the horizontal component of the ice-sheet fragment velocity pointed downhill, causing the forward momentum of the ice-sheet fragment to promote downhill rock slides.  (See section, YD IMPACT BOULDER FIELDS).  In Eastern Pennsylvania, the Hickory Run boulder field and the Ringing Rocks boulder fields are both suggested to be YD impact boulder fields.  Other locations littered with sharp-edged boulders that are nominally-weathered, but not concentrated into discrete boulder fields, could also be secondary impact sites, where only a tiny percentage of secondary impact brecciation of bedrock presumably underwent dynamic rock slides to form concentrated boulder fields, many boulders deep.

¶    There appears to be a high concentration of comet-crust meteorites across Southeastern Pennsylvania, particularly between Harrisburg, PA and Conshohocken, PA which may represent a kilometer-scale ice-sheet fragment with an anomolously-high comet-crust concentration that exploded upon reentry into the atmosphere on its ballistic trajectory, showering the region with crustal material.

¶    If the YD comet fragment included any of the gneissic KBO core, its indistinguishability from metamorphic Earth rocks would render it invisible, where the metamorphic tectonic plates on Earth are suggested here (see section: AQUEOUS DIFFERENTIATION OF KUIPER BELT OBJECTS (KBOs)) to be of extraterrestrial KBO origin emplaced on Earth during the late heavy bombardment.  And ironically, the similarity of igneous comet crust to iron furnace slag also renders igneous comet crust invisible, particularly in light of its economic exploitation for its iron content, which frequently mingles pristine comet crust with its industrial slag aftermath.  Finally, very-large icy impacts are suggested here to cause astroblemes that may distend Earth’s crust downward into round impact basins, but without excavating a traditional bowl-like craters and without creating high-pressure polymorphs, which may largely mask icy impact basins from detection as such.  And the suggested fortuitous ejecta curtain of Laurentide ice sheet fragments raining down from the YD impact created elliptical secondary astroblemes, like the Carolina bays, which deviate even further from classical rocky asteroid impacts.
¶    All aspects of the suggested YD comet impact deviate from the classical understanding of rocky-iron asteroids/chondrites on target bedrock, from its suggested siderophile gneissic core composition and igneous crust with metallic-iron inclusions to its target ice sheet and extensive secondary ejecta curtain of ice sheet fragments.

YD comet-crust exhibits a number of typical features that occur with variable frequency:
– Gray igneous matrix; constituting variable-sized fractured fragments of dense, gray igneous matrix with a high iron-oxide and calcium-oxide content, with specimens often containing variable-sized metallic-iron inclusions.  Some matrix material is highly-vesicular, like scoria, while some matrix material lacks vesicles altogether.  A large percentage of igneous matrix is comprised of coarse, rough conglomerations of weathered granular material that readily fuses into larger masses when exposed to moisture, likely due to pressure solution/dissolution of its soluble calcium carbonate component.
– Metallic iron; constituting variable-sized masses of metallic iron from millimeter-scale inclusions in the gray igneous matrix to isolated masses, some as large as 100 kg.  Some iron is massive (cast) and some is nodular, where nodular iron often appears in larger aggregates that appear to be sintered together.
– Magnetite/hematite; some matrix material shielded from solar plasma that did not reduce iron oxide to metallic iron has a composition similar to terrestrial iron ore, with some specimens less attracted to a magnet (hematite) and some more so (magnetite).
– Some matrix material exhibits one undulating (top) surface, with a typical 10-15 cm undulation radius, with the matrix material typically fractured into pie-shaped ‘slices’, having one rounded surface and the other end wedge shaped, like a slice of pie.
– Some matrix material exhibits apparent fusion crust, and a small percentage of fusion crust exhibits apparent flow lines.
– All types of YD comet crust are typically coated with a white, gritty cement-like coating, to the extent that this cement-like coating is one of the best indicators of comet crust.
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Aqueous differentiation, followed by stellar plasma immersion:
(see section, AQUEOUS DIFFERENTIATION OF KUIPER BELT OBJECTS (KBOs))

¶    Large KBOs presumably underwent aqueous differentiation during formation by streaming instability, a form of gravitational instability, with aqueous differentiation defined here as the melting of water ice by the conversion of potential energy to heat during gravitational collapse.  Large KBOs in which all water ice either melted or sublimed presumably processed all their trifurcation-debris-disk dust and ice through internal saltwater oceans, largely dissolving nebular dust suspended in saltwater, and/or with nebular dust acting as nucleation sites for mineral crystallization.  In the microgravity of internal KBO oceans, authigenic mineral grains grew by crystallization until falling out of aqueous suspension at a sand grain size or larger, forming sedimentary cores with a bulk gneissic composition.  Gneissic banding is attributed to intermittent KBO-quake subsidence events that modulated mineral-species solubilities by way of pH variations, where subsidence shock waves caused CO2 to bubble out of solution, sharply raising the pH.
¶    Over time heat loss caused internal KBO oceans to freeze solid, trapping solutes and suspended mineral grains in the saltwater ice,  with a composition deficient in the bulk chemistry of the gneissic sediments (and siderophile depleted).  This depletion of gneissic silicates left the icy mantle and crust highly-enriched in water-soluble solutes, notably salts, iron, magnesium and calcium oxides and carbonates.

¶    The subsequent plasma immersion of old-classical KBOs in the 4,567 Ma binary spiral-in solar merger LRN is suggested here to have melted the surficial KBO regolith into an igneous crust, with water ice and other more volatile ices subliming and venting through the molten crust, with the escaping gases leaving a variable degree of voids in the igneous crust.  Additionally, most salts and other relative volatiles vaporized from the loose regolith before the more refractory silicates and oxides fused into a liquid igneous mass, depleting comet crust of more volatile compounds.

¶    The chemically-reducing nature of ionized hydrogen and carbon monoxide in the LRN solar plasma chemically reduced exposed iron oxides to metallic iron, with iron droplets merging into centimeter-scale metallic iron inclusions in comet crust before falling out of suspension within the mafic igneous matrix.  Coincidently, carbon monoxide is also the reducing agent for converting iron oxide to metallic iron in industrial iron-smelting furnaces.

¶    Sufficiently-small KBOs would not have reached the melting point of water ice at formation by streaming instability, and intermediate-sized KBOs may have partially aqueously differentiated, where internal melting of water ice may not have extend to the surface.  Plasma immersion of smaller hot-classical KBOs with pristine surfaces that did not undergo melting of water ice would also have acquired an igneous crust at 4,567 Ma, but that crust would not be depleted in bulk gneissic sediments, and thus would exhibit a much-higher silicate concentration, closer to chondritic, but also volatile depleted and siderophile depleted.
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Alternative solar system model:
(see section, STARS, PLANETS, MOONS, MINOR PLANETS AND COMETS)

Symmetrical flip-flop fragmentation:
¶    An alternative star formation mechanism, designated ‘symmetrical flip-flop fragmentation’, is suggested to have ‘condensed’ a twin-binary pair of disk instability objects around a large brown-dwarf-mass protostellar core, where the twin-binary disk instability (DI) objects were much-more massive than the diminutive core.  Orbital interplay progressively transferred kinetic energy and angular momentum from the massive twin-binary DI-object to the diminutive brown dwarf by the mechanism of equipartition of kinetic energy, which evaporated the former core into a circumbinary orbit around the twin-binary DI-objects, as the DI-objects spiraled inward, conserving system energy and angular momentum.  The DI-objects evolved into our former binary-Sun.

Trifurcation and the trifurcation debris disk:
¶    It’s well known that equipartition transfers orbital kinetic energy and angular momentum from more massive objects to less massive objects in close orbital encounters, which is the mass segregation mechanism that evaporates the least massive stars out of globular clusters, causing the most massive stars to sink inward to form a core.  Equipartition is also suggested to transfer rotational energy and angular momentum from large to small objects in close orbital encounters, increasing their rotation rate, causing less-massive objects to ‘spin up’.  Equipartition is suggested to have caused our former brown dwarf to spin up until it distorted into a tri-axial Jacobi ellipsoid and then into a bar-mode instability.  Additional pumping of rotational energy caused the bar-mode instability to fragment into 3 components by ‘trifurcation’, where the twin bar-mode arms of the spun-up brown dwarf gravitationally pinched off into their own Roche spheres to form a twin-binary pair of super-Jupiters-mass objects in orbit around the diminutive residual core.  First-generation trifurcation promotes second-generation trifurcation and etc., ultimately creating 4 trifurcation generations of twin-binary objects in our solar system;
– 1st gen. ― ‘binary-Companion’ (with super-Jupiter-mass components)
– 2nd gen. ― Jupiter-Saturn
– 3rd gen. ― Uranus-Neptune
– 4th gen. ― Venus-Earth
¶    Trifurcation is presumably an inefficient process, spinning off and boiling off a substantial percentage of the trifurcating objects.  Assuming the multi-generational trifurcating objects were internally differentiated, with iron-nickel (siderophile) cores, the resulting trifurcation debris disk would necessarily have been siderophile depleted.  Thus, four generations of trifurcation created a siderophile-depleted ‘trifurcation debris disk’ from the homogenous brown dwarf reservoir, which lay on the 3-oxygen-isotope, terrestrial fractionation line.
¶    And the trifurcation debris disk condensed siderophile-depleted (hot-classical) Kuiper belt objects (KBOs), presumably by streaming instability, against Neptune’s outer 2:3 mean motion resonance.

Binary-Sun spiral-in merger luminous red nova (LRN) at 4,567 Ma:
¶    Secular perturbation between former binary-Sun and former binary-Companion caused binary-Sun to spiral in and merge in at 4,567 Ma in a luminous red nova (LRN), which briefly created a plasma fireball that apparently engulfed the classical Kuiper belt, vaporizing volatiles from the surface of KBOs and melting the remaining refractory material into an igneous, siderophile-depletd rocky-iron crust.
¶    The red giant phase of (stellar-merger) luminous red nova LRN M85OT2006-1 would have reached far into the Kuiper belt, with a fireball estimated at R = 2.0 +.6-.4 x 10^4 R☉, and a peak luminosity of about 5 x 10^6 L☉. (Rau et. al. 2007) “Previously published line indices suggest that M85 has a mean stellar age of 1.6+/-0.3 Gyr. If this mean age is representative of the progenitor of M85 OT 2006-1, then we can further constrain its mass to be less than 2 M☉.” (Ofek et al. 2007) If the size of the less than 2 M☉ LRN M85OT2006-1 fireball was in the range of 74–121 AU (R = 2.0 +.6-.4 x 10^4 R☉), then it’s readily conceivable that our greater than 1 M☉ LRN fireball, at 4,567 Ma, should easily have scorched a preexisting Kuiper belt reservoir centered around 43 AU.
¶    The LRN quickly retreated, leaving a low-angular-momentum ‘LRN debris disk’ in the inner solar system that ‘condensed’ rocky-iron asteroids, presumably by streaming instability against the Sun’s greatly expanded magnetic corotation radius, and later condensed chondrites by streaming instability against Jupiter’s strongest inner resonances, but the low angular momentum content of the LRN debris disk precluded forming a high angular momentum debris disk at the distance of the Kuiper belt.
¶    The dynamic temperature profile of the luminous red nova may partly explain the large centimeter-scale metallic-iron inclusions, which are too large to have been held in molten igneous suspension within the supporting matrix, even in the microgravity of a KBO.  The LRN temperature profile over time caused top down melting of the surface regolith, followed by bottom up solidification, during the exponential cooling phase, measured in months.  Once reaching a peak melt depth, the receding solar plasma allowed the igneous crust to gradually solidify (cool) from the bottom up, even as iron oxide was still being chemically reduced to a molten metallic-iron state at the surface.  Thus as metallic-iron globules rained down onto the rising solidification front, creating pile ups of iron spherules, and since metallic iron melts at a higher temperature than the enveloping mafic matrix, solidified iron pellets presumably piled up at the rising solidification front; however, prolonged exposure to elevated temperatures may have largely sintered these former iron spherules into apparently-solid iron masses.

Binary-Companion spiral-in merger at 650 Ma:
¶    Almost 4 billion years after the binary-Sun merger, the super-Jupiter components of binary-Companion spiraled in to merge at about 650 Ma in an asymmetrical merger explosion that gave the newly-merged Companion escape velocity from the Sun.  The resulting ‘Companion-merger debris disk’ is suggested here to have condensed a young (650 Ma), cold, classical KBO population against Neptune’s outer 2:3 resonance.  And this Companion-merger debris disk also presumably coated the old (> 4,567 Ma) hot, classical KBO population with a thin veneer of binary-Companion merger dust and ice that was not siderophile depleted.  This late veneer is suggested to be the origin of most of the platinum and iridium found in black mats across North America and elsewhere dated to the onset of the Younger Dryas.
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YD comet crust origin and characterization:

¶    YD comet crust has a high calcium oxide content coincident with iron furnace slag.  The fire assay of two comet crust samples yielded 25.69% and 40.28%, which is in line with industrial iron-smelting slag (41.7%) (Chemical composition of iron and steel slag).  The high iron and calcium content of YD comet crust are suggested to be the refractory solutes of the saltwater ocean after precipitation of the gneissic sediments and following the volatile loss of salts and other relative volatiles by the LRN plasma.

Gray igneous matrix with metallic-iron inclusions:
¶    Comet crust is highly variable regarding specimen size, density, matrix to metallic iron ratio, void prevalence, void size, and surface texture.  Specimen size ranges from millimeter-scale gravel up to massive igneous boulders more than a meter across.  Igneous matrix density is highly variable, varying by iron-oxide and metallic-iron concentrations, but comet crust matrix density is always greater than that of iron-furnace slag, where economic competition provided a strong incentive to extract the maximum percentage of iron.  Reasonably-smooth sectioned slabs of matrix have a distinct greasy feel to the touch, with smearing sometimes evident under magnification.
¶    Metallic-iron inclusions in igneous matrix typically range from millimeter-to centimeter-scale, where larger masses of comet-crust iron are mostly devoid of igneous matrix.
¶    Internal voids in gray igneous matrix range in size, and abundance, with specimens having the appearance of volcanic scoria to a complete absence of voids.

Massive and nodular metallic iron:
¶    The centimeter-scale of metallic-iron inclusions, which are nearly 2-½ times as dense as the surrounding matrix, have too much negative buoyancy to remain in suspension even in the microgravity of KBOs, particularly given the typical low-viscosity of mafic melts compared to felsic melts.  Thus special conditions are required for the formation of centimeter-scale metallic-iron inclusions anywhere but in zero gravity.  These special conditions are suggested to be the prolonged (months-long) exposure to reducing conditions that chemically reduced iron oxide to metallic iron, with a solidified floor where spherules of metallic iron accumulate, but at sufficient temperature to sinter together into massive inclusions in the time frame of a stellar-merger LRN, measured in months.  In an industrial iron-smelting furnace, the firebrick floor at the bottom of the furnace is held above the melting point of iron, forming a pool of liquid iron.  In KBOs immersed in LRN plasma, the temperature decreases with increasing depth to where the matrix transitions from liquid to solid.  This effective floor is below the melting point of iron, but presumably not below the temperature at which iron spherules will sinter together into larger inclusions over time.
¶    The shape of many iron inclusions and masses is notable, with many bizarre 3-dimensional shapes.  On Earth, liquid iron will conform to the shape of its floor, but it will always have a flat upper surface, whereas comet-crust iron often has no flat surfaces.
¶    Metallic iron falls into several categories,
1) metallic iron inclusions completely surrounded by gray igneous matrix,
2) massive metallic iron, often with little or no associated igneous matrix, and
3) nodular metallic iron composed of nodules that appear to be sintered together, with little or no accompanying igneous matrix.
¶    The most inexplicable phenomenon for an industrial slag interpretation on our high-gravity planet is the presence of centimeter-scale metallic-iron blebs suspended within the igneous matrix, where the metallic-iron density is about 2-1/2 times that of the surrounding matrix.  By comparison, glassy iron furnace slag from historic Joanna furnace, PA contains zillions of microscopic iron spherules clearly evident in thin glass flakes, backlit under 40X magnification, with a distinct upper size limit.

Gritty, whitish, cement-like coating as a reliable YD comet crust indicator:
¶    Comet crust meteorites typically exhibit a gritty, whitish, cement-like coating.  Calcium carbonate mineral grains apparently constitute a significant percentage of the mineral grains in the cement-like coating, because the coating fizzes when exposed to vinegar.  The whitish cement-like coating was presumably contamination acquired at impact, and may be a combination of terrestrial and extraterrestrial in origin.
¶    Whitish cement-like coating is common on both grey igneous matrix and on comet-crust hematite/magnetite, but it’s uncommon on iron metallic iron nodules and uncommon on massive metallic iron, which could be largely be due to rust exfoliation.
¶    Whitish, cement-like coating is suggested to be the most reliable indicator of YD comet crust; however, its absence is not proof against membership.  Iron furnace slag is often mixed with comet crust in the waste stream of historic iron furnaces, and the two contrasting materials can most readily differentiated by the presence or absence of the cement-like coating.  After years weathering exposure, however, comet crust and have lost its cement-like coating, and freshly fractured surfaces may lack coating as well.
¶  Additionally, cement-like coating contains variable concentrations of shiny black magnetic spherules, visually similar to spherules found at the bottom of the 12,800 year old (YD) black mat in North America and elsewhere, but curiously, the cement-like coating does not also contain transparent glassy spherules, which are common at the bottom of the YD black mat.  Thus the presence of black ferrimagnetic spherules and absence of translucent, magnetic glassy spherules suggests that the black spherules may be extraterrestrial, whereas translucent glassy spherules may be tektites, formed at Earth impact.  This observation and explanation suggests an extraterrestrial origin for the gritty, whitish cement-like coating.
¶  Finally, ‘steam cleaning’ at primary and/or secondary impact(s) may be responsible for bleaching cement-like coating whitish.

High-density magnetite/hematite:
¶    Some comet-crust iron is in the metallic state, some blended into igneous matrix and some in the form of iron ore, with varying degrees of purity.  Comet-crust iron ore comes in two forms, hematite, which is slightly ferrimagnetic with a reddish-brown streak, and magnetite, which is strongly ferrimagnetic with a black streak, both which typically exhibit gritty, whitish cement-like coating.
¶    Magnetite in an igneous context on Earth is often a cumulate rock, where dense cumulate crystals precipitate out of a fractionating magma chamber.  Despite igneous surface conditions, magnetite and hematite are suggested here to to have formed by metasomatism.  The continuous cover of molten igneous rock during the LRN created a pressure cooker environment underneath, with temperatures and pressures held above the triple point (273.16 K, 611.657 Pa) of water, thus creating both liquid water and vapor, with liquid water necessary for authigenic formation of hematite and magnetite.  An overhead heat source would have largely prevented the type of thermal circulation necessary for metasomatism; however, intermittent venting of water vapor through the igneous crust could have locally dropped the vapor pressure, causing liquid water to flash into steam and dump its supersaturated solute load in the form of precipitation or crystallization.  Comet crust iron ore has always been found in discrete lumps and never in physical contact with either metallic iron or igneous matrix, which is to be expected if comet-crust iron ore is metasomatic, while comet-crust matrix and iron is igneous.
¶    Comet-crust iron ore may exhibit a sinewy surface, or a reniform shape, with large crystal size characteristic of pegmatites.

Industrial-slag imitation of comet crust:
¶    Early 18th century industrial bloomers slag can resemble comet-crust iron ore, but bloomery slag never exhibits the gritty cement-like coating that marks comet crust as genuine.  In Phoenixville, PA, early bloomery slag (likely from the 1716 Pool Bloomery Forge near Pottstown) is mixed with later blast-furnace slag and comet-crust material in the waste stream dumped over the south bank of French Creek.
¶    Comet crust was apparently sometimes melted (rather than smelted) for its metallic-iron component in small auxiliary furnaces to larger iron-smelting blast furnaces, leaving behind high-density slag with a high iron-oxide content, but minus its metallic-iron component.  Comet crust melted for its metallic iron content will not exhibit the gritty, whitish cement-like coating.

Comet crust with one rounded surface:
¶    Many comet-crust specimens from Phoenixville, PA are roughly triangular in cross section, with one rounded side, resembling a thick slice of pie, with a typical 10–15 cm radius curvature.  The rounded surface was presumably the outer surface of the KBO directly exposed to LRN plasma.  Progressive subsidence due to igneous densification and volatile losses presumably caused surface wrinkling.  The scale of the subsidence wrinkling was presumably dependent on the viscosity of the igneous matrix and on the micro-gravitational acceleration.
¶    These pie-slice specimens have only been found in Phoenixville, PA, where comet crust material is mingled with industrial iron-smelting slag along French Creek.
¶    In Phoenixville, as elsewhere, comet crust was sometimes apparently melted (rather than smelted) in small auxiliary furnaces for its metallic iron content.  The pie-shaped sections from the wrinkled, undulating igneous surface of the YD KBO contain less metallic iron than the ‘floor’ of the igneous melt, where metallic-iron spherules fell out of suspension and accumulated.  So apparently any comet crust with a rounded surface was sorted out and discarded as uneconomic.

Massive to strongly vesicular:
¶    Comet crust is often dismissed out of hand by meteorite experts due to the typical prevalence of vesicles, since vesicles are very uncommon in inner solar system meteorites.  Comet-crust meteorites make frequent appearances in meteorwrong writeups and meteorwrong image galleries, due to their high density, high metallic-iron content, and ferrimagnetic attraction to a magnet.  The Washington University in St. Louis, Department of Earth and Planetary Sciences, photo gallery of MeteorWrongs appears to include a number of comet-crust specimens, with the following entry numbers; 11, 16, 93, 109, 183, 223, 294, 298, 325.

Fusion crust, some with flow lines:
¶    Fusion crust on comet-crust specimens vary in coloration from brown to jet black, where black fusion crust may be due to atmospheric ablation, whereas brown fusion crust may be due to exposure to superheated supercritical water at impact.  Alternatively, brown fusion crust may merely be more highly weathered than black fusion crust, although no transitional black-to-brown specimens have been found.  Fusion crust is fairly rare on comet crust specimens.  In larger specimens (>10 cm), fusion crust is likely to appear on one side only, whereas on smaller specimens (<10 cm), fusion crust is more likely cover the entire specimen.  Larger specimens are more apt to have fractured upon primary/secondary impact, which may partly explain the difference in fusion crust coverage.   An industrial iron-furnace slag origin can not explain a fusion crust, yet alone, fusion crust on all sides of small hand-sample-sized specimens.
¶    While fusion crust is relatively rare, fusion crust with flow lines is rarer still.  One sample of brown fusion crust with flow lines also exhibits 2 embedded spherules (~ 1 mm dia.).
¶    The counterpart to fusion crust on rocky meteorites are thumbprint-like impressions called regmaglypts on iron meteorites.  No regmaglypts have been identified on metallic-iron comet-crust specimens to date.  There may be some evidence of regmaglypts on comet-crust magnetite, however.

Locations in Southeastern Pennsylvania:

Conshohocken, PA:
¶    A large volume of comet crust has been used to level a triangle of land just off Light Street, Conshohocken, PA (40.0807, -75.3127), readily identifiable on Google satellite due to the herbicidal properties of granulated comet crust.  West Conshohocken also exhibits numerous young diabase boulders with sharp edges formed by relatively-recent (catastrophic) fracturing, suggested to be brecciation of diabase dikes by secondary impacts of Laurentide ice sheet fragments.  Old diabase boulders, by comparison, develop rounded surfaces due to weathering by progressive exfoliation.
¶   Comet-crust material in (East) Conshohocken is variably mixed with iron furnace slag in the waste stream of local iron furnaces.  In some cases, comet crust matrix appears to have been melted (rather than smelted) for its metallic iron content to create brittle cast iron, where melting comet crust for its metallic iron content required much-lower technology and less energy than smelting iron ore.  In the Conshohocken Area, brittle cast iron (likely from melted comet crust) was used to cast window-sash counter weights, with broken chunks of counter weights scattered along the west bank of the Schuylkill River in West Conshohocken.
¶   Remelted comet-crust slag often contains broken pieces of fire brick and lacks macroscopic metallic-iron inclusions, and tellingly, remelted comet crust slag also lacks the whitish, gritty cement-like coating of pristine comet crust.  Remelted comet-crust can be discriminated from smelted iron-furnace slag due to its greater density, due to its high iron-oxide content.

Phoenixville, PA:
¶   In Phoenixville, PA, a significant quantity of triangular pie-slice shaped comet-crust fragments are mixed with a industrial iron furnace slag from the nearby historic Phoenixville iron works.  In Phoenixville, the industrial slag appears to be of two types; low-density slag smelted in the primary Phoenixville iron works blast furnace, and high-density slag, from small adjunct furnaces used to melt (rather than smelt) comet crust for its metallic-iron content.  The high incidence of surficial comet crust, from the wrinkled undulating surface of the former YD KBO, is presumably because comet crust from the surface of the YD KBO contained less metallic iron than underlying comet crust, where metallic iron fell out of suspension from the surface to accumulate on the ‘floor’ of the molten crust.  Several large chunks of metallic iron (~ 100 kg) along French creek may have been too large to melt in the small adjunct furnaces.
¶   Industrial slag and comet-crust material alike was tumbled into the French Creek ravine along the south bank, between N. Main St. and Ashland St. (40.135, -75.513), just east of the Phoenixville Foundry.

Harrisburg, PA:
¶   As elsewhere, comet crust has been used as clean fill in the Harrisburg Area.  Comet crust in combination with iron-furnace slag has been used to build what appears to be an abandoned road spur off Paxton Ave. between Paxton Ministries and Faulkner Honda (40.2545, -76.8505).
¶    Comet crust may also have been used as clean fill on the East Shore of the Susquehanna River to extend residential parking on the river side of Front St. in Enola, PA, unless that material is autochthonous.
¶    Comet crust material can be found scattered on the west side of City Island, in the middle of the Susquehanna River.  The author’s first comet-crust specimens were found on City Island at the end of the boat launch ramp near the southwest end of the island.

Prospecting for comet crust:
¶    A strong rare earth magnet is the only necessary prospecting tool for identifying potential comet crust in Southeastern Pennsylvania.  For confirmation, look for a gritty, whitish cement-like coating,which is the best indicator of authenticity.

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Association with the iron industry:

¶    Secondary-impact concentrations of comet crust concentrations exploited in the 19th and 20th century for its iron content were presumably assumed to be poorly-processed 18th century iron-furnace slag.  Native iron is exceedingly rare on Earth, such that slag-like concentrations in the subsoil containing metallic-iron inclusions and posessing elevated calcium-oxide percentages would naturally be mistaken for poorly-processed colonial iron-furnace slag.
¶    The close connection between comet crust and the iron industry in a siderophile-depleted material so similar to industrial iron furnace slag makes radiometric dating the only chance of establishing comet crust as extraterrestrial.

¶    Presumably metasomatic comet-crust iron ore has significantly-less contaminating embrittlements compared to igneous comet-crust matrix and igneous comet-crust metallic iron.  The apparent extraction of metallic iron from comet crust matrix by simple melting in dedicated auxiliary furnaces suggests that comet crust matrix material was unsuitable for smelting for its iron oxide content in primary blast furnaces.  The brittle metallic iron in comet-crust matrix was apparently a bonus that could easily be extracted with low technology auxiliary furnaces with low energy expenditure by simply melting rather than smelting comet-crust matrix, but the reason so much comet crust material survives is presumably due to the limited market for non-critical ballast applications of brittle comet-crust iron, such window-sash counterweights.

¶    A small ‘failed’ iron furnace is moldering in the woods in West Conshohocken.  The home made iron furnace constructed of fire brick contains several cubic feet of cast iron that apparently solidified before it could be tapped to make pig-iron ingots.  A 1938 nickel found in the immediate vicinity suggests the age of the furnace.
¶    Nearby rests another cottage-industry-scale iron furnace that was considerably more sophisticated, in the form of a 4 ft diameter Bessemer-style furnace.
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Future work:

– Several comet crust samples were analyzed by INAA for iridium, including one analysis on a metallic-iron inclusion, but no iridium was found down to 5 ppb. INAA does not detect platinum, however, which is a prevalent YD black mat marker, and platinum was found in Greenland ice cores from 12,900 B.P. A recent understanding of hybrid nature comet-crust material suggests that the whitish cement-like coating should be analyzed for iridium and platinum.

– An old age determination (> 4.5 Ga) for comet crust would be the gold standard for a new class of siderophile-depleted meteorites which fails multiple other tests, such as, close association with the historic iron industry, low nickel to iron ratio, absence of iridium, igneous origin, and manifold internal voids.
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Theory weakness:

– The apparent complete lack of iron tools of comet-crust origin by indigenous peoples of North America is a significant obstacle to the theory, even if the vast majority of comet crust had been deeply emplaced into subsoil at secondary impact.
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References:

Dietz, R. S., Barring, J. P., (1973), Hudson Bay arc as an astrobleme: A negative search, Meteoritics, Vol. 8, p. 28-29

Moore, Christopher R.; West, Allen; LeCompte, Malcolm A.; Brooks, Mark J.; Daniel Jr., I. Randolph; Goodyear, Albert C.; Ferguson, Terry A.; Investor, Andrew H.; Feathers, James K.; Kennett, James P.; Tankersley, Kenneth B.; Adedeji, A. Victor; Bunch, Ted E., (2017), Widespread platinum anomaly documented at the Younger Dryas onset in North American sedimentary sequences, Scientific Reports 7, Article number: 44031 (2017)

Ofek, E. O.; Kulkarni, S. R.; Rau, A.; Cenko, S. B.; Peng, E. W.; Blakeslee, J. P.; Cote, P.; Ferrarese, L;. Jordan, A.; Mei, S.; Puzia, T.; Bradley, L. D.; Magee, D.; Bouwens, R., (2007), The Environment of M85 optical transient 2006-1: constraints on the progenitor age and mass, arXiv:0710.3192 [astro-ph]

Petaev, Michail I.; Huang, Sichuan; Jacobsen, Stein B.; Zindler, Alan, (2013), Large Pt anomaly in the Greenland ice core points to a cataclysm at the onset of Younger Dryas, PNAS Aug. 6, 2013 110 (32) 12917-12920

Rau, A.; Kulkarni, S. R.; Ofek, E. O.; Yan, L., (2007), Spitzer Observations of the New Luminous Red Nova M85 OT2006-1, The Astrophysical Journal, Volume 659, Issue 2, pp. 1536-1540

Wolbach, Wendy S. et al, (2018), Extraordinary Biomass-Burning Episode and Impact Winter Triggered by the Younger Dryas Cosmic Impact ~12,800 Years Ago. 1. Ice Cores and Glaciers, The Journal of Geology, Volume 126, Number 2, March 2018

Wolbach, Wendy S. et al, (2018), Extraordinary Biomass-Burning Episode and Impact Winter Triggered by the Younger Dryas Cosmic Impact ~12,800 Years Ago. 2. Lake, Marine, and Terrestrial Sediments, The Journal of Geology, Volume 126, Number 2, March 2018
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