Tunguska - the Lake Cheko Affair. Any new input? Thoughts?

[Drifter]

Researching online about meteor impacts lately, I bumped into a 2008 rewritten updated article originally from 2006 by a team from the University of Bologna who did a detailed investigation into Lake Cheko a few years earlier(1999) … drawing the conclusion this might have been formed by a huge fragment from the Tunguska Event. 
 https://onlinelibrary.wiley.com/doi/full/10.1111/j.1365-3121.2007.00742.x

The Russian reply - debunking this theory …. a bit lighter on personal in-the-field scientific experimentation, popped up in 2008.

https://www.univie.ac.at/geochemistry/koeberl/publikation_list/312-Lake-Cheko-not-impact-crater-Terra-Nova-2008.pdf
 

This later article from 2017 below doesn’t add much new but gives an overview from that date - and has some interesting other stuff unrelated.

https://siberiantimes.com/science/casestudy/news/n0854-beautiful-and-mysterious-but-was-lake-cheko-formed-from-the-exploding-tunguska-meteorite/

It’s interesting that there are contradictions in the data between the Italian and Russian findings …. Can that be logically explained by the possibility the huge rock creating the boom blast shockwave that flattened the trees, very fortunately(once again-see Chelyabinsk) landed in a nice existing lake and maybe terra-formed it slightly? - damage to surrounding trees could have been minimal - the throwing up of a mixture of deposits, sediments and mineral complexities giving dating anomalies …. no need for Russians and Italians to fall out …. It’s suggested other lakes along the same trajectory could hold pieces of the same boulder?

The number of thunderclaps and earth tremors and burns recorded in eye witness accounts from 1908 can be read here:

See “Tunguska Event” Wikipedia (copy link STILL not working in SGL)

…. All these accounts seem to have consistency - suggesting a meteor, fragmentation and at least one serious impact - maybe more?

The Italian paper linked above looks the more detailed - the Lake Cheko Theory seems to tick many boxes for me personally ….. what do other SGL members think? …. Finally … mystery solved? (Well, 95%?)

[Icosahedron]

I've also read that the impactor could have been a small comet. I'm sure there is more to the constitution of comets than just icy material but is it reasonable to expect to find fragments now if it was the case?

[Drifter]

Quite like that explanation, Icosahedron…  a comet with a core lump that creates a natural nuclear explosion at it’s high velocity hub end where pressure, temperature and colliding neutrons/particles of certain elements are catalysed to chain-react by the moisture-laden upper atmosphere - H2+O2 split into it explosive basics fuelled by what is in any meteor/comet core? 
A low trajectory burn up, flattened/scorched trees from an enormous shock wave, embedding fragments in bark - with the heart of the comet being less fragmentary than the Chelyabinsk Incident … dropping in isolated marshy ground … redesigning a lake ( in an area largely unnoticed and unexplored for nearly 100 years) …

… sounds like a rough outline with elements that might work? - if nuclear physicists think the right conditions exist here to create sufficient damage?

 

[EntropyTango]

Drifter wrote: "a comet with a core lump that creates a natural nuclear explosion at it’s high velocity...."

Unfortunately even fast travelling comets do not create the temperatures or pressures to create a nuclear explosion (especially Fusion)

 

I would go with the Russian rather than the Italian report.

Not long ago Italian scientists claimed to have measured neutrino's travelling faster than light!

And quite simply a cometary nucleus would leave little debis to be found, especially as it was some time between the event

and the expedition. It just sounds like revisionist scientific history to me.

Edited June 23, 2021 by EntropyTango

[Drifter]

In this particular case the detail in the Italian report looked to have field research results and analysis presented. 
… have the Russian team published additional research?

I’m not sure what mechanism in nature can make comets/meteors of differing core materials explode so spectacularly and leave so few traces. It happens so rarely, I guess it’s a bit early to write the rule book on whether there will be debris or not?  Every case will be unique. Fission/fusion/other - as long as it has the force to flatten trees? I guess the Universe has enough nuclear reactive tricks up it’s sleeve to keep most people happy. Tycho exploded on the Moon surface propelling debris 5,200 km … maybe a similar mechanism to that happened here?

I know the Russians were distracted by a Revolution a few years after this impact … and with it happening in such a remote relatively inaccessible region, maybe an Italian team going in and coming up with something ‘new’ probably ruffled a few feathers?!

Hard to knock the 100 years of Russian research already done - or Italian research in general …. but this particular Russian paper looked a bit light on science - compared to the Bologna University piece. 

17 hours ago, EntropyTango said:

And quite simply a cometary nucleus would leave little debis to be found, especially as it was some time between the event

and the expedition. It just sounds like revisionist scientific history to me.

If locals hadn’t noticed a hole in the ice of Lake Cherbakul soon after the winter impact of the Chelyabinsk meteor … the largest lump of that event would probably have been lost to science and disappeared unnoticed.

I reckon you should dispatch a Sidney team to Lake Cheko  asap … and clear up this mystery! 😋
Still plenty of science to be done on any samples still lying around.
Modern day testing of tree bark fragments might throw up some interesting additional info.

 

[Mr Spock]

There is a lack of evidence supporting an impact event. However, the hole in the ground does look suspicious. A more detailed investigation is required before any conclusions can be drawn. Hopefully someone will see this as important enough to put together an expedition.

[Icosahedron]

I've been reading up on impact events and although there are countless mentions of an asteroid or comet hitting the earth I can't find anything on confirmed comet impacts. However, what I found very interesting is the velocities of the objects relative to earth. One source states a typical 17 km/s for an asteroid (NEA) compared to 51 km/s for a comet, which in my mind puts a comet impact in a different class of event.

As far as the Tunguska event is concerned I think the possibility exists that a suitably sized comet was entirely vapourised in a collision with earth's atmospheric with only an energetic ball of gas making it to the surface.

 

[Drifter]

That speed differential is a v.interesting observation, Ico … Thinking aloud off the cuff … most photos of comets seem to have a giant rock at the core … so for the Tunguska version to suddenly explode as ‘just a gaseous event’ seems rather unlikely? …. If further Lake study reveals the comet’s main core was gratefully neutered in a swamp ….these may explain the few traces of what caused a huge blast in Earth’s oxygen/hydrogen-rich atmosphere, intense burn up and ground aftershocks. Maybe this swamp saved Humanity from another major extinction event.

I feel something unique must be happening to turn a largely invisible inert asteroid rock tumbling through space into a gravity-influenced regular Comet visitor whipped up into an accelerated trajectory that streams a steady trail of fluorescent debris visible to the naked eye each time it passes by.

Here’s an interesting one ….

Note the ‘lion’s mane’ wicking of the rock … and striations down the rear flank of this beast. It suggests the speed of this projectile has reached a critical heat level as it shows itself to viewers nearing the Sun in it’s periodic fly-bys - possibly generating a transformation to a small degree - ‘burn’ on the surface … probably enough to scatter a steady trail of basaltic glass/dust/rock melt trapped with water vapour to give the fine particulate an extra albedo reflectance to the naked eye as the comet’s tail?

Speed may be critical in generating a little EXTRA comet+tail visibility in Space by this known effect when gases are pushed around a rapidly moving object: The ‘wing tip vortices’ effect - as explained here:

https://www.sportskeeda.com/f1/wingtip-vortices-in-formula-one-why-are-they-formed

 

…. this happens admittedly in Earth’s unique atmosphere … even small model aircraft generate it at much slower speeds  … but could be happening to some objects in Space hitting areas of different gases and sublimated water molecules floating around? … an idea worth consideration.

 

Edited June 26, 2021 by Drifter

[DaveS]

Oxygen / hydrogen rich atmosphere? Er, no I don't think so.

Much of the "Tunguska" sized objects kicking around the solar system are probably either barely consolidated rubble piles, perhaps with assorted ices holding them together, or else relatively fragile stony / chondritic objects. Such an object entering Earth's atmosphere would get just so far then disintegrate in an air burst leaving a shotgun pattern of small objects which would bury themselves in the permafrost.

On the scale of impact events Tunguska ranks very low. Enough to have destroyed a city if it had impacted one, but still a local event.

Even a well consolidated stony meteorite will break up if it isn't big enough, witness Chelyabinsk, which resulted in an air burst of around 500 kt, Tunguska was rated about 20 mt.

Something like the Barringer crater needs an iron meteorite impact.

[Drifter]

20 hours ago, DaveS said:

Oxygen / hydrogen rich atmosphere? Er, no I don't think so.

Apologies, I meant atom-rich compared to outside Earth’s atmosphere! … and getting richer as the object gets nearer the Earth’s surface.

Robert Frost, Instructor and Flight Controller at NASA said this interesting comment about objects entering Earth’s atmosphere:

“Objects that enter Earth’s atmosphere burn not because they are falling from great height, but because they are traveling through the atmosphere at great speed. A returning spacecraft enters the atmosphere at about Mach 25.

It’s usually assumed that the mechanism of heating in re-entry is by friction (i.e. viscous drag in the atmosphere). This is the predominant mechanism only at lower altitudes, as air density increases. During the fastest and hottest part of the descent, something different happens.

A re-entering vehicle develops a very energetic pressure wave at its leading surfaces. The energy density is sufficient to cause atmospheric molecules to dissociate, and their component atoms to become ionized. The vehicle thus descends in a superheated shroud of incandescent plasma.

Plasma does not conform to the gas laws of conventional thermodynamics, although it does share one familiar property—a proportionality between pressure and temperature in a contained system. The formation of the pressure wave, therefore, also creates extreme temperatures. The plasma stream is electrostatically charged, too, and so it concentrates at acute surface contours. The resultant effect is particularly intense local heating at the airframe’s leading edges.

An approximate rule-of-thumb used by heat shield designers for estimating peak shock layer temperature is to assume the air temperature in Kelvin to be equal to the entry speed in meters per second—a mathematical coincidence. For example, a spacecraft entering the atmosphere at 7.8km/s would experience a peak shock layer temperature of 7800 K.”

Do you think it’s possible that pressure/friction and heat are fractionating a plasma/burn effect wherever water is either trapped in rock - or present in the atmosphere? - to act as a catalyst at the front end of a moving object travelling at a critical velocity?
If certain piezoelectric minerals are present (to provide the electrostatic charging mentioned by R. Frost)  … and you add metals to this mix … (eg:magnesium) which burn up in our atmosphere easily with bright incandescence … is it possible this accounts for the ‘oxy-acetylene-type effect’ we see in meteor burn up?

I’m trying to think of other elements present - beside hydrogen and oxygen - that might catalyse this - Anyone got any other candidates or mechanisms?

Edited June 27, 2021 by Drifter

[Gfamily]

I'm not sure what 'effect' you're trying to explain, and why you don't think that the usual explanation of heating due to atmospheric compression doesn't cover it.

 

[DaveS]

A quick search found This article in Physics Today about the Chelyabinsk meteor. Wiki has This list of recent (Since 1900) airburst events.

This Paper gives more of the physics, but it's a serious read.

That's probably enough for the moment I may do another search later.

 

Edit: This Wiki page gives a recent overview of the Tunguska event including mention of Lake Cheko, and the outlier natural gas explosion theory. But William of Occam gave a good paradigm where explanations are concerned.

Edited June 27, 2021 by DaveS

[Drifter]

Thanks for those very interesting links Dave … that Chelyabinsk article was a pleasure to read and comprehensive …  The ‘serious’ offering, however, was a challenge of endurance - 65 pages(!)  … but at least it gets us closer to the chemistry and mechanisms that explain why some impacts are more explosive and damaging than others.
Thank the Gods for the Tunguska marshes and Lake Cheko/Chebarkul being able to absorb some of the more damaging aspects of these impacts. 
It’s surprising how different explosive events and scatter patterns can be … even on other planets/moons with limited atmospheres and less varied substrates than planet Earth provides. eg: impacts like Tycho V Aristarchus (5200km spread V more localised spread) ….

It’s also nice to get clues from these reports about what metals/minerals/composites/coatings it’s best to avoid when designing the skins of re-entry vehicles.😋 - I hear the new Sun probes had a major breakthrough when they were able to develop a skin coating tested to protect measuring instruments from some of the worst ravages of solar radiation … let’s hope it works.

 

Edited June 28, 2021 by Drifter

[Gfamily]

1 hour ago, Drifter said:

It’s surprising how different explosive events and scatter patterns can be … even on other planets/moons with limited atmospheres and less varied substrates than planet Earth provides. eg: impacts like Tycho V Aristarchus (5200km spread V more localised spread) ….

It's probably not possible to make a valid assessment on the scale and spread of the impacts on the basis of their current visual appearance, when you consider that the age of Aristachus is approximately four times that of Tycho - therefore there has been four times the darkening of any ejecta.

Another consideration is that Tycho is over twice the diameter of Aristarchus and 70% deeper, so it represents at least 7x the volume of material displaced.

Edited June 28, 2021 by Gfamily

[michael.h.f.wilkinson]

On 27/06/2021 at 09:16, Drifter said:

Apologies, I meant atom-rich compared to outside Earth’s atmosphere! … and getting richer as the object gets nearer the Earth’s surface.

Robert Frost, Instructor and Flight Controller at NASA said this interesting comment about objects entering Earth’s atmosphere:

“Objects that enter Earth’s atmosphere burn not because they are falling from great height, but because they are traveling through the atmosphere at great speed. A returning spacecraft enters the atmosphere at about Mach 25.

It’s usually assumed that the mechanism of heating in re-entry is by friction (i.e. viscous drag in the atmosphere). This is the predominant mechanism only at lower altitudes, as air density increases. During the fastest and hottest part of the descent, something different happens.

A re-entering vehicle develops a very energetic pressure wave at its leading surfaces. The energy density is sufficient to cause atmospheric molecules to dissociate, and their component atoms to become ionized. The vehicle thus descends in a superheated shroud of incandescent plasma.

Plasma does not conform to the gas laws of conventional thermodynamics, although it does share one familiar property—a proportionality between pressure and temperature in a contained system. The formation of the pressure wave, therefore, also creates extreme temperatures. The plasma stream is electrostatically charged, too, and so it concentrates at acute surface contours. The resultant effect is particularly intense local heating at the airframe’s leading edges.

An approximate rule-of-thumb used by heat shield designers for estimating peak shock layer temperature is to assume the air temperature in Kelvin to be equal to the entry speed in meters per second—a mathematical coincidence. For example, a spacecraft entering the atmosphere at 7.8km/s would experience a peak shock layer temperature of 7800 K.”

Do you think it’s possible that pressure/friction and heat are fractionating a plasma/burn effect wherever water is either trapped in rock - or present in the atmosphere? - to act as a catalyst at the front end of a moving object travelling at a critical velocity?
If certain piezoelectric minerals are present (to provide the electrostatic charging mentioned by R. Frost)  … and you add metals to this mix … (eg:magnesium) which burn up in our atmosphere easily with bright incandescence … is it possible this accounts for the ‘oxy-acetylene-type effect’ we see in meteor burn up?

I’m trying to think of other elements present - beside hydrogen and oxygen - that might catalyse this - Anyone got any other candidates or mechanisms?

Whatever effects you try to invoke, there is simply no way fission reactions could take place, let alone fusion. Fission-based nuclear explosion requires very pure nuclear fuel in order to maintain the chain reaction for long enough, plus a means of slowing down the neutrons sufficiently. To create a nuclear explosion based on fusion, the general method is to use a fission bomb as detonator. You need temperatures in the order of tens of millions degrees to get fusion going properly.

However, sudden phase changes (like water or ice suddenly turning to steam) can cause devastating explosions. The damage caused by Krakatoa was caused not so much be the initial volcanic eruption, but by millions of tons of seawater streaming into the resulting caldera , hitting red-hot rock, and suddenly turning to steam, sending a tsunami round the world (it was still measurable in the English channel). A comet containing massive amounts of ice, which suddenly turns to vapour will flatten trees quite nicely, and cause severe burns if you are close enough to the explosion

Regarding metals: any metals in the comet are likely to be bound in oxides or silicates. The only iron seems to be commonly seen in certain meteorites, but I doubt metallic iron, let alone magnesium would be present in a comet in any significant amounts.

 

[DaveS]

Although Tunguska was the biggest attested event during the historical period, This article in Space.com suggests something a lot bigger happened in the early neolithic without killing us all.

[Drifter]

9 hours ago, michael.h.f.wilkinson said:

Whatever effects you try to invoke, there is simply no way fission reactions could take place, let alone fusion. Fission-based nuclear explosion requires very pure nuclear fuel in order to maintain the chain reaction for long enough, plus a means of slowing down the neutrons sufficiently. To create a nuclear explosion based on fusion, the general method is to use a fission bomb as detonator. You need temperatures in the order of tens of millions degrees to get fusion going properly.

However, sudden phase changes (like water or ice suddenly turning to steam) can cause devastating explosions. The damage caused by Krakatoa was caused not so much be the initial volcanic eruption, but by millions of tons of seawater streaming into the resulting caldera , hitting red-hot rock, and suddenly turning to steam, sending a tsunami round the world (it was still measurable in the English channel). A comet containing massive amounts of ice, which suddenly turns to vapour will flatten trees quite nicely, and cause severe burns if you are close enough to the explosion

Regarding metals: any metals in the comet are likely to be bound in oxides or silicates. The only iron seems to be commonly seen in certain meteorites, but I doubt metallic iron, let alone magnesium would be present in a comet in any significant amounts.

 

Is it fair to say that although Aristarchus is older it’s still possible to see it’s scatter patterns are very different to the extreme star light rays of Tycho’s ejecta?.
Aristarchus to me(only?)seems like a dull ‘thud meteor’ with it’s ejecta thrown up - then landing in the vicinity …. where as Tycho on the surface seems more high % metalled/composite comet - exploding in the Tunguska mould but not fragmenting the same way at all … a higher speed of object to Aristarchus creating a deeper crater … but projecting distinct fragments shot laterally like a firework over 5,000km .… at extreme speed, each fragment burning out an individual tapering scatter pattern - fine debris of high albedo reflective ‘glass-locked’ composites that have proven to be understandably very resistant to weathering! 
Is it likely a heavily metalised composite comet would contain the % water needed to catalyse this degree of flash explosion? M.W?

If the water % of the Tycho incident was not sufficient …. can I suggest in this period of Lunar history, the Moon might have had a greater atmosphere and intact subterranean condensate chambers of water created by considerable volcanism? … Tycho’s high metal composite comet incoming then could have had it’s head struck alight by a lingering lunar atmosphere and it’s hot body plunged into a condensate water-rich sublimate area of the lunar surface … Bingo! …. extreme sparks! 
Does that sound plausible?

[Comment … I like to think these condensate reservoirs are probably littered around the base of every super volcano in our Solar System where a network of chambers formed as gases were trapped beneath the hard crust … and as activity died, this condensate collected.
For me, the presence of rilles is a surefire way to pick out which craters on the moon are impact and which are old, well-weathered, low-lipped lava-filled long dead super volcanoes that created the Mares. Guess it’s courting controversy to suggest Herodotus and Prinz are probably not impacts? What’s your view? 
Note the number of rilles around these two that are formed from the eye of a meteor impact? - Ivan, Vera and Aristarchus B …. long after H+P died a volcanic death with the crater filled  … I feel water ooze created these rilles - not lava].

Getting back to these explosive impacts - It’s arguable the sustained light generated by some Moon impacts and Tunguska seems to be so bright and prolonged, in some instances for several seconds, to suggest some sort of ‘chain reaction’ is happening at the heated pressure head of these fast moving projectiles? 
This reaction seems to intensify enormously when they hit an ‘atmosphere’ - often resulting in shattering explosions before ‘vaporising’ mostly to dust - there’s a possibility whatever made up the harder core of the Tunguska ‘bomb’ could still be in the marsh? - and the Bologna team are probably on to something significant that makes a lot of sense in the circumstances … especially in relation to the aftershock and tremors recorded by witnesses who were there at the time.

Dismissing this first hand account testimony is not something modern day scientists should be doing … especially when physical evidence is proving quite elusive. Maybe translating all the Russian reports/studies … tooth-combing them for additional evidence might give clues … and be the best 1st step before proposing new field studies, possibly in other likely impact locations? - flying in modern equipment utilising more advanced analysis techniques with Russian colleagues.

 

 

[Gfamily]

Oh dear! 

[Drifter]

7 hours ago, DaveS said:

Although Tunguska was the biggest attested event during the historical period, This article in Space.com suggests something a lot bigger happened in the early neolithic without killing us all.

Interesting you mention this …. the critical factors that turn large impact events into a domino effect leading to ‘mass extinction’. …. knock out a few key species in one part of the Planet … and the whole food chain comes crashing down! New vegetation/new species evolution takes over completely.

[michael.h.f.wilkinson]

45 minutes ago, Drifter said:

where as Tycho on the surface seems more high % metalled/composite comet - exploding in the Tunguska mould but not fragmenting the same way at all

It would never explode in the Tunguska mold, because the moon lacks an atmosphere.

 

46 minutes ago, Drifter said:

Getting back to these explosive impacts - It’s arguable the sustained light generated by some Moon impacts and Tunguska seems to be so bright and prolonged, in some instances for several seconds, to suggest some sort of ‘chain reaction’ is happening at the heated pressure head of these fast moving projectiles? 

Again, the moon lacks an atmosphere, so the impactor would only start heating up at the very moment of impact. It is quite easily imaginable that the impact site will have been heated to incandescence (molten rock tends to do that), and this will take more than a few seconds to cool down. No (nuclear) chain reaction needed (or indeed possible).

[michael.h.f.wilkinson]

50 minutes ago, Drifter said:

Is it likely a heavily metalised composite comet would contain the % water needed to catalyse this degree of flash explosion? M.W?

Comets are mostly ice (mainly water, but also amonia, carbondioxide, etc), with some rock and dirt thrown in for good measure. You do not need a large proportion of a sizeable comet to suddenly turn to gaseous state to get a huge explosion.

There are various indications that the body may have been a rocky or even iron meteorite some tens of metres across, and models show they too can explode when internal stresses become too great for cohesive forces. This too could cause the object to disintegrate completely. There is a possibility that lake  Cheko holds some remnant of course, but there is no need to invoke nuclear explosions when the old-fashioned "smash stuff together with immense force" will do the job of creating massive bangs. Note that neither rocky nor iron asteroids would contain enough hydrogen (let alone deuterium or tritium) for fusion, nor enough fissible material for fission, and certainly not in the purity needed

[Drifter]

Thanks for that answer, M.W.   
 

On 28/06/2021 at 19:26, michael.h.f.wilkinson said:

There is a possibility that lake  Cheko holds some remnant of course, but there is no need to invoke nuclear explosions when the old-fashioned "smash stuff together with immense force" will do the job of creating massive bangs. Note that neither rocky nor iron asteroids would contain enough hydrogen (let alone deuterium or tritium) for fusion, nor enough fissible material for fission, and certainly not in the purity needed

 

On 28/06/2021 at 19:26, michael.h.f.wilkinson said:

Comets are mostly ice (mainly water, but also amonia, carbondioxide, etc), with some rock and dirt thrown in for good measure. You do not need a large proportion of a sizeable comet to suddenly turn to gaseous state to get a huge explosion.

….Happy to let H2O be the main catalyst here.😄 … Although tektite glass beads sampled at the site of many asteroid impacts is apparently also found in the waste of nuclear reactors. 🤔 
[I recently read the Nördlinger Ries/Steinheim binary asteroid hit (during the Middle Miocene period - which probably contributed to the Middle Miocene Disruption/extinction?) - produced 24km/4km wide impact craters which threw tektites 450 kms apparently - tiny diamonds were created - impact velocity ~20km/s generating an explosive force equivalent to 1.8 million Hiroshima bombs] …. 

On 28/06/2021 at 19:10, michael.h.f.wilkinson said:

It would never explode in the Tunguska mold, because the moon lacks an atmosphere.

I saw a picture recently showing the Moon with a thin misty haze (sublimated gases and moisture?) hugging the surface … suggesting a v. weak thin atmosphere still exists even today (mostly at dawn/dusk in the lunar cycle?) … This suggests the lunar core may still be molten and the magnetosphere v. weak - but active?
My guess is the Moon’s atmosphere was probably a bit thicker with more water/gas vapour sublimation when Tycho hit - that might have ‘lit the fuse’ before it likely hit a reservoir of ‘Volvic’ condensate trapped just below the lunar surface🤔 - Do you think that could give you the explosive event needed to throw incandescent fragments  5,200 km?

With these tektite “glass” dusts being v.resistant to lunar weathering - who can guess when Tycho hit? … possibly much earlier than some predictions.  
This interesting article was dropped by Barry Fitz-Gerald in my recent thread on Lunar Fluorescent Sources.
http://www.psrd.hawaii.edu/Sept04/LunarRays.html

Easy to confuse ‘fresh impact’ dusts with elements with a natural high albedo.
High reflective index materials found in impact scatter.

TiO2

Titanium dioxide occurs in nature as the minerals rutile and anatase. Additionally two high-pressure forms are known minerals: a monoclinic baddeleyite-like form known as akaogiite, and the other is an orthorhombic α-PbO2-like form known as brookite, both of which can be found at the Ries crater in Bavaria.[8][9][10] It is mainly sourced from ilmenite ore. This is the most widespread form of titanium dioxide-bearing ore around the world. Rutile is the next most abundant and contains around 98% titanium dioxide in the ore. The metastable anatase and brookite phases convert irreversibly to the equilibrium rutile phase upon heating above temperatures in the range 600–800 °C (1,110–1,470 °F)Titanium dioxide (B) is found as a mineral in magmatic rocks and hydrothermal veins, as well as weathering rims on perovskite. TiO2 also forms lamellae in other minerals.  
Titanium dioxide is the most widely used white pigment because of its brightness and very high refractive index, in which it is surpassed only by a few other materials (see list of indices of refraction). Titanium dioxide crystal size is ideally around 220 nm (measured by electron microscope) to optimize the maximum reflection of visible light. However, abnormal grain growth is often observed in titanium dioxide, particularly in its rutile phase. The occurrence of abnormal grain growth brings about a deviation of a small number of crystallites from the mean crystal size and modifies the physical behaviour of TiO2. The optical properties of the finished pigment are highly sensitive to purity. As little as a few parts per million (ppm) of certain metals (Cr, V, Cu, Fe, Nb) can disturb the crystal lattice so much that the effect can be detected in quality control. It is often referred to offhandedly as "brilliant white", "the perfect white", "the whitest white", or other similar terms. Opacity is improved by optimal sizing of the titanium dioxide particles.

Silicon Carbide

Ferdinand Henri Moissan discovered the very rare naturally occurring SiC mineral while examining rock samples found in the Canyon Diablo meteorite in Arizona. The mineral was named moissanite in his honor. Moissan also synthesized SiC by several routes, including dissolution of carbon in molten silicon, melting a mixture of calcium carbide and silica, and by reducing silica with carbon in an electric furnace

Edited June 29, 2021 by Drifter

[Drifter]

Just bumped into this which suggests metals are in the mix in a ready form to probably help catalyse aspects of incandescence seen in some impacts.
https://www.space.com/metals-detected-in-comet-atmospheres

[michael.h.f.wilkinson]

Incandescence does not need a catalyst, it just needs heat. The second law of thermodynamics indicates that ultimately, all energy will be converted to heat, so if a heavy object travelling at some tens of km/s is smashed into a stationary object, you will release a lot of heat. If by massive we mean a stone, iron, or even icy object tens or hundreds of meters across at minimum, the heat should be enough to generate photons at visible wavelengths (i.e. enough for incandescence).

[Drifter]

It’s interesting to try and gauge which types of impacts are going to create the most devastating effects … especially impacts hitting a densely populated Earth. 
Looking at this chart, Tunguska and Chelyabinsk are so insignificant in the big picture, (a tiny red cross on this chart) …their traces soon wiped off the face of the Earth.

It would be good if this chart has been updated to show graphically which impacts link to which specific major extinction events … what knocked down the first brick in the domino effect of species collapse (something we are beginning to see today) … the key to the slow lingering demise of many dinosaur species(not just Chicxulub?), the Eocene-Oligocene extinction(not just Popigai?) and Middle Miocene extinction(not just Nördlinger Ries/Steinheim binary asteroid hit?). 
I guess many ocean asteroid hit’s have left few traces that raised sea temperatures, killed coral and dependent species - many hits are yet to be logged -  the data locked in seabed core samples from around the World still needing to be interpreted🤔 … as evidence left may be pretty different to the tektite traces of land impacts?

Logging prevailing winds/direction of scatter influenced by Earth’s global weather system flow at that time in History .. the affects of  magnetosphere strength/Earth’s polarity. Nice to know where crust penetration/tremors/tsunamis were significant enough to trigger earthquakes/volcanic activity and consequently further atmospheric dust scatter into the upper atmosphere - the game changer to making this a Global problem.

 

 

 

Edited July 3, 2021 by Drifter