Kerr Watch

Elapsed time since Richard Kerr failed to inform his Science readers of the confirmation of nanodiamonds at the YDB: 6 years, 2 months, and 1 day

To Australia with love, Michigan

Davias and Harris are wowing them again this week at the Geological Society of America. I will try and get a hold of their wonderful presentation and post…..

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Saginaw bay impact

 

A TALE OF TWO CRATERS: CORIOLIS-AWARE TRAJECTORY ANALYSIS CORRELATES TWO PLEISTOCENE IMPACT STREWN FIELDS AND GIVES MICHIGAN A THUMB

Michael Davias, Stamford, CT and Thomas Harris, Lockheed-Martin (Retired), Orbit Operations, Valley Forge, PA
Pleistocene Epoch cosmic impacts have been implicated in the geomorphology of two enigmatic events. Remarkably, in both cases spirited debates remain unsettled after nearly 100 years of extensive research. Consensus opinion holds that the Australasian (AA) tektites are of terrestrial origin despite the failure to locate the putative crater, while a cosmic link to the Carolina bays is considered soundly falsified by the very same lack of a crater.
Likely >100 km in diameter, these impacts during geologically recent times should be readily detectable on the Earth’s surface. The improbability that two craters have eluded detection informs a hypothesis that a single impact at ~786 ka generated AA tektites as distal ejecta and Carolina bays as progeny of proximal ejecta. The AA astroblem search is focused on SE Asia despite a strewn field encompassing >30% of the Earth’s surface. This spatial scope implies to us that interhemispheric transits should be considered, as does findings that AA tektites were solidified in a vacuum, then ablated on re-entry at ~10 km sec-1. A Coriolis-aware triangulation network operating on the orientations of 44,000 Carolina bays indicates a focus near 43ºN, 84ºW. Referencing the work of Urey and Lin, we propose that a near-tangential strike to the Earth’s limb generated the 150 x 300 km oval depression that excises Saginaw Bay and opens Michigan’s Thumb. That region was likely buried under deep MIS 19 Laurentide ice at 786 ka. Schultz has shown that oblique impacts into continental ice sheets yield non-traditional astroblems, and multiple glaciations have since reworked this site, making identification more challenging. Hypervelocity gun tests show that oblique impacts produce a vertical plume of ejecta, biased slightly down-range. Ballistic trajectories reflecting such a plume deliver tektites to all AA finds when lofted at ~10 km sec-1 and parameterized with the proposed depression’s location and 222º azimuth. Chemical and isotopic characteristics of AA tektites suggest they were sourced from sandstone and greywacke of Mesozoic age, which is congruent with Michigan Basin strata lost when The Thumb developed. The distribution of proximal ejecta may explain anomalous pulses of regolith in moraines and sediment loading in regional drainage basins recently dated ~800 ka using 10Be/26Al methods.
  • Steve Garcia

    I am averse to adding more to that, but think I should point out that there is a good overlap of comets and asteroids, based on various characteristics, not the least of which is having a tail or not. The idea of comets being “dirty ice balls” is long since a misnomer. 67P, for example is certainly not mostly ice.

    I posit the basic idea that comets are essentially the debris that got thrown out away from the Sun – or in toward the Sun and which passed close enough to get slung out very far. SOME of those Sun grazers would have certainly gotten slung UP or DOWN. But most high-inclination comets I think would have been directly exploded up or down.

    I also think that calling them comets or asteroids is misnomer. If the planet had water on it, certainly some fragments would retain the water as ice.

    Scmitt et al 2015 “COMPOSITION OF COMET 67P/CHURYUMOV-GERASIMENKO REFRACTORY CRUST AS INFERRED FROM VIRTIS-M/ROSETTA SPECTRO-IMAGER” seems to suggest my thinking that comets are not dirty snow balls can at least sometimes be correct:

    “The 3.2 µm band: The broad 3.2 µm band can be assigned to OH, CH, H2O, NH/NH2 and NH4+ chemical groups, molecules or ions. The nucleus temperature of 220 K renders negligible a significant contribution from water ice, which is marginally detected in area of the nucleus just emerging from shadow”. http://www.hou.usra.edu/meetings/lpsc2015/pdf/2092.pdf

    Perhaps 67P is only called a comet because of its orbital parameters, not its composition. If it hardly has any ice, what is it?

    I also think that regolith on asteroids and comets is explained nicely by the XP idea. If chunks and dust are thrown out in the same direction and at the same initial velocity, then it seems that the regolith materials could settle more easily than to be picked up out in space somewhere or migrated from a separate large body going at some random relative velocity, across the bow. Going at the same speed and in the same direction, there would be LOTS of time for the dust to migrate down onto the surface. NOT SO, with passing bodies. There would only be an instant of close approach, before the distance increases and the gravitational pull rapidly declines.

    Regolith seems to be fairly ubiquitous – on both comets and asteroids.

    I would even posit that regolith has fooled many earth-based spectrographs – as the olivine dust on Vesta did – by showing up the regolith materials instead of the underlying solid body materials. As such, what are comets and asteroids really made of? Did water vapor drift down as snow onto bodies that spent most of their time far out in the solar system and then fool the astronomers?

    Probably not! I am probably wrong! But for me it is worth thinking about.

  • jim coyle

    Steve; I bet you had too soak your fingers in ice after that last round of postings. Very interesting stuff.

  • @Steve –

    The reason I mentioned Beta Pic was that it was the single system observed with more dust then it should have. That the smart guys suspect comets is as you suggest, it is the newest big thing, as the only CO emissions we have observed are from active comets, ergo comet smash. Proven? Hardly. Best guess? Maybe.

    Still, in over 2000 systems with planets in place or forming Beta Pic is the only place with more dust than it ought to have, which lops away at the notion of an XP. Cheers –

  • Steve Garcia

    Thinking out loud about comets and their outgassing, which is the source of their tails… How strong is the outgassing flow?. . .

    Hollywood movies give the impression of this outgassing as being a violent event like pressurized steam coming out of a pipe (another Hollywood convention). What was the movie with guys getting blown out into space? I am thinking that if they have maneuvering jets, the thrust from the jets is very likely many times as powerful as the outgassing.

    The first thing that comes to mind is to ask how deep within the comet it is being created. It is, after all, simply warming of water and other “volatiles” that can vaporize. Water, especially, in a vacuum at those temps would likely never go liquid – but would sublimate straight to water vapor. So how deep can the warming penetrate?

    Fusion crusts on meteors WITHIN the atmosphere occurs only to a depth of about 3 millimeters. Ablation – melting of the solid rock – only occurs in that same 3 mm, before vaporization that is seen as a glowing, fiery ball and tail.

    These are processes that take many hundreds of degrees – about 2000° C or so, if I remember correctly. And still the heat drops off very rapidly within the body of a meteor with strong PRESSURE and TURBULENCE making the heat transfer REALLY high. Contrast that to essentially zero outside pressure and no outside gases to be turbulent. All the comets have is a SLIGHT internal pressure of the volatiles in the cracks and pores – each one of which has to warm up on its own. We are talking of individual small volumes of volatile gases here. Volatiles in big cracks will be outgassing from smaller cracks and pores in the side walls of the large cracks. (And just a little way inside the direct rays of the Sun can’t penetrate, so no outgassing would occur more than a few feet inside the large cracks. Only when the rotation of the comet lines up the crack with the Sun – which only happens for a few seconds or minutes.)

    All of this suggests that the heat of sunlight on comets in space can only penetrate a short distance under the surface of a comet. That may not be true, but it seems consistent with observations of the fireballs we call meteors in the atmosphere. Silicate rocks, as 67p/Churyumov–Gerasimenko certainly seems to be, are NOT good conductors of heat, and in fact are fairly good insulators. They warm up slowly and cool off slowly. BAD heat transfer.

    I know from my interest in climate that the energy density of sunlight that reaches the top of the Earth’s atmosphere is only 1367 watts per square meter. This translates into about 127 watts per square foot for us Americans – a bit more than the energy of a 100 watt incandescent bulb. This is about 127 joules. So, anything at 1 AU will have the same energy density on its surface. As comets pass the orbit of Earth, then, they are receiving about 127 joules per square foot, and the rotation means that the angle is continually changing (any angle excpet 90° means LESS intensity per square foot). That 1367 is all frequencies of light. At the surface about 53% is infrared, the light energy that heats things up. If we use that 53% value, then the amount available to heat a comet at 1 AU is about 725 watts/sq meter, or 67 watts per sq foot. (A sq meter is about 10.8 sq feet.) So, you can see that the intensity of the energy is pretty damned low.

    And if this low intensity of EM energy is impacting the surface of a comet, and it only goes maybe 3 mm deep (1/8″), the intensity of the heating inside the comet is very low, almost zero – even over time (especially because they don’t spend much time at 1 AU or less). I have to think that the warming doesn’t go at all more than an inch or two deep. And the 3 mm is a conservative value, since the vastly greater heat applied during atmospheric entry of a meteor only goes that deep, versus the very low intensity heat applied to the surface of a comet in space at 1 AU. The outgassing, then, would seem to be very superficial. 3mm thick for a spherical comet the size of 67P (4200 meters across) represents only about about 0.0002% of the total volume. We are talking a VERY small total capacity here for outgassing.

    This leads me to wonder how violent the outgassing velocities can possibly be. Certainly nothing like Hollywood depicts. VERY tenuous gases, released rather slowly. 67 watts of infrared is incapable of warming rapidly. Flow is dependent on F = ma. Or a = F/m. But F comes from pressure, and outgassing into a vacuum means that very low pressures can result in outgassing. Therfore, as SOON as the delta-P is enough to push some gas out, it will. It can’t store up pressure until it builds up to go BOOM. it is like a pressure relief valve that is set to WIDE OPEN setting. Pressure can only exist when there is resistance to flow. Low release pressure, low masses of volatile gasses – release of the gases internally is not done all at once, but instead it seeps out of each pore. Yes, the total area of a comet can be large, but for the most part only the sun-side is outgassing at any given time. The outgassing has to come on slowly, as the comet approaches the Sun – ANOTHER reason that the outgassing can only occur slowly. It is a gradual process, not a rapid one. Yes the slope of the curve increases with proximity to the Sun, but from moment to moment the outgassing increase can’t be great. But that “wide open pressure relief valve” means that each pore outgasses at the lowest possible delta-P.

    The escape velocity of 67P is about 1 m/sec, or about 3 feet/sec – a walking speed. Exceeding this escape velocity threshhold is not difficult at all and requires VERY little energy. It also produces a very low outgassing pressure – probably on the order of 0.01 psi pressure differential, average. Even at such low pressures, the outgassing is enough for SOME of the gasses to exceed the escape velocity.

  • Steve Garcia

    agimarc –

    “Still, in over 2000 systems with planets in place or forming Beta Pic is the only place with more dust than it ought to have, which lops away at the notion of an XP.”

    Not clear what you are saying there… But interested in what you Do mean.

    Yeah, they connect the comets only because of the CO – that is the kind of thinking that to me is not scientific but just jumping to conclusions – and then putting it out for the world to see makes it even worse science. We might as well be back in ancient Greece, where they logic-ed out everything and got it all wrong. Earth, air, water, and fire stuff… Aristotle and his thinking messed up thinking for 2000 years.

  • @Steve – ran out of time last night. Second point on uranium.

    We are using critical the same way – a sustaining reaction where the products of a fission produce additional fissions. Let it run away and things go boom. Controlled criticality is how you generate heat in reactors. Some (most?) of the accidents have been runaways, which is what you need for and explosion.

    Did a back of the envelope calc on total mass of uranium in the earth. Assuming I didn’t completely botch the calc, we end up with a ball around 124 miles (statute) in diameter. If you are only interested in U235, as 238 doesn’t explode, that number decreases to some 38 mi in diameter. Source for the total mass is a paper on using Geo-neutrinos as a measuring device. Link to paper follows: http://arxiv.org/pdf/hep-ph/0501111.pdf

    This is a long way of saying that looking at a nuclear trigger for an XP needs a lot more uranium (or thorium or pick your poison) than we have. The fissionable metal needs to be concentrated in the absence of moderation so that a runaway reaction takes place. And if you start postulating exploding interlopers with higher concentrations of heavy metals, we run smartly into the chicken and egg problem. How do you end up with the additional heavy metals in the first place?

    Like I said previously, we have seen natural reactors on the earth that went critical but did not run away. http://www.scientificamerican.com/article/ancient-nuclear-reactor/

    If you are talking about hydrogen explosions, we already see one of those. Actually there are three examples – Sun, Jupiter and Saturn. Only one of those is actively fusing. The other two give off more heat than they receive from the sun but are not massive enough to sustain a reaction.

    Final point, in the event of excess heat on a rocky body, it simply melts and will not fly apart unless it is spun up to the point where it the centrifugal force is greater than its escape velocity at the equator. As angular momentum must be conserved, what spins it up? Cheers –

  • Steve Garcia

    It may be belaboring the subject of olivine and its window of pressure, but this from Wikipedia about garnets I thought is pretty illustrative of what materials the different pressures under the Earth create (especially since I started the entire subject talking about peridotite (which was present with olivine in the Allende meteorite):

    Garnets are also useful in defining… For instance, eclogite can be defined as a rock of basalt composition [basalts are only in the continental crust, being lighter rocks], but mainly consisting of garnet and omphacite. Pyrope-rich garnet is restricted to relatively high-pressure metamorphic rocks, such as those in the lower crust and in the Earth’s mantle. Peridotite may contain plagioclase, or aluminium-rich spinel, or pyrope-rich garnet, and the presence of each of the three minerals defines a pressure-temperature range in which the mineral could equilibrate with olivine plus pyroxene: the three are listed in order of increasing pressure for stability of the peridotite mineral assemblage (vague). Hence, garnet peridotite must have been formed at great depth in the earth. Xenoliths of garnet peridotite have been carried up from depths of 100 km (62 mi) and greater by kimberlite, and garnets from such disaggegated xenoliths are used as a kimberlite indicator minerals in diamond prospecting. At depths of about 300 to 400 km (190 to 250 mi) and greater, a pyroxene component is dissolved in garnet, by the substitution of (Mg,Fe) plus Si for 2Al in the octahedral (Y) site in the garnet structure, creating unusually silica-rich garnets that have solid solution towards majorite. Such silica-rich garnets have been identified as inclusions within diamonds.

  • Steve Garcia

    agimarc – I agree with you on the U-235 vs U-238. I had that in my mind and didn’t get around to including it for some reason.

    But are you sure about your ratios of U-235 and U-238? The percentage of U-235 in my head is 0.7%. Yep, Wiki gives it as 0.72%. (No, I don’t run around with all those isotope percentages in my head – I am not THAT big of a geek. That was something I’d read several times from my interest in Thorium reactors…) If 124 is the diameter of U-238, then for a volume of .0072 of that, I come up with a radius of 11.97 or a diameter of ~24 miles.

    The fissionable metal needs to be concentrated in the absence of moderation so that a runaway reaction takes place.

    You lost me. A ball of solid uranium 24 or 38 miles in diameter doesn’t constitute concentrating it? Cadmium is a common moderator in nuclear reactors. Is the U-238 considered to be a moderator?

    A study last year discussed their discovery of the inner inner core of the Earth (yes, two “inners”). http://www.dailymail.co.uk/sciencetech/article-2946138/Journey-centre-Earth-Scientists-planet-s-inner-core-core-own.html it talked about geomagnetism coming from iron in the inner core aligning differently from the iron in the outer core, but it did not talk about how big the inner core is. It also did not even mention uranium, which makes no sense. But a 2003 article at http://www.spacedaily.com/news/earth-03k.html talks about a 5 mile diameter inner inner core of uranium.

    I don’t know where you got your 124 mile ball of uranium (I tried, but everything was directed at uranium in the crust). If there is that and then there is a 5 mile ball inside the other, what could that mean?

    Uranium melts at about 2,070°C. The inner core and outer core are said to be at 5700-6000°C. So any uranium in the core is going to be molten – unless the pressure keeps it in some quasi-crystalline state.

    According to two sources, the uranium in the MANTLE keeps the outer core melted. If the outer core is melted, then convection is going to drive the U-238 to the inner core, and the U-235 should follow and form a shell around the U-238. I mean, differentiation is all about heavy materials sinking and lighter materials floating upward. That is basic geology’s meme.

    If the U-238 and U-235 don’t sink to the bottom/center, can you explain why not? And with a molten mantle, too, any uranium in the mantle is doomed to sink down to the core. The reason uranium is semi-rare on the surface is supposedly because the uranium sank during the differentiation. No? Yes? And I’d like to know why n 4.6 billion years the molten uranium isn’t concentrated at the center. If it is fluid (which the temperatures strongly suggest – and the scientists maintain), then it should have been convecting downward for a very long time.

    I am missing something, because how can it sink and still not concentrate the uranium?

  • Article tying the YD cooling event to an impact is up at WUWT. Let the good times roll. Cheers –

    http://wattsupwiththat.com/2015/07/27/younger-dryas-cooling-event-said-to-be-comet-related/

  • George Howard

    I have started a post…

  • Steve Garcia

    (Up all night on this on, agimarc. I didn’t see your comment until like 1:00 am, and went right over to WUWT…)

    GEORGE –

    This comment over there really caught my attention:

    LT July 27, 2015 at 4:52 pm
    During the end of the last glaciation the glaciers were up to 2 miles thick, an impact on a thick glacier would not have left much behind for us to see today. I am a geophysicists and much of the seismic data I have interpreted in the glacial till areas of Canada are a mangled mess.

    “LT” is the guy’s userID.

  • Steve Garcia

    James P. Kennett, et al. Bayesian chronological analyses consistent with synchronous age of 12,835–12,735 Cal B.P. for Younger Dryas boundary on four continents doi: 10.1073/pnas.1507146112 (Paywall)

    http://www.pnas.org/content/early/2015/07/21/1507146112.abstract

  • Steve Garcia

    Trent –

    Just in terms of how much mass is in the steroids, I have to post the question “How many is the mass based on?”

    I want to re-post the link to that asteroid discovery video. At the end, I’d like you to VISUALLY see how many of the buggers are there. He points out that each PIXEL is 500,000 km.

    https://www.youtube.com/watch?t=41&v=xJsUDcSc6hE

    When people talk about the asteroids only comprising X% of the mass of the Moon, I have to ask when they did their numbers, because this is the numbers at different points in time (from the video and I grabbed the last number in each year):

    1980 – 9,425
    1985 – 12,214
    1990 – 15,924
    1995 – 26,748
    2000 – 123,114
    2005 – 343,671
    2010 – 548,914
    2013 – 588,992

    When Tom van Flandern died in 2009, at the end of that year 504,118 were known. Since then the number has increased 16%, adding 84,874. That is 3 times as many ADDED as we knew about in 1995.

    So, my thing to you is partially to LOOK at that later portion of that video and see all those flying around, and imagining that MAYBE might they have came from an XP. Don’t agree. Just imagine.

    They are NOT all in the same plane, and each pixel may harbor quite a few asteroids. I suspect that they do.

    To have THAT many out there for 4.6 billion years and still are surviving, that is amazing. Impossible? If the Oort cloud has comets “bumped” into sunward orbits, with the Oort cloud being 360°x360°, wouldn’t one think that the asteroids would have had most of them bumped sunward and crash into either Jupiter or the Sun by now?

    In the video I was struck by how CLOSE so many orbits came to Mars, and how FAR they were from Jupiter. Obviously, Jupiter swept up the ones close and so did Mars. But the ratio of the width of the two spaces, really illustrated to me the difference in gravitational pull. And if these may happen to be one day found out to be the remnants of an XP, this video illustrates how little protection Mars had.

    Whenever they were created, some asteroids crossed Mars’ orbit and whacked into it. Some crossed it without collision and managed to stay clear all this time – 4.6 billion years. Or maybe 20 million? Or less? There are definitely panels in a couple of Egyptian temples that show an extra planet. So, maybe 3,000 years ago? Hahaha probably not, but what is that extra planet doing there on those hieroglyphic walls?

  • Trent Telenko

    Steve Garcia,

    I just punched that table of yours into Excel for a bar chart and it is absolutely wild.

    The jump between 1990 and 1995 was almost a doubling.

    The jump between 1995 and 2000 was almost a tripling

    And again between 2005 and 2013 almost another double.

    We are living science fiction as science fact.

  • @Steve –

    The larger ball came via the paper I linked which estimated total uranium on the entire planet at some 80x10exp15 Metric Tons. They got that estimate looking at what they called geo-neutrinos from fission of uranium and its isotopes.

    Screwed up on the smaller ball. You are correct at 23 statute mile diameter sphere on the U235. Larger volume is 124 miles diameter.

    The reason it doesn’t concentrate together is due to convection in the outer core and the mantle. Convection is how the internal heat is transferred outwards. It is what drives the mantle currents, plumes and other forms of upwelling. As it is liquid (or if you prefer, plastic) and highly viscous, it cannot concentrate. The inner core started out liquid and transferred its heat outwards, mostly via convection until it got cool enough to solidify.

    Explanation as to why the two isotopes don’t separate: Too little difference between the individual masses. Remember these don’t exist as metal. They exist as molecules of rock, further hampering any tendency to separate via mass.

    Bottom line is you don’t have enough elements that can concentrate and explode to drive an XP. Cheers –

  • Observation on non-planetary objects. It continues to amaze that the more we look, the more we find, especially inside the orbit of Neptune.

    I would submit that an effort to add up the mass of known KBOs will far outweigh everything inside the orbit of Neptune not attached to a planet. Here’s a good place to start.

    http://www2.ess.ucla.edu/~jewitt/kb.html

    Would also submit that what is still in the extended Oort Cloud may not be what our sun started out with. The problem is that the solar systems regularly interacts with other stars, some passing well within the supposed boundaries of the Oort Cloud. These sort of close approaches take place in the range of hundreds of thousands of years or so. Approach distances are within a tenth of a LY. If all stars start out with an array of Oort like objects, won’t these get mixed, matched, captured and scattered over multiple encounters during the billions of years? This leads directly back to the Fred Hoyle panspermia suggestions. Cheers –

    http://www.iflscience.com/space/star-passed-less-light-year-earth

  • Steve Garcia

    Trent – Yeah, way cool.

    Did you happen to look at the video? I was WOWED by it. SOOOO many… At the pixel resolution of 500,000km/pixel, it looks kind of solid, all the way across the Main Belt.

  • Steve Garcia

    agimarc –

    Just discussing, I guess. . .

    The reason it doesn’t concentrate together is due to convection in the outer core and the mantle. Convection is how the internal heat is transferred outwards. It is what drives the mantle currents, plumes and other forms of upwelling. As it is liquid (or if you prefer, plastic) and highly viscous, it cannot concentrate. The inner core started out liquid and transferred its heat outwards, mostly via convection until it got cool enough to solidify.

    Convection, IMHO, is given a lot of street cred that I don’t think it deserves.

    Yes, convection exists. But consider the things convection has going for it and things it had going against it:

    FOR:
    1. Gravity
    2. Density differences
    3. Fluids are non-crystalline and therefore can flow
    4. The more brownian motion (heat energy) present, the more readily fluids flow

    AGAINST:
    1. As one fluid rises, it had to replace the lighter fluid above it
    2. Viscosity – resistance to flow
    3. Pressure – the higher the pressure, the higher the friction (the higher the viscosity)

    In a hotter environment viscosity is lower.

    In a higher pressure environment viscosity is higher.

    So which wins out, in this tug of war? I am not sure.

    Explanation as to why the two isotopes don’t separate: Too little difference between the individual masses. Remember these don’t exist as metal. They exist as molecules of rock, further hampering any tendency to separate via mass.

    Thinking out loud… Cascades of centrifuges are THE method of separating U-235 from U-238, by reason of density. But it is done when the uranium is in gaseous form, as uranium hexafluoride. This lowers the viscosity by a LOT.

    Uranium in the core – as is everything there – is a liquid. I do not know if the conditions of ultra-high pressure is sufficient to allow convection of the liquid uranium.

    I know that in testing the olivine in the Allende meteorite, they needed a super-high pressure laboratory anvil in order to simulate the pressures, just at the depth of the upper mantle. We have a hard time getting much beyond that pressure (about 22 Gpa – or 3 million PSI.

    Something in my head says that when huge pressures exist, materials not only change physical characteristics, but that they do unexpected things. The core pressure is said to be about 360 Gpa – about 16 times as high as the lab anvils.

    Even “only” 3 million PSI is so far above pressures and materials strengths that I’ve dealt (about 10 times more) with that I can hardly fathom what happens to materials. 10 million PSI is the target for fusion. But 360 Gpa? That is pushing 50 million PSI. What this does to materials I haven’t a clue. I am thinking of actually stripping electrons and going all plasma, but that probably is really wrong. I DO believe it is enough to add a super lot of temperature. Enough to even cause fusion or fission? Something in me says yes, but I can’t back that up. Pressure creates heat, and pressure alone creates fission. Massive heat causes fusion, if I read everything well enough (probably not). 50 million PSI is a NASTY level of pressure.

    I am sure the pressure makes convection even harder. At the same time, there are billions of years for the flow to overcome any high viscosity. Which wins out? CAN convective flow separate U-235 from U-238 in a mostly iron core? Not in ten seconds and not in days or hours or years. But on the scale of ~4 billion years?

    I will tell you THIS: It is a CLEAR geological understanding that plumes in the mantle are convection-driven, and the pressure there is well in excess of 3 million PSI, pushing 40 million PSI near the core. If mantle plumes are accepted to exist, saying that U-235 and U-238 – a density difference of 3 protons and 3 neutrons – can not convect, well I don’t think that is a correct assumption. That density difference is about the same as between iron and copper, or hydrogen and helium. I am pretty sure it is more than between warm air and col air.

  • Cevin Q

    This was published today,
    a confirmation of some of Davias’ and Harris’ work,

    “Approximately 790,000 years ago there were multiple cosmic impacts on Earth with global consequences. Geoscientists from Heidelberg University reached this conclusion after dating so-called tektites from various parts of the world. The research group under the direction of Prof. Dr. Mario Trieloff studied several of such rock glasses, which originated during impacts of asteroids or comets. The Heidelberg scientists employed a dating method based on naturally occurring isotopes that allowed them to date the tektites more accurately than ever. Their studies show that the samples from Asia, Australia, Canada and Central America are virtually identical in age, although in some cases their chemistry differs markedly. This points to separate impacts that must have occurred around the same time. The results of their research funded by the Klaus Tschira Foundation were published in the journal Geochimica et Cosmochimica Acta.”

    https://www.sciencedaily.com/releases/2016/02/160222111420.htm