We're not Earthlings — we're colonists from Ceres!
Hey Folks!
I just got done updating my paper on celestial collisions, in response to Lloyd's criticisms. I have settled on the opinion (for now) stated in the topic title — the Earth's continental granites were donations from Ceres via the Late Heavy Bombardment. Without dry land and the shallow seas surrounding it, life wouldn't have evolved so quickly, so the LHB was important for us. It also means that we're standing on material that first solidified on Ceres. Here's the text...
The section on the Titius-Bode Law mentioned the possibility that the asteroid belt between Mars & Jupiter is the debris from a celestial collision, with Ceres as the largest surviving remnant of a planet. The remainder of the debris would have since fallen into the Sun, or impacted other planets & moons, perhaps in what is known as the Late Heavy Bombardment, thought to have occurred 4.1~3.8 billion years ago.
The impacts seem to have remelted the crusts of the Earth, the Moon, and of Mars. The latter two have roughly similar topographies, with highlands that are heavily cratered from the LHB, but also with vast expanses of flood basalts that are sparsely cratered. This means that the "flooding" occurred during the LHB. The mares are believed to have been formed by volcanic megaflows, but it would be an odd coincidence for both the Moon and Mars to undergo the same internal process at roughly the same time, despite their differences. And for this to have occurred by chance, just when both were being subjected to a dramatic external influence, is too many coincidences — it's far more likely that the LHB caused the mares. The thermalization of the impacts would have provided a lot of heat. At the same time, the Sun might have been flaring violently from infalling debris, and thus projecting a lot more heat onto the surfaces of the planets and moons.
It's then no coincidence that the Earth's crust got remelted at the same time. The only difference was that the remelting was more thorough. Rocks pre-dating the LHB have been found in the highlands on both the Moon and on Mars, but not so on Earth.
If the Earth's crust was totally remelted, why didn't the continents slump more? The continents are made of granite, while the oceanic crust is basalt. Granite is lighter than basalt, so the continents "float" like icebergs in the basaltic sea. But if the continents were completely remelted by the LHB, they should have flowed out over the basalt, leaving a thin layer of granite wrapping all of the way around the world. It's possible that the crust didn't get quite hot enough to become that runny during the LHB.
But this reveals an even more fundamental question — why didn't the granite settle out long before the LHB, when the Earth was first forming? Pretty much all of the models of the Earth assume that when it first condensed, it was completely molten. It immediately began cooling by radiative heat loss (i.e., photons). The molten rock would have been good at conducting heat to the surface, but bad at radiating that heat into space, so it would have taken a long time for a crust to have formed. In the meantime, all of the lighter chemicals had plenty of time to bubble up to the surface. The granite would have quickly found its way to the top, and it would have leveled off into a relatively flat layer on top of the basalt. Later, when the surface temperature dropped below the boiling point of water, the steam in the atmosphere would have condensed, forming the oceans. But if the granite layer had been perfectly flat, the oceans should have covered the entire globe — no dry land. So how did the granite get consolidated into continents?
It's possible that the continental granite didn't get distributed during the molten stage, because the granite simply wasn't present yet — it might have arrived during the LHB. In other words, the continents might be what's left of a huge meteorite. Heat from the impact would have remelted everything, but perhaps not so completely that the granite could pancake all of the way around the globe. Rather, it settled into the original supercontinent.
The continental granites have a volume of 7.58 × 109 km3. This is just 0.69% the volume of the Earth (1.08 × 1012 km3), while being 1/3 the volume of the Moon (2.20 × 1010 km3), and 20 times the volume of Ceres (4.21 × 108 km3). So the impacter would have been small by planetary standards, but larger than any extant asteroid, and big enough for all Hadean life forms to have a really bad day.
In conclusion, it seems that thinking of ourselves as Earthlings is a bit of an oversimplification. The stuff of which we are made originally condensed into Ceres. That all came to an end 4.1 billion years ago. But a big chunk of our former planet found a new host here on Earth. The granite created an island in the middle of what had previously been just one big ocean. The shallow seas around the island provided a breeding ground for new life forms, who were our ancestors. So this is not our first planet (and perhaps it won't be our last).
seasmith
Re: We're not Earthlings — we're colonists from Ceres!
Charles wrote: It's possible that the continental granite didn't get distributed during the molten stage, because the granite simply wasn't present yet — it might have arrived during the LHB. In other words, the continents might be what's left of a huge meteorite. Heat from the impact would have remelted everything, but perhaps not so completely that the granite could pancake all of the way around the globe. Rather, it settled into the original supercontinent.
You do know that 'granites' are not a primary igneous formation like a basalt, right ?
Granites around the world in their amazing varieties are all igneous-metamorphic rocks. In other words, some early crustal components, mainly silicates if Earth cooled slowly, would rise naturally toward the surface by simple principles of densities and thermo-dynamics.
This primal crust is then broken up and churned under, during your cataclysmic "continents" building episodes and epochs, when mountains disappear beneath the seas and sea-bottoms are stranded atop mountain ranges. ~~[Encounters between solar system bodies are clearly indicated as roiling agents, i think most around here would agree]
The igneous metamorphose of those primal materials will account for the wide range of granites world-wide; however a single Cereian source would not.
Kudos though for being able to come up with all these constantly revising theories on such a broad range of subjects.
CharlesChandler
Re: We're not Earthlings — we're colonists from Ceres!
seasmith wrote: Kudos though for being able to come up with all these constantly revising theories on such a broad range of subjects.
Thanks (I think ). For me, science isn't a position — it's a process. So it leads to a constantly shifting position, always foraging for more anomalies, and venturing hypotheses to account for them. Indeed, scientific exploration is error-prone, if you want to look at it like that. You don't know what you're going to find until you explore it. The bad news is that it's labor intensive, and sometimes you might feel like you're spending more time exploring blind alleys than making progress. But in order to fully understand the entire problem domain, all of it needs to be explored — blind alleys and all. The good news is that you get a better understanding, and it's exhilarating when the picture comes into clearer focus.
seasmith wrote: You do know that 'granites' are not a primary igneous formation like a basalt, right?
Right. What I want to know is: why aren't the granites primary igneous formations? Let's go back to the fundamental dilemma that I'm trying to get my mind around. If the Earth, when it first formed, was entirely molten, and if it cooled slowly, there should have been plenty of time for near-perfect chemical stratification on the basis of density, before the crust started to solidify. Then, the solidification should have locked in the vertical differentiation. As the Earth cooled, we could expect pressure ridges to appear in the crust, due to the thermal expansion coefficient. (The solid crust takes on a fixed circumference, but the underlying matter is cooling, so it's shrinking, and the crust will buckle.) But that isn't going to produce the continental "churn" that you describe.
seasmith wrote: This primal crust is then broken up and churned under, during your cataclysmic "continents" building episodes and epochs, when mountains disappear beneath the seas and sea-bottoms are stranded atop mountain ranges.
Clearly this happens, but I want to know why, and I don't find continental churn to be an expectation of thermodynamics. I'd expect one layer of granite all of the way around the globe, 14.9 km deep, with a network of pressure ridges, rather than 30% of the Earth's surface being dry land, ~35 km deep. To get the kind of continental churn that we actually observe, I really think that we'd have to assume that the granites didn't bubble up to the surface until substantial cooling had already occurred, and the basalts were already sporting a high viscosity. But that's the part that I don't get. Analogously, do we see chemical differentiation across the surface of frozen lava lakes, where heavier stuff started to solidify first, and then lighter stuff arrived later, creating blobs of distinctly different material? It might not be a 1:1 analogy to the whole Earth, but my point is that given millions of years for the Earth to cool before the crust formed, all of the bubbling should have already occurred.
So what if we walk up to the edge of a mafic lava lake, and we throw a big granite boulder into the middle of it (analogous to my Cereian granite model)? If the granite doesn't get fully remelted, we might still have lateral chemical differentiation, with a granite iceberg floating in a basaltic sea, all of which gets frozen in with subsequent cooling. Now comes the considerations that you raised — will the granite display igneous-metamorphic properties? If we assume that there won't be any churn within the granite, we won't get such properties. But why would we make that assumption? If we saw a perfectly flat frozen lava lake, with a spherical granite iceberg frozen into it, we'd rightfully assume that the granite had retained its original shape, without any internal churn. But if we see a perfectly flat lava lake with a pancaked inclusion, we know that the pancake went through a lot of metamorphosis, to get from its original shape, which was probably spherical, to its present shape, which is definitely relatively flat.
So I guess that what I'm saying is that the "churn" might have still happened, entirely within the granite, after its arrival.
I have no idea how much more road there is, traveling in this direction — it might be just another blind alley. But it still has to be explored.
tekbasse
Re: We're not Earthlings — we're colonists from Ceres!
CharlesChandler,
J Marvin Herndon proposes that the Solar System formation includes an early explosive event to explain a vast set of findings peculiar to the Sol system (as compared to other systems and what is known of exo-planets). You can read about it in the "Major Developments Related to the Solar System" section of the main page of nuclearplanet.com. He presents a compelling base for early solar system history (after an electric universe z-pinch solar system formation of course), and suggests how naturally formed nuclear reactors aka dynamos (think naturally formed electric batteries ie current producers in EU speak) generate strong magnetic fields in gas giant planets and the Earth. He suggests that the Earth started as a gas giant, but was stripped of much of its atmosphere in the early solar system's post-formation explosion. This could explain the formation of a vast quantity of water, the formation of a lithospheric crust and subsequent formation of oceanic plates during decompression. It's quite fascinating even if it isn't an answer to everything --much fits in the EU paradigm.
cheers and happy hunting,
CharlesChandler
Re: We're not Earthlings — we're colonists from Ceres!
tekbasse wrote: He suggests that the Earth started as a gas giant, but was stripped of much of its atmosphere in the early solar system's post-formation explosion.
I didn't see anything on the "explosive event" on his site, at least just skimming it. But is it possible that debris from the break-up of Ceres, falling into the Sun and causing massive flare-ups, would satisfy his requirements for an energy source?
). For me, science isn't a position — it's a process. So it leads to a constantly shifting position, always foraging for more anomalies, and venturing hypotheses to account for them. Indeed, scientific exploration is error-prone, if you want to look at it like that. You don't know what you're going to find until you explore it. The bad news is that it's labor intensive, and sometimes you might feel like you're spending more time exploring blind alleys than making progress. But in order to fully understand the entire problem domain, all of it needs to be explored — blind alleys and all. The good news is that you get a better understanding, and it's exhilarating when the picture comes into clearer focus.
seasmith wrote:Right. What I want to know is: why aren't the granites primary igneous formations? Let's go back to the fundamental dilemma that I'm trying to get my mind around. If the Earth, when it first formed, was entirely molten, and if it cooled slowly, there should have been plenty of time for near-perfect chemical stratification on the basis of density, before the crust started to solidify. Then, the solidification should have locked in the vertical differentiation. As the Earth cooled, we could expect pressure ridges to appear in the crust, due to the thermal expansion coefficient. (The solid crust takes on a fixed circumference, but the underlying matter is cooling, so it's shrinking, and the crust will buckle.) But that isn't going to produce the continental "churn" that you describe.
