Giant meteorite strikes in Earth's distant history may have helped form continents

Catastrophe

"There never was a good war, or a bad peace."
Massive Asteroid Impacts Triggered Early Plate Tectonics, Study Suggests. When and how the Earth evolved from a molten mass into a rocky planetary body continually resurfaced by plate tectonics remain some of the biggest questions in earth sciences.27 Nov 2019
Massive Asteroid Impacts Triggered Early Plate Tectonics ...

. . . . . . . . . and Plate Tectonics is the most important theory in geology

Ergo Is geology founded on meteorite impacts? ;)


Cat :)
 
From the reference paper link, Giant impacts and the origin and evolution of continents, https://www.nature.com/articles/s41586-022-04956-y.epdf?sharing_token=pbAyVDmdzwjiBOpAxZ-xANRgN0jAjWel9jnR3ZoTv0Ot6tquneuQ7dae5T35kqK6lm_48os-ypyZBU10vXEZDnwr8OS5DQIxCDlpliCHw67YcNFTjkp7yt-FLpDm6OsDQCigozX6rECLe0owPh6G-dOgOyaPmICdCXIFWPtMeQtz5TnKmsjlTqoP4oLds6YGvtEe2sjLBfWyoGL61YHQapSHAoDISJYH4hMB_qROsZ8qf6v7ZVj682UeW171OGDqaJ-Dy2sRwT_E7YX94LcpJw==&tracking_referrer=www.space.com

"Earth is the only planet known to have continents, although how they formed and evolved is unclear. Here using the oxygen isotope compositions of dated magmatic zircon, we show that the Pilbara Craton in Western Australia, Earth’s best-preserved Archaean (4.0–2.5 billion years ago (Ga)) continental remnant, was built in three stages. Stage 1 zircons (3.6–3.4 Ga) form two age clusters with one-third recording submantle δ18O, indicating crystallization from evolved magmas derived from hydrothermally altered basaltic crust like that in modern-day Iceland1,2. Shallow melting is consistent with giant impacts that typified the first billion years of Earth history3–5. Giant impacts provide a mechanism for fracturing the crust and establishing prolonged hydrothermal alteration by interaction with the globally extensive ocean6–8. A giant impact at around 3.6 Ga, coeval with the oldest low-δ18O zircon, would have triggered massive mantle melting to produce a thick mafic– ultramafic nucleus9,10. A second low-δ18O zircon cluster at around 3.4 Ga is contemporaneous with spherule beds that provide the oldest material evidence for giant impacts on Earth11. Stage 2 (3.4–3.0 Ga) zircons mostly have mantle-like δ18O and crystallized from parental magmas formed near the base of the evolving continental nucleus12. Stage 3 (<3.0 Ga) zircons have above-mantle δ18O, indicating efficient recycling of supracrustal rocks. That the oldest felsic rocks formed at 3.9–3.5 Ga (ref. 13), towards the end of the so-called late heavy bombardment4, is not a coincidence."

My note. Apparently, we have various giant impacts taking place on Earth some 4 to 3.5 Gyr ago. Other reports indicate during the Precambrian some 3.5 to 2.5 Gyr ago, 10x more impacts took place too.

City-d asteroids smacked ancient Earth 10 times more often than thought, https://forums.space.com/threads/city-d-asteroids-smacked-ancient-earth-10-times-more-often-than-thought.39949/, "...This violent period, which took place between 2.5 and 3.5 billion years ago, saw the planet in upheaval on a regular basis, with the chemistry near its surface undergoing dramatic changes that can be traced in the rocks in the ground even today, the researchers said."

Looks like much catastrophism operated on Earth from 4 Gyr to 2.5 Gyr ago (setting aside the giant impact model for the origin of the Moon), during the evolution of life from non-living matter (abiogenesis) on Earth. Somehow Precambrian life continued to evolve, and avoided mass extinctions, or perhaps more abiogenesis events needed now because of all the bombardments claimed during this early period. Life would need to arise again, again, and again but who is counting :)
 

Catastrophe

"There never was a good war, or a bad peace."
Rod, so am I right?

Massive Asteroid Impacts Triggered Early Plate Tectonics, Study Suggests. When and how the Earth evolved from a molten mass into a rocky planetary body continually resurfaced by plate tectonics remain some of the biggest questions in earth sciences.27 Nov 2019
Massive Asteroid Impacts Triggered Early Plate Tectonics ...

. . . . . . . . . and Plate Tectonics is the most important theory in geology

Ergo Is geology founded on meteorite impacts? ;)


Cat :)
 
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I am wondering why those asteroids were "picking on" just our Earth?

If Earth was getting bombarded with asteroids in that period, why were other planets in our solar system not getting bombarded in the same manner?

And, if they were, why didn't they end up with continents and plate tectonic movements?

Or is it just that we don't know whether other planets have continents and moving plates?
 
Rod, so am I right?

Massive Asteroid Impacts Triggered Early Plate Tectonics, Study Suggests. When and how the Earth evolved from a molten mass into a rocky planetary body continually resurfaced by plate tectonics remain some of the biggest questions in earth sciences.27 Nov 2019
Massive Asteroid Impacts Triggered Early Plate Tectonics ...

. . . . . . . . . and Plate Tectonics is the most important theory in geology

Ergo Is geology founded on meteorite impacts? ;)


Cat :)
Cat, given various reports of giant impacts and different impacts taking place during the Precambrian, 4.5 Gyr to 2.5 Gyr period on early Earth in the model, it does seem to be a good geology major and science folk, you must include *much meteorite study* too, including all the destructive and catastrophic consequences for life said to be evolving on the planet during this time :)
 
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Cat et al. I call attention to another impact related report out now saying Earth water supply came from the asteroids.


"In a quest to shed light on the origins of life and the formation of the universe, researchers are scrutinising material brought back to earth in 2020 from the asteroid Ryugu. The 5.4 grams (0.2 ounces) of rocks and dust were gathered by a Japanese space probe, called Hayabusa-2, that landed on the celestial body and fired an "impactor" into its surface. Studies on the material are beginning to be published, and in June, one group of researchers said they had found organic material which showed that some of the building blocks of life on Earth, amino acids, may have been formed in space."

"In a new paper published in the journal Nature Astronomy, scientists said the Ryugu samples could give clues to the mystery of how oceans appeared on Earth billions of years ago. "Volatile and organic-rich C-type asteroids may have been one of the main sources of Earth's water," said the study by scientists from Japan and other countries, published Monday. "The delivery of volatiles (that is, organics and water) to the Earth is still a subject of notable debate," it said."

Paper, A pristine record of outer Solar System materials from asteroid Ryugu’s returned sample, https://www.nature.com/articles/s41550-022-01745-5

Apparently, we can thank our lucky asteroids from the outer region of the protoplanetary disc that created Earth's abundant water supply :) More bombardments and impacts are needed in geology :)
 
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Catastrophe

"There never was a good war, or a bad peace."
Unc, we would need to know whether the crust or lower structures were brittle, and capable
I am wondering why those asteroids were "picking on" just our Earth?
If Earth was getting bombarded with asteroids in that period, why were other planets in our solar system not getting bombarded in the same manner?

And, if they were, why didn't they end up with continents and plate tectonic movements?

Or is it just that we don't know whether other planets have continents and moving plates?
I am wondering why those asteroids were "picking on" just our Earth?
They were not. Most planets show signs of impact. Mercury has a proportionately larger core because much of its mantle was lost to the Sun after a major impact, Venus rotates backwards compared to the other planets, Earth suffered the Theia impact, and so on. Uranus rotates on its side. . . . . . . Neptune may have been affected more recently Cometary impact on Neptune | Max-Planck-Gesellschaft (mpg.de)
If Earth was getting bombarded with asteroids in that period, why were other planets in our solar system not getting bombarded in the same manner?
They were.

And, if they were, why didn't they end up with continents and plate tectonic movements?
Because their surfaces were different - remember the comet we saw hitting Jupiter in 1994. Jupiter has no solid surface so the pieces were just absorbed.

Or is it just that we don't know whether other planets have continents and moving plates?
We do know. See Unknown Earth: Why does Earth have plate tectonics? | New Scientist to find the conditions necessary for plates to form.

So asteroids were not picking on "just Earth". Your premise is incorrect. Just Earth had the right conditions for plates to form. And the meteoroids also had to be the right size.

Cat :)
 
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Catastrophe

"There never was a good war, or a bad peace."
What are the differences in tectonic activity between Venus and the Earth? Venus does have tectonic activity: faults, folds, volcanoes, mountains, and rift valleys. However, it does not have global tectonics as there is on Earth—plate tectonics. This is thought to be due to the fact that Venus is hot and dry.

FAQ - Venus | Planetary Science Institute


. . . . . . . . . and does not have subduction.

Cat :)
 
Cat, Interesting, but I note that Venus does have continents, which are the subject of this article, particularly their creation on Earth by large meteor impacts early in Earth's history.

So, it seems that Venus may also have had continents formed by large meteor impacts early in its history, too, since it has continents and was most probably hit by large meteors (or small planets) during its early formation.

What seems to be different between Earth and Venus is that the continents slide around the surface on Earth, but not on Venus. And, that is attributed to the lack of water on Venus, compared to Earth.

So, the thing that seems to make Earth unique is really the water on its surface.
 
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Just my simple summary here. Using the giant impact and impact scenarios used for the period 4.5 to 2.5 Gyr during Precambrian, Earth received a moon created via giant impact. Earth received continents, plate tectonics, and water via various impacts. Earth during this catastrophic bombardment era somehow managed to create life from non-living matter via abiogenesis and that life flourished during episodes of intense bombardment from 4.5 to 2.5 Gyr ago. Both geology and abiogenesis workers must include more meteorite impact studies into their work :)
 
Warning: THREAD DRIFT!!!

As we contemplate the comparison of Earth and Venus, has anybody seriously looked at the possibility that Venus is what "collided" with Earth in the very early solar system? It seems to me that a "glancing" type collision, maybe with minimal or no surface contact, might have slowed the rotation of Venus while pulling out the material (from both planets) that formed our moon. The moon seems "chunky", with very non-uniform mass distributions (that cause weird orbit geometries), so it probably coalesced from more than fine matter left in orbit around Earth following the collision.

I know that Velikovsky proposed something similar in the past, but he is not noted for realistic analysis - so has anybody tried to realistically assess the concept?
 

Catastrophe

"There never was a good war, or a bad peace."
We know that Earth was struck by Theia.

Scientists have long agreed that the Moon formed when a protoplanet, called Theia, struck Earth in its infancy some 4.5 billion years ago. Now, a team of scientists has a provocative new proposal: Theia's remains can be found in two continent-size layers of rock buried deep in Earth's mantle.
Wiki as also:

Remains of impact that created the Moon may lie deep within ...


Cat :)
 
Actually, we do not know that Earth was struck by a planet nearly as big as Earth. The link even states that. It is a theory, or maybe not even a theory, yet. It is just a concept that is the darling of the popular media at this time, and is portrayed as "truth" there.

The link you provided says that "Theia" may not have been as massive as some suggest, and that it may only be one of many things that have created non-homogeneous lumps in Earth's crust/mantel. The link recognizes the uncertainty in the data being used to support the concept.

So, my position is that it is far too early to decide that we know one particular history for Earth's formation is "true" and nothing else should even be considered.
 

Catastrophe

"There never was a good war, or a bad peace."
If Earth and Venus struck each other, being so similar in size, they would not both still be around. There are consequences when objects of different sizes impact, and I must go off and find them for you.

Cat :)
 
Cat, it is going to depend on how much of a glancing type of "strike" it is. Quoting from your previous link:

" The theory invoked an impactor the size of Mars or—in recent variants—much smaller. But recent work from Yuan's co-author, ASU Tempe astrophysicist Steven Desch, suggests Theia was nearly as big as Earth."

And

"Less massive LLSVPs could complicate the idea that Theia was nearly the size of a proto-Earth, says Jennifer Jenkins, a seismologist at Durham University. Yuan's picture, she adds, "is not inconsistent with what we know, but I'm not entirely convinced."

So, even the idea that it was an impact that merged the impactor(s) with the Earth has not yet really settled down to a firm scenario.

What I am asking is whether scenarios where the major "impactor" that created the moon did not end up merging with Earth. Don't get hung-up on the word "impactor", since tidal forces of a tight passage would probably have disrupted the surfaces of both bodies, and even "touching" does not necessarily ensure merging, depending on the relative velocities, sizes of interacting bodies, etc.
 

Catastrophe

"There never was a good war, or a bad peace."
I do not believe that Venus came anywhere near Earth or vice versa. However, if it did you have anything from head on to a glancing blow. Not to mention a very near miss, or a wide near passage.

If the two came close enough to effect a glancing blow, what about the Roche limit? Is that going to cause any problems. Would both planets have survived? Were both destroyed and reconstituted? I frankly am not concerned. Interested, OK. Concerned? No.

I know that there was a lot of moving around in the early Solar System. It is probably not impossible that Earth and Venus may have come near enough, even for a glancing blow. I do not believe that is/was possible, but hey ho, who cares? I don't. Earth and Venus are safely where they are at the moment and are unlikely to move from their present orbits in the near future, and I am 83. I am not worried about that.

Cat :)
 
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Cat in post #19 said, "I know that there was a lot of moving around in the early Solar System."

My observation. Timely comment in view of the report on hot jupiters published in the October 2022 issue of Sky & Telescope magazine. Star Huggers, Sky & Telescope 144(4):28-33, 2022.

An interesting report on hot jupiters in the October issue of Sky & Telescope magazine, Oct-2022. HD 80606 b is an example. The exoplanet orbits its host star from 0.03 au out to 0.89 au (quite a bit of moving around). Attempting to explain the population of hot jupiters documented today in astronomy is difficult. 3 models are used. 1. in situ formation 2. disc migration (outer region to inner region) 3. tidal migration (planet-planet scattering interactions).

The article on page 30 shows most hot jupiters orbit their parent stars about 0.10 au or closer compared to Mercury, Venus, and Earth in our solar system. So, our solar system configuration is very different than the hot jupiter population documented today, a population of exoplanets that could rearrange smaller, rocky planets in those systems and make them very nasty places to live on.

As the report wrap ups, "This continued work is important because giant planets set the landscape for small planets. We think the formation and habitability of the solar system's rocky planets were affected by our giants' early history. Now that we know giant planets' histories vary dramatically from system to system, we can expect a wide range of consequences for rocky worlds. As the gas giants jostle each other, they can kick comets toward the star, delivering water to otherwise dry, rocky worlds. In other cases, violent encounters between larger planets disturb the paths of smaller ones, causing collisions and atmospheric loss. Giant planets migrating inward during the gas-disk stage may also bring icy embryos along for the ride, which then grow and merge into watery worlds. Far from being a story solely about giant planets, then, the answer to how these worlds came to be could have implications for small planets as well, including whether life could arise as it did here."

My observation. This model of exoplanet origins depends heavily upon catastrophism during planet formation, time, chance, and random impacts to create our Earth with life on it today as well as the postulated, protoplanetary disc sizes and masses needed in various simulations.

Using models like this for our solar system origin, the proto-earth avoided catastrophic consequences when evolving from the postulated disc. We have a Moon formed via giant impact(s), continents formed from various bombardments, plate tectonics from various impacts, water delivered via impacts, and life emerges and evolves during the period 4.5 to 2.5 Gyr ago in the Precambrian, that now appears to be a very impact active time. Indeed, solar system objects would be moving all around in the early solar system with catastrophic bombardments taking place as the chief means of creating life here on Earth :)
 
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Nov 16, 2019
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Here is my thinking:

The Thea impact that calved off Earth’s Moon left a stump…hottest at its core…and as that settled back as Earth rounded back to a sphere-THAT’S when tectonics started.
 
Nov 19, 2021
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I read somewhere many years ago an explanation I cannot find anymore. It said that the early Earth was a ball of molten rock with chunks of iron, all evenly distributed. The iron chunks came from the broken pieces of earlier planets that had formed iron cores and then got broken up. At some point there was a slight imbalance caused by an excess of iron on one side of Earth. The molten material surged downward with lighter material rising on the opposite side of the Earth. This form of convection is called toroidal convection. In a matter of a few weeks, most of the iron had settled at the core. The surface movement from such convection caused some lighter components to gather at the spot where the iron had dropped down, forming the first continent.
Over time, the farther side of the Earth lost more heat than the side with the continent. Upwelling of hot material tore the continent apart and caused it to gather again on the opposite side of the Earth. This back and forth movement has occured perhaps a dozen times since. We still see it today in the opening of the Atlantic Ocean and closing of the Pacific.
I don't know if this is true but it makes a certain amount of sense.
 
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