A remnant of a protoplanet may be hiding inside Earth

rod

Oct 22, 2019
2,635
1,091
5,560
I found this interesting in the report here. "To supply the moon with so much light hydrogen, Theia must have been very large, nearly the size of Earth at the time of impact, and very dry, since water formed in interstellar space would contain a heavy form of hydrogen called deuterium, which Theia lacked, the authors concluded. Meanwhile, the interior of the hulking protoplanet would have held a dense, iron-rich mantle, Science reported."

Various models of Theia are published and this is a very good size here :) Here is another report out on the topic. New theory suggests large blobs of material in Earth's mantle are remnants of protoplanet Theia, https://phys.org/news/2021-03-theory-large-blobs-material-earth.html

Here is the link cited in the Phys.org report to the two page PDF report. https://www.hou.usra.edu/meetings/lpsc2021/pdf/1980.pdf, GIANT IMPACT ORIGIN FOR THE LARGE LOW SHEAR VELOCITY PROVINCES. "Introduction: The Moon is widely recognized as formed from the “Giant Impact”: when at least a Mars sized planetary embryo Theia collided with the proto-Earth during the last stage of terrestrial planet formation [1]–[4]. Such a model is well aligned with some key physical aspects of Earth-Moon system, including anomalous high angular momentum of Earth-Moon system, small iron core of the Moon and its high mass ratio compared to the Earth [2], [4]. However, one of the most critical issues related to this scenario is that no evidence has been found for the existence of the hypothesized planetary embryo Theia. This is in part because of its widely debated size ranging from 0.1~0.45 Earth mass (M⊕)..."

The size and composition of Theia has different models. A key comment I see in the Phys.org report "In their model, Theia winds up mostly destroyed, with pieces flung into space to create the moon, and much of its mantle breaking into fragments, which make it all the way into Earth's mantle. Over billions of years, the fragments merge, forming the LLSVPs."

The fragments of Theia that merge to form the LLSVPs (large blobs) is billions of years later after the giant impact. The giant impact model for the origin of the Moon is looking for physical evidence of a *piece* of Theia left behind after the giant impact event with the proto-earth and formation of the proto-moon, proto-earth is referenced 3x in the two page report. There are a variety of models for the proto-earth size and mass too before the giant impact with Theia.
 
  • Like
Reactions: Catastrophe

rod

Oct 22, 2019
2,635
1,091
5,560
babs, I did a search on space.com site using *theia* and found many reports like, https://www.space.com/earth-moon-different-compositions-surprise.html

The proto-earth forms in the solar nebula model in the accretion disk starting out as a tiny dust grain(s). Later, another proto-planet object named Theia shows up, collides with the proto-earth, then a ring of dust forms that accretes into the proto-moon, and the two objects apparently continue to grow in size and mass for a period after that. Conditions are all very different in the giant impact model for the origin of the Moon than what we see in the sky today including Earth's mass and the Moon's mass today and distance between the Earth and Moon as well as Earth's length of day. Various articles on space.com if you search using Theia will show up for reading.
 

rod

Oct 22, 2019
2,635
1,091
5,560
FYI. I went back to mid-1950s studies and found that the Earth was not considered a proto-earth 4.56 billion years ago. Age of meteorites and the earth, https://ui.adsabs.harvard.edu/abs/1956GeCoA..10..230P/abstract, October 1956, Clair Patterson. Interesting how the model has developed and changed since those earlier days.

"Within experimental error, meteorites have one age as determined by three independent radiometric methods. The most accurate method (Pb 207/Pb 206 gives an age of 4.55 ± 0.07 × 10^9 yr. Using certain assumptions which are apparently justified, one can define the isotopic evolution of lead for any meteoritic body. It is found that earth lead meets the requirements of this definition. It is therefore believed that the age for the earth is the same as for meteorites. This is the time since the earth attained its present mass."

During those days there was no giant impact model in use for the origin of the Moon like today and over the last several decades. Much more catastrophism in the early solar system seems to be used now to explain origins :)
 
Feb 23, 2020
109
20
585
I half-recollect something,
and put the question to the table
-do you think the collision with Theia is in any way related to the massive thermal energy within Earth's core?
could the effect of this collision still power Earth internally?

--the 1950s science is still conjunctive with current estimates for Earth's age
 
  • Like
Reactions: rod

rod

Oct 22, 2019
2,635
1,091
5,560
Particle Article, interesting questions in post #8 concerning Earth's core. I do not know :) A proto-earth before giant impact and proto-earth after impact are in the computer models, what happens in the Earth's core I have not read about or at least seen widely disclosed until this recent report and large blobs related to a piece of Theia. What I do find interesting, when I dig into earlier reports on the Moon like from a 1963 Wonder Book :) The Earth has a 5 hour day, the Moon has a 24 hour orbital period and the Moon is about 20x closer to Earth but no giant impact. These parameters are not much different than various giant impact model reports I read calculating changes in Earth's mass, Earth's rotation rate, the Moon, thus changes to the Earth-Moon system after giant impact.

When I look at these Earth-Moon system changes, here is my observation. This suggest the Moon could be 3 earth radii or so distance from earth in the 1963 model in the beginning. I used present earth and moon mass to calculate and orbital eccentricity = 0. The Moon's angular size somewhat larger than 10-degrees in the sky compared to about 0.5-degree today.

How can I show the Moon was some 20x closer to Earth originally, and had an angular size in the sky some 10-degrees or more? :) The large blobs report may be more promising here than what I am looking for using my telescopes :)
 
Last edited:
Feb 23, 2020
109
20
585
I suggest u could try to quote your reference?heh
-if that is your inclination to how you intuit it,
I would not refute it, although to concur, I am willing to read ur post a few more times heh
I think it's really hard to be sure how our local bodies were placed

-personally I don't actually know the comparitive radii of Earth to Moon distance now

{edit} it is around 60 of Earth's radii to the Moon

I'm just becoming a space afficiando
--well you can't beat it for company 8D

that's interesting Rod mate
 
Last edited:

rod

Oct 22, 2019
2,635
1,091
5,560
I suggest u could try to quote your reference?heh
-if that is your inclination to how you intuit it,
I would not mind, although to concur, I am willing to read ur post a few more times heh
I think it's really hard to be sure how our local bodies were placed
The 1963 book is Sutton, F., Wolf, D. D. authors, The Moon, The How and Why Wonder Book of the Moon, by Wonder Books, Inc. Much is discussed on pages 4-6 on the origin of the Moon theories and pages 14-15 covering the changes in the Earth-Moon system over time.

https://phys.org/news/2021-03-track-spacecraft-earth.html, this report shows early Earth had a 6 hour day or perhaps 8 hour day.
 
  • Like
Reactions: Particle Article
Jul 17, 2020
8
3
15
Sometimes things do get a little out of hand, proto-Earth for example leads one to think that there was something different . In truth, Earth is probably an agglomeration of bits and pieces of debris . At any point along its time line you could call it 'proto-Earth, ' and for all we know what we stand upon today may be another proto-Earth
 
it’s interesting to compare this two-blob model with the two-moon model that argues the impact produced two orbiting debris blobs that later united to form our Moon. :). Perhaps Theia separated near or during impact, which was a much lengthier event than one would expect.
 
  • Like
Reactions: rod

rod

Oct 22, 2019
2,635
1,091
5,560
Here is more from the source I cited in post #11. See pages 4-6 of this 1963 book. "One theory is the Moon was a piece of the Earth thrown out when the "semi-liquid form, its rapid revolution around the sun caused it to assume the shape of a lop-sided dumbbell. The smaller part of the dumbbell broke away and became the moon. A corollary to this theory is that after the earth had begun to solidify, a huge chunk of it was torn loose from what is now the basin of the Pacific Ocean…Other scientists believe that the moon is actually older than the earth. They contend that the moon is a relic of an earlier stage of the solar system than that during which the earth was formed. Toward the end of the earth's formation, it caught the moon in the force of its gravity and captured the moon as a permanent satellite."

Here is some more info on the Moon from 1963 :) On page 6, "Most scientists today, however, accept the theory that the moon and the earth were formed at the same time and of the same basic materials. They think that several billion years ago our solar system was nothing but a cloud of cold dust particles whirling aimlessly through the nothingness of deep space. Then, in response to the laws of gravity, these particles gradually came together to form a huge, spinning disk. As it spun, the disk separated into rings. The nucleus of the disk became the sun, and the particles in the outer rings became the planets. When both earth and moon had been formed, the moon, being much the smaller, was captured by the stronger gravity of the earth and so began to orbit about it just as the earth orbits the sun."

My observation. Interesting, this 1963 book on pages 14-15 discusses the slowing of earth's rotation and lengthening of the day and the moon slowly expanding its orbit and moving away from earth due to tides. "…as a result our days are becoming longer, at the rate of about 1/1,000th of a second a century…These changes due to tidal friction have been going on for billions of years, just as they are still going on. The earth-day, which was originally less than five hours, has lengthened to 24 hours. And the moon-month, which was originally the same length as the earth-day, has increased to about four weeks."

I find it interesting to review past origin theories on the Moon and compare with the present view, giant impact with Theia. In terms of the length of day billions of years ago and the lunar month (about 24 hours in the 1963 book), not much has changed with the giant impact using Theia. Demonstrating Theia is a real body that hit the proto-earth (other than in computer models) is a work in progress it seems. If I ask about the Moon so close to Earth billions of years ago and what evidence there is, that is another story :)
 
My observation. Interesting, this 1963 book on pages 14-15 discusses the slowing of earth's rotation and lengthening of the day and the moon slowly expanding its orbit and moving away from earth due to tides. "…as a result our days are becoming longer, at the rate of about 1/1,000th of a second a century…These changes due to tidal friction have been going on for billions of years, just as they are still going on. The earth-day, which was originally less than five hours, has lengthened to 24 hours. And the moon-month, which was originally the same length as the earth-day, has increased to about four weeks."
Yes, that comes from the grandfather of all Moon models that count as being scientific. This was from George Darwin (son of Charles). The outward increase in distance means that, if we rewind the clock, the Moon would have started with a ~5-hour rotating Earth, per his model.

Although that the math is correct, that tight of an orbit for the early Moon would have been to unstable to survive. But Darwin was important in establishing the tidal effect affecting the lunar orbit, and Earth's rotation rate.

I find it interesting to review past origin theories on the Moon and compare with the present view, giant impact with Theia. In terms of the length of day billions of years ago and the lunar month (about 24 hours in the 1963 book), not much has changed with the giant impact using Theia. Demonstrating Theia is a real body that hit the proto-earth (other than in computer models) is a work in progress it seems. If I ask about the Moon so close to Earth billions of years ago and what evidence there is, that is another story :)
Of course it will be challenging to go back billions of years and produce hard evidence of what really happened. The early models didn't have the challenge of explaining things like isotope ratios. :)

The Theia impact model received scorn and laughter, apparently, when first introduced. But the evidence seems to favor an impact model by far than any other model.

The Two-Moon model explains some odd discrepancies between the farside and nearside of the Moon. The thicker crust and thinner KREEP on the farside may favor a large "splat" model rather than large impacts. A second blob at a Lunar L4 or L5 would not have the impact results seen normally but would have had more of a "splat", per the book, explaining a lot of what we observe, apparently.
 
  • Like
Reactions: rod

rod

Oct 22, 2019
2,635
1,091
5,560
Helio's post #16 favors isotope ratios and a Two Moon model. Other giant impact model reports sometimes provide more details. Here is an example.

Supercomputer simulations could unlock mystery of Moon's formation, https://www.sciencedaily.com/releases/2020/12/201204110254.htm, December 2020.

"Summary: Astronomers have taken a step towards understanding how the Moon might have formed out of a giant collision between the early Earth and another massive object 4.5 billion years ago." "Scientists led by Durham University, UK, ran supercomputer simulations on the DiRAC High-Performance Computing facility to send a Mars-sized planet -- called Theia -- crashing into the early Earth. Their simulations produced an orbiting body that could potentially evolve into a Moon-like object. While the researchers are careful to say that this is not definitive proof of the Moon's origin, they add that it could be a promising stage in understanding how our nearest neighbour might have formed...Researchers ran simulations to track material from the early Earth and Theia for four days after their collision, then ran other simulations after spinning Theia like a pool ball. The simulated collision with the early Earth produced different results depending upon the size and direction of Theia's initial spin. "

My observation, more transparency is needed, this report shows some more details clearly, other than assumptions about initial isotope ratios for example. Different sizes and spin rates can alter much in the simulations and the outcomes of giant impacts. This model reported in December 2020, features a proto-earth with a 3 hour day after the giant impact so the 5 hour day from 1963 is still in the ball park and no giant impact was used :) Here is the link from the December 2020 report. The effect of pre-impact spin on the Moon-forming collision, https://academic.oup.com/mnras/article/500/3/2861/6007797, "ABSTRACT We simulate the hypothesized collision between the proto-Earth and a Mars-sized impactor that created the Moon."

On page 4, Table 1 is provided showing a proto-earth with 3 hour day or so. The effects of a spinning Theia are presented and on page 5, here are some stats provided, "We consider an impact between a target proto-Earth of mass 0.887 M⊕ and an impactor, Theia, of mass 0.133 M⊕. Both are differentiated into an iron core and rocky mantle, constituting 30 per cent and 70 per cent of the total mass, respectively, modelled using the Tillotson (1962) iron and granite equations of state."

My observation. As computer models become more detailed in the giant impact simulations, more and more special initial conditions arise that seem needed to make everything work :)
 
  • Like
Reactions: Helio
Helio's post #16 favors isotope ratios and a Two Moon model. Other giant impact model reports sometimes provide more details. Here is an example.

Supercomputer simulations could unlock mystery of Moon's formation, https://www.sciencedaily.com/releases/2020/12/201204110254.htm, December 2020.
Nice little article but many other simulations have been done as well.

I am intrigued with the two-blob model since the L4 and L5 points were so strong for any proto-moon. As migration moved outward over time, these points became less stable.

Since the impact would certainly not have spit a nice round ball outward, but an accretion disk, perhaps more simulations will take L4 an L5 more seriously into the 2 or 3 blob model. I'm not sure what difference it may make, but it's funny how serendipity can come around.

My observation, more transparency is needed, this report shows some more details clearly, other than assumptions about initial isotope ratios for example. Different sizes and spin rates can alter much in the simulations and the outcomes of giant impacts. This model reported in December 2020, features a proto-earth with a 3 hour day after the giant impact so the 5 hour day from 1963 is still in the ball park and no giant impact was used :)
...
My observation. As computer models become more detailed in the giant impact simulations, more and more special initial conditions arise that seem needed to make everything work :)
Yes, and this is probably always the case. All physics, I expect, begin with taking a stab at initial conditions. If the results are promising, begin tweaking those initial conditions and the modeling itself.

The models indicate, apparently, that any angle > 60 degrees becomes a hit and run. About 1/2 of impacts are > 60 deg. Mercury, as some suggest, may have impacted up to three others. So, Mercury could be a lucky ( 3 heads) survivor, and others not as lucky, including Theia.
 
  • Like
Reactions: rod

rod

Oct 22, 2019
2,635
1,091
5,560
FYI, here is another model from 2018 :) Moonfalls: collisions between the Earth and its past moons, https://ui.adsabs.harvard.edu/abs/2018MNRAS.479.1711M/abstract, September 2018. "During the last stages of the terrestrial planet formation, planets grow mainly through giant impacts with large planetary embryos. The Earth's Moon was suggested to form through one of these impacts. However, since the proto-Earth has experienced many giant impacts, several moons (and also the final Moon) are naturally expected to form through/as-part-of a sequence of multiple (including smaller scale) impacts. Each impact potentially forms a sub-Lunar mass moonlet that interacts gravitationally with the proto-Earth and possibly with previously formed moonlets. Such interactions result in either moonlet-moonlet mergers, moonlet ejections or infall of moonlets on the Earth. The latter possibility, leading to low-velocity moonlet-Earth collisions is explored here for the first time."

I note in the arXiv paper link, https://arxiv.org/pdf/1805.00019.pdf, the proto-earth has a rotation period less than 1.5 hours for the length of day (as well as different angles of impact in the report).

"The last free parameter is the proto-Earth’s pre-collision rotation rate... We consider ω = 0, 0.1, 0.25 and 0.5
ωmax, where ωmax is the planetary rotation rate at breakup, and corresponds to a 1.475 h rotation period. This choice is taken to be compatible with Rufu et al. (2017). For ω > 0, we consider both prograde and retrograde impacts. We note that while ω = 0 is inconsistent with the assumption of moonlet tidal migration (and subsequent gravitational perturbations leading to infall), we still consider it as a viable (though unlikely) possibility, since an additional accretion event can theoretically terminate the proto-Earth’s rotation during migration and prior to infall..."

My observation. Initial proto-earth mass and rotation period is important, also Theia mass and spin rate, velocity and impact angle as well as where Theia first formed in the solar system, and later, hit the proto-earth. Thus, how long was Theia a proto-planet in orbit around the Sun before hitting the proto-earth? If for example Theia had a stable orbit around the Sun for millions or even hundreds of millions of revolutions, we should still see Theia in the solar system today (perhaps).

Verifying that the proto-earth had an initial length of day some 1.5 hours or 3 hours seems difficult (e.g. geologic evidence for this rotation period). Computer simulations can be wonderful tools and calculate a variety of variables.

As Helio says in post #18, "Yes, and this is probably always the case. All physics, I expect, begin with taking a stab at initial conditions. If the results are promising, begin tweaking those initial conditions and the modeling itself."

My observation. Some initial conditions like the proto-earth rotation rate before Theia impact used in the computer simulations, verification seems difficult to show the early Earth (proto-earth) ever had such a short length of day or a Moon with a very short lunar month, 24 hour period or less apart from the inputs used in the computer simulations.
 
I note in the arXiv paper link, https://arxiv.org/pdf/1805.00019.pdf, the proto-earth has a rotation period less than 1.5 hours for the length of day (as well as different angles of impact in the report).
I think this rate is fast enough to fling out debris from Earth with no impact.

That seems really odd. That equatorial speed is about 17,000 mph! Volcanoes might be extremely active as magma is flung outward towards the surface. Their plumes could easily form quite a disk, no doubt.

That may work fine on a computer simulation but as Einstein told Lemaitre, "your math is fine but your physics is abominable!". [Ok, Einstein was wrong... but right most all other times. :)]


My observation. Initial proto-earth mass and rotation period is important, also Theia mass and spin rate, velocity and impact angle as well as where Theia first formed in the solar system, and later, hit the proto-earth.
Yes, those are important, and more parameters as well. It's been said for this modeling that it is surprising how hard it is to do simulations on "dirt". :)

Thus, how long was Theia a proto-planet in orbit around the Sun before hitting the proto-earth? If for example Theia had a stable orbit around the Sun for millions or even hundreds of millions of revolutions, we should still see Theia in the solar system today (perhaps).
Yeah. But there is other evidence that our young solar system was behaving like a pin-ball machine. Jupiter and Saturn moved in and out, wreaking havoc from these two, not to mention other migrations.

My observation. Some initial conditions like the proto-earth rotation rate before Theia impact used in the computer simulations, verification seems difficult to show the early Earth (proto-earth) ever had such a short length of day or a Moon with a very short lunar month, 24 hour period or less apart from the inputs used in the computer simulations.
The very fast post-impact rotation rate would be needed to account for migration of the likely proto-Moon's close orbital distance after we rewind the clock from now till then. The high rotation rate would have enough tidal effects, IMO, to help begin that migration, thus minimizing the likelihood of instability bringing it crashing back down onto Earth. I'm not qualified, however, to address this complicated behavior of tidal stresses and a multitude of blob-like bodies in odd orbits due to an impact.
 
  • Like
Reactions: rod

rod

Oct 22, 2019
2,635
1,091
5,560
Helio, et al. The rapid rotation periods used is common. Other reports show the proto-earth with a 2-3 hour day. The 17,000 mph spin rate depends upon mass, density, and radius that varies in the proto-earth size and range used in the simulations. https://ui.adsabs.harvard.edu/abs/2016CeMDA.126...89W/abstract, shows the earth with 2 hour length of day.

http://phys.org/news/2016-10-theory-moon.html, this report shows the 2 hour length of day.

https://ui.adsabs.harvard.edu/abs/2018SSRv..214..101N/abstract shows a 3 hour length of day. It does say clearly in the abstract "...Pure pebble accretion cannot explain the mixing observed in the asteroid belt, the fast proto-Earth spin rate, or the tilt of Uranus. No current observation requires pebble accretion to have operated in the inner solar system, but the thermal and compositional consequences of pebble accretion have yet to be explored in detail."

There are plenty of initial conditions being used now to explore in detail :)
 

ASK THE COMMUNITY

Latest posts