Could the Moon be the cooled remains of a planets core?

[Jack23454]

I was reading an article over the weekend that the Moon has evidence of a "final" volcano on it's "far side." I am working on something that suggests the Moon would be too small to have had volcanoes, and this didn't fit with my assumption. I then reasoned that based on size, and based on the different types of cratering from impacts over time, that it would be a fair assumption to consider that the Moon is the now cooled core and is all that remains of a once thriving larger planet perhaps similar to ours. Could the Moon be the yolk of a once cracked egg type planet such as ours. Could we have had a twin?

As the molten core took hits over time as it cooled, and finally perhaps one big hit causing a final volcano to erupt before final cooling of the entire mass. Has this possibility been considered? Is it realistic to assume such a scenario.

Of course this assumption would suggest that a cataclysmic event occurred that caused the tectonic plates and all mass between the core and those plates to be thrown into space, only leaving the now cooled once molten core. What happened to the rest of the planet if this occurred?

This is my second post on Physics Forums so I hope I am staying within the guidelines.

 

[Ryan_m_b]

You posted this question elsewhere and I replied, the Moon is not the core of a planet but the result of a giant impact with Earth long ago in its past http://en.wikipedia.org/wiki/Giant_impact_hypothesis

 

[Jack23454]

You posted this question elsewhere and I replied, the Moon is not the core of a planet but the result of a giant impact with Earth long ago in its past http://en.wikipedia.org/wiki/Giant_impact_hypothesis

Thanks ryan_m_b I did post on the "ask a stupid question ..." forum on Saturday I believe it was. I only had one reply in my email but not yours.
Anyway, I read that hypthothesis you referenced in wikipedia. It does mention that there are some unresolved concerns with that particular hypothesis. If that hypotheses is not accurate, could my assumption be considered valid? To add to that thought, could the Earth have had a twin and if so, how would that twin planet lose all it's mass except for the core. Again I'm suggesting that the Moon is a cooled core of a planet that could well have been similar in size to ours. Is the Moon about the right volume compared to what we assume the Earth's core to be?

 

[Ryan_m_b]

There is no evidence that the Moon is the core of another planet. Firstly where would the rest of the mass go? Considering you are suggesting a planet of comparable mass to Earth ~6e24kg and the mass of the Moon is ~7.35e22kg where did the other ~99% of the mass of this planet go? If we were a double planet system at some point in the past any event that would have removed 99% of the mass of the other planet would have utterly decimated Earth.

You assumption is not valid because there is no evidence for your assumption I'm afraid and a lot of evidence to suggest that the Moon formed out of the debris cloud of a large impact.

 

[FlexGunship]

Further (in support of ryan_m_b):

A core of a planet it traditionally the most dense portion of that body (being that highly dense materials settle closer to the central point of gravitation).

The average density of the Earth (as a whole) is: 5.52 g/cm³
The average density of the Earth's core is: 13 g/cm³

In contrast, the average density of the moon is: 3.35 g/cm³

Your theory would have to take into account how the "cooled core" of a planet could be so radically light given its origins. Even Saturn (the least dense planet in the solar system at 0.7 g/cm³) is likely to have a core of iron and nickel.

Your idea, while possibly interesting, has no supporting evidence, and seems to contradict some routinely observable evidence.

 

[Jack23454]

Further (in support of ryan_m_b):

A core of a planet it traditionally the most dense portion of that body (being that highly dense materials settle closer to the central point of gravitation).

The average density of the Earth (as a whole) is: 5.52 g/cm³
The average density of the Earth's core is: 13 g/cm³

In contrast, the average density of the moon is: 3.35 g/cm³

Your theory would have to take into account how the "cooled core" of a planet could be so radically light given its origins. Even Saturn (the least dense planet in the solar system at 0.7 g/cm³) is likely to have a core of iron and nickel.

Your idea, while possibly interesting, has no supporting evidence, and seems to contradict some routinely observable evidence.

I appreciate your knowledge and the references on the subject.

It was the scientific response mentioned in the article here, "http://www.time.com/time/health/article/0,8599,2085558,00.html that gave rise to my assumption because it appears these scientists seem to be suggesting that questions as to the origin have arisen in the penultimate paragraph of the article.

In regards to your second point about density, I assumed density at the core was because of pressure by P equals m/v and assumed that if a core was exposed it would expand?

I was just reading about Muller's CMB avalanche model here http://www.lbl.gov/Science-Articles/Archive/Phys-earth-core.html and his theories that related to the stripping of the core mantle boundary by an oblique impact vs. a more vertical impact.

I was assuming that since Earth has tectonic plates that a very large impact could more readily dislodge matter because of the plate structure and that the planets would perhaps have been further apart in orbit prior to the impact. I also took a look to see if I could find what the trajectory of the debris field was when the rocket hit the comet in the "Deep Impact" mission to give a clue what path the debris might have taken after impact. It is not easy to find on the NASA Deep Impact Legacy Site that I can see.

I'll leave it there for now as I have other more pressing problems to solve. Thank you for the feedback.

 

[ViewsofMars]

Here is an excerpt (p.2) from the following pdf "Why the Moon is important for Solar System Science" that was submitted to The Inner Planets Panel, NRC Decadal Survey for the Planetary Sciences Division, Science Mission Directorate, NASA:

The Moon is our closest celestial neighbor and represents a nearly complete picture of the processes that have influenced the inner solar system over time, especially the period >3 b.y. ago, which has been obscured/lost on Earth. The Moon also represents the only other planetary body that humans have visited. Investigations carried out on the lunar surface, coupled with returned samples and lunar meteorites, and data from orbital missions, have allowed sophisticated scientific questions to be posed regarding the formation and evolution of the Moon and the inner Solar System. Many of the discoveries from our studies of the Moon have become the paradigms for the evolution of the terrestrial planets. Three fundamental scientific concepts emerged: (1) lunar origin by giant impact, (2) the existence of an early lunar magma ocean, and (3) the potential of an impact cataclysm at 3.9 billion years ago [1,2].

As often occurs with scientific discovery, however, these ideas have raised more questions than they have answered. For example:
• The Giant Impact theory proposes that the Moon formed as a result of a collision between a large protoplanet and the growing Earth [3,4]. Although the idea that the Earth-Moon system owes its existence to a single, random event was initially viewed as radical, it is now believed that such large impacts were commonplace during the end stages of terrestrial planet formation (e.g., [5,6]). Sophisticated numerical models suggest that a giant impact can indeed produce a disk of rocky/vapor material orbiting the Earth. However, we do not yet know whether such a disk can evolve into the Moon observed today, particularly given the existence of significant volatile reservoirs in the lunar mantle.
• The Late Heavy Bombardment (LHB) refers to a period ~4.0-3.8 Ga during which several large lunar basins formed. The nature of the LHB is debated: one view is that the LHB marked the end of a steadily declining bombardment from remnants of planet accretion [7]. Another proposes that the LHB was a short-lived "cataclysm" of dramatically increased impact rates [8], and still another proposes that large basin formation was continuous or episodic throughout the period 4.5-3.8 Ga [9]. We are still unable to observationally distinguish between these three fundamentally different models. The NRC [1] report ranks testing the cataclysm hypothesis and constraining the early lunar impact record as its two top science goals.
• While fundamental questions remain, we believe that over the last decade, there has been a revolution in our understanding of the origin of the Solar System. Theoretical and computational breakthroughs make it possible to realistically model the Moon-forming impact on the proto-Earth and to track the collisional and dynamical evolution of planets and small bodies for billions of years to evaluate the lunar and Solar System bombardment history, and its subsequent differentiation and evolution. In addition, significant improvements in laboratory techniques for dating and analysis of rocks, coupled with improvements in crater counting due to digital image processing, allow us to better assess the compositions and ages of lunar terranes, and to understand their origins and relationships to the deep lunar interior.

With these gains in hand, we now stand on the brink of new fundamental insights into the formation and evolution of the Moon. However, the implications of further lunar exploration go far beyond the Moon as constraints on the lunar origin and evolution can also be used to constrain Solar System evolution. If the Moon is given a high priority by this decadal survey, we will be able to address high priority lunar and broader Solar System science questions, which have significant traceability to planning documents from the 1980’s to the present (e.g., [1,2, 10-18]). The Moon can also be used to develop mission-enabling technologies and protocols for wider Solar System exploration (both robotic and manned). Thus, the Moon holds the promise of being the "Rosetta Stone" for understanding the evolution of the Solar System as a whole.

Please read on . . .
http://lunarscience.arc.nasa.gov/pdf/WhytheMoon.pdf

 

[Ryan_m_b]

I appreciate your knowledge and the references on the subject.

It was the scientific response mentioned in the article here, "http://www.time.com/time/health/article/0,8599,2085558,00.html that gave rise to my assumption because it appears these scientists seem to be suggesting that questions as to the origin have arisen in the penultimate paragraph of the article.

Firstly this is not a scientific article and you would be amazed at how distorted actually scientific discoveries can become in magazines and newspapers. I would advise you to find the original, peer-reviewed research. Secondly I don't see how that article helps your hypothesis, the volcano may or may not point to something we didn't know before but it hardly suggests that there is scope for an Earth sized planet that somehow disappeared.

In regards to your second point about density, I assumed density at the core was because of pressure by P equals m/v and assumed that if a core was exposed it would expand?

The inner core of the Earth is estimated to be 80% iron with the last 20% made up from nickel, lead, uranium and other trace elements. These elements have densities of ~7.8g/cm³, ~8.9g/cm³, ~11.3g/cm³ and 19.1g/cm³ respectively. I imagine that the severe temperature of the core is what gives rise to the density seen there. According to these numbers if the core was to cool it would actually shrink.

I was just reading about Muller's CMB avalanche model here http://www.lbl.gov/Science-Articles/Archive/Phys-earth-core.html and his theories that related to the stripping of the core mantle boundary by an oblique impact vs. a more vertical impact.

Again you are going to have to provide some peer-reviewed research here. This CMB avalanche model still doesn't give any credibility to how 99% of your hypothetical planetary mass disappeared.

I was assuming that since Earth has tectonic plates that a very large impact could more readily dislodge matter because of the plate structure and that the planets would perhaps have been further apart in orbit prior to the impact.

It doesn't matter if the planet has tectonic plates or not you still need a fantastic amount of energy to remove 99% of the mass from a planet. I'm afraid that this planetary core hypothesis has no evidence and contradicts a lot we do know.

 

[ViewsofMars]

Could the Moon be the yolk of a once cracked egg type planet such as ours. Could we have had a twin?

Hi Jack. You have a great imagination. Never heard of the 'cracked egg type planet'. I do think the Earth and the Moon share a common thing:

Brown University
May 26, 2011
Scientists detect Earth-equivalent amount of water in the moon

The moon has much more water than previously thought, a scientific team including Brown University has discovered. First-time measurements of lunar melt inclusions show that some parts of the lunar mantle have as much water as the Earth’s upper mantle. The results may change the prevailing theory about the Moon’s origin as well as shed new light on the origin of water at the lunar poles. Results appear in Science Express [1].

PROVIDENCE, R.I. [Brown University] — There is water inside the moon – so much, in fact, that in some places it rivals the amount of water found within the Earth.

The finding from a scientific team including Brown University comes from the first measurements of water in lunar melt inclusions. Those measurements show that some parts of the lunar mantle have as much water as the Earth’s upper mantle.

Lunar melt inclusions are tiny globules of molten rock trapped within crystals that are found in volcanic glass deposits formed during explosive eruptions. The new finding, published this week in Science Express, shows lunar magma water contents 100 times higher than previous studies have suggested.

The result is the culmination of years of investigation by the team searching for water and other volatiles in volcanic glasses returned by NASA Apollo missions in the late 1960s and early 1970s. In a paper in Nature in 2008, the same team led by Alberto Saal, associate professor of geological sciences at Brown, reported the first evidence for the presence of water and used models to estimate how much water was originally in the magmas before eruption.

“The bottom line,” said Saal, an author on the Science Express paper and the principal investigator on the research grants, “is that in 2008, we said the primitive water content in the lunar magmas should be similar to the water content in lavas coming from the Earth’s depleted upper mantle. Now, we have proven that is indeed the case.”

The new finding got a critical assist from a Brown undergraduate student, Thomas Weinreich, who found the melt inclusions that allowed the team to measure the pre-eruption concentration of water in the magma and to estimate the amount of water in the Moon’s interior. In a classic needle-in-the-haystack effort, Weinreich searched through thousands of grains from the famous high-titanium "orange soil" discovered by astronaut Harrison Schmitt during the Apollo 17 mission before finding ten that included melt inclusions.

“It just looks like a clear sample with some black specks in it,” said Weinreich, the second author on the paper. (Read about Weinreich’s lunar research summer job.)

Compared with meteorites, Earth and the other inner planets contain relatively low amounts of water and volatile elements, which were not abundant in the inner solar system during planet formation. The even lower quantities of these volatile elements found on the Moon has long been claimed as evidence that it must have formed following a high-temperature, catastrophic giant impact. But this new research shows that aspects of this theory must be reevaluated.

“Water plays a critical role in determining the tectonic behavior of planetary surfaces, the melting point of planetary interiors and the location and eruptive style of planetary volcanoes,” said Erik Hauri, a geochemist with the Carnegie Institution of Washington and lead author of the study. “We can conceive of no sample type that would be more important to return to Earth than these volcanic glass samples ejected by explosive volcanism, which have been mapped not only on the moon but throughout the inner solar system.”

The research team measured the water content in the inclusions using a state-of-the-art NanoSIMS 50L ion microprobe.

“In contrast to most volcanic deposits, the melt inclusions are encased in crystals that prevent the escape of water and other volatiles during eruption. These samples provide the best window we have on the amount of water in the interior of the Moon,” said James Van Orman of Case Western Reserve University, a member of the science team.

The study also puts a new twist on the origin of water ice detected in craters at the lunar poles by several recent NASA missions. The ice has been attributed to comet and meteor impacts, but it is possible some of this ice could have come from the water released by eruption of lunar magmas.

Please read on . . .
http://news.brown.edu/pressreleases/2011/05/moonwater

1. From the American Association for the Advancement of Science - Science is a peer-reviewed journal:

High Pre-Eruptive Water Contents Preserved in Lunar Melt Inclusions:

Erik H. Hauri1,*, Thomas Weinreich2, Alberto E. Saal2, Malcolm C. Rutherford2, James A. Van Orman3
Author Affiliations

1Department of Terrestrial Magnetism, Carnegie Institution of Washington, Washington, DC 20015, USA.
2Department of Geological Sciences, Brown University, Providence, RI 02912, USA.
3Department of Geological Sciences, Case Western Reserve University, Cleveland, OH 44106, USA.
[snip]
Abstract
The Moon has long been thought to be highly depleted in volatiles such as water, and indeed published direct measurements of water in lunar volcanic glasses have never exceeded 50 parts per million (ppm). Here, we report in situ measurements of water in lunar melt inclusions; these samples of primitive lunar magma, by virtue of being trapped within olivine crystals before volcanic eruption, did not experience posteruptive degassing. The lunar melt inclusions contain 615 to 1410 ppm water and high correlated amounts of fluorine (50 to 78 ppm), sulfur (612 to 877 ppm), and chlorine (1.5 to 3.0 ppm). These volatile contents are very similar to primitive terrestrial mid-ocean ridge basalts and indicate that some parts of the lunar interior contain as much water as Earth’s upper mantle.
http://www.sciencemag.org/content/333/6039/213.abstract?sid=788a5a09-bcb9-4aca-a8a3-765305e67544

 

[Jack23454]

Thanks for the reference.

 

[Jack23454]

Hi Jack. You have a great imagination. Never heard of the 'cracked egg type planet'. I do think the Earth and the Moon share a common thing:



1. From the American Association for the Advancement of Science - Science is a peer-reviewed journal:

Interesting stuff. I talked to an Aeronautical Engineer from NASA about a year or so ago, he told me that when they impacted the Moon the reason water was identified was because someone had left a bottle of Naive water, ..sorry Evian water in the rocket. He was probably kidding right?