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Evidence record

Where did the Moon come from?

Every sentence on the exploration belongs to at least one claim below. Each says what kind of statement it is, what it rests on, what the evidence does not establish, and how far it was checked. Nothing here is a score, and none of it is a verdict on a belief or a theory.

Last checked 24 September 2026.

  • A judgement, not a fact: 9
  • Source checked: 45
  • Presented as open: 3
  • Partly checked: 5

If something here is wrong, misquoted, out of date or unfair, write to support@unknownoceans.com and give the claim number, which does not change.

What the question takes for granted

A question about a past event, answered from samples and simulations. The impact itself is the field’s leading account; which impact, and how the Moon came to match Earth, is not settled.

  • The Moon formed in a giant impact

    Established

    The leading account since 1984 and the frame for every model on the page; established as the field’s account, not as an observed event.

  • The Moon is isotopically like Earth

    Established

    Measured in oxygen, titanium and other elements; the 2024 oxygen result finds no difference at all.

  • The impactor was isotopically unlike Earth

    Contested

    The canonical puzzle depends on it. Some researchers think an Earth-like impactor improbable, others that bodies from the same region would match.

How the question is labelled

Claim: Made of us

Kind
This page’s reading. A judgement the page makes from the evidence. Others read it differently.
Review
A judgement, not a fact. Reviewed for whether it is fairly put and follows from the checked claims. No source can confirm it.

The title names the isotopic match the page is about.

What this does not establish

The Moon matching Earth in its isotopes is measured; whether it is mostly made of Earth material is the open question the page describes.

Claim 1 · checked 24 September 2026 · AI-assisted audit

Claim: The Moon

Kind
Framing. Signposting. It asserts nothing a source could check.

The question

Claim: The rocks brought back are isotopically almost identical to Earth

Kind
Observation. Something measured or seen, as the named source reports it.
Review
Source checked. The cited passage was read, and it says this.

What this does not establish

Apollo samples come from the lunar surface; the comparison is of those rocks and Earth’s mantle.

Later work looked for

Crossref, 2021 on, "oxygen isotope Earth Moon": Fischer and others (PNAS, December 2024) find no Earth-Moon difference at 0.2 ± 1.6 ppm and no heterogeneity among lunar rock types, against Cano and others (2020); page now reports the 2024 result.

Claim 3 · checked 24 September 2026 · AI-assisted audit

Claim: which is a problem for the theory that explains nearly everything else

Kind
What scholars argue. A report of what specialists argue, or where they disagree.
Review
Source checked. The cited passage was read, and it says this.

  • Supports

    Origin of the Moonsection 3.2, Canonical impact

    Cited · Link answered, 19 October 2026 · Read in full, 24 September 2026 · Review of the field

    The source reads: The key difficul ty for a canoni cal impact is accounting for Earth -Moon isotopic similarities.

  • Supports

    Origin of the Moonsection 3.2, Canonical impact, and section 1

    Cited · Link answered, 19 October 2026 · Read in full, 24 September 2026 · A simulation · Review of the field

    The source reads: can produce an iron-depleted Moon and a planet-disk system whose angular momentum is ... account for the Earth -Moon system angular momentum and the Moon's mass

  • Qualifies

    Origin of the Moonsection 6, Conclusions and open issues

    Cited · Link answered, 19 October 2026 · Read in full, 24 September 2026 · Review of the field

    The source reads: has been a longstanding issue for a giant impact origin

    The Moon’s orbital tilt is not explained by a single impact on its own.

Corrected

24 September 2026. Previously: “The rocks brought back are isotopically almost identical to Earth, which is a problem for the theory that explains everything else.” The review lists things the impact does not by itself explain, such as the Moon’s orbital tilt.

Claim 4 · checked 24 September 2026 · AI-assisted audit

Claim: A giant impact early in the solar system explains the Moon’s size, the spin of the Earth-Moon pair and the Moon’s lack of iron.

Kind
What a model says. What a theory or model predicts or describes, which is not the same as what has been observed.
Review
Source checked. The cited passage was read, and it says this.

  • Supports

    Origin of the Moonsection 1 and section 3.2, Canonical impact

    Cited · Link answered, 19 October 2026 · Read in full, 24 September 2026 · A simulation · Review of the field

    The source reads: the impact of a Mars -sized body at the end of Earth's accretion could account for the main physical properties of the Earth -Moon system ... can produce an iron-depleted Moon and a planet-disk system whose angular momentum is ... account for the Earth -Moon system angular momentum and the Moon's mass

  • Supports

    Origin of the Moonsection 1, Introduction

    Cited · Link answered, 19 October 2026 · Read in full, 24 September 2026 · Astronomical observation · Review of the field

    The source reads: The Moon has a tiny core, perhaps with only ~ 1% of its mass, in contrast to Earth whose core contains nearly 30% of its mass

  • Supports

    Moon FactsFormation

    Cited · Link answered, 19 October 2026 · Read in full, 24 September 2026 · Reference work

    The source reads: The Moon likely formed after a Mars-sized body collided with Earth several billion years ago.

  • Qualifies

    Origin of the Moonsection 6, Conclusions and open issues

    Cited · Link answered, 19 October 2026 · Read in full, 24 September 2026 · Review of the field

    The source reads: has been a longstanding issue for a giant impact origin

    The Moon’s orbital tilt is not explained by a single impact on its own.

What this does not establish

A model that reproduces these properties in simulation; the Moon’s orbital tilt is a separate, unresolved problem for it.

Corrected

24 September 2026. Previously: “A giant impact early in the solar system explains the Moon’s size, its orbit and its lack of iron.” “Its orbit” overstated: the impact accounts for the system’s angular momentum, while the orbit’s tilt is a longstanding problem for it (review, section 6).

Claim 5 · checked 24 September 2026 · AI-assisted audit

Claim: Its standard version also predicts that most of the Moon should be made of the impactor, and the samples say otherwise.

Kind
What a model says. What a theory or model predicts or describes, which is not the same as what has been observed.
Review
Source checked. The cited passage was read, and it says this.

  • Supports

    Origin of the Moonsection 1, Introduction

    Cited · Link answered, 19 October 2026 · Read in full, 24 September 2026 · Review of the field

    The source reads: this so -called “canonical impact” left a conundrum: it predicted the Moon formed primarily from material from the impactor, whereas the similarity in isotopic composition of the Earth and Moon

  • Supports

    Origin of the Moonsection 3.2, Canonical impact

    Cited · Link answered, 19 October 2026 · Read in full, 24 September 2026 · A simulation · Review of the field

    The source reads: In canonical impacts, most of the disk, typically ... 70 to 80%, originates from the impactor's mantle

  • Supports

    Oxygen isotope identity of the Earth and Moon with implications for the formation of the Moon and source of volatilesResults

    Cited · Link answered, 19 October 2026 · Read in full, 24 September 2026 · Artefacts and sites · Measurement

    The source reads: the Earth and Moon are within ... 0.2 ± 1.6 ppm isotopically identical

What this does not establish

The prediction is from simulations of the canonical impact; one modified code (Hosono and others, 2019, reported in the review) gets an Earth-dominated disc.

Corrected

24 September 2026. Previously: “It also predicts that most of the Moon should be made of the impactor, and the samples say otherwise.” The prediction belongs to the canonical impact, not to every impact model, as the page itself goes on to say.

Claim 6 · checked 24 September 2026 · AI-assisted audit

Claim: Several fixes exist and none is agreed.

Kind
Open question. Something the page says is not known.
Review
Presented as open. The page says this is unresolved, and the review found that it is.

The review surveys several impact scenarios and concludes none is established.

  • Supports

    Origin of the Moonsection 6, Conclusions and open issues

    Cited · Link answered, 19 October 2026 · Read in full, 24 September 2026 · Review of the field

    The source reads: Current models provide an array of possible solutions, but all involve conditions whose likelihood appears small or remains highly uncertain.

Claim 7 · checked 24 September 2026 · AI-assisted audit

Claim: The Moon is absurdly large for a planet this size

Kind
Observation. Something measured or seen, as the named source reports it.
Review
Source checked. The cited passage was read, and it says this.

  • Supports

    Origin of the Moonsection 1, Introduction

    Cited · Link answered, 19 October 2026 · Read in full, 24 September 2026 · Astronomical observation · Review of the field

    The source reads: The Moon is roughly ¼ the radius of the Earth ... than all known satellites other than Pluto’s Charon

Later work looked for

A ratio of sizes, not a finding later work revises.

Claim 8 · checked 24 September 2026 · AI-assisted audit

Claim: its iron core is tiny

Kind
Observation. Something measured or seen, as the named source reports it.
Review
Source checked. The cited passage was read, and it says this.

  • Supports

    Origin of the Moonsection 1, Introduction

    Cited · Link answered, 19 October 2026 · Read in full, 24 September 2026 · Astronomical observation · Review of the field

    The source reads: The Moon has a tiny core, perhaps with only ~ 1% of its mass, in contrast to Earth whose core contains nearly 30% of its mass

  • Supports

    Moon FactsStructure

    Cited · Link answered, 19 October 2026 · Read in full, 24 September 2026 · Astronomical observation · Reference work

    The source reads: The Moon’s core is proportionally smaller than other terrestrial bodies' cores. The solid, iron-rich inner core is 149 miles (240 kilometers) in radius. It is surrounded by a liquid iron shell 56 miles (90 kilometers) thick.

Later work looked for

Crossref, 2022 on, "lunar inner core radius": Briaud and others (Nature, 2023, abstract) give an inner core radius of 258 ± 40 km, consistent with NASA’s 240 within its uncertainty; page unchanged.

Corrected

24 September 2026. Previously: “it has almost no iron core” The core is small, about 1 per cent of the Moon’s mass by the review’s estimate, but it is there: NASA gives it a radius of about 330 kilometres.

Claim 9 · checked 24 September 2026 · AI-assisted audit

Claim: and it is drifting away from us by a few centimetres a year.

Kind
Observation. Something measured or seen, as the named source reports it.
Review
Source checked. The cited passage was read, and it says this.

  • Supports

    Moon FactsSize and Distance

    Cited · Link answered, 19 October 2026 · Read in full, 24 September 2026 · Astronomical observation · Reference work

    The source reads: The Moon is slowly moving away from Earth, getting about an inch farther away each year.

What this does not establish

NASA rounds the rate to about an inch a year; the page does not give a more precise figure.

Later work looked for

Crossref, 2016 on, "lunar recession rate laser ranging": nothing that changes a rate of a few centimetres a year.

Corrected

24 September 2026. Previously: “and it is receding from us at about the speed a fingernail grows.” The comparison with a fingernail had no source; the rate is now NASA’s.

Claim 10 · checked 24 September 2026 · AI-assisted audit

Claim: One collision accounts for the first two

Kind
What a model says. What a theory or model predicts or describes, which is not the same as what has been observed.
Review
Source checked. The cited passage was read, and it says this.

  • Supports

    Origin of the Moonsection 3.2, Canonical impact, and section 1

    Cited · Link answered, 19 October 2026 · Read in full, 24 September 2026 · A simulation · Review of the field

    The source reads: can produce an iron-depleted Moon and a planet-disk system whose angular momentum is ... account for the Earth -Moon system angular momentum and the Moon's mass

  • Supports

    Origin of the Moonsection 1, Introduction

    Cited · Link answered, 19 October 2026 · Read in full, 24 September 2026 · Astronomical observation · Review of the field

    The source reads: The Moon is roughly ¼ the radius of the Earth ... than all known satellites other than Pluto’s Charon

What this does not establish

In simulation; which version of the collision is right is the open question.

Corrected

24 September 2026. Previously: “One event accounts for all three.” The Moon’s drift is caused by tides, not by the impact; the impact explains where it started (review, section 3.1.1).

Claim 11 · checked 24 September 2026 · AI-assisted audit

Claim: and would have left the Moon close to Earth, from where tides have been pushing it outward ever since.

Kind
What a model says. What a theory or model predicts or describes, which is not the same as what has been observed.
Review
Source checked. The cited passage was read, and it says this.

  • Supports

    Origin of the Moonsection 3.1.1, Constraints

    Cited · Link answered, 19 October 2026 · Read in full, 24 September 2026 · Review of the field

    The source reads: has caused the Earth’s spin to slow and the Moon’s orbit to expand while conserving angular momentum. A newly-formed Moon orbiting just outside the Roche limit

What this does not establish

A newly formed Moon just outside the Roche limit is the review’s working assumption for impact models.

Claim 12 · checked 24 September 2026 · AI-assisted audit

Claim: The difficulty is in the isotopes.

Kind
What scholars argue. A report of what specialists argue, or where they disagree.
Review
Source checked. The cited passage was read, and it says this.

The review names the isotopic similarity as the key difficulty for the canonical impact.

  • Supports

    Origin of the Moonsection 3.2, Canonical impact

    Cited · Link answered, 19 October 2026 · Read in full, 24 September 2026 · Review of the field

    The source reads: The key difficul ty for a canoni cal impact is accounting for Earth -Moon isotopic similarities.

Claim 13 · checked 24 September 2026 · AI-assisted audit

What the rocks say

Claim: What the rocks say

Kind
Framing. Signposting. It asserts nothing a source could check.

What the samples show

Claim: What the samples show

Kind
Framing. Signposting. It asserts nothing a source could check.

Claim: The Moon as a whole holds less than a tenth of its mass in iron, although its mantle is relatively rich in it

Kind
Observation. Something measured or seen, as the named source reports it.
Review
Source checked. The cited passage was read, and it says this.

  • Supports

    Origin of the Moonsection 3.1.1, Constraints

    Cited · Link answered, 19 October 2026 · Read in full, 24 September 2026 · Astronomical observation · Review of the field

    The source reads: The mantle of the Moon is relatively iron ... but overall, the Moon contains less than ... 10% of its mass in the element iron due to its small core

Later work looked for

A bulk property stated by the review; the 2023 inner-core study (Briaud and others, abstract) is consistent with a small core. No further search.

Corrected

24 September 2026. Previously: “Lunar rock is depleted in iron and in volatile elements relative to Earth, consistent with material that was once vaporised and had already lost its metal.” Lunar rock is not iron-depleted: the review says the Moon’s mantle is relatively iron-rich and that the whole Moon is iron-poor because its core is small. The cause of the volatile loss is given as Day and Moynier give it.

Claim 16 · checked 24 September 2026 · AI-assisted audit

Claim: what is missing is the metal.

Kind
This page’s reading. A judgement the page makes from the evidence. Others read it differently.
Review
A judgement, not a fact. Reviewed for whether it is fairly put and follows from the checked claims. No source can confirm it.

Follows from the review’s statement that the mantle is iron-rich and the bulk Moon iron-poor because of its small core.

  • Supports

    Origin of the Moonsection 3.1.1, Constraints

    Cited · Link answered, 19 October 2026 · Read in full, 24 September 2026 · Astronomical observation · Review of the field

    The source reads: The mantle of the Moon is relatively iron ... but overall, the Moon contains less than ... 10% of its mass in the element iron due to its small core

Claim 17 · checked 24 September 2026 · AI-assisted audit

Claim: Its rocks are also depleted in volatile elements relative to Earth

Kind
Observation. Something measured or seen, as the named source reports it.
Review
Source checked. The cited passage was read, and it says this.

Later work looked for

Fischer and others (2024, read in full) restate the depletion and its two candidate sources; no further search.

Claim 18 · checked 24 September 2026 · AI-assisted audit

Claim: most probably by evaporation, during the impact or in a later ocean of magma.

Kind
What scholars argue. A report of what specialists argue, or where they disagree.
Review
Partly checked. Only part of the source could be read. What was not read is listed.

What this does not establish

Only the abstract was read. The authors say problems exist for the impact route and that a magma-ocean phase may explain the loss better.

Claim 19 · checked 24 September 2026 · AI-assisted audit

Claim: The iron core reaches only about 330 kilometres out, a solid inner core of 240 inside a liquid shell 90 thick, in a body whose radius is about 1,740.

Kind
Observation. Something measured or seen, as the named source reports it.
Review
Source checked. The cited passage was read, and it says this.

  • Supports

    Moon FactsStructure

    Cited · Link answered, 19 October 2026 · Read in full, 24 September 2026 · Astronomical observation · Reference work

    The source reads: The Moon’s core is proportionally smaller than other terrestrial bodies' cores. The solid, iron-rich inner core is 149 miles (240 kilometers) in radius. It is surrounded by a liquid iron shell 56 miles (90 kilometers) thick.

  • Supports

    Moon FactsSize and Distance

    Cited · Link answered, 19 October 2026 · Read in full, 24 September 2026 · Astronomical observation · Reference work

    The source reads: With a radius of about 1,080 miles (1,740 kilometers)

What this does not establish

The core’s size is inferred from seismic and tidal data, not measured directly; a 2023 study gives an inner core of 258 ± 40 kilometres.

Later work looked for

Crossref, 2022 on, "lunar inner core radius": Briaud and others (Nature, 2023, abstract) give an inner core radius of 258 ± 40 km, consistent with NASA’s 240 within its uncertainty; page unchanged.

Corrected

24 September 2026. Previously: “in a body whose radius is 1,737” Matched to the cited source, which gives about 1,740 kilometres.

Claim 20 · checked 24 September 2026 · AI-assisted audit

Claim: Proportionally it is smaller than any other rocky world’s

Kind
Observation. Something measured or seen, as the named source reports it.
Review
Source checked. The cited passage was read, and it says this.

  • Supports

    Moon FactsStructure

    Cited · Link answered, 19 October 2026 · Read in full, 24 September 2026 · Astronomical observation · Reference work

    The source reads: The Moon’s core is proportionally smaller than other terrestrial bodies' cores. The solid, iron-rich inner core is 149 miles (240 kilometers) in radius. It is surrounded by a liquid iron shell 56 miles (90 kilometers) thick.

Later work looked for

Crossref, 2022 on, "lunar inner core radius": Briaud and others (Nature, 2023, abstract) give an inner core radius of 258 ± 40 km, consistent with NASA’s 240 within its uncertainty; page unchanged.

Corrected

24 September 2026. Previously: “Proportionally it is far smaller than any other rocky world’s.” NASA says “proportionally smaller”; “far smaller” is carried only for Earth, whose core holds nearly 30 per cent of its mass (review).

Claim 21 · checked 24 September 2026 · AI-assisted audit

Claim: and far smaller than Earth’s, which holds nearly a third of the planet’s mass.

Kind
Observation. Something measured or seen, as the named source reports it.
Review
Source checked. The cited passage was read, and it says this.

  • Supports

    Origin of the Moonsection 1, Introduction

    Cited · Link answered, 19 October 2026 · Read in full, 24 September 2026 · Astronomical observation · Review of the field

    The source reads: The Moon has a tiny core, perhaps with only ~ 1% of its mass, in contrast to Earth whose core contains nearly 30% of its mass

Later work looked for

Standard figures stated by the review; not something later work revises.

Claim 22 · checked 24 September 2026 · AI-assisted audit

Claim: Its oxygen and titanium isotope ratios, though, match Earth’s to high precision.

Kind
Observation. Something measured or seen, as the named source reports it.
Review
Source checked. The cited passage was read, and it says this.

  • Supports

    Oxygen isotope identity of the Earth and Moon with implications for the formation of the Moon and source of volatilesResults

    Cited · Link answered, 19 October 2026 · Read in full, 24 September 2026 · Artefacts and sites · Measurement

    The source reads: the Earth and Moon are within ... 0.2 ± 1.6 ppm isotopically identical

  • Supports

    Origin of the Moonsection 2.3

    Cited · Link answered, 19 October 2026 · Read in full, 24 September 2026 · Artefacts and sites · Review of the field

    The source reads: a robust conclusion is that the Earth and shallow Moon have ... 17O values within ~0.01‰ (10 ppm) of each other, whereas samples derived from the deeper lunar interior exhibit differences up to about 20 ppm

  • Context

    The proto-Earth as a significant source of lunar materialabstract

    Cited · Link answered, 19 October 2026 · Abstract only, 24 September 2026 · Artefacts and sites · Measurement

    The source reads: we find that the 50Ti/47Ti ratio of the Moon is identical to that of the Earth within about four parts per million, which is only 1/150 of the isotopic range documented in meteorites

    Read as an abstract only; the claim is carried by the full-text sources.

What this does not establish

Earlier studies disagreed at the level of a few parts per million, and one argued that deep-sourced samples differ by about 20; the 2024 study found no such difference.

Later work looked for

Crossref, 2021 on, "oxygen isotope Earth Moon": Fischer and others (PNAS, December 2024) find no Earth-Moon difference at 0.2 ± 1.6 ppm and no heterogeneity among lunar rock types, against Cano and others (2020); page now reports the 2024 result.

Claim 23 · checked 24 September 2026 · AI-assisted audit

Claim: The Moon’s 50Ti/47Ti sits within about four parts per million of Earth’s, a hundred and fiftieth of the range meteorites cover

Kind
Observation. Something measured or seen, as the named source reports it.
Review
Partly checked. Only part of the source could be read. What was not read is listed.

  • Supports

    The proto-Earth as a significant source of lunar materialabstract

    Cited · Link answered, 19 October 2026 · Abstract only, 24 September 2026 · Artefacts and sites · Measurement

    The source reads: we find that the 50Ti/47Ti ratio of the Moon is identical to that of the Earth within about four parts per million, which is only 1/150 of the isotopic range documented in meteorites

What this does not establish

Only the abstract of Zhang and others was read; the figures are the abstract’s own.

Later work looked for

Crossref, 2013 on, "titanium isotope Moon Earth lunar samples": nothing that revises it; the 2021 review still cites it as the titanium constraint.

Claim 24 · checked 24 September 2026 · AI-assisted audit

Claim: and a 2024 oxygen study, working at a precision earlier ones could not reach, found no difference down to a part or two per million.

Kind
Observation. Something measured or seen, as the named source reports it.
Review
Source checked. The cited passage was read, and it says this.

What this does not establish

One laboratory’s measurement of 14 lunar samples; earlier studies reported small differences, and whether any remains is argued.

Later work looked for

Crossref, 2021 on, "oxygen isotope Earth Moon": Fischer and others (PNAS, December 2024) find no Earth-Moon difference at 0.2 ± 1.6 ppm and no heterogeneity among lunar rock types, against Cano and others (2020); page now reports the 2024 result.

Corrected

24 September 2026. Previously: “” Added: the most recent high-precision oxygen result, which the page did not report.

Claim 25 · checked 24 September 2026 · AI-assisted audit

Claim: Mars and most meteorites carry isotopic fingerprints of their own, and the Moon carries ours.

Kind
Observation. Something measured or seen, as the named source reports it.
Review
Source checked. The cited passage was read, and it says this.

  • Supports

    Origin of the Moonsection 3.1.1, Constraints

    Cited · Link answered, 19 October 2026 · Read in full, 24 September 2026 · Artefacts and sites · Review of the field

    The source reads: while meteorites from Mars and the asteroid belt differ substantially

  • Supports

    Oxygen isotope identity of the Earth and Moon with implications for the formation of the Moon and source of volatilesIntroduction

    Cited · Link answered, 19 October 2026 · Read in full, 24 September 2026 · Artefacts and sites · Review of the field

    The source reads: Many elements (O, Si, S, Ti, Cr, and W) show distinct, partly mass-independent isotope heterogeneity among solar system bodies (planets and asteroids) but show no (O, Si, S, Ti, and Cr) or only very small (O and W) differences between the Earth and Moon

Later work looked for

Crossref, 2021 on, "isotopic dichotomy meteorites Earth Moon nucleosynthetic": nothing that changes it; Fischer and others (2024) restate it.

Corrected

24 September 2026. Previously: “Each body in the solar system has its own isotopic fingerprint, and the Moon has ours.” Not every body differs: enstatite meteorites are close to Earth in oxygen (review, section 2.3). The sentence now names what the sources compare.

Claim 26 · checked 24 September 2026 · AI-assisted audit

The giant impact explains almost everything

Claim: The giant impact explains almost everything

Kind
This page’s reading. A judgement the page makes from the evidence. Others read it differently.
Review
A judgement, not a fact. Reviewed for whether it is fairly put and follows from the checked claims. No source can confirm it.

A heading; the passage below lists what the impact accounts for.

  • Supports

    Origin of the Moonsection 3.2, Canonical impact

    Cited · Link answered, 19 October 2026 · Read in full, 24 September 2026 · A simulation · Review of the field

    The source reads: can produce an iron-depleted Moon and a planet-disk system whose angular momentum is

  • Qualifies

    Origin of the Moonsection 6, Conclusions and open issues

    Cited · Link answered, 19 October 2026 · Read in full, 24 September 2026 · Review of the field

    The source reads: has been a longstanding issue for a giant impact origin

    The Moon’s orbital tilt is not explained by a single impact on its own.

What this does not establish

The Moon’s orbital tilt and its isotopes are not explained by the standard impact on its own.

Claim 27 · checked 24 September 2026 · AI-assisted audit

Claim: In the standard version a body about the size of Mars struck the young Earth obliquely.

Kind
What a model says. What a theory or model predicts or describes, which is not the same as what has been observed.
Review
Source checked. The cited passage was read, and it says this.

  • Supports

    Origin of the Moonsection 3.2, Canonical impact

    Cited · Link answered, 19 October 2026 · Read in full, 24 September 2026 · A simulation · Review of the field

    The source reads: can produce an iron-depleted Moon and a planet-disk system whose angular momentum is

  • Supports

    Moon FactsFormation

    Cited · Link answered, 19 October 2026 · Read in full, 24 September 2026 · Reference work

    The source reads: The Moon likely formed after a Mars-sized body collided with Earth several billion years ago.

  • Supports

    Origin of the Moonsection 3.1.1, Constraints

    Cited · Link answered, 19 October 2026 · Read in full, 24 September 2026 · Review of the field

    The source reads: An oblique collision(s) is a natural source of Earth’s early rapid spin

What this does not establish

The canonical impact in simulation; the size and angle are what the model needs, not something observed.

Claim 28 · checked 24 September 2026 · AI-assisted audit

Claim: The collision threw mantle material into orbit, most of it the impactor’s, where it gathered into the Moon, and left Earth spinning fast.

Kind
What a model says. What a theory or model predicts or describes, which is not the same as what has been observed.
Review
Source checked. The cited passage was read, and it says this.

  • Supports

    Origin of the Moonsection 3.2, Canonical impact

    Cited · Link answered, 19 October 2026 · Read in full, 24 September 2026 · A simulation · Review of the field

    The source reads: In canonical impacts, most of the disk, typically ... 70 to 80%, originates from the impactor's mantle

  • Supports

    Origin of the Moonsection 3.1.1, Constraints

    Cited · Link answered, 19 October 2026 · Read in full, 24 September 2026 · Review of the field

    The source reads: An oblique collision(s) is a natural source of Earth’s early rapid spin

  • Supports

    Origin of the Moonsection 1, Introduction

    Cited · Link answered, 19 October 2026 · Read in full, 24 September 2026 · Astronomical observation · Review of the field

    The source reads: The Earth-Moon system has a high total angular momentum, implying a rapidly spinning Earth when the Moon formed

What this does not establish

In simulation. Most of the disc being the impactor’s is exactly what the isotopes contradict.

Corrected

24 September 2026. Previously: “The collision stripped mantle material into orbit, where it condensed into the Moon, and left Earth spinning fast.” In the canonical model the orbiting material is mostly the impactor’s mantle (review, section 3.2); the old wording left that out, which is the point of the next section.

Claim 29 · checked 24 September 2026 · AI-assisted audit

Claim: That accounts for the Moon’s mass, the angular momentum of the pair and the missing iron

Kind
What a model says. What a theory or model predicts or describes, which is not the same as what has been observed.
Review
Source checked. The cited passage was read, and it says this.

  • Supports

    Origin of the Moonsection 3.2, Canonical impact, and section 1

    Cited · Link answered, 19 October 2026 · Read in full, 24 September 2026 · A simulation · Review of the field

    The source reads: can produce an iron-depleted Moon and a planet-disk system whose angular momentum is ... account for the Earth -Moon system angular momentum and the Moon's mass

What this does not establish

In simulation, for a narrow range of impact angles and speeds.

Corrected

24 September 2026. Previously: “That accounts for the Moon’s mass, the angular momentum of the pair, the missing iron and the missing volatiles.” Day and Moynier give the impact and a later magma ocean as the two candidates for the volatile loss, and name problems for the impact route.

Claim 30 · checked 24 September 2026 · AI-assisted audit

Claim: and offers one route to the missing volatiles.

Kind
What scholars argue. A report of what specialists argue, or where they disagree.
Review
Source checked. The cited passage was read, and it says this.

What this does not establish

The cause of the volatile loss is argued; a magma-ocean phase is the other candidate.

Claim 31 · checked 24 September 2026 · AI-assisted audit

Claim: It is not a fringe idea

Kind
What the field holds. The settled view of a field, as a review, a consensus statement or a reference work gives it. Not one study.
Review
Source checked. The cited passage was read, and it says this.

  • Supports

    Origin of the Moonsection 1, Introduction

    Cited · Link answered, 19 October 2026 · Read in full, 24 September 2026 · Review of the field

    The source reads: Origin via a giant impact with the Earth emerged from the 1984 “Origin of the Moon” conference as the leading hypothesis

  • Supports

    Origin of the Moonsection 5.5, Discussion

    Cited · Link answered, 19 October 2026 · Read in full, 24 September 2026 · Review of the field

    The source reads: large impacts are efficient producers of moons

  • Supports

    Moon FactsFormation

    Cited · Link answered, 19 October 2026 · Read in full, 24 September 2026 · Reference work

    The source reads: The Moon likely formed after a Mars-sized body collided with Earth several billion years ago.

Later work looked for

Crossref, 2021 on, "Moon-forming giant impact": work since (Kegerreis 2022, Fischer 2024, Hopp 2025) all works within the impact framework.

Claim 32 · checked 24 September 2026 · AI-assisted audit

Claim: and it is not in trouble as a class of explanation.

Kind
This page’s reading. A judgement the page makes from the evidence. Others read it differently.
Review
A judgement, not a fact. Reviewed for whether it is fairly put and follows from the checked claims. No source can confirm it.

The review’s authors work within the impact framework; what the isotopes challenge is a particular impact.

  • Supports

    Origin of the Moonsection 5.5, Discussion

    Cited · Link answered, 19 October 2026 · Read in full, 24 September 2026 · Review of the field

    The source reads: large impacts are efficient producers of moons

  • Supports

    Origin of the Moonsection 6, Conclusions and open issues

    Cited · Link answered, 19 October 2026 · Read in full, 24 September 2026 · Review of the field

    The source reads: Current models provide an array of possible solutions, but all involve conditions whose likelihood appears small or remains highly uncertain.

Other readings

Melosh (2014), quoted in the review, called the isotopic problem an “isotopic crisis” for the giant impact model.

Claim 33 · checked 24 September 2026 · AI-assisted audit

Where the theory strains

Claim: Where the theory strains

Kind
Framing. Signposting. It asserts nothing a source could check.

Claim: Mars and most meteorites have signatures of their own.

Kind
Observation. Something measured or seen, as the named source reports it.
Review
Source checked. The cited passage was read, and it says this.

  • Supports

    Origin of the Moonsection 3.1.1, Constraints

    Cited · Link answered, 19 October 2026 · Read in full, 24 September 2026 · Artefacts and sites · Review of the field

    The source reads: while meteorites from Mars and the asteroid belt differ substantially

  • Supports

    Oxygen isotope identity of the Earth and Moon with implications for the formation of the Moon and source of volatilesIntroduction

    Cited · Link answered, 19 October 2026 · Read in full, 24 September 2026 · Artefacts and sites · Review of the field

    The source reads: Many elements (O, Si, S, Ti, Cr, and W) show distinct, partly mass-independent isotope heterogeneity among solar system bodies (planets and asteroids) but show no (O, Si, S, Ti, and Cr) or only very small (O and W) differences between the Earth and Moon

Later work looked for

Crossref, 2021 on, "isotopic dichotomy meteorites Earth Moon nucleosynthetic": nothing that changes it; Fischer and others (2024) restate it.

Corrected

24 September 2026. Previously: “Every other body in the solar system has its own signature.” Enstatite meteorites are close to Earth in oxygen; the line now names what the sources compare.

Claim 35 · checked 24 September 2026 · AI-assisted audit

Claim: The Moon has ours.

Kind
Observation. Something measured or seen, as the named source reports it.
Review
Source checked. The cited passage was read, and it says this.

Later work looked for

Crossref, 2021 on, "oxygen isotope Earth Moon": Fischer and others (PNAS, December 2024) find no Earth-Moon difference at 0.2 ± 1.6 ppm and no heterogeneity among lunar rock types, against Cano and others (2020); page now reports the 2024 result.

Claim 36 · checked 24 September 2026 · AI-assisted audit

Why the Moon is not made of the impactor

Claim: Why the Moon is not made of the impactor

Kind
This page’s reading. A judgement the page makes from the evidence. Others read it differently.
Review
A judgement, not a fact. Reviewed for whether it is fairly put and follows from the checked claims. No source can confirm it.

A heading stating the puzzle the section describes.

  • Supports

    Origin of the Moonsection 1, Introduction

    Cited · Link answered, 19 October 2026 · Read in full, 24 September 2026 · Review of the field

    The source reads: this so -called “canonical impact” left a conundrum: it predicted the Moon formed primarily from material from the impactor, whereas the similarity in isotopic composition of the Earth and Moon

What this does not establish

Whether the Moon is mostly Earth material, or a thorough mix, is what the section says is unsettled.

Claim 37 · checked 24 September 2026 · AI-assisted audit

Claim: Simulations of the classic version put most of the Moon’s material from the impactor rather than from Earth.

Kind
What a model says. What a theory or model predicts or describes, which is not the same as what has been observed.
Review
Source checked. The cited passage was read, and it says this.

  • Supports

    Origin of the Moonsection 3.2, Canonical impact

    Cited · Link answered, 19 October 2026 · Read in full, 24 September 2026 · A simulation · Review of the field

    The source reads: In canonical impacts, most of the disk, typically ... 70 to 80%, originates from the impactor's mantle

  • Context

    Making the Moon from a Fast-Spinning Earth: A Giant Impact Followed by Resonant Despinningabstract

    Cited · Link answered, 19 October 2026 · Abstract only, 24 September 2026

    The source reads: simulations of the current giant impact hypothesis for Moon formation find that most lunar material originated from the impactor, which should have had a different isotopic signature

    Read as an abstract only.

  • Context

    Forming a Moon with an Earth-like Composition via a Giant Impactabstract (PMC author manuscript)

    Cited · Link answered, 19 October 2026 · Abstract only, 24 September 2026

    The source reads: Prior impact simulations predict that much of the disk material originates from the impacting planet.

    Read as an abstract only.

What this does not establish

One modified code reported in the review gives an Earth-dominated disc for the same impact.

Claim 38 · checked 24 September 2026 · AI-assisted audit

Claim: Unless that body happened to be isotopically almost identical to Earth, or the two were mixed thoroughly afterwards, the samples should show it.

Kind
What a model says. What a theory or model predicts or describes, which is not the same as what has been observed.
Review
Source checked. The cited passage was read, and it says this.

  • Supports

    Origin of the Moonsection 3.2, Canonical impact

    Cited · Link answered, 19 October 2026 · Read in full, 24 September 2026 · Review of the field

    The source reads: In general, a canonical Moon-forming impact requires either an impactor with an Earth ... or that the compositional signature of the impactor in the disk was erased by vapor mixing

  • Supports

    Oxygen isotope identity of the Earth and Moon with implications for the formation of the Moon and source of volatilesDiscussion

    Cited · Link answered, 19 October 2026 · Read in full, 24 September 2026 · Argument

    The source reads: The isotope identity of Moon and Earth, as illustrated in diagram Fig. 3 requires either Theia and proto-Earth having the same composition (16), vigorous mixing of Theia and Earth after the Moon-forming impact (37–39), or a combination of both.

What this does not establish

Whether vapour mixing after the impact could do this is itself unresolved.

Corrected

24 September 2026. Previously: “Unless that body happened to have an isotopic composition identical to Earth’s, which is not what the rest of the solar system looks like, the samples should show it.” The old sentence left out mixing after the impact and stated as settled that an Earth-like impactor is implausible, which the review reports as argued both ways.

Claim 39 · checked 24 September 2026 · AI-assisted audit

Claim: Some researchers think such a twin unlikely; others argue that neighbours built from the same material would match.

Kind
What scholars argue. A report of what specialists argue, or where they disagree.
Review
Source checked. The cited passage was read, and it says this.

  • Supports

    Origin of the Moonsection 3.1.1, Constraints

    Cited · Link answered, 19 October 2026 · Read in full, 24 September 2026 · Review of the field

    The source reads: The case has been made that an isotopically Mars-like impactor is most likely (Pahlevan & Stevenson 2007), although counter arguments for an Earth ... composition impactor have also been advanced

  • Supports

    Oxygen isotope identity of the Earth and Moon with implications for the formation of the Moon and source of volatilesIntroduction

    Cited · Link answered, 19 October 2026 · Read in full, 24 September 2026 · Review of the field

    The source reads: Such a mode of accretion of Theia and proto-Earth in the same feeding zone may also explain the similarity of the Earth and Moon in oxygen, titanium, and chromium.

  • Supports

    Immediate origin of the Moon as a post-impact satellitesection 1, Introduction

    Cited · Link answered, 19 October 2026 · Read in full, 24 September 2026 · Argument

    The source reads: it seems unlikely, though perhaps possible, that the impactor would already match the proto-Earth target’s composition

Later work looked for

Crossref, 2023 on, "Theia Moon-forming impactor origin isotopes": Hopp and others (Science, 2025, abstract) find Theia and proto-Earth both inner Solar System material; it does not settle whether Theia was isotopically identical, so the page reports the disagreement.

Claim 40 · checked 24 September 2026 · AI-assisted audit

Claim: Two fixes were published together in 2012.

Kind
Historical claim. A statement about the past that historical evidence can test.
Review
Partly checked. Only part of the source could be read. What was not read is listed.

What this does not establish

Established from the publication records and abstracts; the papers themselves were not read.

Claim 41 · checked 24 September 2026 · AI-assisted audit

Claim: In one the impactor is much larger than the canonical Mars-sized body, comparable in mass to the proto-Earth, and the collision leaves a disc with the composition of Earth’s mantle.

Kind
What a model says. What a theory or model predicts or describes, which is not the same as what has been observed.
Review
Source checked. The cited passage was read, and it says this.

  • Supports

    Origin of the Moonsection 3.5, Half-Earth impact

    Cited · Link answered, 19 October 2026 · Read in full, 24 September 2026 · A simulation · Review of the field

    The source reads: Somewhat asymmetric collisions with an impactor whose mass is > 40% of the Earth’s mass can produce disk-planet compositional differences as small as

  • Context

    Forming a Moon with an Earth-like Composition via a Giant Impactabstract (PMC author manuscript)

    Cited · Link answered, 19 October 2026 · Abstract only, 24 September 2026

    The source reads: Here we simulate impacts involving larger impactors than previously considered. We show these can produce a disk with the same composition as the planet’s mantle

    Read as an abstract only.

What this does not establish

In simulation; the impactor holds more than 40 per cent of Earth’s mass in the successful cases.

Claim 42 · checked 24 September 2026 · AI-assisted audit

Claim: In the other the Earth is spinning very fast before a smaller body strikes it, and the Moon forms largely from Earth’s own mantle.

Kind
What a model says. What a theory or model predicts or describes, which is not the same as what has been observed.
Review
Source checked. The cited passage was read, and it says this.

  • Supports

    Origin of the Moonsection 3.4, Fast-spinning Earth impact

    Cited · Link answered, 19 October 2026 · Read in full, 24 September 2026 · A simulation · Review of the field

    The source reads: Relatively small, fast impactors ... produced potential Moon-forming disks with ... with the disk material originating overwhelmingly from the target’s mantle

  • Context

    Making the Moon from a Fast-Spinning Earth: A Giant Impact Followed by Resonant Despinningabstract

    Cited · Link answered, 19 October 2026 · Abstract only, 24 September 2026

    The source reads: typical last giant impacts onto a fast-spinning proto-Earth can produce a Moon-forming disk derived primarily from Earth's mantle

    Read as an abstract only.

What this does not establish

In simulation; it assumes an Earth spinning near its breakup limit before the impact.

Claim 43 · checked 24 September 2026 · AI-assisted audit

Claim: Both leave the pair turning too fast, and both rely on a later resonance between the Moon and the Sun to shed the excess.

Kind
What a model says. What a theory or model predicts or describes, which is not the same as what has been observed.
Review
Source checked. The cited passage was read, and it says this.

  • Supports

    Origin of the Moonsection 3.4, Fast-spinning Earth impact

    Cited · Link answered, 19 October 2026 · Read in full, 24 September 2026 · Review of the field

    The source reads: Both require a subsequent dynamical mechanism to bring the system to the present-day angular momentum

  • Context

    Forming a Moon with an Earth-like Composition via a Giant Impactabstract (PMC author manuscript)

    Cited · Link answered, 19 October 2026 · Abstract only, 24 September 2026

    The source reads: Such impacts require subsequent removal of angular momentum from the Earth-Moon system through a resonance with the Sun as recently proposed.

    Read as an abstract only.

  • Context

    Making the Moon from a Fast-Spinning Earth: A Giant Impact Followed by Resonant Despinningabstract

    Cited · Link answered, 19 October 2026 · Abstract only, 24 September 2026

    The source reads: a faster-spinning early Earth-Moon system can lose angular momentum and reach the present state through an orbital resonance between the Sun and Moon

    Read as an abstract only.

What this does not establish

The later reduction of spin is a separate calculation from the impact itself.

Claim 44 · checked 24 September 2026 · AI-assisted audit

Claim: Later work finds the resonance can do that only in a limited range of conditions, and a 2026 study that follows the young Earth as it cools finds it unlikely to manage alone.

Kind
What scholars argue. A report of what specialists argue, or where they disagree.
Review
Source checked. The cited passage was read, and it says this.

Canup, an author of the 2026 study, proposed one of the two 2012 models.

What this does not establish

One modelling study; its authors list caveats about the atmosphere and the Moon’s tidal properties, and a second mechanism (an orbital instability) is not tested by it.

Later work looked for

Crossref, 2021 on, "evection resonance Moon angular momentum": Rufu, Canup and Korenaga (2026) find the Moon leaves the resonance too early in every case they model; page updated.

Corrected

24 September 2026. Previously: “” Added: the review finds the resonance works only for limited parameters, and Rufu, Canup and Korenaga (2026) find it unlikely to remove enough spin on its own.

Claim 45 · checked 24 September 2026 · AI-assisted audit

Claim: Other routes exist: vapour mixing the disc with Earth after the impact, a Moon built from many smaller impacts, and a hot, vaporised, fast-spinning body called a synestia.

Kind
Hypothesis. A proposed explanation, not an established one.
Review
Source checked. The cited passage was read, and it says this.

  • Supports

    Origin of the Moonsection 2.3

    Cited · Link answered, 19 October 2026 · Read in full, 24 September 2026 · Review of the field

    The source reads: it has been argued that the Earth–Moon similarity in O isotopes could reflect isotopic equilibration between the terrestrial magma ocean and protolunar disk via the vapor phase

  • Supports

    Origin of the Moonsection 3.7, Multiple impacts

    Cited · Link answered, 19 October 2026 · Read in full, 24 September 2026 · Review of the field

    The source reads: In the Rufu et al. (2017) multiple impact model, the Moon forms from a sequence of medium- to large-size collisions

  • Supports

    Origin of the Moonsection 3.6

    Cited · Link answered, 19 October 2026 · Read in full, 24 September 2026 · Review of the field

    The source reads: Lock and Stewart (2017) and Lock et al. (2018) found that a wide range of giant impacts produce a so-called synestia – a partially vaporized, rapidly rotating and distended planetary body

What this does not establish

Each is proposed, not established; the review calls the likelihood of mixing highly uncertain.

Later work looked for

Crossref, 2021 on, "Moon-forming giant impact" and "immediate origin of the Moon": Kegerreis and others (2022) and Fischer and others (2024) add routes; nothing found that selects one model. The 2021 review by the models’ own authors is the most recent field-level account read.

Corrected

24 September 2026. Previously: “A third option arrived in 2022, from simulations run with far more particles than the earlier ones: on some impacts a satellite of the right mass and iron content is placed into orbit within hours, rather than accreting from a disc, and its outer layers come out around sixty per cent proto-Earth material.” The 2022 result was not the third option: mixing (2007), multiple impacts (2017) and synestias (2017) were already proposed. And only the outer layers reach 60 per cent proto-Earth; the whole satellite is 30 to 40 per cent (Kegerreis and others, section 3.3).

Claim 46 · checked 24 September 2026 · AI-assisted audit

Claim: In 2022 simulations run with far more particles than the earlier ones found that some impacts place a satellite of about the right mass and iron content into orbit almost at once, rather than accreting it from a disc.

Kind
Experimental result. What an experiment or trial found, under its own conditions. A result in animals, cells or a simulation is not a result in people.
Review
Source checked. The cited passage was read, and it says this.

  • Supports

    Immediate origin of the Moon as a post-impact satelliteabstract

    Cited · Link answered, 19 October 2026 · Read in full, 24 September 2026 · A simulation · Model

    The source reads: Above a high resolution threshold for simulations, we find that giant impacts can immediately place a satellite with similar mass and iron content to the Moon into orbit far outside the Earth’s Roche limit.

  • Supports

    Immediate origin of the Moon as a post-impact satellitesection 1, Introduction

    Cited · Link answered, 19 October 2026 · Read in full, 24 September 2026 · A simulation · Model

    The source reads: here with orders of magnitude more particles, we find that stable satellites are produced

What this does not establish

A simulation result, above a resolution threshold; the authors say later evolution needs bespoke study.

Later work looked for

Crossref, 2021 on, "Moon-forming giant impact" and "immediate origin of the Moon": Kegerreis and others (2022) and Fischer and others (2024) add routes; nothing found that selects one model. The 2021 review by the models’ own authors is the most recent field-level account read.

Claim 47 · checked 24 September 2026 · AI-assisted audit

Claim: Its outer layers come out around sixty per cent proto-Earth material, though the satellite as a whole is still mostly impactor.

Kind
Experimental result. What an experiment or trial found, under its own conditions. A result in animals, cells or a simulation is not a result in people.
Review
Source checked. The cited passage was read, and it says this.

  • Supports

    Immediate origin of the Moon as a post-impact satelliteabstract

    Cited · Link answered, 19 October 2026 · Read in full, 24 September 2026 · A simulation · Model

    The source reads: the outer layers of these directly formed satellites are molten over cooler interiors and are composed of around 60% proto-Earth material

  • Supports

    Immediate origin of the Moon as a post-impact satellitesection 3.3, Satellite compositions and interiors

    Cited · Link answered, 19 October 2026 · Read in full, 24 September 2026 · A simulation · Model

    The source reads: Here, the immediate satellites typically have moderately higher bulk compositions of around 30–40% proto-Earth material.

What this does not establish

In simulation. If the layers later mixed, the authors estimate the Moon would be little better matched than in the canonical model.

Later work looked for

Crossref, 2021 on, "Moon-forming giant impact" and "immediate origin of the Moon": Kegerreis and others (2022) and Fischer and others (2024) add routes; nothing found that selects one model. The 2021 review by the models’ own authors is the most recent field-level account read.

Claim 48 · checked 24 September 2026 · AI-assisted audit

Claim: Each works under some set of conditions.

Kind
This page’s reading. A judgement the page makes from the evidence. Others read it differently.
Review
A judgement, not a fact. Reviewed for whether it is fairly put and follows from the checked claims. No source can confirm it.

Follows from the review’s account of each scenario and its requirements.

  • Supports

    Origin of the Moonsection 6, Conclusions and open issues

    Cited · Link answered, 19 October 2026 · Read in full, 24 September 2026 · Review of the field

    The source reads: Current models provide an array of possible solutions, but all involve conditions whose likelihood appears small or remains highly uncertain.

Corrected

24 September 2026. Previously: “All three work in simulation. None has been singled out by the samples, and each requires conditions that have to be assumed rather than derived.” The judgement is now the review’s, in its words, rather than the page’s.

Claim 49 · checked 24 September 2026 · AI-assisted audit

Claim: None has been singled out by the samples

Kind
Open question. Something the page says is not known.
Review
Presented as open. The page says this is unresolved, and the review found that it is.

  • Supports

    Origin of the Moonsection 6, Conclusions and open issues

    Cited · Link answered, 19 October 2026 · Read in full, 24 September 2026 · Review of the field

    The source reads: Current models provide an array of possible solutions, but all involve conditions whose likelihood appears small or remains highly uncertain.

Claim 50 · checked 24 September 2026 · AI-assisted audit

Claim: and a review written by several of the models’ own authors says all of them involve “conditions whose likelihood appears small or remains highly uncertain”.

Kind
Quotes a source. The words of a named text, checked against the source.
Review
Source checked. The cited passage was read, and it says this.

Canup, Ćuk, Stewart, Lock and Rufu, among the review’s authors, proposed several of the models described.

  • Supports

    Origin of the Moonsection 6, Conclusions and open issues

    Cited · Link answered, 19 October 2026 · Read in full, 24 September 2026 · Review of the field

    The source reads: Current models provide an array of possible solutions, but all involve conditions whose likelihood appears small or remains highly uncertain.

Claim 51 · checked 24 September 2026 · AI-assisted audit

Claim: The evidence and the awkwardness

Kind
Framing. Signposting. It asserts nothing a source could check.

Claim: The Moon has a tiny iron core.

Kind
Observation. Something measured or seen, as the named source reports it.
Review
Source checked. The cited passage was read, and it says this.

  • Supports

    Origin of the Moonsection 1, Introduction

    Cited · Link answered, 19 October 2026 · Read in full, 24 September 2026 · Astronomical observation · Review of the field

    The source reads: The Moon has a tiny core, perhaps with only ~ 1% of its mass, in contrast to Earth whose core contains nearly 30% of its mass

  • Supports

    Moon FactsStructure

    Cited · Link answered, 19 October 2026 · Read in full, 24 September 2026 · Astronomical observation · Reference work

    The source reads: The Moon’s core is proportionally smaller than other terrestrial bodies' cores. The solid, iron-rich inner core is 149 miles (240 kilometers) in radius. It is surrounded by a liquid iron shell 56 miles (90 kilometers) thick.

Later work looked for

Crossref, 2022 on, "lunar inner core radius": Briaud and others (Nature, 2023, abstract) give an inner core radius of 258 ± 40 km, consistent with NASA’s 240 within its uncertainty; page unchanged.

Corrected

24 September 2026. Previously: “The Moon has almost no iron core.” The core is small but real (review; NASA).

Claim 53 · checked 24 September 2026 · AI-assisted audit

Claim: It formed from mantle material, after a body had already separated its metal into a core.

Kind
What a model says. What a theory or model predicts or describes, which is not the same as what has been observed.
Review
Source checked. The cited passage was read, and it says this.

  • Supports

    Origin of the Moonsection 3.1.1, Constraints

    Cited · Link answered, 19 October 2026 · Read in full, 24 September 2026 · Review of the field

    The source reads: It is typically assumed that a successful impact must produce an iron -depleted disk, although alternatively the disk could evolve into an iron-depleted state via post-impact vapor mixing with the Earth’s mantle

Other readings

The review notes the disc could instead have become iron-poor by vapour mixing with Earth’s mantle after the impact.

Claim 54 · checked 24 September 2026 · AI-assisted audit

Claim: Earth and Moon share isotopic ratios to high precision.

Kind
Observation. Something measured or seen, as the named source reports it.
Review
Source checked. The cited passage was read, and it says this.

Later work looked for

Crossref, 2021 on, "oxygen isotope Earth Moon": Fischer and others (PNAS, December 2024) find no Earth-Moon difference at 0.2 ± 1.6 ppm and no heterogeneity among lunar rock types, against Cano and others (2020); page now reports the 2024 result.

Claim 55 · checked 24 September 2026 · AI-assisted audit

Claim: Either the Moon is mostly Earth, or the impactor was a twin, or the collision mixed both thoroughly.

Kind
What a model says. What a theory or model predicts or describes, which is not the same as what has been observed.
Review
Source checked. The cited passage was read, and it says this.

  • Supports

    Oxygen isotope identity of the Earth and Moon with implications for the formation of the Moon and source of volatilesDiscussion

    Cited · Link answered, 19 October 2026 · Read in full, 24 September 2026 · Argument

    The source reads: The isotope identity of Moon and Earth, as illustrated in diagram Fig. 3 requires either Theia and proto-Earth having the same composition (16), vigorous mixing of Theia and Earth after the Moon-forming impact (37–39), or a combination of both.

  • Supports

    Origin of the Moonsection 3.2, Canonical impact

    Cited · Link answered, 19 October 2026 · Read in full, 24 September 2026 · Review of the field

    The source reads: In general, a canonical Moon-forming impact requires either an impactor with an Earth ... or that the compositional signature of the impactor in the disk was erased by vapor mixing

What this does not establish

These are the routes the sources list; they can also combine.

Claim 56 · checked 24 September 2026 · AI-assisted audit

Claim: The pair carries a large amount of angular momentum.

Kind
Observation. Something measured or seen, as the named source reports it.
Review
Source checked. The cited passage was read, and it says this.

  • Supports

    Origin of the Moonsection 1, Introduction

    Cited · Link answered, 19 October 2026 · Read in full, 24 September 2026 · Astronomical observation · Review of the field

    The source reads: The Earth-Moon system has a high total angular momentum, implying a rapidly spinning Earth when the Moon formed

Later work looked for

A measured property of the system; not something later work revises.

Claim 57 · checked 24 September 2026 · AI-assisted audit

Claim: An oblique collision.

Kind
What a model says. What a theory or model predicts or describes, which is not the same as what has been observed.
Review
Source checked. The cited passage was read, and it says this.

  • Supports

    Origin of the Moonsection 3.1.1, Constraints

    Cited · Link answered, 19 October 2026 · Read in full, 24 September 2026 · Review of the field

    The source reads: An oblique collision(s) is a natural source of Earth’s early rapid spin

What this does not establish

An inference from the spin, not an observation of the impact.

Corrected

24 September 2026. Previously: “A grazing collision.” The canonical impact is at 40 to 50 degrees (review, section 3.2), oblique rather than grazing.

Claim 58 · checked 24 September 2026 · AI-assisted audit

Claim: The difficulty is that the versions which fit the isotopes leave extra spin that something must later remove.

Kind
What a model says. What a theory or model predicts or describes, which is not the same as what has been observed.
Review
Source checked. The cited passage was read, and it says this.

  • Supports

    Origin of the Moonsection 3.4, Fast-spinning Earth impact

    Cited · Link answered, 19 October 2026 · Read in full, 24 September 2026 · Review of the field

    The source reads: which could satisfy the oxygen isotopic data even in the limit of a Mars -like composition impactor ... Both require a subsequent dynamical mechanism to bring the system to the present-day angular momentum

What this does not establish

Whether the extra spin could be removed is unresolved; see the passage above.

Corrected

24 September 2026. Previously: “The difficulty is that the versions which fit the isotopes leave too much spin to shed.” “Too much to shed” said it could not be removed; the review says it must be, and that whether it could is unclear.

Claim 59 · checked 24 September 2026 · AI-assisted audit

What would settle it

Claim: What would settle it

Kind
Framing. Signposting. It asserts nothing a source could check.

Claim: The models differ in how much impactor they leave in the Moon, so measuring the isotopes more precisely in more elements is one lever.

Kind
What scholars argue. A report of what specialists argue, or where they disagree.
Review
Source checked. The cited passage was read, and it says this.

  • Supports

    Origin of the Moonsection 3.2, Canonical impact

    Cited · Link answered, 19 October 2026 · Read in full, 24 September 2026 · A simulation · Review of the field

    The source reads: In canonical impacts, most of the disk, typically ... 70 to 80%, originates from the impactor's mantle

  • Supports

    Origin of the Moonsection 3.5, Half-Earth impact

    Cited · Link answered, 19 October 2026 · Read in full, 24 September 2026 · A simulation · Review of the field

    The source reads: Somewhat asymmetric collisions with an impactor whose mass is > 40% of the Earth’s mass can produce disk-planet compositional differences as small as

  • Supports

    Origin of the Moonsection 2.3

    Cited · Link answered, 19 October 2026 · Read in full, 24 September 2026 · Review of the field

    The source reads: Future data may better constrain the relative Earth -Moon oxygen isotopic compositions.

Corrected

24 September 2026. Previously: “The isotopic difference the theories predict is small, and measuring it more precisely in more elements is the main lever.” The canonical model predicts a large difference, not a small one; and the review lists Venus, and the physics of mixing and spin loss, alongside better measurements.

Claim 61 · checked 24 September 2026 · AI-assisted audit

Claim: Another is Venus: if a planet that size proved isotopically Earth-like, an Earth-like impactor would look less like luck.

Kind
What scholars argue. A report of what specialists argue, or where they disagree.
Review
Source checked. The cited passage was read, and it says this.

  • Supports

    Origin of the Moonsection 6, Conclusions and open issues

    Cited · Link answered, 19 October 2026 · Read in full, 24 September 2026 · Review of the field

    The source reads: If Venus proved Earth-like, the likelihood of an Earth-like impactor would be increased

Claim 62 · checked 24 September 2026 · AI-assisted audit

Claim: So is sampling the parts of the Moon the Apollo and Luna collections do not cover.

Kind
This page’s reading. A judgement the page makes from the evidence. Others read it differently.
Review
A judgement, not a fact. Reviewed for whether it is fairly put and follows from the checked claims. No source can confirm it.

Follows from the argument, reported in the review, that samples from deeper in the Moon may differ from the surface.

  • Supports

    Origin of the Moonsection 2.3

    Cited · Link answered, 19 October 2026 · Read in full, 24 September 2026 · Artefacts and sites · Review of the field

    The source reads: a robust conclusion is that the Earth and shallow Moon have ... 17O values within ~0.01‰ (10 ppm) of each other, whereas samples derived from the deeper lunar interior exhibit differences up to about 20 ppm

  • Supports

    Oxygen isotope identity of the Earth and Moon with implications for the formation of the Moon and source of volatilesDiscussion

    Cited · Link answered, 19 October 2026 · Read in full, 24 September 2026 · Measurement

    The source reads: The rocks that were brought back by the Apollo astronauts were all collected from the lunar surface.

Claim 63 · checked 24 September 2026 · AI-assisted audit

Claim: The far side has now been sampled.

Kind
Historical claim. A statement about the past that historical evidence can test.
Review
Partly checked. Only part of the source could be read. What was not read is listed.

What this does not establish

Only the abstract was read. One site, in the South Pole-Aitken basin.

Corrected

24 September 2026. Previously: “The far side is no longer one of them.” One far-side site has been sampled; the far side is not covered.

24 September 2026. Previously: “The far side has now been sampled once.” The Chang’e-6 abstract says samples were collected from the far side; it does not say this is the only time, so "once" is gone.

Claim 64 · checked 24 September 2026 · AI-assisted audit

Claim: Chang’e-6 returned material from the South Pole-Aitken basin, and a 2024 study dated basalt from it at 2,830 million years, give or take five.

Kind
Observation. Something measured or seen, as the named source reports it.
Review
Partly checked. Only part of the source could be read. What was not read is listed.

What this does not establish

Only the abstract was read; the date is for one basalt sample.

Later work looked for

Crossref, 2024 on, "Chang’e-6 farside basalt age": a separate team (Zhang and others, Nature, November 2024) dated Chang’e-6 basalt at about 2.8 billion years in the same weeks, so the page no longer calls this the first date; a 2025 Science abstract gives a U-Pb age of 2823.0 ± 5.9 million years, consistent.

Corrected

24 September 2026. Previously: “Chang’e-6 returned material from the South Pole-Aitken basin in 2024, and the first basalt dated from it came out at 2,830 million years, give or take five.” Another team published a date in the same weeks, so “first” is not supportable; and the year is the study’s, which the sources read carry.

Claim 65 · checked 24 September 2026 · AI-assisted audit

Claim: The deep interior is still out of reach.

Kind
This page’s reading. A judgement the page makes from the evidence. Others read it differently.
Review
A judgement, not a fact. Reviewed for whether it is fairly put and follows from the checked claims. No source can confirm it.

No returned sample comes from the deep interior; what is known of it is inferred from volcanic rocks with deep sources.

  • Supports

    Origin of the Moonsection 2.3

    Cited · Link answered, 19 October 2026 · Read in full, 24 September 2026 · Artefacts and sites · Review of the field

    The source reads: a robust conclusion is that the Earth and shallow Moon have ... 17O values within ~0.01‰ (10 ppm) of each other, whereas samples derived from the deeper lunar interior exhibit differences up to about 20 ppm

Claim 66 · checked 24 September 2026 · AI-assisted audit

Claim: It is waiting on ideas as much as on rocks.

Kind
This page’s reading. A judgement the page makes from the evidence. Others read it differently.
Review
A judgement, not a fact. Reviewed for whether it is fairly put and follows from the checked claims. No source can confirm it.

Follows from the review’s list of open issues, which includes theory as well as samples.

  • Supports

    Origin of the Moonsection 6, Conclusions and open issues

    Cited · Link answered, 19 October 2026 · Read in full, 24 September 2026 · Review of the field

    The source reads: The potential for planet-disk equilibration and theoretical, numerical and/or observational tests for or against equilibration.

  • Supports

    Origin of the Moonsection 6, Conclusions and open issues

    Cited · Link answered, 19 October 2026 · Read in full, 24 September 2026 · Review of the field

    The source reads: Interaction of the Moon with the evection resonance can enable the needed angular momentum extraction for limited parameter regimes ... but whether this is likely for realistic models of the post

Corrected

24 September 2026. Previously: “This is a question waiting on rocks rather than on ideas, which is an unusual and comfortable position for a planetary science problem.” The review’s open issues include the physics of mixing and of spin loss, not only new samples.

Claim 67 · checked 24 September 2026 · AI-assisted audit

Claim: Whether vapour could really have mixed the Moon and Earth, and whether the resonance could shed as much spin as the models ask of it, are both still open.

Kind
Open question. Something the page says is not known.
Review
Presented as open. The page says this is unresolved, and the review found that it is.

  • Supports

    Origin of the Moonsection 6, Conclusions and open issues

    Cited · Link answered, 19 October 2026 · Read in full, 24 September 2026 · Review of the field

    The source reads: The potential for planet-disk equilibration and theoretical, numerical and/or observational tests for or against equilibration.

  • Supports

    Origin of the Moonsection 6, Conclusions and open issues

    Cited · Link answered, 19 October 2026 · Read in full, 24 September 2026 · Review of the field

    The source reads: Interaction of the Moon with the evection resonance can enable the needed angular momentum extraction for limited parameter regimes ... but whether this is likely for realistic models of the post

Claim 68 · checked 24 September 2026 · AI-assisted audit

What was read