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Evidence record

Where did Earth’s water 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.

  • Source checked: 31
  • A judgement, not a fact: 5
  • Partly checked: 2
  • Presented as open: 3

If something here is wrong, misquoted, out of date or unfair, write to support@unknownoceans.com and give the claim number, which does not change.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 origins that is answered by matching: the hydrogen isotope ratio of Earth’s water is compared with that of candidate sources. The measurements are real; what is open is how to weigh them, and whether the target ratio has itself changed since Earth formed.

  • A body’s hydrogen isotope ratio records where and how its water formed

    Established

    The ratio is a tracer of formation conditions, which is why the matching works at all. It can also shift later, through dust in a comet’s coma or escape from an early atmosphere, and the page reports both.

  • Earth’s water had to come from somewhere other than the material Earth was mostly built from

    Contested

    The usual view, because the inner solar system was too warm for ice. A 2020 study finds enough hydrogen in enstatite chondrites, which resemble Earth’s building blocks, to have supplied it from the start.

  • The oceans’ ratio today is the ratio Earth’s water began with

    Contested

    One model of an early hydrogen-rich atmosphere raises it by a factor of two to nine; a 2012 synthesis finds no need for escape fractionation; a 2026 calculation adds a shift from core formation.

How the question is labelled

Claim: The delivery

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

A title, not a finding: the page reports that some of the water may have been built in rather than delivered.

Claim: Water

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

The question

Claim: Earth formed in a part of the disc too warm for ice

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.

What this does not establish

This is the standard picture of the disc, not a measurement of it. Too warm for ice is not the same as dry: the page later reports hydrogen in inner solar system meteorites.

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

Claim: and it is covered in ocean.

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

A present-day fact about Earth; not something later work revises.

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

Claim: Hydrogen isotopes are one of the best ways of testing where it came from.

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.

Other tracers are used too: the 2012 synthesis the page cites leans on nitrogen and noble gases as well.

Corrected

24 September 2026. Previously: “Hydrogen isotopes are how the question is being answered.” The sources call hydrogen isotopes a key tracer and one of the best means, not the only one; the 2012 synthesis the page cites also uses nitrogen and noble gases.

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

Claim: Water carries a fingerprint: the ratio of heavy hydrogen to ordinary hydrogen, which depends on where and how cold it formed.

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

    A nearly terrestrial D/H for comet 67P/Churyumov-GerasimenkoIntroduction

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

    The source reads: At increasing distances from the Sun, decreasing PSN temperature and density reduced the efficiency of isotopic exchange, allowing more of the initially enriched D/H to be preserved in water ice.

What this does not establish

The ratio can also change after the water forms. The page reports two ways: ice on dust in a comet’s coma, and escape from an early atmosphere.

Later work looked for

How the method works; not a finding later work revises.

Corrected

24 September 2026. Previously: “Water carries a fingerprint: the ratio of heavy hydrogen to ordinary hydrogen, set by where and how cold it formed.” "Set by" implied the ratio is fixed at formation. The page’s own sources show it can shift afterwards (Genda and Ikoma 2008; Mandt and others 2024).

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

Claim: Measuring that ratio in Earth, in asteroids and in comets has narrowed the candidates and has not closed the case.

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 claims below: the solar nebula alone is far too light, the carbonaceous chondrites match, and the comets are reopened by a disputed reanalysis.

Corrected

24 September 2026. Previously: “has narrowed the candidates considerably and has not closed the case.” Since 2020 the candidates have widened as well as narrowed: enstatite chondrites (Piani and others 2020) and the Jupiter-family comets (Mandt and others 2024) are back in contention.

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

Claim: The inner solar system was too warm for ice when the planets assembled.

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.

What this does not establish

The standard picture of the disc, stated by the sources as the premise they test.

Corrected

24 September 2026. Previously: “The inner solar system was hot when the planets assembled. Ice does not survive there,” Tightened to the source’s wording, and the present tense removed: the claim is about the disc then.

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

Claim: The material Earth was built from has generally been presumed dry.

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.

Corrected

24 September 2026. Previously: “so the material Earth was built from should have been dry.” A presumption the field held, and which a 2020 study challenges: enstatite chondrites carry enough hydrogen to supply several oceans (Piani and others 2020). The page reports that below.

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

Claim: It is not a small discrepancy.

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.

Introduces the amount of water in claim 11.

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

Claim: There is enough water here to cover the whole planet to a depth of nearly three kilometres if the surface were smooth.

Kind
Present-day figure. A count, survey or report finding, as the named source gives it.
Review
Source checked. The cited passage was read, and it says this.

  • Supports

    Origin of the ocean on the Earth: Early evolution of water D/H in a hydrogen-rich atmospheresection 1, Introduction

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

    The source reads: the mass of the ocean on the Earth (~ 1.4×10²¹ kg)

    Notation restored: The superscript restored from the arXiv PDF (0709.2025), whose glyph boxes read with pdftotext -bbox show the 21 raised and set smaller, read 2026-09-24. The text as extracted reads: the mass of the ocean on the Earth (~ 1.4×10 21 kg)

    1.4×10²¹ kg of water is about 1.4×10¹⁸ cubic metres; spread over Earth’s surface of about 5.1×10¹⁴ square metres, that is a layer about 2.7 kilometres deep, which the page calls nearly three.

What this does not establish

The oceans only. The page later reports estimates that much more water is held inside the Earth.

Later work looked for

A standard figure, used unchanged by the 2020 source; nothing that changes it.

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

How it is traced

Claim: How it is traced

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

Water has a fingerprint

Claim: Water has a fingerprint

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

A heading for claims 14 and 15.

Claim: A fraction of the hydrogen in any water is deuterium, a heavier isotope.

Kind
About a word. What a word in the original language means, or how it is translated.
Review
Source checked. The cited passage was read, and it says this.

Claim 14 · checked 24 September 2026 · AI-assisted audit

Claim: The ratio depends on the temperature and conditions where that water formed, which is what makes it useful: the same measurement made on meteorites, comets and moons can say where each of them formed.

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.

What this does not establish

A tracer of formation conditions, not a reading of them: the ratio can be changed after the fact, which the page takes up in its second half.

Later work looked for

How the method works; not a finding later work revises.

Corrected

24 September 2026. Previously: “which is what makes it useful: the study cited here compares the hydrogen in 86 primitive meteorites with comets and with Enceladus to say where those bodies formed.” The 2012 study was described twice on the page. The general point is now carried by the 2024 source’s account of the method, and the study is described once, in the next passage.

Claim 15 · checked 24 September 2026 · AI-assisted audit

Claim: So the question can be asked as a matching problem.

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

Claim: Earth’s oceans have a particular ratio; any proposed source has to have that ratio or be mixed from things that average to it.

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 matching assumes the oceans’ ratio has not changed since the water arrived. Genda and Ikoma, the source for this claim, go on to question exactly that (claim 46).

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

Asteroids match better than comets

Claim: Asteroids match better than comets

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

On hydrogen alone the gap is narrower than the heading suggests: Jupiter-family comets sit near Earth’s ratio. Nitrogen is what still separates comets from Earth in the 2012 synthesis.

Later work looked for

Crossref and Europe PMC, 2024 on, "comet D/H water" and "67P D/H": the 2024 reanalysis narrows the comet gap for one family and is disputed (claim 26); nothing reverses the chondrite match.

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

Claim: A 2012 study measured hydrogen isotopes in 86 primitive meteorites and found the water in carbonaceous chondrites distinct from the water in comets, with the hydrogen and nitrogen of the CI group suggesting it was the principal source of Earth’s volatiles.

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

Read from the abstract and the journal’s summary; the paper itself was not available. "Suggest" is the authors’ word.

Later work looked for

Crossref, 2013 on, "carbonaceous chondrite deuterium Earth water source": Sarafian and others 2014 support an early carbonaceous source; Piani and others 2020 propose enstatite chondrites instead, now reported on the page.

Corrected

24 September 2026. Previously: “A 2012 study measured hydrogen isotopes in 86 primitive meteorites and found the carbonaceous chondrites distinct from comets and close to Earth, with the CI group the best match for Earth’s volatiles.” "Close to Earth" is not in what could be read of this study (the chondrite match is carried by the module row, from Marty 2012), and "the best match" hardened the abstract’s "suggest".

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

Claim: That implies their parent bodies formed in a different region from the comets, contrary to what recent dynamical models had predicted.

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

The authors’ inference, read from the abstract; the paper was not available.

Corrected

24 September 2026. Previously: “Their parent bodies did not form where the comets did, which several dynamical models had required.” The abstract says "implying" and "predictions", not a settled fact and not a requirement.

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

Claim: Comets have been measured one at a time, and the ratios differ between them by as much as a factor of four.

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

    A nearly terrestrial D/H for comet 67P/Churyumov-GerasimenkoIntroduction, D/H in comets

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

    The source reads: D/H measurements from one comet to the next can vary by as much as a factor of four.

What this does not establish

The 2024 authors suggest some of that spread may be dust in the comae rather than the comets themselves.

Later work looked for

Crossref and Europe PMC, 2024 on, "comet D/H": nothing found that changes the range.

Corrected

24 September 2026. Previously: “Comets have been tested one at a time as spacecraft reach them, and the ratios differ between them by as much as a factor of four.” Rosetta’s is described by its team as a direct in situ measurement; the sources do not describe the other comets’ ratios as spacecraft measurements, so the page no longer says they were.

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

Claim: The comet Rosetta reached in 2014 measured about three times Earth’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.

Later work looked for

Crossref, 2015 on, "67P D/H": Müller and others 2022 confirm a high value (5.01 × 10^-4) over the whole mission; Mandt and others 2024 dispute it. Both are on the page.

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

Claim: and that brought its family into question as a source.

Kind
Historical claim. A statement about the past that historical evidence can test.
Review
Source checked. The cited passage was read, and it says this.

Corrected

24 September 2026. Previously: “which was read at the time as ruling its family out.” The discovery paper concluded only that the family cannot be made solely of Earth-like water; "ruling out" overstated it.

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

Claim: A 2024 reanalysis of the whole mission challenges that reading.

Kind
Historical claim. A statement about the past that historical evidence can test.
Review
Source checked. The cited passage was read, and it says this.

Corrected

24 September 2026. Previously: “A reanalysis of the whole mission in 2024 undid that reading.” One team’s reanalysis, which disputes a 2022 analysis of the same instrument’s data (Müller and others), does not settle the value.

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

Claim: Its authors find that ice on dust grains in the coma releases water far richer in deuterium than the nucleus, and that the ratio measured where the gas is well mixed is 1.2 to 1.6 times Earth’s, in line with the other Jupiter-family comets measured.

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

    A nearly terrestrial D/H for comet 67P/Churyumov-GerasimenkoDiscussion

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

    The source reads: the D/H can be 3 to 10 times the terrestrial value when influenced by dust, but outside of the influence of dust is only 1.2 to 1.6 times the terrestrial value. As shown in Fig. 1A, this places 67P/C-G in line with other JFCs

  • Supports

    A nearly terrestrial D/H for comet 67P/Churyumov-Gerasimenkoabstract

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

    The source reads: The isotope ratio measured at a distance from the nucleus where the gas is well mixed is close to terrestrial

  • Supports

    A nearly terrestrial D/H for comet 67P/Churyumov-GerasimenkoIntroduction, How dust influences the local coma composition

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

    The source reads: HDO was preferentially adsorbed onto dust grains, allowing for very high D/H in the ice on the dust grains

  • Cuts against

    High D/H ratios in water and alkanes in comet 67P/Churyumov-Gerasimenko measured with Rosetta/ROSINA DFMSabstract

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

    The source reads: This suggests that the D /H ratio in 67P’s coma is independent of heliocentric distance, level of cometary activity, as well as spacecraft location with respect to the nucleus.

What this does not establish

One team’s reanalysis of archived data, using a new way of separating two overlapping signals. A 2022 analysis of the same instrument’s data found no dependence on where the spacecraft was (claim 26).

Later work looked for

Crossref and Europe PMC, November 2024 on, "67P D/H dust coma": no published reply or confirmation found; conference abstracts only.

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

Claim: A 2022 analysis of the same instrument’s data had found the ratio high and steady wherever the spacecraft was, and that is the result the reanalysis disputes.

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.

Both groups worked from the ROSINA mass spectrometer’s data; Mandt and others cite the 2022 paper as the analysis they revisit.

  • Supports

    High D/H ratios in water and alkanes in comet 67P/Churyumov-Gerasimenko measured with Rosetta/ROSINA DFMSabstract

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

    The source reads: All D/H ratio measurements were compatible, within 1σ, with the mean value of 5.01 × 10⁻⁴ and its relative variation of 2.0%.

    Notation restored: The superscript restored from the arXiv PDF (2202.03521), whose glyph boxes read with pdftotext -bbox show the −4 raised and set smaller, read 2026-09-24. The text as extracted reads: All D/H ratio measurements were compatible, within 1σ, with the mean value of 5.01× 10−4 and its relative variation of 2.0%.

  • Supports

    High D/H ratios in water and alkanes in comet 67P/Churyumov-Gerasimenko measured with Rosetta/ROSINA DFMSsection 5, Summary & conclusions

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

    The source reads: The D /H ratio in water in 67P’s coma, measured with ROSINA/DFMS, is independent of the heliocentric distance, the level of cometary activity, the spacecraft’s phase angle and the sub-spacecraft latitude.

  • Supports

    A nearly terrestrial D/H for comet 67P/Churyumov-GerasimenkoResults

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

    The source reads: To date, no notable change in the D/H ratio has been reported over time (32) or spatially between the two lobes of the comet nucleus (33). However, these results are determined based on only 150 measurements.

Later work looked for

Crossref, November 2024 on, "67P D/H": no reply from either side found.

Corrected

24 September 2026. Previously: “” The page reported the 2024 reanalysis as settling the value. It is contested by an earlier analysis of the same instrument’s data, which the page did not mention.

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

Claim: Matching by isotope

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

Claim: Carbonaceous chondrites cluster near Earth’s deuterium ratio.

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, 2013 on, "carbonaceous chondrite deuterium Earth water": nothing that changes the match; Zhang and others 2026 tabulate CI and CM values either side of the oceans’.

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

Claim: Their parent bodies are a plausible source, and probably formed in a different region from the comets.

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 claims 19, 20 and 28.

Corrected

24 September 2026. Previously: “Their parent bodies are a plausible bulk source, and they did not form where the comets did.” The source implies the different birthplace rather than establishing it; "bulk" was unclear and is not in the sources.

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

Claim: On the 2024 reanalysis, Rosetta’s comet measured three to ten times Earth’s ratio where dust affected the gas, and 1.2 to 1.6 times it where the gas was well mixed.

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

Disputed by a 2022 analysis of the same data (claim 26).

Later work looked for

As for claim 25: no reply or confirmation found.

Corrected

24 September 2026. Previously: “Rosetta’s comet measured three times Earth’s ratio close in and 1.2 to 1.6 times it further out.” Attributed to the reanalysis, which is disputed, and given its own range and criterion (dust, not distance alone).

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

Claim: If the reanalysis holds, the case against the Jupiter-family comets leaned on a dust-affected value, and it is open again.

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 claims 23, 25 and 26.

Other readings

Nitrogen isotopes still count against comets in the 2012 synthesis, whatever their hydrogen (claim 18).

Corrected

24 September 2026. Previously: “The case against the Jupiter-family comets rested on the close-in value, and it is open again.” Made conditional on a reanalysis that is disputed.

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

Claim: Comet ratios vary from one comet to another by up to a factor of four.

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

    A nearly terrestrial D/H for comet 67P/Churyumov-GerasimenkoIntroduction, D/H in comets

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

    The source reads: D/H measurements from one comet to the next can vary by as much as a factor of four.

Later work looked for

As for claim 21: nothing found that changes the range.

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

Claim: One measurement does not characterise a population, and the population is being sampled a few objects at a time.

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 claims 21 and 32.

  • Context

    A nearly terrestrial D/H for comet 67P/Churyumov-GerasimenkoResults, Determining D/H in the nucleus

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

    The source reads: Because dust can influence D/H in a coma, it is possible that some of the spread in cometary values shown in Fig. 1A could be caused by dust influences on the coma.

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

What is unresolved

Claim: What is unresolved

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

Claim: The target of the match may have drifted for four and a half billion years.

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

What this does not establish

A possibility the sources raise, not a finding that it happened; a 2012 synthesis argues the isotopes need no such drift (claim 48).

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

How much arrived late

Claim: How much arrived late

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.

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

Claim: Delivery by impacts after Earth had largely formed is one model: a small late addition of water-rich material from the outer solar system.

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

Other readings

The same source describes this delivery as possible during or after Earth’s main growth, and the 2012 synthesis equates Earth’s volatiles to about two per cent of carbonaceous chondrite material, added by a few wet bodies while Earth was still growing.

Corrected

24 September 2026. Previously: “Delivery by impacts after Earth had formed is one model.” Stated as the source describes the model.

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

Claim: Another has the water built in from the start.

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

Introduces claims 39 and 40.

Corrected

24 September 2026. Previously: “” Introduces the enstatite chondrite result added below.

Claim: Enstatite chondrites, meteorites whose isotopes resemble Earth’s rocks, were presumed dry because they formed in the inner solar system; a 2020 study found enough hydrogen in them to have supplied at least three times the water in the oceans.

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.

What this does not establish

Thirteen meteorites measured. The authors call their higher estimates upper limits, because water may have been lost as Earth grew, and cannot rule out some terrestrial contamination in part of the hydrogen.

Later work looked for

Europe PMC, 2021 on, "Earth’s water D/H enstatite": Zhang and others 2026 find EC-dominated accretion consistent with bulk-Earth hydrogen, a model that supports rather than revises it.

Corrected

24 September 2026. Previously: “” The page described only late delivery and a nebular source, and omitted the 2020 result that makes Earth’s own building blocks a candidate.

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

Claim: And some may have come from the nebula itself, dissolved into an early magma ocean from a thick primordial atmosphere whose traces are still in the mantle, though one estimate puts that share at a tenth or less of the mantle’s volatiles.

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

  • Supports

    The origins and concentrations of water, carbon, nitrogen and noble gases on Earthsection 2.2

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

    The source reads: Retention of a nebular, H2-rich atmosphere might have taken place when the proto-Earth was larger than ~1000 km in diameter ... the probable contribution of greenhouse warming by the massive atmosphere (Sasaki, 1990). Consequently, solar gases like neon would have been dissolved in the growing proto-Earth magmas.

  • Supports

    The origins and concentrations of water, carbon, nitrogen and noble gases on Earthabstract

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

    The source reads: Remnants of the proto-solar nebula (PSN) are still present in the mantle, presumably signing the sequestration of PSN gas at an early stage of planetary growth.

  • Supports

    The origins and concentrations of water, carbon, nitrogen and noble gases on Earthsection 5, Conclusions

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

    The source reads: A small (≤10 %) fraction of mantle volatiles might have been derived from the protosolar nebula during an early stage of the proto-Earth growth.

What this does not establish

The traces are solar-like neon; whether they came from a captured atmosphere or from dust carrying solar wind is still discussed in the same source.

Later work looked for

Europe PMC, 2021 on, "Earth’s water nebular hydrogen": Zhang and others 2026 model nebular gas resetting planetesimals’ hydrogen, a different route that the page does not describe.

Corrected

24 September 2026. Previously: “Another has water incorporated during accretion, dissolved into an early magma ocean from a thick primordial atmosphere whose traces are still in the mantle.” The source for this model puts the nebular share at ten per cent or less, which the page left out.

24 September 2026. Previously: “And some may have come from the nebula itself, dissolved into an early magma ocean from a thick primordial atmosphere whose traces are still in the mantle, though one estimate puts that share at a tenth or less.” Marty's 10 per cent or less is a fraction of the mantle's volatiles, not of Earth's water; the denominator is now named.

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

Claim: These are not exclusive, and the mixture is what is being argued about.

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.

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

Claim: Much of the water may not be in the oceans at all: one mass balance puts up to nine tenths of it in the mantle, and work on core formation suggests the core took most of the planet’s hydrogen.

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

Two different estimates, not one to be added to the other. Marty’s is high against other mantle estimates by his own account; the core figure rests on experiments and simulations of how hydrogen splits between metal and rock, which the 2026 authors say is still debated at lower pressures.

Later work looked for

Europe PMC, 2024 on, "Earth’s water D/H": Zhang and others 2026 (core); page updated.

Corrected

24 September 2026. Previously: “Most of the water is not in the oceans at all: mass balances put as much as nine tenths of it inside the Earth, and where that came from is a separate accounting problem.” The nine tenths is one author’s upper estimate, which he says is high against other work; it was stated as fact and as several mass balances. The core estimates (Zhang and others 2026, summarising experiments and simulations) are added, and "a separate accounting problem" is replaced by claim 43, because the 2026 work treats the interior and the oceans as one accounting.

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

Claim: The mantle’s hydrogen is also lighter than the oceans’, so matching the oceans tests only part of the inventory.

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

The first half is an observation about mantle rocks; "tests only part of the inventory" is the page’s inference from it and from claim 42.

Later work looked for

Europe PMC, 2024 on, "mantle D/H": Zhang and others 2026 cite mantle values of −60 to −150 per mil; nothing that changes the direction.

Corrected

24 September 2026. Previously: “” Replaces "where that came from is a separate accounting problem": the sources compare candidate meteorites with the mantle as well as the oceans.

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

Whether the isotope argument is as tight as it looks

Claim: Whether the isotope argument is as tight as it looks

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.

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

Claim: The ratio in Earth’s oceans today is not necessarily the ratio Earth started with.

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

What this does not establish

A possibility, which claims 46 to 48 argue for and against.

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

Claim: Hydrogen escapes to space preferentially over deuterium, and one model of an early hydrogen-rich atmosphere raises the ocean’s ratio by a factor of two to nine, which would mean the match with the meteorites does not by itself point to them.

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.

What this does not establish

A model that assumes the early Earth held a hydrogen-rich atmosphere comparable in mass with its water; the authors say recent formation theories predict one.

Other readings

The 2012 synthesis finds no isotopic sign of such escape (claim 48).

Corrected

24 September 2026. Previously: “which would make the match with the meteorites a coincidence.” The authors conclude only that the similarity "does not necessarily support" a chondritic origin, not that it is a coincidence.

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

Claim: A 2026 calculation adds core formation, which it finds drew light hydrogen into the core and left the rest of the planet richer in deuterium.

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

    Light hydrogen isotopes in terrestrial coreabstract

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

    The source reads: We find that core formation enriched the silicate Earth in deuterium while concentrating isotopically light hydrogen in the core

What this does not establish

First-principles and machine-learning simulations of molten rock and metal, not a measurement of the core. The shift they model is tens of per mil, far smaller than the escape model’s factor of two to nine.

Corrected

24 September 2026. Previously: “” Newer work bearing directly on whether the target ratio moved.

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

Claim: Against that, a 2012 synthesis finds terrestrial hydrogen and nitrogen inside the meteorite range, and explains them by mixing two reservoirs without needing any escape fractionation.

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.

Corrected

24 September 2026. Previously: “Against that, terrestrial hydrogen and nitrogen sit inside the meteorite range and can be produced by mixing two reservoirs with no escape fractionation at all.” Attributed to its author, and "do not require" is weaker than "no escape fractionation at all".

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

Claim: The matching exercise assumes a target that may have moved, and whether it moved is itself unsettled.

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.

Sums up claims 45 to 48, which report both sides.

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

What was read