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Evidence record

How deep does life go?

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.

  • Partly checked: 30
  • Source checked: 21
  • A judgement, not a fact: 8
  • Presented as open: 1

If something here is wrong, misquoted, out of date or unfair, write to support@unknownoceans.com and give the claim number, which does not change.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 scientific question with a measured part and an unmeasured part. Cells have been counted in cores from kilometres below the sea floor; how far down life goes everywhere, and how much of it there is, rest on a few drill sites and on extrapolations the field itself calls highly uncertain.

  • There is life below the surface of the Earth, in sediment and rock

    Established

    Cells native to deeply buried sediment have been counted and their metabolism detected at more than one drill site, with contamination tracked during coring.

  • Life has a depth limit, and temperature sets it

    Open

    Temperature rises with depth and there is a highest temperature at which cells are known to multiply, but whether heat itself, the energy available, or the cost of repairing heat damage is what stops life in the rock is not settled.

  • The size of the deep biosphere can be estimated from the places sampled

    Contested

    Two estimates published in 2018 differ by more than twofold, one of them gives its own figures a tenfold uncertainty, and whole environments are barely sampled.

How the question is labelled

Claim: The rock is inhabited

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.

The page’s title. Much of what the page describes is buried sediment and coal rather than hard rock; the continental compilation covers rock as well.

  • Supports

    The biomass and biodiversity of the continental subsurfaceabstract

    Cited · Link answered, 19 October 2026 · Abstract only, 24 September 2026 · Research in microbes · Review of the field

    The source reads: we compiled cell concentration and microbial diversity data from continental subsurface localities around the globe

  • Supports

    Exploring deep microbial life in coal-bearing sediment down to ~2.5 km below the ocean floorabstract

    Cited · Link answered, 19 October 2026 · Abstract only, 24 September 2026 · Research in microbes · Observational study: associations, not causes

    The source reads: Here we provide evidence for the existence of microbial communities in ~40° to 60°C sediment associated with lignite coal beds at ~1.5 to 2.5 km below the seafloor

What this does not establish

Both papers were read as abstracts.

Later work looked for

Europe PMC, 2016 on, "Expedition 337" and "Nankai C0023": later work at both drill sites reports living cells at depth (Trembath-Reichert 2017, Beulig 2022); nothing that changes it.

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

Claim: Deep life

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

The question

Claim: A drill went two and a half kilometres below the sea floor and kept finding cells

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

The deep hole was spot-cored, so cells were counted in cores taken along it rather than in a continuous column. The article itself was read as an abstract.

Later work looked for

Europe PMC, 2016 on, "Expedition 337" coal: Trembath-Reichert and others (2017) grew cells from the same coal beds; nothing that changes it.

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

Claim: and in the coal beds they looked like the microbes of a forest soil

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

    Exploring deep microbial life in coal-bearing sediment down to ~2.5 km below the ocean floorabstract

    Cited · Link answered, 19 October 2026 · Abstract only, 24 September 2026 · Research in microbes · Observational study: associations, not causes

    The source reads: Peak concentrations occurred in lignite layers, where communities differed markedly from shallower subseafloor communities and instead resembled organotrophic communities in forest soils.

What this does not establish

A resemblance in gene sequences, read here from the abstract; the main paper’s comparison was not read.

Later work looked for

Europe PMC, 2016 on, "Expedition 337" coal: later cultivation work at the site; nothing found that revises the comparison.

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

Claim: A biosphere exists inside the crust, in rock and sediment

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

Both read as abstracts.

Later work looked for

Europe PMC, 2016 on, "Expedition 337" and "Nankai C0023": more drill sites with living cells; nothing that changes it.

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

Claim: running on chemistry rather than sunlight

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

The claim says no light reaches these cells. It does not say where the buried organic matter they feed on first came from.

Later work looked for

Europe PMC, 2016 on, "Expedition 337" and "Nankai C0023": nothing that changes it.

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

Claim: and, where energy is scarce, at metabolic rates so slow that its biomass turns over in centuries to millennia.

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

    Microbial life under extreme energy limitationabstract

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

    The source reads: Microbial cells in these very stable and oligotrophic settings ... turn over biomass on timescales of centuries to millennia rather than hours to days

  • Qualifies

    Rapid metabolism fosters microbial survival in the deep, hot subseafloor biosphereDiscussion

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

    The source reads: The high cell-specific catabolic rates result in biomass turnover times of hours to weeks, which is extremely short for the very deep subseafloor biosphere.

    In hot sediment rich in acetate, turnover can be far faster. These are potential rates from incubations.

Later work looked for

Europe PMC, 2016 on, deep subseafloor growth and turnover: Trembath-Reichert 2017 measured growth of months to over a century in the coal beds; Beulig 2022 hours to weeks in hot sediment; page scoped.

Corrected

24 September 2026. Previously: “and at metabolic rates so slow that biomass may turn over once a millennium.” The review gives a range, centuries to millennia, for stable nutrient-poor settings; a 2022 study of hot sediment measured turnover of hours to weeks, so the claim is scoped.

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

Claim: Its extent and its total mass are estimated from sparse sampling, and the estimates are wide and have been revised sharply downward.

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

    The biomass distribution on EarthDiscussion

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

    The source reads: Studies in these environments are scarce, meaning that our estimates have particularly high uncertainty ranges and unknown systematic biases.

  • Supports

    The biomass distribution on EarthDiscussion

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

    The source reads: global estimates of marine deep subsurface prokaryote biomass reduced by about two orders of magnitude due to an increased diversity of sampling locations

  • Context

    The biomass and biodiversity of the continental subsurfaceabstract

    Cited · Link answered, 19 October 2026 · Abstract only, 24 September 2026 · Research in microbes · Review of the field

    The source reads: roughly 4 to 10 times less than previous estimates

Corrected

24 September 2026. Previously: “Its extent and its total mass are estimated from sparse boreholes,” The continental compilation draws on subsurface localities of several kinds; its abstract does not say boreholes, and the census that describes the sampling calls it scarce.

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

Claim: Drilling into the sea floor brings up sediment buried millions of years ago.

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

    Exploring deep microbial life in coal-bearing sediment down to ~2.5 km below the ocean floorSupplementary Materials, Study site and coring operations

    Cited · Link answered, 19 October 2026 · Abstract only, 24 September 2026 · Earth and its record · Observational study: associations, not causes

    The source reads: coal layers that were deposited in terrigenous to shallow marine environments, such as coastal wetlands or deltaic lagoons, during the late Paleogene and early Neogene

What this does not establish

Read from one drill site. How old the sediment is depends on how deep a hole goes and where.

Later work looked for

Describes what drilling recovers; not a finding later work revises.

Corrected

24 September 2026. Previously: “Drilling into the sea floor was done to read the climate of the past.” No cited source carries the history of why the sea floor was drilled, and the Nankai expedition the page leans on was drilled to explore the habitability of the deep, hot subseafloor (Beulig and others, Methods).

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

Claim: It kept turning up cells.

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

The Inagaki article was read as an abstract.

Later work looked for

Europe PMC, 2016 on, "Expedition 337" and "Nankai C0023": nothing that changes it.

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

Claim: Not contamination, and not survivors of a recent burial.

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

Contamination was tracked and subtracted rather than excluded: the supplement estimates the native share of each sample’s sequences, and the counts it reports are the cells judged native after that step.

Later work looked for

Europe PMC, 2016 on, "Expedition 337" and drilling contamination: 2025 papers on contaminants in ocean drilling and on the origin of one fungal strain from these coal beds, seen by title only, concern isolates rather than the corrected counts; nothing read that changes it.

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

Claim: A population living on so little energy that everything is slow,

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

    Microbial life under extreme energy limitationabstract

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

    The source reads: subsist with energy fluxes that are 1,000-fold lower than the typical culture-based estimates of maintenance requirements

Later work looked for

Europe PMC, 2016 on, deep subseafloor energy limitation: Beulig 2022 finds fast metabolism in hot sediment, which is why the claim names energy rather than depth.

Corrected

24 September 2026. Previously: “A population living where the temperature and pressure make everything slow,” The review the page cites puts the slowness down to energy limitation in stable, nutrient-poor settings. Heat speeds reactions up, and in hot sediment cells were found metabolising fast (Beulig and others).

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

Claim: and which has apparently been there for a very long time.

Kind
Hypothesis. A proposed explanation, not an established one.
Review
Partly checked. Only part of the source could be read. What was not read is listed.

What this does not establish

The authors say the evidence suggests it, and the page says apparently. That the same lineages persisted since burial is an inference from community composition, not a measurement of age.

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

What has been found

Claim: What has been found

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

There are cells two and a half kilometres down

Claim: There are cells two and a half kilometres down

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

The article was read as an abstract, with its supplement.

Later work looked for

Europe PMC, 2016 on, "Expedition 337": later work on the same cores; nothing that changes it.

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

Claim: An expedition off Japan drilled through coal-bearing sediment to about 2.5 kilometres below the sea floor and counted cells in cores from 1.3 kilometres to the bottom of the hole.

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

    Exploring deep microbial life in coal-bearing sediment down to ~2.5 km below the ocean floorabstract; Supplementary Materials, title and Study site and coring operations

    Cited · Link answered, 19 October 2026 · Abstract only, 24 September 2026 · Earth and its record · Observational study: associations, not causes

    The source reads: at ~1.5 to 2.5 km below the seafloor in the Pacific Ocean off Japan ... Exploring deep microbial life in coal-bearing sediment down to ~2.5 km below the ocean floor ... resumed drilling and advanced the total borehole depth down to 2466 mbsf with spot-coring of sediments

  • Supports

    Exploring deep microbial life in coal-bearing sediment down to ~2.5 km below the ocean floorSupplementary Materials, fig. S7 caption

    Cited · Link answered, 19 October 2026 · Abstract only, 24 September 2026 · Research in microbes · Observational study: associations, not causes

    The source reads: For cell concentrations in “deep” (1279.1 to 2458.8 mbsf, Expedition 337) subseafloor, raw data of fluorescence image-based cell counts

What this does not establish

The hole was spot-cored, so the counts are from cores along it, not a continuous profile.

Later work looked for

Europe PMC, 2016 on, "Expedition 337": nothing that changes the counts.

Corrected

24 September 2026. Previously: “An expedition off Japan drilled through coal-bearing sediment to about 2.5 kilometres below the sea floor and counted cells the whole way down.” The supplement gives the deep samples as 1279.1 to 2458.8 m below the sea floor, spot-cored; the shallow samples came from the upper 365 m of a neighbouring hole in 2006. There was no count across the kilometre between.

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

Claim: Cores from the upper few hundred metres at the same site held more than ten million per cubic centimetre.

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

    Exploring deep microbial life in coal-bearing sediment down to ~2.5 km below the ocean floorSupplementary Materials, Study site and coring operations; Quality assessment and control

    Cited · Link answered, 19 October 2026 · Abstract only, 24 September 2026 · Research in microbes · Observational study: associations, not causes

    The source reads: sediment cores were sampled throughout the upper 365 m below the seafloor (mbsf) in Hole C of JAMSTEC Site C9001 (i.e., “shallow” subseafloor sediment samples) ... We obtained a large amount of DNA from high-biomass (>10⁷ cells cm⁻³) “shallow” subseafloor sediment core samples

    Notation restored: Superscripts restored from the Supplementary Materials PDF (Caltech Authors copy), where the 7 and the −3 are raised, read from glyph positions 2026-09-24. The text as extracted reads: sediment cores were sampled throughout the upper 365 m below the seafloor (mbsf) in Hole C of JAMSTEC Site C9001 (i.e., “shallow” subseafloor sediment samples) ... We obtained a large amount of DNA from high-biomass (>107 cells cm-3) “shallow” subseafloor sediment core samples

    The supplement prints the figure as 10 to the 7th cells per cubic centimetre; the superscript is lost in the extracted text. It defines the shallow samples as the upper 365 m.

What this does not establish

Read from the supplement; the main paper’s depth profile was not read.

Later work looked for

Europe PMC, 2016 on, "Expedition 337": nothing that changes it.

Corrected

24 September 2026. Previously: “They thin with depth.” The thinning is what the numbers show, so the page now gives the numbers the supplement carries rather than the summary.

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

Claim: Below 1.5 kilometres, in sediment at 40 to 60 degrees Celsius, the count runs from fewer than ten per cubic centimetre to about ten thousand,

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

These are counts corrected for contamination; the supplement gives raw, most likely and most conservative estimates.

Later work looked for

Europe PMC, 2016 on, "Expedition 337": Trembath-Reichert 2017 reports 50 to 2,000 cells per cubic centimetre in the coal and shale it incubated, inside this range.

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

Claim: far below what the global trend with depth predicts,

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 supplement.

Later work looked for

Europe PMC, 2016 on, "Expedition 337": nothing that changes it.

Corrected

24 September 2026. Previously: “” Added from the supplement, which says it in these terms.

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

Claim: and the peaks are in the lignite coal beds.

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.

Later work looked for

Europe PMC, 2016 on, "Expedition 337": Trembath-Reichert 2017 describes the coal beds as hypothesized hot spots for life; nothing that changes it.

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

Claim: Those coal-bed communities resemble the organotrophs of a forest soil rather than the subseafloor above them,

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

A resemblance in 16S rRNA gene sequences, read from the abstract.

Later work looked for

Europe PMC, 2016 on, "Expedition 337": nothing that changes it.

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

Claim: which is a clue about origin:

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 23: soil-like communities in coal that formed on or near land point to where they came from.

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

Claim: the coal was laid down in settings such as coastal wetlands and deltaic lagoons and then buried,

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.

  • Supports

    Exploring deep microbial life in coal-bearing sediment down to ~2.5 km below the ocean floorSupplementary Materials, Study site and coring operations

    Cited · Link answered, 19 October 2026 · Abstract only, 24 September 2026 · Earth and its record · Observational study: associations, not causes

    The source reads: coal layers that were deposited in terrigenous to shallow marine environments, such as coastal wetlands or deltaic lagoons, during the late Paleogene and early Neogene

What this does not establish

Read from the supplement, which cites the expedition report for the geology.

Corrected

24 September 2026. Previously: “the sediment was laid down in coastal wetlands and deltaic lagoons and buried,” The supplement says this of the coal layers, and gives wetlands and lagoons as examples of terrigenous to shallow marine settings.

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

Claim: and the paper reads the resemblance as a sign that such sediment keeps members of its original community tens of millions of years after burial.

Kind
Hypothesis. A proposed explanation, not an established one.
Review
Partly checked. Only part of the source could be read. What was not read is listed.

What this does not establish

The authors say “suggests”. It is inferred from community composition; nobody watched the community persist.

Corrected

24 September 2026. Previously: “and the paper reads the resemblance as a community retained tens of millions of years after burial.” The paper says the sediments retain community members, not that a whole community was retained, and it offers this as a suggestion.

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

A large share of the prokaryotes

Claim: A large share of the prokaryotes

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.

  • Supports

    The biomass distribution on Earthabstract

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

    The source reads: bacteria (≈70 Gt C) and archaea (≈7 Gt C) are predominantly located in deep subsurface environments

  • Supports

    Bacteria and archaea on Earth and their abundance in biofilmsabstract

    Cited · Link answered, 19 October 2026 · Abstract only, 24 September 2026 · Earth and its record · Review of the field

    The source reads: deep oceanic subsurface (4 × 10²⁹), upper oceanic sediment (5 × 10²⁸), deep continental subsurface (3 × 10²⁹)

    Notation restored: Superscripts restored from the abstract as rendered on the nature.com article page, which marks them with <sup>, read 2026-09-24. The text as extracted reads: deep oceanic subsurface (4 × 1029), upper oceanic sediment (5 × 1028), deep continental subsurface (3 × 1029)

    Of about 1.2 × 10³⁰ bacterial and archaeal cells in all, the review puts about 7 × 10²⁹ in the deep oceanic and continental subsurface, a little under three fifths.

  • Supports

    The biomass and biodiversity of the continental subsurfaceabstract

    Cited · Link answered, 19 October 2026 · Abstract only, 24 September 2026 · Research in microbes · Review of the field

    The source reads: Despite accounting for a significant portion of the Earth’s prokaryotic biomass

What this does not establish

How large a share depends on which estimate is used, and the estimates differ widely (claim 28).

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

Claim: A 2018 synthesis compiled cell counts from continental subsurface sites around the world and put the population there at 2 to 6 times 10 to the 29 cells, with bacteria more abundant than archaea.

Kind
Present-day figure. A count, survey or report finding, as the named source gives it.
Review
Partly checked. Only part of the source could be read. What was not read is listed.

  • Supports

    The biomass and biodiversity of the continental subsurfaceabstract

    Cited · Link answered, 19 October 2026 · Abstract only, 24 September 2026 · Research in microbes · Review of the field

    The source reads: we compiled cell concentration and microbial diversity data from continental subsurface localities around the globe ... we estimated that the continental subsurface hosts 2 to 6 × 10^29 cells ... we found that bacteria are more abundant than archaea

What this does not establish

Read as an abstract. The estimate is scaled up from the sites compiled using heat flow, surface temperature, depth and rock type.

Later work looked for

Crossref and Europe PMC, 2019 on, global subsurface cell numbers: Flemming and Wuertz (2019) put the deep continental subsurface at 3 × 10^29 cells, inside this range.

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

Claim: Folded into the existing literature, that gives a global prokaryotic biomass of 23 to 31 billion tonnes of carbon.

Kind
Present-day figure. A count, survey or report finding, as the named source gives it.
Review
Partly checked. Only part of the source could be read. What was not read is listed.

  • Supports

    The biomass and biodiversity of the continental subsurfaceabstract

    Cited · Link answered, 19 October 2026 · Abstract only, 24 September 2026 · Research in microbes · Review of the field

    The source reads: Using our updated continental subsurface cellular estimate and existing literature, we estimate that the total global prokaryotic biomass is approximately 23 to 31 Pg of carbon C (PgC)

  • Qualifies

    The biomass distribution on Earthabstract; Table 1

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

    The source reads: bacteria (≈70 Gt C) and archaea (≈7 Gt C)

    A census published the same year reached a figure more than twice as high.

What this does not establish

Read as an abstract. A petagram is a billion tonnes.

Later work looked for

Crossref and Europe PMC, 2018 on, global prokaryotic biomass: Bar-On and others (2018) give about 77 Gt C; no later global biomass figure found. Page now reports both.

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

Claim: It is 4 to 10 times below earlier estimates, and it is not the only figure: a census published the same year put bacteria at about 70 billion tonnes of carbon and archaea at about 7, most of both deep underground, each uncertain by a factor of ten or more.

Kind
Present-day figure. A count, survey or report finding, as the named source gives it.
Review
Partly checked. Only part of the source could be read. What was not read is listed.

  • Supports

    The biomass and biodiversity of the continental subsurfaceabstract

    Cited · Link answered, 19 October 2026 · Abstract only, 24 September 2026 · Research in microbes · Review of the field

    The source reads: roughly 4 to 10 times less than previous estimates

  • Supports

    The biomass distribution on Earthabstract

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

    The source reads: bacteria (≈70 Gt C) and archaea (≈7 Gt C) are predominantly located in deep subsurface environments

  • Supports

    The biomass distribution on EarthTable 1

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

    The source reads: Bacteria 70 10 Fungi 12 3 Archaea 7 13

    Mass in Gt C, then uncertainty as a fold change, akin to a 95 per cent interval: tenfold for bacteria, thirteenfold for archaea.

What this does not establish

Neither figure is a measurement of the whole: both scale up from the places sampled. The Magnabosco paper was read as an abstract.

Later work looked for

Crossref and Europe PMC, 2018 on, global prokaryotic biomass and deep subsurface cell numbers: Flemming and Wuertz (2019) count cells rather than carbon; no newer global biomass estimate found.

Corrected

24 September 2026. Previously: “It is 4 to 10 times below the estimate it replaced.” The paper compares itself with previous estimates in the plural, and the page presented its figure as the settled one. Bar-On and others, published four months earlier, reach about 77 billion tonnes with tenfold and thirteenfold uncertainties.

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

Claim: The subsurface did not shrink.

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 page’s reading of claims 28 and 30: what fell was an estimate, as sampling widened.

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

Claim: The estimates have fallen as more places were counted,

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

    The biomass distribution on EarthDiscussion

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

    The source reads: global estimates of marine deep subsurface prokaryote biomass reduced by about two orders of magnitude due to an increased diversity of sampling locations

What this does not establish

Bar-On and others say this of the marine subsurface. The continental revision in claim 28 is attributed to an updated compilation, which the abstract does not break down further.

Corrected

24 September 2026. Previously: “What shrank was the confidence in the extrapolation,” No source read says confidence shrank. The census says estimates fell because sampling covered more kinds of place.

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

Claim: and the 2018 synthesis reports that neither the organic carbon in continental rock nor the cells in its groundwater predict how many cells the rock holds.

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 biomass and biodiversity of the continental subsurfaceabstract

    Cited · Link answered, 19 October 2026 · Abstract only, 24 September 2026 · Research in microbes · Review of the field

    The source reads: other variables such as total organic carbon and groundwater cellular abundances do not appear to be predictive of cell concentrations in the continental subsurface

What this does not establish

Read as an abstract. The paper did find cell numbers related to heat flow, temperature, depth and rock type, which is how it made its estimate.

Later work looked for

Crossref and Europe PMC, 2019 on, continental subsurface cell abundance: nothing found that revises it.

Corrected

24 September 2026. Previously: “and the same paper reports that it could find no reliable predictor of how many cells a place will hold.” The paper’s “no reliable predictor” is about species richness. For cell numbers it used heat flow, temperature, depth and lithology, and found only organic carbon and groundwater counts unpredictive.

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

Claim: What the drilling found

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

Claim: 2.5 km

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

Rounded from 2,466 metres.

Later work looked for

Describes the depth of a hole; not a finding later work revises.

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

Claim: Below the sea floor

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

Claim: Cells counted in cores to the bottom of the hole, in coal beds laid down tens of millions of years ago.

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

The deepest count is at 2,459 metres, a few metres above the bottom of the hole.

Later work looked for

Europe PMC, 2016 on, "Expedition 337": nothing that changes it.

Corrected

24 September 2026. Previously: “Cells counted the whole way down, in sediment buried tens of millions of years ago.” The cores were spot samples from 1.3 km down, not a continuous count; the burial age the paper gives is for the coal-bearing sediment.

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

Claim: centuries

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

    Microbial life under extreme energy limitationabstract

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

    The source reads: turn over biomass on timescales of centuries to millennia rather than hours to days

What this does not establish

The lower end of the review’s range, for energy-starved settings.

Later work looked for

Europe PMC, 2016 on, deep subseafloor turnover: Beulig 2022 measures hours to weeks in hot sediment; the note beside this figure is scoped to energy-scarce settings.

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

Claim: Biomass turnover time

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

Claim: Where energy is scarce, subsurface cells turn over their biomass on timescales of centuries to millennia, not hours to days.

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

    Microbial life under extreme energy limitationabstract

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

    The source reads: Microbial cells in these very stable and oligotrophic settings ... turn over biomass on timescales of centuries to millennia rather than hours to days

  • Qualifies

    Rapid metabolism fosters microbial survival in the deep, hot subseafloor biosphereDiscussion

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

    The source reads: The high cell-specific catabolic rates result in biomass turnover times of hours to weeks

Later work looked for

Europe PMC, 2016 on, deep subseafloor growth: Beulig 2022 (hot sediment, hours to weeks) and Trembath-Reichert 2017 (coal, months to over a century); scoped.

Corrected

24 September 2026. Previously: “Subsurface cells turn over their biomass on timescales of centuries to millennia, not hours to days.” The review says this of stable, nutrient-poor settings. In hot Nankai sediment turnover was estimated at hours to weeks.

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

Claim: 23 to 31 Gt

Kind
Present-day figure. A count, survey or report finding, as the named source gives it.
Review
Partly checked. Only part of the source could be read. What was not read is listed.

What this does not establish

One of two 2018 estimates; the other is about 77 (claim 28).

Later work looked for

Crossref and Europe PMC, 2018 on, global prokaryotic biomass: Bar-On 2018 higher; nothing newer found.

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

Claim: Global prokaryotic biomass, in tonnes of carbon

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

Claim: One 2018 figure.

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

    The biomass distribution on Earthabstract

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

    The source reads: bacteria (≈70 Gt C) and archaea (≈7 Gt C)

    The other 2018 figure.

  • Context

    The biomass and biodiversity of the continental subsurfaceabstract

    Cited · Link answered, 19 October 2026 · Abstract only, 24 September 2026 · Research in microbes · Review of the field

    The source reads: approximately 23 to 31 Pg of carbon C (PgC)

Later work looked for

Crossref and Europe PMC, 2018 on, global prokaryotic biomass: nothing newer found.

Corrected

24 September 2026. Previously: “The 2018 figure.” Bar-On and others published a different figure the same year.

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

Claim: Earlier estimates were 4 to 10 times higher.

Kind
Present-day figure. A count, survey or report finding, as the named source gives it.
Review
Partly checked. Only part of the source could be read. What was not read is listed.

What this does not establish

Read as an abstract.

Later work looked for

Crossref and Europe PMC, 2018 on, global prokaryotic biomass: nothing newer found.

Corrected

24 September 2026. Previously: “The estimate it replaced was 4 to 10 times higher.” The paper compares itself with previous estimates in the plural, and it did not replace them: a higher figure was published the same year.

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

What it is doing

Claim: What it is doing

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

What sets the limit

Claim: What sets the limit

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

Claim: Temperature rises with depth,

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 physical property of the crust; not a finding later work revises.

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

Claim: and life stops somewhere.

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

    Living at the extremes: extremophiles and the limits of life in a planetary contextsection on temperature

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

    The source reads: current environmental and theoretical studies suggest that the upper limit of life might lay near ∼150°C, due primarily to the instability of macromolecules above this temperature

What this does not establish

Where it stops is the open question of claim 56.

Later work looked for

Europe PMC, 2019 on, upper temperature limit of life: nothing found that removes the limit.

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

Claim: The highest temperature at which cell proliferation has been demonstrated is 122 degrees Celsius, by a methanogen held at 20 megapascals:

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
Partly checked. Only part of the source could be read. What was not read is listed.

What this does not establish

One strain, Methanopyrus kandleri 116, in laboratory culture. The Takai paper was read as an abstract, which speaks of “possible” proliferation at 122; the review, read in full, treats it as the record.

Later work looked for

Europe PMC, 2019 on, "Methanopyrus kandleri" and 122: the 2019 review still gives 122 degrees as the upper bound for metabolic activity; nothing later found that raises it.

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

Claim: at 0.4 megapascals the same organism stops at 116.

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
Partly checked. Only part of the source could be read. What was not read is listed.

What this does not establish

Read as an abstract.

Later work looked for

Europe PMC, 2019 on, "Methanopyrus kandleri": nothing that changes it.

Corrected

24 September 2026. Previously: “at ordinary pressure the same organism stops at 116.” The paper’s lower pressure is 0.4 MPa, about four atmospheres, not ordinary pressure.

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

Claim: What depth that corresponds to varies enormously with the local geothermal gradient.

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.

Two sites off Japan: 120 degrees at 1.2 km in the Nankai Trough, 40 to 60 degrees at 1.5 to 2.5 km off Shimokita.

What this does not establish

Two sites illustrate the range; the Inagaki paper was read as an abstract.

Later work looked for

A physical property of the crust; not a finding later work revises.

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

Claim: A borehole in the Nankai Trough reached 120 degrees at 1.2 kilometres

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

Europe PMC, 2021 on, "Nankai C0023": nothing that changes it.

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

Claim: and found cells almost all the way down, though very few.

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

    Rapid metabolism fosters microbial survival in the deep, hot subseafloor biosphereResults, first paragraph

    Cited · Link answered, 19 October 2026 · Read in full, 24 September 2026 · Research in microbes · Observational study: associations, not causes

    The source reads: Despite the high temperatures, microbial cells were detected almost throughout the entire sediment column, albeit at extremely low concentrations of <500 cells per cm3 in sediment above ~50 °C

Later work looked for

Europe PMC, 2021 on, "Nankai C0023": nothing that changes it.

Corrected

24 September 2026. Previously: “and found life most of the way.” The counts are of cells, not of life, and they were extremely low: under 500 per cubic centimetre once the sediment is above about 50 degrees.

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

Claim: Above 45 degrees ordinary cells become a hundred times scarcer, spores outnumber them more than six thousand to one,

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

“Ordinary cells” is the page’s word for vegetative cells, as against endospores, the resistant resting form some bacteria take.

  • Supports

    Temperature limits to deep subseafloor life in the Nankai Trough subduction zoneabstract

    Cited · Link answered, 19 October 2026 · Read in full, 24 September 2026 · Research in microbes · Observational study: associations, not causes

    The source reads: Above 45°C, concentrations of vegetative cells drop two orders of magnitude and endospores become more than 6000 times more abundant than vegetative cells.

  • Supports

    Temperature limits to deep subseafloor life in the Nankai Trough subduction zoneauthors’ manuscript, main text, on endospores

    Cited · Link answered, 19 October 2026 · Read in full, 24 September 2026 · Research in microbes · Observational study: associations, not causes

    The source reads: cell ratio exceeds 6,000 in sediments below 350 mbsf

    An average over the hot part of the column, from the authors’ manuscript.

Later work looked for

Europe PMC, 2021 on, "Nankai C0023": nothing that changes it.

Corrected

24 September 2026. Previously: “” Added from the abstract. The page said the borehole found life most of the way without saying that above 45 degrees most of what is there is spores.

Claim 52 · checked 24 September 2026 · AI-assisted audit

Claim: and the inhabited zones alternate with gaps, one of them 192 metres thick, where no microbes could be detected.

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

    Temperature limits to deep subseafloor life in the Nankai Trough subduction zoneabstract

    Cited · Link answered, 19 October 2026 · Read in full, 24 September 2026 · Research in microbes · Observational study: associations, not causes

    The source reads: Above 45°C, populated zones alternate with zones up to 192 meters thick where microbes were undetectable.

  • Supports

    Temperature limits to deep subseafloor life in the Nankai Trough subduction zoneauthors’ manuscript, main text, first results paragraph

    Cited · Link answered, 19 October 2026 · Read in full, 24 September 2026 · Research in microbes · Observational study: associations, not causes

    The source reads: sediments harboring microbial communities with up to 400 vegetative cells cm-3 are interspersed within intervals of up to 192 m thickness, in which no cells were detected

What this does not establish

Undetectable means below what the counts could register; Beulig and others give the quantification limit for these counts as 16 cells per cubic centimetre.

Later work looked for

Europe PMC, 2021 on, "Nankai C0023": nothing that changes it.

Corrected

24 September 2026. Previously: “Above 45 degrees the inhabited zones alternate with gaps, one of them 192 metres thick, where nothing could be detected at all.” The paper says microbes were undetectable, which is narrower than nothing at all. Joined to the sentence about spores, which shares its threshold.

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

Claim: Methane is made and consumed biologically until the sediment reaches 80 to 85 degrees,

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

    Temperature limits to deep subseafloor life in the Nankai Trough subduction zoneabstract

    Cited · Link answered, 19 October 2026 · Read in full, 24 September 2026 · Earth and its record · Observational study: associations, not causes

    The source reads: Methane is biologically produced and oxidized until sediments reach 80° to 85°C.

  • Qualifies

    Rapid metabolism fosters microbial survival in the deep, hot subseafloor biosphereResults, first paragraph

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

    The source reads: it is not possible to unequivocally infer active metabolism of the observed cells based on observations of in-situ geochemical gradients as these are potentially relics of metabolism that occurred at lower temperatures in the past

  • Qualifies

    Rapid metabolism fosters microbial survival in the deep, hot subseafloor biosphereResults

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

    The source reads: In our discrete samples, which span the range of sediment temperatures, microbial activity, based on 35S-SO42− and 14C-DIC radiotracer experiments, was consistently well above the background level of the control samples

    Later radiotracer incubations of cores from the same hole, by a team that includes Heuer, measured potential methane production above background in samples spanning the site’s temperatures.

What this does not establish

Inferred from methane chemistry and isotopes in the sediment, which may record activity at lower temperatures in the past.

Later work looked for

Europe PMC, 2021 on, "Nankai C0023": Beulig 2022 found potential methanogenesis in hotter sediment by radiotracer incubation; recorded as a qualification.

Corrected

24 September 2026. Previously: “Methane is made and consumed biologically up to about 85 degrees,” The paper gives a range, 80 to 85 degrees.

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

Claim: and between 100 and 120 degrees the isotopes and a rise in cell numbers record hyperthermophiles degrading acetate.

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

    Temperature limits to deep subseafloor life in the Nankai Trough subduction zoneabstract

    Cited · Link answered, 19 October 2026 · Read in full, 24 September 2026 · Research in microbes · Observational study: associations, not causes

    The source reads: In 100° to 120°C sediments, isotopic evidence and increased cell concentrations demonstrate the activity of acetate-degrading hyperthermophiles.

What this does not establish

Geochemical signals of this kind can be relics of past activity, as Beulig and others note of the same site.

Later work looked for

Europe PMC, 2021 on, "Nankai C0023": Beulig 2022 reports active populations in hot sediment by incubation, which agrees.

Corrected

24 September 2026. Previously: “and between 100 and 120 degrees the isotopes record hyperthermophiles degrading acetate.” The paper rests the inference on both lines of evidence.

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

Claim: Whether the true limit is temperature, available energy, or the rate at which damaged molecules can be repaired is not resolved.

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 56 · checked 24 September 2026 · AI-assisted audit

Claim: In stable, nutrient-poor settings, subsurface cells subsist on energy fluxes a thousand times below what laboratory cultures are thought to need simply to maintain themselves.

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

    Microbial life under extreme energy limitationabstract

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

    The source reads: Microbial cells in these very stable and oligotrophic settings ... subsist with energy fluxes that are 1,000-fold lower than the typical culture-based estimates of maintenance requirements

Later work looked for

Europe PMC, 2016 on, subseafloor energy limitation: Beulig 2022 (fast metabolism in hot sediment); page scoped.

Corrected

24 September 2026. Previously: “Subsurface cells subsist on energy fluxes a thousand times below what laboratory cultures are thought to need simply to maintain themselves.” The review says this of stable, oligotrophic settings, and the next sentence reports a hot setting where it does not hold.

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

Claim: Yet in the hottest Nankai sediment, incubations found a small population metabolising at rates close to those of surface sediment and laboratory cultures,

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

    Rapid metabolism fosters microbial survival in the deep, hot subseafloor biosphereabstract

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

    The source reads: deeply buried marine sediment from the Nankai Trough subduction zone, heated to extreme temperature (up to ~120 °C). The small microbial community subsisted with high potential cell-specific rates of energy metabolism, which approach the rates of active surface sediments and laboratory cultures.

What this does not establish

Potential rates from radiotracer incubations of recovered sediment near in situ temperature, not rates measured in the rock.

Later work looked for

Europe PMC, 2022 on, "Nankai C0023": nothing later found on metabolic rates at the site.

Corrected

24 September 2026. Previously: “” Added. The currency search found this 2022 result from the same borehole, which qualifies the page’s account of subsurface life as uniformly slow.

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

Claim: apparently spending most of its energy on repairing heat damage.

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 calculation from published repair costs set against the measured rates, not a measurement of repair.

Corrected

24 September 2026. Previously: “” Added with claim 58; the authors say “appear”, and the page says apparently.

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

Whether they are alive in the ordinary sense

Claim: Whether they are alive in the ordinary sense

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

Claim: In those settings, subsurface cells catabolise ten thousand to a million times more slowly than model organisms in a rich culture, and turn over their biomass on timescales of centuries to millennia.

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

    Microbial life under extreme energy limitationabstract

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

    The source reads: Microbial cells in these very stable and oligotrophic settings catabolize 10⁴- to 10⁶-fold more slowly than model organisms in nutrient-rich cultures, turn over biomass on timescales of centuries to millennia

Later work looked for

Europe PMC, 2016 on, deep subseafloor growth rates: Trembath-Reichert 2017 measured growth of months to over a century in the coal beds, consistent; Beulig 2022 far faster in hot sediment, hence the scope.

Corrected

24 September 2026. Previously: “Subsurface cells catabolise ten thousand to a million times more slowly” Scoped to the settings the review describes, as in claim 57.

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

Claim: At those rates the distinction between a very slow metabolism and a long dormancy is hard to draw with the measurements available.

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 52 and 61: at these rates, and with spores making up most of what is counted in hot sediment, a count of cells does not say which are active.

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

Claim: This is not a semantic problem.

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 page’s judgement, explained by the sentence after it.

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

Claim: It determines whether the subsurface is a working ecosystem or an archive of things that were buried alive.

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 page’s framing of what is at stake. Beulig and others draw the same contrast, between selective survival in cold sediment and an active population in hot sediment.

Other readings

The answer need not be one or the other: the evidence on this page points to different answers in different settings.

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

How far it goes

Claim: How far it goes

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

Claim: Sampled by borehole, and boreholes are drilled where someone had a reason.

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 page’s point that sampling is not random. The Nankai hole is an example: it was sited for its heat.

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

How much of it there is

Claim: How much of it there is

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

Claim: The sampling is by borehole, and boreholes are drilled where someone wanted to drill.

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.

As the interlude before it: sampling follows where holes are drilled, as claim 66 notes.

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

Claim: Whole environments are barely sampled, the deep aquifers and the ocean crust among them.

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

    The biomass distribution on EarthDiscussion

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

    The source reads: there are entire environments for which our knowledge is very limited, namely, the deep subsurface environments such as deep aquifers and the ocean’s crust

Corrected

24 September 2026. Previously: “Vast volumes of crust have never been sampled at all, including most of the deep ocean crust.” No cited source measures how much crust has never been sampled. The census says knowledge of these environments is very limited, and the page now says that.

Claim 69 · checked 24 September 2026 · AI-assisted audit

Claim: Any number for the size of the deep biosphere is an extrapolation from an unrepresentative sample,

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 8 and 69. The census the page cites says the same of its own deep-subsurface figures: high uncertainty and unknown systematic biases.

  • Supports

    The biomass distribution on EarthDiscussion

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

    The source reads: Future research could reduce the uncertainty of current estimates by sampling more environments, which will better represent the diverse biosphere on Earth.

Claim 70 · checked 24 September 2026 · AI-assisted audit

Claim: and the 2018 synthesis opens by saying that the controls on how many microbes live in the continental subsurface are poorly understood.

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.

  • Supports

    The biomass and biodiversity of the continental subsurfaceabstract, first sentence

    Cited · Link answered, 19 October 2026 · Abstract only, 24 September 2026 · Research in microbes · Review of the field

    The source reads: controls on the abundance and biodiversity of microorganisms residing in the continental subsurface are poorly understood

What this does not establish

Read as an abstract.

Corrected

24 September 2026. Previously: “and the synthesis behind the current one opens by saying that the controls on subsurface abundance are poorly understood.” There is no single current number (claim 28), and the paper speaks of the continental subsurface, not the subsurface as a whole.

Claim 71 · checked 24 September 2026 · AI-assisted audit

What was read