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Are the proposed markers (microspherules, nanodiamonds, shocked quartz, meltglass) reproducible and diagnostic of impact?

Asked 26 Oct 2026 by ·Part of Did an extraterrestrial impact or airburst occur at the onset of the Younger Dryas, about 12,800 years ago?·3 answers·0·0 following
Most likely: the markers are background cosmic dust, volcanic or anthropogenic spherules, fire products or misidentified…Ahead on the evidence, not yet confirmed. It needs two reviews to be accepted.

Where it stands

Three answers have been proposed. The markers are background cosmic dust, volcanic or anthropogenic spherules, fire products or misidentified… leads, with evidence 3 for: supported by its tests. Two are still possible.

Why it matters

The physical evidence is microscopic, and its identification and counting depend on methods that differ between laboratories⁠[1]. The review of 2023 argues that most markers also form by ordinary processes⁠[2].

Answers 3

Evidence: 3 for
Most likely
None of these.
Not tested enough to call either way
Evidence: none yet
Still possible
Evidence: 2 for, 2 against
Disputed

History

  1. Kennett et al.: nanodiamonds were reported at 10 to 3,700 ppb in the boundary layer and not above or below.For: The markers form only at the temperatures and pressures of impacts and airbursts, and they peak at the…
  2. Surovell et al.: the 2009 independent study found no support at seven sites, including two of the originals.For: The markers are background cosmic dust, volcanic or anthropogenic spherules, fire products or misidentified…
  3. Daulton et al.: claimed nanodiamonds were identified as graphene and graphene-oxide aggregates.For: The markers are background cosmic dust, volcanic or anthropogenic spherules, fire products or misidentified…
  4. Pinter et al. puts forward: the markers are background cosmic dust, volcanic or anthropogenic spherules, fire products or misidentified…
  5. Wittke et al. puts forward: the markers form only at the temperatures and pressures of impacts and airbursts, and they peak at the…
  6. Wittke et al.: about 700 SEM-EDS analyses of spherules from 18 sites are said to be inconsistent with volcanic, cosmic…For: The markers form only at the temperatures and pressures of impacts and airbursts, and they peak at the…
  7. Holliday et al.: no standard criteria exist for identifying magnetic spherules, and the blind test found them in a…Against: The markers form only at the temperatures and pressures of impacts and airbursts, and they peak at the…
  8. Sun et al.: osmium isotopes at Hall's Cave point to volcanic sources for the boundary anomalies.For: The markers are background cosmic dust, volcanic or anthropogenic spherules, fire products or misidentified…
  9. The PLOS One Editors: material presented as cosmic spherule fragments in the Baffin Bay paper was identified as foraminifera.Against: The markers form only at the temperatures and pressures of impacts and airbursts, and they peak at the…
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