20.500.12556/DiRROS-31183 Cosmic dust flux during the quaternary the record of large scoriaceous and unmelted micrometeorites from the transantarctic mountains collection We estimate the cosmic dust flux to Earth through the study of rare micrometeorites that preserve part of their precursor features during atmospheric entry heating, namely unmelted and scoriaceous subtypes. Combining high-precision mass balance measurements, X-ray computed microtomography and scanning electron microscopy, we studied mass, size and petrography of 207 micrometeorites recovered from sediment traps in the Transantarctic Mountains (TAM), ranging from ∼170 to ∼1650 µm. Chondrules were identified in ∼14% of the micrometeorites, particularly among coarse-grained and composite particles. The analysed population shows a bimodal size-frequency distribution, with peaks at ∼305 µm and ∼470 µm. A similar bimodal distribution was previously reported from the TAM cosmic spherule population, yet shifted towards lower sizes. This size-shift is consistent with an average mass loss of ∼87% during atmospheric entry heating. The mass-size relationship follows a power-law, where the spherical equivalent diameter (dµm) and mass (mµg) of the micrometeorite are related by: � =1.07 ×10−6 �2.96 . The size-frequency distribution of the fine- and coarse-grained micrometeorites reveals two well-separated clusters, with peaks at ∼315 µm and ∼550 µm, respectively. These observations suggest that the bimodal distribution in the micrometeorite flux reflects contrasting lithological end-member components with different physical properties and fragmentation behaviours during dust production in space. Based on earlier mass flux estimates from TAM melted micrometeorites and accounting for the mass loss due to atmospheric entry derived here, we calculate a time-averaged pre-atmospheric mass flux of ∼12,000 (±6,000) t/yr over the Quaternary, suggesting that the influx has remained stable over the last few million years. micrometeorites quaternary cosmic dust tomography mikrometeoriti kvartar kozmični prah tomografija true false true John Wiley & Sons Angleški jezik Slovenski jezik © 2026. The Author(s) Neznano 2026-07-20 10:33:35 2026-07-20 10:39:49 2026-07-21 03:57:08 0000-00-00 00:00:00 2026 0 0 str. 1-20 issue 7 Vol. 131 Jul. 2026 0000-00-00 Zaloznikova Objavljeno NiDoloceno 0000-00-00 0000-00-00 2026-07-06 55 2169-9100 10.1029/2026JE009650 284330243 https://doi.org/10.1029%2F2026JE009650 0 b4fc43b7-8415-11f1-82f3-001a4af901a5 https://dirros.openscience.si/Dokument.php?lang=slv&id=48102 https://doi.org/10.5281/zenodo.20184378 0 7800e021-8416-11f1-82f3-001a4af901a5 https://dirros.openscience.si/Dokument.php?lang=slv&id=48103 RAZ_Folco_Luigi_2026.pdf RAZ_Folco_Luigi_2026.pdf 1 CEB67F81400D051FAA65CEDBA7759DE8 f6964b3457002e200c48009efc75d88aee031dcecf33af41e3490ba43443165c 81863eea-8416-11f1-82f3-001a4af901a5 https://dirros.openscience.si/Dokument.php?lang=slv&id=48104 Zavod za gradbeništvo Slovenije 0 0 0