<figure><img src="image_1.png" /></figure>

# The extraterrestrial dust accretion rate on Earth at Dome C, Antarctica: a fresh look with ³He

G. Fénisse<sup>a, *</sup> <sup>●</sup>, D.V. Bekaert<sup>a, ●</sup>, P.-H. Blard<sup>a, b, ●</sup>, J. Duprat<sup>c</sup>, I. Mattia<sup>d</sup>, M. Genge<sup>d</sup>, M.D. Suttle<sup>d, ●</sup>, O. Barres<sup>e, ●</sup>, C. Engrand<sup>f, ●</sup>, Y. Marrocchi<sup>a, ●</sup>

<figure><img src="image_2.png" /></figure>

## ARTICLE INFO

Editor: Dr O Mousis

Dataset link: https://doi.org/10.24396/ORDAR-152

Keywords:

Cosmic dust

Concordia station

Dome C

Comic dust extraction

Granulometric-sorting

Noble gas database

³HeET and cosmic dust mass fluxes

## ABSTRACT

Interplanetary dust particles (IDPs) and micrometeorites (MMs), from 1 µm to 5 mm, are the primary source of extraterrestrial (ET) material currently accreted on Earth. The flux of ET particles smaller than ~50 µm is typically determined through optical counting, but it remains uncertain and may deviate from predictions made by numerical simulations. The volatile element content carried by this flux is still not well-constrained and is influenced by the potential effects of atmospheric heating.

We developed a clean, pressurized system to extract cosmic dust from ~38 kg of clean snow collected near the Concordia station (Dome C, Antarctica). We measured helium isotope concentrations in various granulometric fractions (> 62 µm, 25–62 µm, 5–25 µm and < 5 µm). The inferred global ³HeET annual flux is (1.25±0.03) × 10⁻¹² ccSTP·cm⁻²·ka⁻¹ (weighted mean±1SD), consistent with previous ³HeET flux estimates from marine sediments and polar samples. Our data shows that the majority of the ³HeET flux (70 %) is carried by particles in the 5–25 µm size range, with 20 % attributed to the 25–62 µm fraction. Using an empirical relationship between ³HeET concentrations and cosmic particle mass, we convert these fluxes into a global ET mass flux for particle diameters < 100 µm of (3.5±0.5) kilotons·a⁻¹ (weighted mean±1SD). This result is about 3 times higher than collection estimates from (Rojas et al., 2021) and aligns with CABMOD-ZoDy modeling, after atmospheric entry (Carrillo-Sánchez et al., 2020). This ³HeET method is suited for detecting particles smaller than 100 µm, while collection results are more relevant for larger fractions.

## 1. Introduction

Interplanetary Dust Particles (IDPs; ranging in size from < 1 µm up to a few tens µm) are collected in outer space and the stratosphere, while micrometeorites (MMs; few µm to 1 mm) are extraterrestrial (ET) particles that reached the Earth's surface. Counting of MMs in deep-sea sediments, deserts, polar ice caps, snow samples, urban environments, as well as observations of IDPs from space and modeling approaches, show that this cosmic dust flux dominates the total mass flux of ET matter arriving on our planet (e.g., Takayanagi and Ozima, 1987; Taylor et al., 1998; Yada et al., 2004; Brook et al., 2009; Genge et al., 2017;

Gardner et al., 2014; Rojas et al., 2021). It is by several orders of magnitude larger than the flux carried by larger objects in the meteorite size range (e.g., Wetherill, 1976). The total ET mass flux reaching the top of the Earth atmosphere is 40±20 kilotons·a⁻¹ (Love and Brownlee, 1993), but this number is reduced to a few thousand tons per year by vaporization of the meteoroids during their atmospheric entry (e.g., Duprat et al., 2001; Peucker-Ehrenbrink, 1996). This reduction primarily affects particles with diameters > 200 µm (e.g., Farley et al., 1996; Suttle and Folco, 2020). However, most dust flux estimates appear to be method-dependent and are limited to a given size fraction (e.g., Mathews et al., 2001; Plane, 2012; Rojas et al., 2021), making them

<footnote><sup>a</sup> Centre de Recherches Pétrographiques et Géochimiques, CNRS, Université de Lorraine, UMR 7358, 15 Rue Notre Dame des Pauvres, 54 500 Vandoeuvre-lès Nancy, France</footnote>

<footnote><sup>b</sup> Laboratoire de Glaciologie, Département de Géosciences, Environnement et Société, ULB, Brussels, Belgium</footnote>

<footnote><sup>c</sup> Institut de Minéralogie, Physique des Matériaux et de Cosmochimie, UMR 7590, Muséum National d'Histoire Naturelle, CNRS, Sorbonne Université, Paris 75 231, France</footnote>

<footnote><sup>d</sup> Department of Earth Science and Engineering, Imperial College London, South Kensington, London SW7 2AZ, UK</footnote>

<footnote><sup>e</sup> Université de Lorraine, CNRS, GeoRessources Laboratory, France</footnote>

<footnote><sup>f</sup> Centre de Sciences Nucléaires et de Sciences de la matière (CSNSM), Université Paris-Sud, UMR 8609-CNRS/IN2P3, 91 405, Orsay, France</footnote>

<footnote>* Corresponding author.</footnote>

<footnote>E-mail address: gabriel.fenisse@univ-lorraine.fr (G. Fénisse).</footnote>
uncertain especially for the smallest cosmic particles (< 50 µm, Rojas et al., 2021). Cosmic dust is essentially composed of anhydrous silicate, carbonaceous and hydrous phase aggregates (some of which are rich in volatiles; e.g., Kurat et al., 1994; Engrand et al., 2018), Fe-Ni sulfides and magnetite minerals (Mukhopadhyay and Farley, 2006). Two typical types of particles - unmelted (uMMs) and cosmic spherules (CSs) - are defined based on their shape and petrography, that directly result from the temperature they experienced during their atmospheric entry, determined by their mass, entry angle and velocity in Earth's atmosphere (Flynn, 1989). The transformation of hydrous minerals into olivine and pyroxene takes place at temperatures ≥ 800 °C (Greshake et al., 1998). However, the deposition and preservation of cosmic dust, as well as the collection procedures, may affect these compositions and lead to a sampling bias in favor of the largest particles melted upon atmospheric entry (especially CSs) (Maurette et al., 1987; Taylor et al., 2000; Toppani et al., 2001). While IDPs have also been collected in the stratosphere by high altitude aircrafts from the NASA JSC (Johnson Space Center) (e.g., Brownlee et al., 1994), they remain much less well documented than larger particles.

The central regions of Antarctica are an ideal location to constrain the flux of ET dust on Earth since it is far from terrestrial dust sources and anthropogenic contamination (Duprat et al., 2007, 2010; Rojas et al., 2021). At the vicinity of the Concordia station (75°06'S, 123°20'E and 3200 m elevation, Dome C), the snow accumulation rate low and well constrained (2.7±0.1 g.cm⁻².a⁻¹, water equivalent, Frezzotti et al., 2005; Le Meur et al., 2018). This low accumulation rate allows for the accumulation of a significant amount of ET dust in a reasonable volume of snow (Duprat et al., 2007; Rojas et al., 2021) Antarctica remains the only place on Earth where fragile, unmelted particles such as UCAMMs (so-called Ultra-CARBONaceous MicroMeteorites) have been recovered (Duprat et al., 2010). These UCAMMs contain abundant (up to 50 wt.% C) labile organic matter components (e.g., Engrand et al., 2018), pointing to a high preservation potential of cosmic dust in such Antarctic sites. Rojas et al. (2021) used some ultra-clean snow samples of Concordia to collect large numbers of MMs and determine the size distribution of both melted and unmelted MMs in the 20–200 µm size range. The global ET flux deduced from this study is 5.2±1.5 kilotons.a⁻¹. For the smallest fractions (< 50 µm), the ET particle mass-distribution at Concordia exhibits strong discrepancies with simulations, especially CABMOD-ZoDy, which is the combination of the University of Leeds Chemical Ablation MODel and the Dynamical model of the Zodiacal Cloud from Carrillo-Sánchez et al. (2020). This apparent contradiction may be due to the limits of the identification protocol, as the optical counting of ET dust can be complicated by the presence of anthropogenic and terrestrial dust contaminations (Rojas et al., 2021). Models simulating ET mass fluxes are limited by assumptions and empirical constraints related to the dust sources (e.g., Nesvorny et al., 2006). New approaches to identify and quantify the ET dust particles in snow samples are thus necessary to improve our understanding of the global ET mass flux on Earth.

The use of ³He is a well-known approach to quantify the abundance of ET particles in terrestrial material (Farley and Patterson, 1995). While ⁴He is a radiogenic isotope mainly produced by the radioactive decay of ²³⁵U, ²³²Th and ¹⁴⁷Sm at the Earth's surface, terrestrial ³He is mostly of primordial origin, inherited from Earth's accretion (Tolstikhin, 1975). The high ³He concentrations observed in ET particles are due to both the surface-implantation of solar wind and ³He production by cosmic rays (e.g., Pepin et al., 2000). Due to their high specific surface areas, the smallest IDPs are thus expected to contain the largest ³He concentrations from solar wind implantation (e.g., Eberhardt et al., 1965; Stuart et al., 1999). ET and terrigenous reservoirs have distinct ³He/⁴He isotopic ratios (~200 Ra vs. 0.02 Ra, respectively, where Ra = 1.384 × 10⁻⁶ (Ozima and Podosek, 2002 is the atmospheric ratio). The bulk ³He/⁴He measured in terrestrial matrices (e.g., sediments, ice core and firn snow) reflects a mixture of these two reservoirs and is highly sensitive to trace

ET contributions, especially in the finest fractions (< 50 µm) that are difficult to quantify with optical counting (McGee and Mukhopadhyay, 2013).

Since ³HeET incorporated in sediments has been proven to be preserved for multi-million-year timescales (Patterson et al., 1998; Mukhopadhyay and Farley, 2006), ³He concentrations in sediment records the ET particle fluxes through geological times and can also be used in some cases to determine sedimentation rates (e.g., Farley and Patterson, 1995; Winckler and Fischer, 2006; McGee and Mukhopadhyay, 2013; Blard et al., 2023). For instance, Takayanagi and Ozima (1987) used marine sediments to estimate an average ³HeET flux of (1.5±1.0) × 10⁻¹² cc STP.cm⁻².ka⁻¹ (pcc STP.cm⁻².ka⁻¹, hereafter pcc STP.cm⁻².ka⁻¹) over the last 40 Myr. In 2013, McGee and Mukhopadhyay (2013) compiled ³HeET concentrations from deep-sea sediments over various timescales, offering the possibility to constrain variations in past sedimentation rates and/or ³HeET flux.

Brook et al. (2000) measured ³He in the GISP2 ice core (Greenland) and 3.8 ka-old ice core from Vostok (Antarctica) to derive global ³He fluxes of 0.62±0.27 pcc STP.cm⁻².ka⁻¹ and 0.77±0.25 pcc STP.cm⁻².ka⁻¹, respectively. Brook et al. (2009) filtered 9 replicates of 3.8 ka-old Vostok ice using 0.45 µm silver filters. These authors derived an average ³He concentration of (525±174) × 10⁻⁶ pcc STP per gram of ice, and a global ³He flux of 0.77±0.25 pcc STP.cm⁻².ka⁻¹. They also showed that the 5–10 µm and 0.45–5 µm fractions represent 74 % and 10 % of the total flux, respectively. Additionally, Farley et al. (2021) measured ³HeET flux of (1.4±1.2) pcc STP.cm⁻².ka⁻¹ and (1.2±0.3) pcc STP.cm⁻².ka⁻¹ at high temporal resolution in modern air and in a shallow (201 m long) ice core (Antarctica, South Pole), respectively.

By measuring the amount of ³HeET, Os and Ir accumulated in deep-sea sediments and assuming average concentrations, Takayanagi and Ozima (1987), Peucker-Ehrenbrink and Ravizza (2000) derived variable estimates for the flux of ET material, with values ranging from 0.4 up to 30 kilotons.a⁻¹. However, mass estimates of dust based on element abundance measurements are significantly dependent on concentrations used for the abundance-to-concentration ratios, forming a methodological bottleneck.

Using MMs recovered from ice cores drilled collection at Dome C, Yiou et al. (1989) deduced an ET flux of ~1.5 kilotons.a⁻¹. Using the CS collection (50–700 µm) from the South pole of the water well (bottom part) at the Scott-Amudsen station (South Pole Water, SPWW), the flux and mass distribution of melted cosmic dust was estimated to be 2.7±1.4 kilotons.a⁻¹ (Taylor et al., 1998). The accretion rate before atmospheric entry inferred from craters observed on the LDEF NASA satellite (Long Duration Exposure Facility) is estimated at 20 to 60 kilotons.a⁻¹ in the 20–400 µm size range (Love and Brownlee, 1993). The comparison of this flux with the value inferred by Taylor et al. (1998) suggests that ~90 % of submillimeter cosmic dust is vaporized during atmospheric entry. In Greenland, using optical counting, Maurette et al. (1987) deduced an ET flux of about 2.2 kilotons.a⁻¹. However, poor age constraints and the post-depositional weathering of particles from blue ice might bias these results.

Here, we aim to document the ³HeET and the cosmic dust flux recorded in the modern snow of Concordia by analyzing the helium isotopic inventory of variable size fractions of the dust, using a new, pressurized filtering system to separate cosmic dust into distinct granulometric fractions (from < 5 µm to > 62 µm). Our dataset is used to derive a mean ³HeET flux, that we compare to previous estimates from various archives (snow, ice and marine sediments). Using a new exhaustive review of He abundances measured in cosmic dust particles of various masses, we use the obtained ³HeET flux to derive a total ET mass flux for several granulometric fractions from 5 µm to 100 µm. Finally, we discuss the ability of the ³HeET approach to trace the largest ET particles (> 100 µm).
## 2. Materials & methods

### 2.1. Cosmic dust in the clean snow from the Concordia station

We extracted cosmic dust from ~38 kg of clean snow from the French-Italian Concordia station, about 1100 km from the closest coast (Fig. 1). Because of the low snow accumulation rate (2.7±0.1 g.cm⁻².a⁻¹ water equivalent; Frezzotti et al., 2005; Le Meur et al., 2018) and the high elevation and remote location, the concentration of cosmic dust relative to terrestrial particles is exceptionally high in the firn, allowing reliable reconstruction of the ET mass flux with low uncertainty (Duprat et al., 2007; Rojas et al., 2021). We processed and melted 4 different snow samples covering the 1960 to 2006 period: 16 kg of snow from F4 snow tank, 15 kg from F6 tank and 4 sub-samples ranging from 1 to 3 kg each from F1 snow tank. Each snow sample was weighed with a 1 g-precision scale before melting. This mass, divided by the average snow accumulation rate of 2.7 g.cm⁻².a⁻¹, allows us to infer an exposure parameter S (m².a), a key metric to derive an ET flux estimate (Farley et al., 1996; Rojas et al., 2021). The detailed characteristics of the snow samples analyzed in this study are reported in Appendix A.

### 2.2. Extraction pressurized system and granulometric sorting of ET particles

Previous extraction systems used water pumping vacuum or gravitational setting (Yada et al., 2004; Brook et al., 2009) to concentrate MMs. Here, we built a dedicated stainless-steel system to extract cosmic particles from melted snow in a clean room. This extraction system was designed by adapting a “pressure cooker” connected to a nitrogen gas flow high pressure regulator (up to 2 bars). Below this water reservoir, we used three steel filters of 62, 25 and 5 µm mesh sizes. Finally, the melted snow that flowed through the 5 µm filter and carried the smallest particles was evaporated in aluminum capsules of ~20 mL on hot-plates under a laminar flow hood. This experimental step was designed to tentatively collect and analyze particles smaller than those analyzed in previous studies (e.g., Engrand and Maurette, 1998; Duprat et al., 2007; Brook et al., 2009; Rojas et al., 2021). More information about this extraction system is available in Appendix B. We observed microplastic contaminants of various sizes, mostly on the 5 µm filters, that probably

originate from firn tanks (described in Appendix C). This protocol did not permit to check that the largest ET particles were not fragmented during the sieving, nor that smallest particles were not encased in larger terrestrial dusts or plastic contaminants.

### 2.3. Measurement of Helium-3 and 4 abundances

Helium isotopes were measured at CRPG (Centre de Recherches Pétrographiques et Géochimiques, Vandoeuvre-lès-Nancy) following the procedure described in Blard et al. (2023) and Blard (2021). After heating the filters at 1500 °C for 15 min under vacuum in a stainless-steel induction furnace (Zimmermann et al., 2018), extracted gases were purified using three successive charcoal traps cooled in liquid N₂ and four Ti-sponge getters. Once purified, helium was concentrated on a cryogenic head at 12 K, before being released at 75 K into a GV Instrument Helix Split Flight Tube mass spectrometer (Blard et al., 2015). The Helix SFT (Thermo Fisher Helix SFT, Split Flight Tube) was calibrated with a daily analysis of the HESJ gas standard (He Standard of Japan, R = 20.63 Ra; Matsuda et al., 2002), yielding ⁴He and ³He sensitivities of 7.04 × 10¹³±0.5 % mV.mol⁻¹ and 4.16 × 10¹⁸±0.9 % cps. mol⁻¹, respectively. In each carouse, we measured CRONUS-P pyroxene standards that yielded ³He concentrations in agreement with published values (Blard et al., 2015; Schaefer et al., 2016). Helium measurements were corrected for furnace blanks ((3.10±0.19)×10⁹ at of ⁴He and below detection limit for ³He). These blanks accounted for 0.1 to 16 % of the measured ⁴He abundance in filtered samples. We also measured and subtracted the helium blank contributions from the steel filters and Al capsules, whose masses are reported in Appendix D. Steel filters contained (3.41±0.27)×10¹⁰ atoms of ⁴He.g.steel⁻¹, while ³He contents were below the detection limit. These ⁴He blank corrections represented from 1 % to 69 % of the ⁴He measured in the samples (average 14 %). The Al capsule contained (6.06±0.54)×10⁵ atoms of ³He.g.Al⁻¹ and (1.11±0.13)×10¹⁰ atoms of ⁴He.g.Al⁻¹. Blank contributions from Al capsules accounted for 2 and 28 % of the measured ³He, and 36 and 39 % of the measured ⁴He signals, respectively. Stainless steel filters (5 µm, 25 µm and 62 µm; n = 6) and aluminum evaporation-capsules (n = 3) resulting from the filtering of the 3 snow tanks (F1, F4, F6, with F1 snow tank being split into 4 different bags to test the homogeneity of particle concentrations in ~2 kg of snow) were analyzed for ³He and ⁴He

<figure><img src="image_3.png" /><figcaption>**Fig. 1.** Map of Antarctica showing the locations where cosmic dust has previously been collected and analyzed for light noble gases. NASA stratospheric collections are given in black. Cosmic dust expeditions are more detailed in Appendix A.</figcaption></figure>
concentrations.

## 3. Results

All results are reported in Appendix D, $^3$He and $^4$He concentrations from each sample and granulometric fractions on Fig. 2. The $^3$He concentrations (at.g⁻¹) in snow measured for each granulometric fractions vary over several order of magnitudes, ranging from (1.84±0.52)x10¹ at.g⁻¹ to (1.34±0.02)x10⁴ at.g⁻¹, while $^4$He concentrations range from < 10⁶ at.g⁻¹ up to (3.76±0.01)x10⁸ at.g⁻¹ (Fig. 2). Despite inter-tank variability beyond analytical uncertainties, we find a clear granulometric control on He concentrations: both $^3$He and $^4$He concentrations are the highest in the 5–25 µm particles, followed by the 25–62 µm fractions. The helium concentrations measured in the smallest (< 5 µm) and the largest (> 62 µm) fractions are by far the lowest. The $^3$He/$^4$He ratios measured in all granulometric fractions range from 0.55±0.08 Ra to 85±1 Ra, with most of the values standing between 20 and 40 Ra. Using an isotopic mixing model considering ET and terrestrial end-members with $^3$He/$^4$He ratios of 200 and 0.02 Ra, respectively (McGee and Mukhopadhyay, 2013), our data indicate that >99 % of the measured $^3$He is of ET origin in almost all samples (Appendix D). We also find that terrestrial $^4$He represents from 29 % to 100 % of the total $^4$He measured in these samples, reflecting the inter-sample variability of the terrestrial dust contributions.

Combining helium contributions from all granulometric fractions, the total $^3$He$_{ET}$ concentrations measured in the three tanks range from (8.17±0.11)x10³ at.g⁻¹ to (1.52±0.01)x10⁴ at.g⁻¹, and $^4$He from (1.61±0.01)x10⁸ at.g⁻¹ to (5.19±0.03)x10⁸ at.g⁻¹ (sum of all size fractions±1SD) (Appendix D).

## 4. Discussions

### 4.1. The global $^3$He$_{ET}$ flux and mass-distribution of $^3$He-bearing dust

#### 4.1.1. $^3$He/$^4$He and He source deconvolution

In the two largest granulometric ranges (> 62 µm and 62–25 µm), the averages of $^3$He/$^4$He ratios from Concordia samples (Appendix D) are similar to those measured in Vostok, 47±5 Ra and 25±4 Ra in > 63 µm and 63–20 µm size fractions, respectively (Brook et al., 2009). However, the average of $^3$He/$^4$He ratios of the 25–5 µm size ranges is much lower (43±11 Ra) than the value reported in Vostok core (209±5 Ra). Noticeably, these values are below that reported in individual stratospheric IDPs, which display $^3$He/$^4$He ratios around 219±83 Ra (mean±1SD) (Nier and Schlutter, 1992). The observed variability of $^3$He/$^4$He ratios in snow samples most probably reflects variable abundances of ET and terrestrial dust fractions. Finally, it is important to emphasize that these $^3$He/$^4$He ratios (from 13.6±0.2 Ra to 55.9±0.7 Ra, sum of all size fractions±1SD), demonstrate that $^3$He is nevertheless mostly extraterrestrial (>99 %) in all snow samples.

#### 4.1.2. Variability of $^3$He$_{ET}$ concentrations per granulometric size range

Based on the helium abundances of snow tanks (F4, F6 and F1), MMs smaller than 25 µm represent the largest contribution (65 %) of the total $^3$He$_{ET}$, while ~28 % is carried by 25–62 µm particles (Fig. 2). This result is consistent with previous observations (Brook et al., 2009; Mukhopadhyay and Farley, 2006; McGee and Mukhopadhyay, 2013; Torfstein, 2012), supporting the hypothesis that most of the $^3$He$_{ET}$ is carried by cosmic dust smaller than 50 µm. Suttle et al. (2023) demonstrated that fossil MM sizes and He signatures are not directly correlated by

<figure><img src="image_4.png" /><figcaption>**Fig. 2.** (a) $^3$He and (b) $^4$He concentrations from different filtered samples of Concordia snow. Three snow tanks were processed, F1, F4 and F6. The red spots indicate the arithmetic means of $^3$He$_{ET}$ fluxes for each granulometric size range. The right box called 'All size ranges' integrates contributions from all size fractions of each snow sample. During the analysis period, we lost one filter of 25 µm mesh size.</figcaption></figure>
investigation of fossil MM abundance across the Miocene $^3$He peak (~8.5 Ma). By modeling the size-dependent heating of ET particles during their atmospheric entry, Farley et al. (1996) established that MMs ranging from 3 to 35 µm bring 70 % of the total $^3$He$_{ET}$ flux, with a maximum contribution from the ~7 to 10 µm particles, in agreement with most observations (Mukhopadhyay and Farley, 2006; Brook et al., 2009; Torfstein, 2012; this study). Importantly, this result is observed in a variety of substrates, including Holocene snow and ice (Brook et al., 2009) and pelagic clays having very different deposition ages, from the modern to the Eocene (Mukhopadhyay and Farley, 2006; Torfstein, 2012).

Interestingly, the $^3$He$_{ET}$ contribution of the < 5 µm fraction differs from that reported in Vostok ice: in the Concordia snow, the smallest fraction yields $^3$He$_{ET}$ concentration of 41±1 at.g⁻¹, ~18 times lower than the value reported by Brook et al. (2009) (752±54 at.g⁻¹). This discrepancy might result from a protocol bias. The cause of this mismatch may be explained either (i) by a loss of the smallest particles (< 5 µm) during the evaporation step, via airborne escape in the laminar flow hood, or (ii) the fact that the smallest cosmic dusts may have been encased in larger terrestrial aerosols, hampering their recovery in the proper granulometric fraction during the sieving procedure.

### 4.1.3. Estimating a global $^3$He$_{ET}$ flux

Taking into account the mass of processed snow and the local accumulation rate (2.7±0.1 g.cm⁻².a⁻¹ at Dome C, Frezzotti et al., 2005; Le Meur et al., 2018), the inferred exposure parameters range from 0.41±0.02 to 1.24±0.05 cm².ka for the 4 sub-samples of tank F1, and 2.83±0.11, 5.87±0.22 and 5.55±0.21 cm².ka (±1SD) for the full snow tanks F1, F4 and F6, respectively. The total $^3$He$_{ET}$ fluxes from each four

bags of F1 show a significant variability: (1.52±0.05) pcc STP.cm⁻².ka⁻¹, (0.82±0.02) pcc STP.cm⁻².ka⁻¹, (1.24±0.04) pcc STP.cm⁻².ka⁻¹ and (0.92±0.03) pcc STP.cm⁻².ka⁻¹ (Mean Square Weighted Deviation (MSWD) = 74, Figs. 3 and 4a; Ludwig, 2003). This heterogeneity is probably due to the small masses of ice processed (from 1 to 3 kg). With such small masses, the low number of particles can introduce a statistical bias as well as nugget effects (Farley et al., 1996; Rojas et al., 2021; Fig. 5).

Taking into account the $^3$He$_{ET}$ concentrations measured in each granulometric fraction, it is possible to compute an average number of cosmic dust particles present in each fraction of the F1 sub-bag samples (e.g., Taylor et al., 2020; Blard et al., 2023). This suggests that there is 0 to 1 particle > 62 µm, 1 to 30 particles in the 25–62 µm size range, and 3 to 9 in the 5–25 µm size range. The particle counting statistics are determined by Poisson’s law (sigma = 1/√n) and are compatible with the inter bag heterogeneity observed between the bags of F1 (for masses ranging from 1 to 3 kg). The undersampling effect (coupled with a nugget effect) of the F1 bags, whose He analyses are highly heterogeneous, results in a statistical effect that increases for lower exposure parameters (<10⁻³ m².a), as described by Farley et al. (1996). This statistical effect significantly affects the largest size range. The number of particles present in the ~15 kg of snow from tanks F4 and F6 is much larger (i.e., 2 to 3 particles larger than 62 µm, 20 to 25 particles between 25 and 62 µm, and up to 100 particles in the 5–25 µm fraction), as shown by the agreement between the $^3$He$_{ET}$ fluxes determined from these two tanks.

Using a weighted mean (Ludwig, 2003) for the four sub-bags of F1, we obtained total $^3$He$_{ET}$ fluxes of (1.09±0.13) pcc STP.cm⁻².ka⁻¹ for tank F1, (1.27±0.04) pcc STP.cm⁻².ka⁻¹ for F4 and (1.25±0.05) pcc STP.cm⁻².

<figure><img src="image_5.png" /><figcaption>**Fig. 3.** $^3$He$_{ET}$ flux brought by cosmic dust trapped in the Concordia station (Antarctica). Boxplot compilation of $^3$He$_{ET}$ flux (in pcc STP.cm⁻².ka⁻¹) are reported for different size ranges, from 5 µm to 62 µm of 6 snow samples. The red spots indicate the arithmetic means of $^3$He$_{ET}$ fluxes for each granulometric size range.</figcaption></figure>
<figure><img src="image_6.png" /><figcaption>Fig. 4. (a) $^3$He$_{ET}$ flux results from the 4 sub-bags of the F1 tank (blue), (b) $^3$He$_{ET}$ flux from tank F1 (blue, mean of data shown in Fig. 4b), F4 and F6 (yellow) and weighted mean, and (c) $^3$He$_{ET}$ flux (pcc STP.cm$^{-2}$.ka$^{-1}$) vs. exposure parameter (m$^2$.a) of each sample. Best fit calculated with the maximum likelihood with overdispersion model of York et al. (2004). Errors are 1 σ.</figcaption></figure>

<figure><img src="image_7.png" /><figcaption>Fig. 5. Comparison of Quaternary $^3$He$_{ET}$ fluxes estimated from marine sediments, polar ice cores, and Antarctic snow samples (triangle, square and circle shapes). Blue circle shows our result of 1.25±0.03 pcc STP.cm$^{-2}$.ka$^{-1}$. Horizontal dashed lines show the weighted averages for three different matrices: sediments (0.79±0.06 pcc STP.cm$^{-2}$.ka$^{-1}$), ice cores (0.78±0.08 pcc STP.cm$^{-2}$.ka$^{-1}$) and firn snow samples (1.25±0.03 pcc STP.cm$^{-2}$.ka$^{-1}$). Differences with published value may result from our choice of recalculating weighted mean for all dataset, in a homogeneous way. Colorscale shows exposure parameters in m$^2$.a for each study. Sampling stations, locations, and references are available in Appendix E.</figcaption></figure>

ka$^{-1}$ for F6 tank (±1SD) (Fig. 4b), and a weighted mean $^3$He$_{ET}$ flux of (1.25±0.03) pcc STP.cm$^{-2}$.ka$^{-1}$ (±1SD, MSWD = 0.8). Note that the calculation of the weighted mean approach assumes a gaussian distribution of the three fluxes deduced from these tanks (Appendix E).

Fig. 4 summarizes the impact of sample size on the statistical representativity of $^3$He$_{ET}$ analysis. This issue is critical for studies using $^3$He$_{ET}$ as a proxy of net snow accumulation rate from ice core samples,

given that this precious material is only available in limited quantities. If samples of 1 kg are analyzed, then the inter-samples heterogeneity due to the scarcity of cosmic dust implies a relative standard deviation of ~20 % on the estimate of the $^3$He$_{ET}$ concentrations.

The average of $^3$He$_{ET}$ fluxes derived from the three Concordia snow tanks are close to previous literature estimates from snow and ice collected at other Antarctica locations (Fig. 5). To compare these flux
results to those from the literature, we recalculated the mean ³HeET flux of replicates for each study using the weighted mean method (Ludwig, 2003) as shown in Fig. 5. All data and statistical tests are available in Appendix E. Our average flux from the Concordia is notably in agreement with the Vostok ice core and the SPWW firn estimates of 1.11±0.20 and 1.19±0.07 pcc STP.cm⁻².ka⁻¹, respectively (weighted average±1SD) (Brook et al., 2009; Taylor et al., 2020). Interestingly, in Fig. 5, we observe a significant difference between the mean ³HeET flux recalculated (i.e., using weighted mean from Ludwig, 2003) derived from the firn (1.24±0.03 pcc STP.cm⁻².ka⁻¹) and those derived from marine sediments (0.79±0.06 pcc STP.cm⁻².ka⁻¹) and polar ice cores (0.78±0.08 pcc STP.cm⁻².ka⁻¹). These differences between firn, ice and marine sediments do not seem to result from a latitudinal control (Evatt

et al., 2020), but rather from differential conservation of the ET matter. ³HeET in silicate particles (especially fragile unmelted MMs) could partially escape from old marine sediments. Moreover, the contribution of particles in the > 62 µm size fraction to the total ³HeET flux observed in this Concordia snow (8%; Appendix D) is lower than the previous estimates (of c.a. 20 %) derived from pelagic sediment analyses by Mukhopadhyay and Farley, 2006.

Considering the potential under-sampling factor of 18 for the smallest < 5 µm cosmic dusts (Section 4.1.2; Brook et al., 2009), our total ³HeET flux would increase by only 2 % (1.28±0.03 vs. 1.25±0.03 pcc STP.cm⁻².ka⁻¹), the contribution of this granulometric class being in any case almost negligible in Antarctic ice (Brook et al., 2009; McGee and Mukhopadhyay, 2013).

<figure><img src="image_8.png" /><figcaption>**Fig. 6.** (a) ³HeET concentrations and (b) ³HeET abundance vs. mass for Antarctica cosmic dust with various degrees of atmospheric (literature database, 14 references in color). For the smallest unweighted particles, calculation assumes mean density of 1 g.cm⁻³. The types of particles are reported using different symbol shapes. Regression: log₁₀([³HeET]) = -(0.94±0.05).log₁₀(Mass) + (15.03±0.68), n = 170 and MSWD = 30, Dispersion = 0.75±0.04. Errors are reported at 1σ. Liner regressions shown on Fig. 6a are derived from bootstrap aggregating and weighted by ³He analytical errors.</figcaption></figure>
Using a Monte-Carlo modeling approach (described in Appendix E), we computed an average number of cosmic particles per size fraction in the total amount of snow we analyzed here (~38 kg): 4 particles (m²·a⁻¹)⁻¹ for 62–250 µm, 35 particles (m²·a⁻¹)⁻¹ for 25–62 µm and 140 particles (m²·a⁻¹)⁻¹ for 5–25 µm. No estimate of the number of dust particles < 5 µm is provided due to under-constrained He concentrations.

## 4.2. Cosmic dust database of light noble gas concentrations

Helium isotopic abundances have previously been reported for ET particles from several Antarctic locations (Fig. 1) to constrain both the sources and thermal histories of these ET materials (e.g., Stuart et al., 1999; Osawa et al., 2000, 2003; Osawa and Nagao, 2002; Baecker et al., 2018, 2022). Here, we compile and exploit an exhaustive dataset of He concentrations to (i) determine an empirical relationship between ³HeET concentrations and ET particle sizes, and (ii) combine this relationship with the new helium data to derive the mass fluxes of ET material for each granulometric fraction. In practice, we generated an exhaustive database containing all published light noble gas data (³He, ⁴He and ²⁰Ne) measured in IDPs and MMs collected in the stratosphere and Antarctica (Figs. 1 and 6, Appendix F). >40 % of this database is composed of IDPs (stratospheric particles) (e.g., Kehm et al., 2006).

In these publications, 65 % of cosmic dust were directly weighed (> 0.1 µg) (e.g., Bajo et al., 2011). For the remaining particles, we rely on their published dimensions to compute their individual weights, as follows: the observed longest (a) and shortest (b) lengths of cosmic dust were used in Equ. 1 to compute the equivalent diameter (D<sub>eq</sub>, in cm):

$$Deq = \sqrt[3]{a \cdot b^2} \qquad (1)$$

Then, we considered their equivalent spherical volume and assigned an average bulk density ρ of 1 g·cm⁻³ to all particles (Love et al., 1994). We then calculated individual masses (m, in g) using Equ. 2:

$$m = \frac{4}{3} \cdot \pi \cdot \left(\frac{Deq}{2}\right)^3 \cdot \rho \qquad (2)$$

### 4.2.1. He concentration pattern

Noble gas concentrations measured in CSs and MMs range over eight orders of magnitude, from 10⁸–10¹⁷ at·g⁻¹ of ³HeET. In Fig. 6a, the data reveal a clear anticorrelation between ³HeET concentrations and sizes of cosmic dust (log₁₀([³HeET]) = -(0.94±0.05)·log₁₀(Mass) + (15.03±0.68), n = 170 and MSWD = 30, Dispersion = 0.75±0.04) (Table of Appendix D). This negative correlation was previously suggested by Eberhardt et al. (1965), Suttle et al. (2023) from a smaller dataset. This relationship most likely results from surface-dependance effects, as the helium originating from solar wind implementation is expected to be located at the surface of the ET particle, this effect being amplified by atmospheric entry heating, leading larger particles to be more degassed. The smallest particles are indeed characterized by both the highest surface-to-volume ratios and the highest helium concentrations (e.g., Eberhardt et al., 1965; Stuart et al., 1999).

Interestingly in Fig. 6b, we observe that the ³HeET abundances (from

10⁴ to 10⁸ at) are greater in the unmelted or partially melted cosmic dust (i.e., uMMs and SCs, Scoriaceous), likely because of lower degrees of atmospheric heating (Farley et al., 1996; Füri et al., 2013). From our ³HeET database, we note that the heated particles (CSs and SCs) are less abundant than unmelted particles and represent only 32 % of the total (Appendix F). It is worth noting that this proportion of melted particles is similar to the one reported by optical counting from the Concordia firn (39 %, from Table 1 extracted from Rojas et al., 2021), suggesting that there is no sampling bias that would favor undegassed ET particles. Finally, we also note that this database includes a larger proportion of > 100 µm particles than expected from the repartition established by optical counting (Rojas et al., 2021).

### 4.2.2. He and Ne isotopic ratios and origin of these noble gases in cosmic dusts

In Fig. 7, the high ³He/⁴He ratios point to a dominant contribution from solar-derived components, with data points plotting near the fractionated solar wind (FSW) endmember (³He/⁴He ratio FSW = (2.17 ±0.05) × 10⁻⁴, Ozima and Podosek, 2002). This relative excess of ³He above the SW (Solar Wind) endmember may indicate an additional contribution of cosmogenic ³He in these particles. Hence, for the majority of the samples, the distribution ³He/⁴He ratios primarily reflects a mixing between SW, FSW and limited atmospheric (EA) and cosmogenic contributions.

In a Ne-three isotope plot (Appendix G), most data appear consistent with a dominant solar wind-derived contribution. They show a minor contribution of cosmogenic Ne, in line with previous observations on Antarctic MMs by Baecker et al. (2022). These samples also correspond to the ones that exhibit ³He/⁴He ratios well above SW-derived values (Fig. 7), consistent with significant contributions of cosmogenic ³He and ²¹Ne.

The lack of large cosmogenic noble gas excesses in the majority of IDPs and MMs suggests rather short lifetimes of cosmic dust particles in interplanetary environments (Pepin et al., 2000), likely due to the Poynting-Robertson effect which decreases cosmic-ray exposure ages for small particles.

Based on infrared and lidar observations (Light Detection And Ranging, Gardner et al., 2014), the CABMOD-ZoDy model combines a chemical ablation model (CABMOD, Carrillo-Sánchez et al., 2020; Carrillo-Sánchez, 2020) with a Zodiacal Cloud Model (ZoDy), before atmospheric entry, to predict the ET mass contributions of three dust sources (70 %, 21 % and 9 % from short-period (JFCs), longer-period Halley-type comets (HTC) and asteroid belt (AST), respectively). Similarly, the composition of the flux predicted after atmospheric entry from CABMOD-ZoDy modelling is 87 %, 10 % and 3 % for JFCs, HTCs and AST, respectively.

## 4.3. The mass flux-distribution of cosmic dust on the filters

We use the measured ³HeET flux observed in the Concordia firn (at. cm⁻²·ka⁻¹, shown on Fig. 3) to calculate mean ET mass fluxes for several granulometric fractions (< 5 µm, 5–25 µm, 25–62 µm and 62 µm to 100, 250 and 500 µm) (g·m⁻²·a⁻¹, Figs. 9 and 10). For this, we divide the ³HeET

<caption>**Table 1**</caption>

Computed ³HeET concentrations (at·g⁻¹) from the two methods (linear regression and weighted mean by the particle masses) considering three different densities. Errors are 1 σ.

<table><thead><tr><th rowspan="2"></th><th rowspan="2">Density</th><th colspan="6">Size ranges (µm)</th></tr><tr><th>&lt; 5</th><th>5–25</th><th>25–62</th><th>62–100</th><th>62–250</th><th>62–500</th></tr></thead><tbody><tr><td rowspan="3">Weighted mean</td><td>0.8</td><td>–</td><td>(7.3±0.5) × 10<sup>14</sup></td><td>(4.8±0.4) × 10<sup>13</sup></td><td>(9.7±0.7) × 10<sup>12</sup></td><td>(4.9±0.4) × 10<sup>12</sup></td><td>(1.2±0.1) × 10<sup>12</sup></td></tr><tr><td>1</td><td>–</td><td>(5.9±0.5) × 10<sup>14</sup></td><td>(3.9±0.3) × 10<sup>13</sup></td><td>(9.1±0.7) × 10<sup>12</sup></td><td>(4.6±0.4) × 10<sup>12</sup></td><td>(1.1±0.1) × 10<sup>12</sup></td></tr><tr><td>2.2</td><td>–</td><td>(2.7±0.2) × 10<sup>14</sup></td><td>(2.4±0.2) × 10<sup>13</sup></td><td>(7.6±0.6) × 10<sup>12</sup></td><td>(3.9±0.4) × 10<sup>12</sup></td><td>(8.2±0.9) × 10<sup>11</sup></td></tr><tr><td rowspan="3">Regression</td><td>0.8</td><td>(3.9±0.7) × 10<sup>18</sup></td><td>(1.5±0.4) × 10<sup>15</sup></td><td>(4.2±1.1) × 10<sup>13</sup></td><td>(5.9±2.0) × 10<sup>12</sup></td><td>(1.6±0.6) × 10<sup>12</sup></td><td>(6.0±2.2) × 10<sup>11</sup></td></tr><tr><td>1</td><td>(3.8±0.6) × 10<sup>18</sup></td><td>(1.5±0.3) × 10<sup>15</sup></td><td>(4.2±1.1) × 10<sup>13</sup></td><td>(5.9±1.7) × 10<sup>12</sup></td><td>(1.6±0.5) × 10<sup>12</sup></td><td>(6.0±2.0) × 10<sup>11</sup></td></tr><tr><td>2.2</td><td>(3.7±0.7) × 10<sup>18</sup></td><td>(1.5±0.5) × 10<sup>15</sup></td><td>(4.1±1.5) × 10<sup>13</sup></td><td>(5.7±2.4) × 10<sup>12</sup></td><td>(1.6±0.7) × 10<sup>12</sup></td><td>(5.8±2.7) × 10<sup>11</sup></td></tr></tbody></table>
<figure><img src="image_9.png" /><figcaption>Fig. 7. $^{3}$He/$^{4}$He isotopic ratios of cosmic dust. Plot of $^{3}$He/$^{4}$He ratios vs. particle size in log-log scale encompassing the SW, FSW and EA values. Isotopic end-members: $^{3}$He/$^{4}$He (SW) = (4.645±0.008) × 10⁻⁴ (Huss and Lewis, 1994); $^{3}$He/$^{4}$He = (2.17±0.05) × 10⁻⁴ (Ozima and Podosek, 2002) and $^{3}$He/$^{4}$He (atmo) = 1.384 × 10⁻⁶ (Kurz, 1986). Errors are reported as 1σ.</figcaption></figure>

flux by the average $^{3}$He concentrations measured in these cosmic dusts (at.g⁻¹), as shown in Equ. 3:

$$ET \ Mass \ Flux_{a-b} = \frac{^{3}He_{ET} \ flux}{[^{3}He_{ET}]_{a}^{b}}, \qquad (3)$$

where $[^{3}He_{ET}]_{a}^{b}$ is the average $^{3}$He$_{ET}$ concentration of each fraction belonging to the size range a-b (< 5 µm, 5–25 µm, 25–62 µm and 62 µm to 100, 250 and 500 µm).

Since the $^{3}$He$_{ET}$ concentration in cosmic dust is strongly dependent on the dust size (Fig. 6a, Appendix F), we consider different

<figure><img src="image_10.png" /><figcaption>Fig. 8. ET mass fluxes calculated with by 3 different densities (0.8, 1 and 2.2 g.cm⁻³) from the (a) weighted mean and (b) regression methods. Error bars, reported as 1σ, integrate the density variability.</figcaption></figure>
concentrations for each analyzed granulometric fraction (see Section 4.2). In order to account for possible bias induced by the use of the empirical relationship between ³HeET concentration and cosmic dust mass (Fig. 6a), we propose to estimate [³HeET]a/b using two different approaches. First, we compute an average ³HeET concentration for each granulometric interval by weighting each ³HeET concentration by the corresponding particle mass. However, in the absence of data for particles smaller than 5 µm, this method does not permit to calculate ³HeET concentrations in the finest fraction. Second, we calculated [³HeET]a/b integrating the linear relationship between ³HeET concentrations and the cosmic dust mass (Fig. 6a), following Eq. (4):

$$ \overline{[^3\text{He}_{\text{ET}}]_a}^b = 10^a \int_{a}^{b} \left( (\text{slope} \pm \text{sigma}) \cdot x + (\text{intercept} \pm \text{sigma}) \right) dx \times \frac{1}{b-a}, \quad (4) $$

where slope and intercept are the best fit parameters presented in Fig. 6a.

We considered a mean density of 1 g.cm⁻³ (Love et al., 1994), assuming ET particles are a 90–10 mixture of cometary (0.8 g.cm⁻³) and asteroid material (2.2 g.cm⁻³) (Carrillo-Sánchez et al., 2020). We also performed sensitivity tests to evaluate the impact of density on the computed ET fluxes, by using these two endmember values: 0.8 g.cm⁻³ for cometary particles (Fulle et al., 2016) and 2.2 g.cm⁻³ for asteroidal particles (Consolmagno et al., 2008) (Appendix H).

The impact of the density value on the calculated ET mass flux is larger using the mass weighted mean approach than the linear regression approach (Table 1 and Fig. 8a and b). This is because the particles that were not directly weighed require an assumption on their density to convert their sizes in mass. This lack of knowledge is overrepresented among the smallest ET particles (typically < 100 µm, ~65 % of the total dataset, Appendix F) and hence significantly impacts the results based on the weighted mean, while the linear regression approach is less sensitive to this assumption since it is buffered by the 65 % particles belonging to size ranges that were directly weighed.

Using the mass weighted mean method, a mean density of 1 g.cm⁻³

and two extreme densities of 0.8 and 2.2 g.cm⁻³, we obtain total ET mass fluxes integrated over the 5–100 µm size range: 5.2±³.³ µg.m⁻².a⁻¹, 6.8±².⁴ µg.m⁻².a⁻¹, 5.4±¹.⁹ µg.m⁻².a⁻¹ for F1, F4 and F6 snow tanks, respectively (Fig. 8a, Appendix D). Using the regression method (Fig. 6a) and a density of 1 g.cm⁻³, the total ET mass fluxes over the 0–100 µm fraction are: 4.9±1.1 µg.m⁻².a⁻¹, 9.1±2.0 µg.m⁻².a⁻¹, 7.3±1.9 µg.m⁻².a⁻¹ for F1, F4 and F6 snow tanks, respectively (Fig. 8b, Appendix D). Considering the extreme densities of 0.8 and 2.2 g.cm⁻³, these estimates would be shifted by <3 % (Fig. 8b). The ET mass flux computed from the F1 snow tank results are peculiar, because they are one order of magnitude lower than those observed in F4 and F6 for the 62–100 µm fraction, while they are 5 times greater for the 25–62 µm size fraction (Fig. 9a and b). All tanks yield a negligible contribution of < 5 µm particles.

Combining all granulometric fractions smaller than 100 µm from F1, F4 and F6 snow tanks, we obtain a global ET mass flux of 5.7±¹.⁵ µg.m⁻². a⁻¹ (i.e., 2.9±⁰.⁸ kilotons.a⁻¹ considering the whole Earth surface) and 6.8±1.0 µg.m⁻².a⁻¹ (i.e., 3.5±0.5 kilotons.a⁻¹) using the mass weighted mean and the regression method, respectively (Fig. 9).

These two methods yield similar mass fluxes for the 5–25 µm and the 25–62 µm fractions (Fig. 9). However, the contribution of the largest size fraction (62–100 µm) on the total flux is larger using the regression method than the mass weighted mean method (67 % vs. 50 %). Since there was no sieve larger than 62 µm in our filtering protocol, our He measurement in the largest fraction might also incorporate cosmic particles larger than 100 µm. Although the presence of such > 100 µm particles is unlikely (Section 4.1.3), we also computed the ET flux using higher values for the upper limit of the integration interval (250 and 500 µm, Equ. 4 and Table 1). For the 62–250 µm interval, this yields ET mass fluxes of 5.8±¹.¹ µg.m⁻².a⁻¹ and 6.5±3.6 µg.m⁻².a⁻¹; from the mass weighted mean and the regression method, respectively. Considering the 62–500 µm interval, this yields ET mass fluxes 24.4±⁷.⁶ µg.m⁻².a⁻¹ and 44.2±10.1 µg.m⁻².a⁻¹.

Given that the largest particles (> 62 µm) are over-represented in the

<figure><img src="image_11.png" /><figcaption>Fig. 9. Cosmic dust mass fluxes by granulometric ranges deduced from (a) the [³HeET] weighted mean method and (b) the [³HeET]-regression empirical fit (µg.m⁻².a⁻¹) from the three analyzed snow tanks (F1, F4 and F6). Results from the smallest fraction are intentionally not represented to avoid expanding this figure (Appendix D). The red spots indicate the arithmetic means of ET mass fluxes for each granulometric size range.</figcaption></figure>
He database, this could bias the ³HeET concentration derived from the mass weighted mean approach, while the regression method is less sensitive to this bias (Figs. 6 and 9). We hence consider that the ET mass flux derived from the regression method is more robust and only report the values based on this method in the next section.

### 4.3. Comparison with previous ET mass flux estimates

Our global ET mass flux estimate of all ET particles smaller than 100 µm is 3.5±0.5 kilotons·a⁻¹, which is about 3 times the 1.1±0.5 kilotons·a⁻¹ estimate from optical determination in the same Concordia snow samples (Rojas et al., 2021) (Fig. 10). Similarly, our estimate is significantly above other ET mass flux estimates derived from previous other Antarctic collections (e.g., Maurette et al., 1987; Taylor et al., 1998). Suttle and Folco (2020) derived a global ET flux of 1.5±0.8 kilotons·a⁻¹ of MMs (100–2000 µm) from the Transantarctic Mountains (TAMs), an estimate in close agreement with the SPWW flux (1.6±0.3 kilotons·a⁻¹; Taylor et al., 2000). However, both of these estimates do not take into account the contributions of particles from the smallest size fractions (< 100 µm) to the total ET mass flux, a limitation that our ³HeET-based approach is able to overcome. The Indian deep-sea sediment collections of CSs (Prasad et al., 2018) yielded a lower flux of 0.24±0.11 kilotons·a⁻¹, probably because there is more alteration in marine environments than in polar snow (Murell et al., 1980; Taylor et al., 2000).

Our estimate of the < 100 µm ET mass flux is in very good agreement with the net value of 3.5 kilotons·a⁻¹ derived from the CABMOD-ZoDy model (Carrillo-Sánchez et al., 2020), taking into account atmospheric heating (Fig. 10). Comparing the relative contribution of each granulometric fraction in previous flux estimates, we note that MMs in the largest size range (62–100 µm) account for ~70 % of the total mass flux. This result is in disagreement with the optical counting from the Concordia collection (99%; Rojas et al., 2021), but very consistent with the CABMOD-ZoDy results (67%; Carrillo-Sánchez et al., 2020). However, the flux of the 25–62 µm fraction derived from our ³HeET approach is ~25 % lower than CABMOD-ZoDy fluxes after atmospheric heating.

Moreover, even if the 5–25 µm fraction carries the majority of the ³HeET (Fig. 3), its contribution to the total ET mass flux is only 3 % (Fig. 10).

Considering together the ET mass flux reaching the top of the Earth atmosphere (~18 kilotons·a⁻¹; Love and Brownlee, 1993), and our estimate of 3.5±0.5 kilotons·a⁻¹, the atmospheric entry heating implies a 5 fold reduction of this flux.

Because it is not straightforward to estimate an upper granulometric limit for the validity of our ³HeET-based approach, it is useful to compare our ET mass flux estimates with those from other models using upper integration limits of 250 µm and 500 µm. In both cases, the ³HeET-estimated ET mass fluxes are higher than the values predicted by the CABMOD-ZoDy model before atmospheric heating (Carrillo-Sánchez et al., 2020) (Fig. 10). Since this discrepancy cannot be explained by any documented process, we conclude that the ³HeET-based method becomes less accurate for estimating the flux of ET particles larger than 100 µm, and that classical optical counting approaches should be favored in such cases. Thus, the two methods are complementary: the ³HeET method is the most sensitive and accurate for estimating fluxes of particles smaller than 100 µm.

### 5. Conclusion

Using a new cosmic dust extraction system to process ~38 kg of Concordia firn (Dome C, Antarctica), we derived a global ³HeET flux of (1.25±0.03) pcc STP·cm⁻²·ka⁻¹ (weighted mean±1SD) at Earth's surface, where 31 % and 65 % of this flux correspond to cosmic dust in the 25–62 µm and the 5–25 µm size ranges, respectively. These ³HeET fluxes are consistent with previous flux estimates from both sediments and ice core, and more precise than previous estimates (twice as precise, with an average of 0.08 compared to 0.04).

After compiling a new exhaustive noble gas database in cosmic particles, we establish a negative relationship between ³HeET concentrations and particle masses. By using these concentrations, we use our new ³HeET data to estimate an ET mass flux of (3.5±0.5) kilotons·a⁻¹ (weighted mean±1SD) of particles < 100 µm. This value is in agreement

<figure><img src="image_12.png" /><figcaption>**Fig. 10.** Cosmic mass flux distribution of the Concordia dust compared to the optical counting approach and the CABMOD-ZoDy simulation. The total mass flux of cosmic material derived from our ³He data, integrated across size ranges (red and orange, from two methods), is compared to various estimates: the direct optical counting of Rojas et al., 2021 (green) and the CABMOD-ZoDy model estimates (before and after atmospheric entry) from Carrillo-Sánchez et al. (2020) (light and dark blue). The cosmic mass fluxes derived from ³HeET measurement at Earth's surface were deduced from the [³HeET]-mass relationship (Fig. 6a). Mass flux errors from the mass weighted mean method integrate the two extreme densities of 0.8 and 2.2 g·cm⁻³. Values are reported in Appendix D.</figcaption></figure>
with predicted mass fluxes after atmospheric entry from the CABMOD-ZoDy model (Carrillo-Sánchez et al., 2020). Importantly, these mass flux estimates are approximately 3 times higher than the value previously reported by optical counting by Rojas et al. (2021) in the same granulometric range. Our results support the complementarity of the two approaches, the ³HeET method being more suited to detect < 100 µm particles than the optical method, which should be favored for determining largest cosmic material.

### CRediT authorship contribution statement

G. Fénisse: Writing – review & editing, Writing – original draft, Visualization, Validation, Software, Resources, Project administration, Methodology, Investigation, Funding acquisition, Formal analysis, Data curation, Conceptualization. D.V. Bekaert: Writing – review & editing, Validation, Supervision, Resources, Project administration, Methodology, Investigation, Conceptualization. P.-H. Blard: Writing – review & editing, Validation, Supervision, Resources, Project administration, Methodology, Investigation, Funding acquisition, Formal analysis, Data curation, Conceptualization. J. Duprat: Writing – review & editing, Validation, Project administration, Methodology, Investigation, Conceptualization. I. Mattia: Writing – review & editing, Validation, Software, Resources, Formal analysis. M. Genge: Writing – review & editing, Validation, Resources, Methodology. M.D. Suttle: Writing – review & editing, Validation, Resources, Methodology. O. Barres: Writing – original draft, Validation, Formal analysis, Data curation. C. Engrand: Writing – review & editing, Validation, Resources, Methodology. Y. Marrocchi: Writing – review & editing, Validation, Methodology, Investigation.

### Declaration of competing interest

The authors declare that they have no known competing financial interests or personal relationships that could have appeared to influence the work reported in this paper.

### Acknowledgements

The snow samples used in this study were collected at Concordia Station with the financial support of the French Polar Institute (IPEV) in the course of the micrometeorite@DC program (project #1120). J. Duprat and C. Engrand are grateful to IPEV and PNRA staff for logistical help. This work was partially funded by the European Union (ERC, Green2Ice, 101072180, co PI P.-H. Blard). Views and opinions expressed are however those of the authors only and do not necessarily reflect those of the European Union or the European Research Council Executive Agency. Neither the European Union nor the granting authority can be held responsible for them. Other funding that supported this work are CNES MIAMI H2 and DIM ACAV+project C3E (J. Duprat and C. Engrand) and ANR (ANR-22-CPJ2-0005-01 to D.V. Bekaert). This work was partly done using one of the infrared spectrometers of the GeoResources laboratory (Nancy, France).

### Supplementary materials

Supplementary material associated with this article can be found, in the online version, at doi:10.1016/j.epsl.2025.119396.

### Data availability

https://doi.org/10.24396/ORDAR-152 (All data including the exhaustive 3He database from the literature and the new helium data from CONCORDIA are available in the online open repository ORDAR:)

### References

Baecker, B., Ott, U., Cordier, C., Folco, L., Trieloff, M., Ginneken, M.V., Rochette, P., 2018. Noble gases in micrometeorites from the Transantarctic Mountains. Sci. Direct Geochim. Cosmochim. Acta 242, 266-297.

Baecker, B., Ott, U., Trieloff, M., Engrand, C., Duprat, J., 2022. Noble gases in Dome C micrometeorites - an attempt to disentangle asteroidal and cometary sources. Icarus 376, 114884. https://doi.org/10.1016/j.icarus.2022.114884.

Bajo, K., Akaida, T., Ohashi, N., Noguchi, T., Nakamura, T., Nakamura, Y., Sumino, H., Nagao, K., 2011. Single grain noble gas analysis of antarctic micrometeorites by stepwise heating method with a newly constructed miniature furnace. Earth Planets Space 63, 1097-1111. https://doi.org/10.5047/eps.2011.08.001.

Blard, P.-H., 2021. Cosmogenic 3He in terrestrial rocks: a review. Chem. Geol. 586, 120543. https://doi.org/10.1016/j.chemgeo.2021.120543.

Blard, P.-H., Balco, G., Burnard, P.G., Farley, K.A., Fenton, C.R., Friedrich, R., Jull, A.J.T., Niedermann, S., Pik, R., Schaefer, J.M., Scott, E.M., Shuster, D.L., Stuart, F.M., Stute, M., Tibari, B., Winckler, G., Zimmermann, L., 2015. An inter-laboratory comparison of cosmogenic 3 He and radiogenic 4 He in the CRONUS-P pyroxene standard. Quat. Geochronol. 26, 11-19. https://doi.org/10.1016/j.quageo.2014.08.004.

Blard, P.-H., Suchéras-Marx, B., Suan, G., Godet, B., Tibari, B., Dutilleul, J., Mezine, T., Adatte, T., 2023. Are marl-limestone alternations mainly driven by CaCO3 variations at the astronomical timescale? New insights from extraterrestrial 3He. Earth Planet. Sci. Lett. 614, 118173. https://doi.org/10.1016/j.epsl.2023.118173.

Brook, E.J., Kurz, M.D., Curtice, J., 2009. Flux and size fractionation of 3He in interplanetary dust from antarctic ice core samples. J. Geophys. Res. Lett. 286, 565-569. https://doi.org/10.1016/j.epsl.2009.07.024.

Brook, E.J., Kurz, M.D., Curtice, J., Cowburn, S., 2000. Accretion of interplanetary dust in polar ice. Geophys. Res. Lett. 27, 3145-3148. https://doi.org/10.1029/2000GL011813.

Brownlee, D.E., Joswiak, D.J., Love, S.G., Bradley, J.P., Nier, A.O., Schlutter, D.J., 1994. Identification and analysis of cometary IDs. In: Presented at the Lunar Planets Science Conf, pp. 185-186.

Carrillo-Sánchez, J.D., 2020. Injection of meteoric phosphorus into planetary atmospheres. Planet. Space Sci. 187, 104926. https://doi.org/10.1016/j.pss.2020.104926.

Carrillo-Sánchez, J.D., Gómez-Martín, J.C., Bones, D.L., Nesvorný, D., Pokorný, P., Benna, M., Flynn, G.J., Plane, J.M.C., 2020. Cosmic dust fluxes in the atmospheres of Earth, Mars, and Venus. Icarus 335, 113395. https://doi.org/10.1016/j.icarus.2019.113395.

Consolmagno, G.J., Britt, D.T., Macke, R.J., 2008. The significance of meteorite density and porosity. Chem. Erde 68, 1-29.

Duprat, J., Dobrica, E., Engrand, C., Aléon, J., Marrocchi, Y., Mostefaoui, S., Meibom, A., Leroux, H., Rouzaud, J.N., Gounelle, M., 2010. Extreme deuterium excesses in ultracarbonaceous micrometeorites from Central antarctic snow. Sci 328, 742-745.

Duprat, J., Engrand, C., Maurette, M., Kurat, G., Gounelle, M., Hammer, C., 2007. Micrometeorites from Central Antarctic snow: the Concordia collection. Science 39, 605-611.

Duprat, J., Maurette, M., Engrand, C., Matrajt, G., Immel, G., Hammer, C., Gounelle, M., Kurat, G., 2001. An estimation of the contemporary micrometeor flux obtained from surface snow samples collected in central Antarctica. Meteorit. Planet. Sci. 36, A52.

Eberhardt, P., Eugster, O., Marti, K., 1965. A redetermination of the isotopic composition of atmospheric neon. Z. Naturforsch. 20a, 623-624.

Engrand, C., Dartois, E., Duprat, J., Charon, E., Leroux, H., 2018. Composition of ultracarbonaceous antarctic micrometeorites (UCAMMs). In: Comparison with Rosetta/COSIMA Analyses. Presented at the Meteoritical Society Meeting. Moscou, Russia, p. 6223.

Engrand, C., Maurette, M., 1998. Carbonaceous micrometeorites from Antarctica. Meteorit. Planet. Sci. 33, 565-580. https://doi.org/10.1111/j.1945-5100.1998.tb01665.x.

Evatt, G.W., Smedley, A.R.D., Joy, K.H., Hunter, L., Tey, W.H., Abrahams, I.D., Gerrish, L., 2020. The spatial flux of Earth's meteorite falls found via Antarctic data. Geology 48, 683-687. https://doi.org/10.1130/G46733.1.

Farley, K.A., Love, S.G., Patterson, D.B., 1996. Atmospheric entry heating and helium retentivity of interplanetary dust particles. Geochim. Cosmochim. Acta 61, 2309-2316.

Farley, K., Taylor, S., Treffkorn, J., Lever, J.H., Gow, A.L., 2021. 3He flux obtained from South Pole air and snow-ice and its connection to interplanetary dust particles. Meteorit. Planet. Sci. 56, 988-2001. https://doi.org/10.1111/maps.13759.

Farley, K.A., Patterson, D.B., 1995. A 100-kyr periodicity in the flux of extraterrestrial He-3 to the sea. Floor. Nature 378, 600-603. https://doi.org/10.1038/378600a0.

Flynn, G.J., 1989. Atmospheric entry heating: a criterion to distinguish between asteroidal and cometary sources of interplanetary dust. Icarus 77, 287-310.

Freddotti, M., Pourchet, M., Flora, O., Gandolfi, S., Gay, M., Urbini, S., Vincent, C., Becagli, S., Gragnani, R., Proposito, M., Severi, M., Traversi, R., Udisti, R., Fily, M., 2005. Spatial and temporal variability of snow accumulation in East Antarctica from traverse data. J. Glaciol. 51, 113-124. https://doi.org/10.3189/17276505781829502.

Fulle, M., Della Corte, V., Rotundi, A., Rietmeijer, F.J.M., Green, S.F., Weissman, P., Accolla, M., Colangeli, L., Ferrari, M., Ivanovski, S., Lopez-Moreno, J.J., Epifani, E. M., Morales, R., Ortiz, J.L., Palomba, E., Palumbo, P., Rodriguez, J., Sordini, R., Zakharov, V., 2016. Comet 67P/Churyumov-Gerasimenko preserved the pebbles that formed planetesimals. Mon. Not. R. Astron. Soc. 462, S132-S137. https://doi.org/10.1093/mnras/stw2299.
Füri, E., Aléon-Toppani, A., Marty, B., Zimmermann, L., 2013. Effects of atmospheric
entry heating on the noble gas and nitrogen content of micrometeorites. Earth
Planet. Sci. Lett. 377-378, 1-12. https://doi.org/10.1016/j.epsl.2013.07.031.

Gardner, C.S., Liu, A.Z., Marsh, D.R., Feng, W., Plane, J.M.C., 2014. Infrerring the global cosmic dust influx to the Earth's atmosphere from lidar observations of the vertical flux of mesospheric Na. J. Geophys. Res. Space Phys. 119, 7870-7879. https://doi.org/10.1002/2014JA020383.

Genge, M.J., Larsen, J., Van Ginneken, M., Suttle, M.D., 2017. An urban collection of modern-day large micrometeorites: evidence for variations in the extraterrestrial dust flux through the quaternary. Geology 45, 119-122. https://doi.org/10.1130/G38352.1

Greshake, A., Klöck, W., Arndt, P., Maetz, M., Flynn, G.J., Bajt, S., Bischoff, A., 1998. Heating experiments simulating atmospheric entry heating of micrometeorites: clues to their parent body sources. Meteorit. Planet. Sci. 33, 267-290. https://doi.org/10.1111/j.1945-5100.1998.tb01632.x

Huss, G.R., Lewis, R.S., 1994. Noble gases in presolar diamonds I: three distinct components and their implications for diamond origins. Meteoritics 29, 791-810.

Kehm, K., Flynn, G.J., Hohenberg, C., 2006. Noble gas space exposure ages of individual interplanetary dust particles. Meteorit. Soc. Sci. 41, 1199-1217.

Kurat, G., Koeberl, C., Presper, T., Brandstatter, F., Maurette, M., 1994. Petrology and geochemistry of antarctic micrometeorites. Geochim. Cosmochim. Acta 58, 3879-3904. https://doi.org/10.1016/0016-7037(94)90369-7, 1010160016-703794903697-9 3879-3904.

Kurz, M.D., 1986. In situ production of terrestrial cosmogenic helium and some applications to geochronology. Geochim. Cosmochim. Acta 50, 2855-2862. https://doi.org/10.1016/0016-7037(86)90232-2.

Le Meur, E., Magand, O., Arnaud, L., Fily, M., Frezzolato, M., Cavitte, M., Mulvaney, R., Urbini, S., 2018. Spatial and temporal distributions of surface mass balance between Concordia and Vostok stations, Antarctica, from combined radar and ice core data: first results and detailed error analysis. The Cryosphere 12, 1831-1850. https://doi.org/10.5194/tc-12-1831-2018.

Love, S.G., Brownlee, D.E., 1993. A direct measurement of the terrestrial mass accretion rate of cosmic dust. Science 162, 550-553.

Love, S.G., Joswiak, D.J., Brownlee, D.E., 1994. Densities of stratosphere micrometeorites. Icarus 111, 227-236.

Ludwig, K.R., 2003. User's Manual for Isoplot/Ex, Version 3.00, A Geochronological

Toolkit for Microsoft Excel. Berkeley Geochronol. Cent. Spec. Publ, Berkeley.

Mathews, J.D., Janches, D., Meisel, D.D., Zhou, Q.H., 2001. The micrometeoroid mass flux into the upper atmosphere: Arecibo results and a comparison with a prior estimates. Geophys. Res. Lett. 28, 1929-1932.

Matsuda, J., Matsumoto, T., Sumino, H., Nagao, K., Yamamoto, J., Miura, Y., Kaneoka, N., Takahata, N., Sano, Y., 2002. The 3He/4He ratio of new internal He standard of Japan (HESJ). Geochim. Cosmochim. Acta 70, 5061-5073. https://doi.org/10.1016/j.gca.2006.06.1566.

Maurette, M., Jéhanno, C., Robin, E., Hammer, C., 1987. Characteristics and mass distribution of extraterrestrial dust from the Greenland ice cap. Nature 328, 699-702. https://doi.org/10.1038/328699a0.

McGee, D., Mukhopadhyay, S., 2013. Extraterrestrial He in sediments: from recorder of asteroid collisions to timekeeper of global environmental changes. In: Burnard, P. (Ed.), The Noble Gases as Geochemical Tracers, Advances in Isotope Geochemistry. Springer Berlin Heidelberg, Berlin, Heidelberg, pp. 155-176. https://doi.org/10.1007/978-3-642-28836-4_7.

Mukhopadhyay, S., Farley, K.A., 2006. New insights into the carrier phase(s) of extraterrestrial 3He in geologically old sediments. Geochim. Cosmochim. Acta 70, 5061-5073. https://doi.org/10.1016/j.gca.2006.06.1566.

Murell, M.T., Davis, P.A., Nishizumi, K., Millard, H.T., 1980. Deep-sea spherules from Pacific clay: mass distribution and influx rate. Geochim. Cosmochim. Acta 2067-2074. https://doi.org/10.1016/0016-7037(80)90204-5.

Nesvorny, D., Vokrouhlicky, D., Bottke, W., Sykes, M., 2006. Physical properties of asteroid dust bands and their sources. Icarus 181, 107-144. https://doi.org/10.1016/j.icarus.2005.10.022.

Nier, A.O., Schlutter, D.J., 1992. Extraction of helium from individual interplanetary dust particles by step-heating. Meteoritics 27, 166-173. https://doi.org/10.1111/j.1945-5100.1992.tb00744.x.

Osawa, T., Nagao, K., 2002. Noble gas compositions of antarctic micrometeorites collected at the Dome Fuji Station in 1996 and 1997. Meteorit. Planet. Sci. 91-936. https://doi.org/10.1111/j.1945-5100.2002.tb00867.x.

Osawa, T., Nagao, K., Nakamura, T., Takaoka, N., 2000. Noble gas measurement in individual micrometeorites using laser gas-extraction system. Antarct. Meteor. Res. 12, 322-341.

Osawa, T., Nagao, K., Noguchi, T., Nakazawa, A., Mikada, J.I., 2003. Remnant extraterrestrial noble gases in Antarctic cosmic spherules. Antarct. Meteor. Res. 16, 196-219.

Ozima, M., Podosek, F.A., 2002. Noble Gas Geochemistry. Cambridge University Press.

Patterson, D.B., Farley, K.A., Schmitz, B., 1998. Preservation of extraterrestrial 3He in 480-ma-old marine limestones. Earth Planet. Sci. Lett. 163, 315-325. https://doi.org/10.1016/S0012-821X(98)00197-6.

Pepin, R.O., Palma, R.L., Schlutter, D.J., 2000. Noble gases in interplanetary dust particles: I: the excess helium-3 problem and estimates of the relative fluxes of solar wind and solar energetic particles in interplanetary space. Meteorit. Planet. Sci. 35, 495-504.

Peucker-Ehrenbrink, B., 1996. Accretion of extraterrestrial matter during the last 80 million years and its effect on the marine osmium record. Geochim. Cosmochim. Acta 60, 3187-3196.

Peucker-Ehrenbrink, B., Ravizza, G., 2000. The effects of sampling artifacts on cosmic dust flux estimates: a reevaluation of nonvolatile tracers (Os, Ir). Geochim. Cosmochim. Acta 64, 1965-1970. https://doi.org/10.1016/S0016-7037(99)00429-9.

Plane, J.M.C., 2012. Cosmic dust in the earth's atmosphere. Chem. Soc. Rev. 41, 6507. https://doi.org/10.1039/c2cs35132c.

Prasad, M.S., Rudraswami, N.G., De Araujo, A.A., Khedekar, V.D., 2018. Characterisation, sources and flux of unmelted micrometeorites on Earth during the last ~50,000 years. Sci. Rep. 8, 8887. https://doi.org/10.1038/s41598-018-27158-x.

Rojas, J., Duprat, J., Engrand, C., Dartois, E., Delauche, L., Godard, M., Gounelle, M., Carrillo-Sánchez, J.D., Pokorný, P., Plane, J.M.C., 2021. The micrometeorite flux at Dome C (Antarctica), monitoring the accretion of extraterrestrial dust on Earth. Earth Planet. Sci. Lett. 560, 116794. https://doi.org/10.1016/j.epsl.2021.116794.

Schaefer, J.M., Winckler, G., Blard, P.-H., Balco, G., Shuster, D.L., Friedrich, R., Jull, A.J. T., Wieler, R., Schluechter, C., 2016. Performance of CRONUS-P—A pyroxene reference material for helium isotope analysis. Quat. Geochronol. 31, 237-239. https://doi.org/10.1016/j.quageo.2014.07.006.

Stuart, F.M., Harrop, P.J., Knott, S., Turner, G., 1999. Laser extraction of helium isotopes from Antarctic micrometeorites:source of Heand implications for the flux of extraterrestrial 3He to Earth. Geochim. Cosmochim. Acta 63, 2653-2665.

Suttle, M.D., Campanale, F., Folco, L., Tavazzani, L., Meier, M.M.M., Miller, C.G., Hughes, G., Genge, M.J., Salge, T., Spratt, J., Anand, M., 2023. Fossil micrometeorites from Monte dei Corvi: searching for dust from the Veritas asteroid family and the utility of micrometeorites as a palaeoclimate proxy. Geochim. Cosmochim. Acta 355, 75-88. https://doi.org/10.1016/j.gca.2023.06.027.

Suttle, M.D., Folco, L., 2020. The extraterrestrial dust flux: size distribution and mass contribution estimates inferred from the Transantarctic Mountains (TAM) micrometeorite collection. J. Geophys. Res. Planets 125, e2019JE006241. https://doi.org/10.1029/2019JE006241.

Takayanagi, M., Ozima, M., 1987. Temporal variation of $^3$He/$^4$He ratio recorded in deep-sea sediment cores. J. Geophys. Res. Solid Earth 92, 12531-12538. https://doi.org/10.1029/JB092ib12p12531.

Taylor, S., Lever, J.H., Burgess, K.D., Stroud, R.M., Brownlee, D.E., Nittler, L.R., Bardyn, A., Alexander, C.M.O., Farley, K.A., Treffkorn, J., Messenger, S., Wozniakiewicz, P.J., 2020. Sampling interplanetary dust from Antarctic air. Meteorit. Planet. Sci. 55, 1128-1145. https://doi.org/10.1111/maps.13438.

Taylor, S., Lever, J.H., Harvey, R.P., 2000. Numbers, types, and compositions of an unbiased collection of cosmic spherules. Meteorit. Planet. Sci. 35, 651-666. https://doi.org/10.1111/j.1945-5100.2000.tb01450.x.

Taylor, S., Lever, J.H., Harvey, R.P., 1998. Accretion rate of cosmic spherules measured at the South Pole. Nature 392, 899-903. https://doi.org/10.1038/31894.

Tolstikhin, I.N., 1975. Helium isotopes in the earth's interior and in the atmosphere: a degassing model of the earth. Earth Planet. Sci. Lett. 26, 88-96. https://doi.org/10.1016/0012-821X(75)90180-6.

Toppani, A., Liboureel, G., Engrand, C., Maurette, M., 2001. Experimental simulation of atmospheric entry of micrometeorites. Meteorit. Planet. Sci. 36, 1377-1396. https://doi.org/10.1111/j.1945-5100.2001.tb01831.x.

Torfstein, A., 2012. Size fractionation, reproductibility and provenance of helium isotopes in north-equatorial pacific pelagic clays. Earth Planet. Sci. 399-340, 151-163.

Wetherill, G.W., 1976. Where do the meteorites come from? A re-evaluation of the earth-crossing apollo objects as sources of chondritic meteorites. Geochim. Cosmochim. Acta 40, 1297-1317. https://doi.org/10.1016/0016-7037(76)90120-4.

Winckler, G., Fischer, H., 2006. 30,000 years of cosmic dust in antarctic ice. Science, 3135786491. https://doi.org/10.1126/science.1127469.

Yada, T., Nakamura, T., Takaoka, N., Noguchi, T., Terada, K., Yano, H., Nakazawa, T., Kojima, H., 2004. The global accretion rate of extraterrestrial materials in the last glacial period estimated from the abundance of micrometeorites in Antarctic glacier ice. Earth Planets Space 56, 67-79. https://doi.org/10.1186/BF03352491.

Yiou, F., Raisbeck, G.M., Jeehanno, C., 1989. Influx of cosmic spherules to the Earth during the last ~105 years as deduced from concentrations in Antarctica ice cores. Meteoritics 24, 344.

York, D., Evensen, N.M., Martínez, M.L., De Basabe Delgado, J., 2004. Unified equations for the slope, intercept, and standard errors of the best straight line. Am. J. Phys. 72, 367-375. https://doi.org/10.1119/1.1632486.

Zimmermann, L., Avice, G., Blard, P.-H., Marty, B., Füri, E., Burnard, P.G., 2018. A new all-metal induction furnace for noble gas extraction. Chem. Geol. 480, 86-92. https://doi.org/10.1016/j.chemgeo.2017.09.018.