In this TA visit, the team investigated the abundance and isotopic composition of noble gases (He – Xe) in CM chondrites that record both aqueous and thermal metamorphism. These unusual meteorites are likely good analogues for the types of material found on the surfaces of primitive C-type asteroids; however, the timing and mechanism of the metamorphism remains unknown.
The team measured He – Xe in five CM chondrites that experienced peak metamorphic temperatures of <300°C to >750°C using stepped-heating and the “ALBATROS” mass spectrometer at the ETH Zürich Geo- and Cosmochemistry Noble Gas Laboratory. Preliminary results show that the concentrations of 4He and 22Ne are depleted in the lowest temperature steps (300 and 450°C) for all samples, consistent with degassing during (a) metamorphic event(s). Peaks in the concentration of both light and heavy noble gases in the 660°C and 800°C steps agree with previous estimates of metamorphic temperatures based on mineralogy and H2O loss. Isotopic compositions are mainly a mixture of primordial (so-called Q/HL) and cosmogenic components. In addition, EET 96029 and WIS 91600 contain a trapped solar wind component, suggesting that these meteorites may have been heated by impacts during residence in the asteroid regolith. Comparison of the data to unheated CM chondrites will be used to further constrain the thermal history of C-type asteroids in the early Solar System.
Report Summary: This study investigates the Neoarchaean to Paleoproterozoic Transvaal Supergroup sedimentary sequence in Botswana that formed in the centre of the Kaapvaal Craton during the early oxygenation of the atmosphere. We used U-Pb dating on magmatic and sedimentary zircons from throughout the sedimentary sequence to determine the tectono-magmatic evolution of the hinterland basement. This approach constrains regional crustal growth, uplift and erosion events and establishes if additional cratons were in the hinterland, e.g. Pilbara. Knowledge of zircon provenance will allow critical comparison to known tectonic scenarios, e.g. Alpine style molasse basin and any potential change in Neoarchaean tectonics by considering erosion and crustal growth-reworking. The geochronology results help evaluate spatial and temporal variations in depositional environments associated with oxygenation of the atmosphere. Results indicate that the age of the basement, Gaborone Granite and the Kanye volcanic are indistinguishable (2768.9 ± 6.0 Ma). Sediments deposited from 2.642 Ga to 2.550 Ga are also dominated (> 90%) by zircons of ~2.77 Ga. This implies that there was a major crustal growth event in the Kanye region at 2.77 Ga that included minimal crustal reworking. Erosion products to the Kanye Basin are derived from this juvenile crust throughout the Archaean and Proterozoic until > 2.0 Ga. Only then are older and younger basement rocks recorded in the sedimentary sequence. This region of the planet yields no evidence of a major tectono-magmatic event associated with the oxygenation of the atmosphere.
This project was designed to improve the understanding of biosignatures in analogue terrestrial surfaces, volcanic rocks, that result as a consequence of microbial colonisation and weathering. During the visit, the automatic medium-volume sampling system PNS DM — modified to run on batteries charged with solar panels — was assembled, tested, and calibrated in the laboratory of Matis.
Due to a delay in shipment of the solar panels, the installation of the system at the field site could not be performed but will be finalised by the host institution in the near future. As a part of the visit, the area of the Fagradalsfjall volcano was visited and the location where the sampling system will be installed was discussed. Once the sampler system will be installed in proximity of the Fagradalsfjall volcano crater, aerosol samples will be collected continuously for a year along with replicate rock samples in order to investigate the impact of aerosol deposition on rock microbial community assembly, using microbial, chemical and physical analysis. This will be performed in collaboration between the team of Prof. Viggó Þór Marteinsson and the team of Assoc. Prof. Tina Santl-Temkiv and will result in greatly improved understanding of colonisation, community assembly, and biosignature emergence in analogue terrestrial surfaces.
Report Summary: Fifteen high-pressure experiments on the PISL end-loaded piston cylinder press were performed at 1 GPa and 1873 K to systematically investigate the effects of Cu and Ni on metal- and sulfide-silicate partitioning of highly siderophile elements (HSE) Pd, Ru, Pt and Ir. Run times at peak conditions varied around 60-90 minutes. The starting compositions consisted of silicate, sulfide and metal powders with added metallic Si. The experimental run products consist of well-segregated metallic and sulfide blobs in a silicate glass. The addition of metallic Si and the initial reduction of the experiments result in the suppression of nugget formation. The glass does contain minute specks typical of S- saturated silicate melts – subsequent LA-ICP-MS measurements of the run products show that these specks do not contain HSE, as initially hypothesized. Electron microprobe and LA-ICP-MS analyses further show that the experimental run products are homogeneous and no compositional zoning was observed. Initial results show that the addition of Cu and Ni to the sulfide liquid decreases the O content of that sulfide liquid at a given FeO value of the silicate melt. This will most certainly affect the partitioning of the elements of interest – preliminary results for Pt confirm this by its variation by three orders of magnitude at a given FeO content. Preliminary results also show that Pd, Ru, Pt, Ir are all preferentially partitioned into the metallic liquid instead of the sulfide melt, confirming their preference for S-poor alloys relative to S-rich liquids.
Report Summary: Twelve high-pressure experiments on a piston cylinder press were performed at 1 GPa and 1673-1873 K to systematically investigate the sulfide-silicate partitioning of chalcophile elements as a function of (non-FeO) silicate melt compositional terms. Run times at peak conditions varied around 70 to 220 minutes. The starting compositions consisted of silicate and sulfide powders. The experimental run products consist of well-segregated sulfide blebs in a silicate glass. The glass contains minute sulfur blebs but subsequent LA-ICP-MS measurements showed that these blebs do not contain the elements of interest and are composed of Fe-S-O. Electron microprobe and LA-ICP-MS analyses further showed that the experimental run products are homogeneous and no compositional zoning was observed.
Initial results show that variations in silicate melt composition affect the partitioning of chalcophile elements in a non-ideal way – i.e. FeO activity varies significantly across different melt compositions, thereby affecting the geochemical behavior of the elements of interest. Therefore, it can be expected that in an arc-type differentiation suite the sulfide-silicate partitioning behavior may vary significantly, purely due to variations in FeO activity due to variable silicate melt compositions.
Analyses of Martian meteorites and their components predicts the existence of three main geochemical reservoirs on Mars, namely an enriched crust, a complementary depleted lithospheric mantle, and, lastly, a primitive asthenospheric mantle. Investigating the oxygen isotope composition of these reservoirs is critical for a full understanding of the accretion history of Mars. The Δ17 O composition of ~0.3‰, defined by the SNCs is believed to reflect the primary planetary composition of the martian mantle (1). However, analyses of ancient (>4.5 Ga) individual zircons and minerals from the NWA 7533 regolith breccia, record Δ17 O values that are characterized by a much heavier Δ17 O composition and thus different from the SNCs (2,3). A population of young zircons (<1.5 Ga), also from NWA 7533, are derived from a primitive reservoir located in the deep martian interior, as they are characterized by chondritic-like initial Hf isotope composition (4).
The oxygen isotope composition of a single grain from this population, indicate that this reservoir may be characterised by a different Δ17 O than the SNCs. If correct, the SNCs might not be representative of the bulk martian composition, but plausibly reflecting interaction with a heavy Δ17 O surface reservoir. Therefore, a main objective behind this study was to obtain high-precision oxygen isotope composition of 10 SNC meteorites to potentially detect Δ17 O heterogeneity. However, initial results show no isotopic variability, thus suggesting that the SNC source reservoir has not experienced interaction with surface reservoir, or that any heterogeneity has been erased.
One of the major unresolved questions in the field of cosmochemistry is to understand the source(s) and timing of volatile delivery in the inner Solar System. The goal of this project was to examine primitive achondrites which volatile inventory has not yet been investigated, in order to determine what portion of these volatiles was incorporated in the early stages of the Solar System history, relative to late-veneer delivery. In this regard, primitive achondrite acapulcoites and lodranites were selected as they sample a common parent body, hence allowing to also investigate the effect of various degrees of planetary differentiation on volatile abundances and isotopic compositions.
Using the NanoSIMS 50L at the Open University, we analysed chlorine and water content, as well as their associated isotopic composition in phosphates from three acapulcoites and two lodranites. Our results suggest that the acapulcoite-lodranite parent body incorporated a similar source of volatiles than ordinary chondrites, which chemical composition is similar to the chondritic precursor of acapulcoites and lodranites, arguing for a common reservoir of both Cl and H in the inner Solar System.
20-EPN2-052: Water in silica-bearing iron meteorites – implications for early Solar System dichotomy
Visit by Ana Černok, Freie Universität Berlin (Germany)/University of Trieste (Italy) to TA2 Facility 21 – OU NanoSIMS 50L (UK). Dates of visit: 14-21 November 2022 and virtual visit from 28 November – 20 December 2022
Understanding the volatile inventory of the earliest Solar System is inseparable from understanding which sources contributed to the volatiles of the oldest and relatively dry non-carbonaceous (NC) objects formed in the inner Solar System, and if they were different from wet carbonaceous (CC) materials, formed in the outer Solar System.
Two questions remain largely unanswered in this respect: (i) What are the abundances and isotopic composition of volatiles in the oldest NC objects and (ii) What were their sources? These questions can be answered by investigating some of the oldest objects in the Solar System, namely, the NC iron meteorites.
This Europlanet visit to the NanoSIMS facility was focused on trying to determine the content and isotopic composition of H or H2O inside minerals within iron meteorites. The iron meteorites are some of the oldest formed materials in the Solar System and hold key evidence if there has been any water available when they formed, and if there was: where did this water originate from?
Here we focused on understanding water abundance and its isotopic composition in some of the oldest NC silica bearing iron meteorites (IVA type): Muonionalusta, Gibeon and Steinbach. Other investigated irons did not contain any silica. The lowest water content was measured in Gibeon (< 10 ppm) and Muonionlusta (15–20 ppm), while minerals in Steinbach contained significantly more water (40–120 ppm). The δD values for Gibeon show a large range and greater uncertainties, due to low measured water contents. The δD values in Muonionalusta and Steinbach cluster between ~0–300 ‰. In fact, silica phases in both minerals cluster between ~0–200 ‰, while low-water cpx in Steinbach shows the highest δD values (200–300 ‰). The difference in δD values between mineral phases in Steinbach likely reflects the difference in their crystallisation history, where opx may have lost H resulting in increased D/H ratio (higher δD) due to degassing. Overall, the source of water in these NC irons is very similar to that of the Earth and the chondrites, while low-D reservoirs have not been detected.
Report Summary: A vast range of different gully morphologies occurs on Mars: from the classical gullies, which resemble gullies on Earth, to linear gullies that do not have an Earth counterpart and are found on Martian dunes. Previous experiments have shown that the sublimation of CO2 ice can fluidise and transport sediment in the classical gullies on Mars. However, the linear gullies are hypothesised to form by a different, although related CO2-driven mechanism. For linear dune gullies, it is hypothesised that they form by a block of CO2-ice sliding down the dune. This process has, however, never been observed in real life.
With our visit to the Mars chamber at the Open University, we aimed at deciphering the triggering and forming mechanisms of linear dune gullies on Mars. We identified the possible triggering mechanisms based on hypotheses presented in the literature. The identified mechanisms are; 1) the breaking off and sliding down of CO2-ice blocks, and 2) wind-blown sand being deposited on CO2 frost. We systematically tested these mechanisms in the Mars Chamber at the Open University by means of experiments. For all identified triggering mechanisms a parameter space was used to test the influence of e.g. CO2-ice block size, surface slope and grain size.
With our experiments, we show that CO2-ice blocks slide downslope and create small narrow gullies when dumped on top of fluvial sand, with a large grain-size distribution. However, when dumped on a finer aeolian sand under Martian atmosphere, they do not slide downslope but they dig themselves into the sand, slowly digging a gully downslope by vigorous sublimation and sediment mobilisation. We also show that when a small amount of warm sand is dumped on top of a CO2-frosted the sand is mobilised by CO2 sublimation, but that this process does not create the typical linear gullies we see on Mars.
Report Summary: This project was designed to extend previous research of mud behaviour in the low-pressure conditions – with implications for potential sedimentary volcanism on Mars. The main objective was to test the effect of ice (or combined ice-sand) substrate to flow abilities and finite morphology of mudflows. As secondary objectives, testing of various inclinations of the surface, investigation of potential thermal erosion and extended study of another type of surfaces were implemented.
In the first part of the project, nine successful experiments, with pure and variously inclined (2-10°) ice surface, confirmed a different style of mud propagation than in case of the frozen sandy surface. The major observations are: 1) dominant and prevailing boiling of mud mixture during the propagation over deeply frozen ice surface (confirms significance of latent heat related to melting/recrystallization), 2) explosive potential of ice when in contact with the boiling mud (fracturing, contraction-dilatation). The effect of slope in tested range has no significant impact on these observations.
The second type of experiments tested combined ice-sand upper lid. Here, transition between boiling and freezing of mudflows was faster and finite morphology was more similar to lava-like flows which were described by Brož et al. (2020a).
In both cases, the thermal erosion was not confirmed. Moreover, during sectioning and investigation of the finite mudflow shapes and their base, the developed bumps, irregularities or even increased porosity of ice lid were discovered. This might refer to more complex thermal exchange between ice and mud with a sequential melting and re-freezing.
Report Summary: High latitude, ice marginal regions are efficient sources for atmospheric dust. Dust plays a fundamental role in the Earth’s climate system both driving and responding to climate change. Last glacial loess deposits in NW Europe potentially record past dust emissions from regions marginal to the former Eurasian Ice Sheet. However, uncertainties over the age of these deposits essentially limit their potential in reconstructing past dust activity. This project aims to build a detailed chronology of last glacial dust deposition in NW Europe through combined luminescence and 14C dating of loess on Jersey (Channel Islands).
During the Europlanet-funded 6-day research visit to the 14C accelerator mass spectrometry laboratory in Debrecen, Hungary radiocarbon dating of fossil gastropods embedded in the loess was conducted. Preliminary results are in good agreement with the existing, yet unpublished luminescence chronology. However, some ages may underestimate the depositional age due contamination from post depositional carbonate leaching. Nevertheless, the 14C ages from gastropod shells serve as valuable cross check of the OSL data and help to build a more robust age model for the loess section based on two independent dating methods.
Report Summary: The experiments initially proposed aimed to investigate the formation and chemical evolution of both glycine and alanine under space relevant conditions. Following a systematic approach, the TA was divided into three projects carried out by a multidisciplinary group of scientist (chemists, biologists, astrophysicists and engineers): looking at (i) experimental insights into the microphysics of molecule destruction and sputtering of CO2 exposed to cosmic rays analogues; (ii) the formation of methyl formate and its isomers (glycolaldehyde and acetic acid) through the systematic irradiation of H2 CO:CO, H2 CO:CH4 , and H2 CO:CH3 OH ice mixtures with 1 MeV and 200 keV H+ ; (iii) and 1 MeV H+ irradiation of pure Glycine and Glycine:CH4 interstellar relevant ice mixtures, exploring the survivability and stability of this amino acid in astrophysical relevant environments.
The three projects were designed with incremental molecular complexity to investigate the chemistry of many precursors of simple amino acids. Moreover, the sub-projects were designed to be connected to other awarded TAs either at ICA or AQUILA (PIs: Ivlev, Ioppolo, and Hopkinson) in a synergic manner. For instance, the work of H2 CO completes the systematic study on methyl formate and its isomers, started at this Europlanet facility 2 years ago, trying to improve the understanding of the standing dichotomy on the formation of glycolaldehyde, methyl formate, and acetic acid. All these species are detected in space in star-forming regions and are considered prebiotic molecules.
Report Summary: The surface of Europa is host to a rich radiation environment, in which ions from the giant Jovian magnetosphere drive physico-chemical transformations of surface ices and minerals. Although a number of previous studies have looked into the irradiation of surface ice analogues in order to better constrain the chemistry occurring on Europa, considerably fewer studies have investigated the radiation chemistry of plausible mineral analogues.
Therefore, in this study, we have irradiated four mineral species (halite, fayalite, epsomite, and berthierine) using 1 MeV H+ and 1 MeV S+ ions to better understand the dissociation pathways of these minerals and the associated radiolysis products. Our preliminary results have shown that irradiation brings about significant changes in the appearances of the minerals that signify alterations in the structures and chemical compositions. Further infrared, visible, and ultraviolet spectroscopic analyses of retained mineral samples (both irradiated and pristine) are planned for the near future.
Report Summary: Cosmogenic nuclide (CN) surface-exposure dating (SED) has revolutionised geomorphology in recent years, enabling the direct determination of both the rate and age of Earth surface-processes. However, SED relies on strict quantification of CN production rates (PRs) for both the time-period and location in question; for many sites and times periods such data is rare. As a result, calculated exposure ages may vary significantly depending upon the assumptions and model schemes employed in calculations. The impact of geomagnetic field variability on nuclide production is particularly uncertain.
The goal of this project is to test explicitly the methods used to calculate exposure ages, and to assess their viability over space and time. To do this, we measured cosmogenic helium-3 within a series of Peruvian lavas of varying age at the Stable Rare Gas and Radiogenic Isotope Facility, CRPG (France). Paired with later Ar/Ar age determination, we are using these new cosmogenic helium data to produce a series of discrete CN production rates from a single geographic region, and so will assess the variability of nuclide production through time. Our preliminary results indicate the research plan is viable: cosmogenic helium data from single lava flows are internally consistent. Lavas analysed range in age from ~1.6 ka to ~175 ka, and so provide a dataset that spans a period sufficient to assess changes in PR and the potential impact of magnetic field variability on CN PRs. We anticipate sharing final project results within a peer-reviewed, open-access publication within the calendar year.
Report Summary: The project aims to understand the astronomical processes leading to the late Eocene shower of extraterrestrial (ET) material onto Earth. The 3He-carrier phases responsible for the ~ 2 million years enduring 3He anomaly will be characterised geochemically by producing a combined 3He and Ir dataset.
Here, 23 samples of marine micro-fossil ooze form the ODP 689B core, Maud Rise, Southern Ocean were measured at the CRPG Nancy noble gas laboratory. These samples cover the Eocene Oligocene transition (38 to 33 Ma) and these new data document the amplitude and duration of the 3HeET anomaly and confirms that the late Eocene 3He anomaly reported from the Massignano outcrop (Italy) is a global phenomenon. The here-investigated 689B micro-fossil ooze is exceptional because its low terrigenous mineral content and low iridium concentration of 5-15 ppt Ir. These Ir values are close to the expected ET contribution of 12 ppt Ir, as calculated using the current global/annual ET flux and the sedimentation rate and dry density of the 689B deposits.
The 3He data set acquired during the TA visit combined with literature data on Ir concentrations show that the flux of 3He rich ET particles increase by 4 times whereas the Ir concentrations in 689B remain at background values. New Ir data with low detection limits will further constrain the relation between ET 3He and total Ir during the late Eocene shower. ET 3He does not correlate with Ir indicating that the late Eocene 3He anomaly was caused by 3He-rich and Ir poor dust particles. The study illuminates the potential of marine micro-fossil ooze for planetary science.
Report Summary: The advent of non-traditional isotopic systems (e.g., Ti, Cr, Mo) revealed that chondrites—the most primitive witnesses of the early solar system—display a fundamental isotopic dichotomy, with carbonaceous chondrites (CCs) showing large nucleosynthetic anomalies relative to terrestrial standards that are not observed in non-carbonaceous chondrites (NCs). NC and CC reservoirs may thus represent the primordial inner and outer parts of the solar system, respectively.
The scientific goal of this project is to combine several isotopic systems (O, Ti, Cr) for deciphering the conditions and chronology of chondrule formation in the NC reservoir. A key parameter of this approach is to also have access to the formation ages of these chondrules. This requires in situ measurements with a secondary ion mass spectrometer for determining the 26Al ages of chondrule crystallisation.
To do so, 16 chondrules were separated from the minimally altered ordinary chondrite NWA 5206. They were split into two pieces for determining their (i) Cr and Ti isotopic compositions (bulk measurements) and (ii) O isotopic compositions and 26Al ages. These chondrules show no 54Cr or 50Ti excesses and classical oxygen isotopic composition (with ∆17 O ranging from -1 to + 1 ‰). 26Al ages are coherent with previous estimates showing that NC chondrules formed over several million years during the evolution of the inner disk.
Report Summary: Here we have searched for a source of D-enriched Martian groundwater previously discovered in the Martian meteorite Lafayette (up to δD 4725‰) within olivine defects below the secondary mineral phyllosilicate. These groundwaters which are known flowed through this sample 670 Ma were sourced from the Martian atmosphere, or had equilibrated with it, and diffused up to ~1.5 µm into the olivine via shock-formed defects in vein walls. In this project we want to determine a calibration line to resolve the water content on the Martian olivines and find a potential location of new water within the defects.
Two 1 inch indium mounts were prepared with olivine plus glass standards and paired Martian nakhlite samples (Yamato 593, 802, 749, Lafayette and Nakhla) to confirm this source of Martian ground water. Work was conducted with Dr Johan Villeneuve and Dr Laurette Piani on the Cameca IMS 1270 E7 ion probe at CRPG, Nancy. The new obtained/formed standards provided calibration to measurements of water contents (H2O%) within the Martian olivines and when combined with standards from CRPG δD values were roughly constrained. Owing to the unique surfaces of each Martian altered olivine it was impossible to confirm pre analyses if defects hosting water would be present in the outer olivine surfaces. Results show a location where an enriched δD was present, further investigations such as Transmission Electron Microscopy (TEM) are required to confirm this.
Report Summary: One way to study the origin of water and other volatiles which accreted onto rocky planets such as Earth during the formation of the Solar System is to study meteorites that fall from asteroids and other planetary bodies. Hydrogen isotope ratios within meteorites can be used as a tracer for the source of a body’s water, and to an extent spatial and temporal information about the formation of parent bodies.
Previously, we measured the D/H ratios of bulk powders of a wide range of unequilibrated ordinary chondrites (UOCs), and found wide variations which did not fit into current H-distribution models. Using SIMS, we measured the H, D, C, and Si contents of the fine-grained matrix of 13 of these previously studied UOCs (only falls) ranging from types 3.00 – 3.9. Preliminary results confirm the wide previously observed spread of D/H ratios between samples, including high elevations in a handful of UOCs. C/H ratios will be used to determine the D contribution within samples specific to water, however initial observations confirm contributions from both hydrated and organic components. The results from this visit will be combined with other in-situ studies carried out at the home institution to determine exactly what phases are hosting this highly D-rich material, and how these chondrites affect models of water transport in the early Solar System.
Report Summary: Experiments and thermodynamic modelling clearly show that sulfates are a common alteration product under the high temperature, CO2-SO2-rich conditions at the surface of Venus. The exact sulfates present depend on the original basalt composition, with anhydrite (CaSO4) and thernardite (Na2SO4) having been observed in the lab (Reid et al., 2023).
Alteration rates calculated from these experiments suggest that sulfate coatings may develop geologically fast and therefore alteration coatings may obscure the original protolith. Additionally, the spectral features of these high temperature sulfates are not well constrained. Although many critical sulfate minerals are stable to temperatures > 500C, previous analytical data has generally explored sulfate-temperature spectral relations to ~100C. The surface of Venus is significantly hotter at 470C. Thus is makes sense to investigate both the effects of variable thickness sulfate coatings and the spectral properties of sulfates under Venus surface conditions to gain a better understanding of their behaviour.
The next set of Venus missions will have observational capabilities in the thermal emission spectrum (range) and high T sulfate spectra are presented in another paper (Dyar ref); here we present data for the effects of high T on visible near-infrared (VNIR) sulfate spectra. In addition, we have conducted experiments to determine the effects of sulfate coating thickness on the underlying surface spectra. The data presented may help determine future mission capabilities to both recognise and analyse sulfate-bearing materials under high T conditions as well as constrain the original, unaltered surface composition.
This project supports a collaboration between the US and personnel at the Planetary Spectroscopy lab in DLR Berlin to understand the interrelationships among high temperature emissivity and high or ambient temperature reflectance measurements of rocks and minerals present on the surfaces of rocky bodies (planets, moons, and asteroids). We are investigating the extent to which spectral features in the near-IR wavelength region shift and change in intensity as a function of temperature and measurements type. These changes are easiest to understand when comparisons can be made for single mineral species.
With Europlanet support, we acquired hemispherical and bidirectional reflectance and emissivity spectra of planetary-analog minerals at the PSL at DLR Berlin. Minerals studied included pyroxene, feldspar, olivine, sulfates, and calcite minerals. Significant differences between hemispherical and biconical reflectance data were observed; as we write up the results, we will explore the underlying physical characteristics of each mineral group and relate them to the magnitude of those changes. We also observed significant differences between bidirectional reflectance spectra and emissivity results in preliminary results. This outcome suggests that laboratories seeking to make Venus-relevant measurements cannot draw conclusions about spectral intensities on the basis of bidirectional data.
Report summary: Ash Injection and settling experiments have been carried out using the environmentally controlled recirculating wind tunnel facility at Aarhus University, in order to understand the processes controlling deposition and segregation of ash from volcanic plumes at stratospheric altitudes.
Ash particles erupted from the Campi Flegrei volcano (Italy) and smaller than 63 micron were injected in the wind tunnel either from the upwind extremity in the presence of wind (1 m/s) or from the side in the absence of wind. The atmospheric pressure in the wind tunnel was systematically varied to simulate the corresponding elevation in the atmosphere from 10 to 50 km. The vertical and horizontal velocity of the particles was measured, as well as the plume opacity, proxy for particle concentration over time.
Settled particles were sampled at different times during the experiments and then analysed for their abundance and size distribution. Both the opacity measurements and the number of particles sampled over time display the decay of particle concentration over time in the suspended plume. The rate of decay is strongly dependent on the atmospheric elevation in a nonlinear way, with modest changes from 10 to 20 km elevation and much larger changes for higher elevations.
From these data we will retrieve experimentally the settling velocity of volcanic ash particles at a range of elevations that is of interest for both aviation and climate modelling implications.
Europlanet 2024 RI has received funding from the European Union's Horizon 2020 research and innovation programme under grant agreement No 871149.
Europlanet AISBL (Association Internationale Sans But Lucratif - 0800.634.634) is hosted by the Department of Planetary Atmospheres of the Royal Belgian Institute for Space Aeronomy (BIRA-IASB), Avenue Circulaire 3, B-1180 Brussels, Belgium.