Oxygen isotopes are a powerful tool to determine the parent bodies of cosmic spherules, which are the entirely melted endmember of micrometeorites. After considering the fractionation processes affecting their original oxygen isotope signatures, >90% of cosmic spherules larger than 200 μm appear to be related to chondrite clans established studying chondritic meteorites.
About 10% of cosmic spherules that show clear chondritic major element compositions display unusual 16O-poor oxygen isotopic compositions that are not linked to chondritic material present in present-day meteorite collections. Simultaneously, a subset of porphyritic (Po) cosmic spherules labelled Cumulate Porphyritic Olivine (CumPo) particles exhibits textures testifying to the settling of olivine crystals during atmospheric deceleration. This unusual texture suggests these particles entered the Earth’s atmosphere at velocity of ⁓16 km s-1 , which corresponds to orbital eccentricities >0.3 and is considered higher than most asteroidal dust bands.
By establishing a potential link between the CumPo particles and a subset of the 16O-poor spherules and characterising relict mineral grains in a selection of particles from the Sør Rondane Mountains and Larkman Nunatak micrometeorite collections using the Open University NanoSIMS, a parentage with the newly defined CY carbonaceous chondrite group is proposed. This implies that about 10% of the cosmic spherules reaching the Earth’s surface have a near-Earth origin. As such connection is rare in the meteorite collection, demonstrating the importance of fully characterising the flux of micrometeorites to understand the composition of the Solar System.
Report Summary: The flux of extraterrestrial material falling to Earth is dominated by micrometeorites. They originate from asteroids and comets and their analysis provides a complementary perspective to the insights obtained from the study of larger meteorites and from space mission sample returns. Oxygen isotope compositions can be used to match micrometeorites to parent body sources based on distinctive δ17O and δ18O ratios.
We studied a population of seven giant Antarctic micrometeorites using high-precision, spatially resolved oxygen isotope analyses to measure the composition of fine-grained matrix in hydrated and dehydrated micrometeorites.
A characteristic feature of all micrometeorites was large intrasample isotopic variation (>15‰ in δ18O). In addition, most particles could be matched to known meteorite groups, including identification of CM, CV, CR and, potentially CY parentage. This is consistent with petrographic studies which conclude that the micrometeorite flux is dominated by material from hydrated carbonaceous chondrite asteroids. One particle (TAM5-30) has petrographic characteristics intermediate between the CO and CM chondrite groups. Oxygen isotope analyses of its fine-grained matrix plot either in the CO or CM chondrite fields. This particle is interpreted as a CO-like C2 ungrouped chondrite and may represent material from an otherwise unsampled parent body.
Report Summary: Evidence of a rapid increase in the radiocarbon concentration of the tree rings for the year 775 CE was initially presented by Miyake et al in 2012 (henceforth called M12). Since then, other events similar to the M12 have been confirmed for different periods. This project aims to provide new information about the increase in concentration of radiocarbon in the period of abrupt solar activity. For the study we have chosen the periods in XIth and XIIIth century CE and in VIIth century BCE, in which increase of radiocarbon concentration was noted. The samples have been collected from dendro-chronologically dated trees, and the annual rings has been extracted for measurement.
During the Europlanet TA visit in the Isotoptech Zrt. AMS laboratory, all the samples were prepared to be measured using MICADAS AMS system. Each set of measurement was accompanying with standardsamples (of known radiocarbon concentration) to control the quality of the measurement. To obtain high precision (<2 ‰) the measurement time was extended. The results show occurrence of Miyake events in analyzing periods. For the analyzing period in VIIth century we were able to determinate the occurrence during the year, by dividing the annual ring into three parts early-wood, early-late wood and late wood. During the TA visit we have possibility to learn about the procedures used in the laboratory to prepare samples (of different kinds) for radiocarbon measurement using AMS system. We had a fruitful discussion on possible future cooperation, including joint submission of a research project proposal.
Report Summary: Submarine groundwater discharge (SGD) has been shown to be an important mechanism in transporting solutes from the terrestrial to the marine environment. Despite being a well-documented process, our knowledge about the timing of offshore groundwater emplacement is extremely scarce. We aim to develop an age-dependent numerical model in our study area to investigate the relationship between SGD and the carbon cycle, whereby the obtained 14C age of the groundwater is used as a constraint. Our goal is to analyze all the carbon pools present in our cores (i.e. TIC, TOC, DIC and CH4) for 14C, so that we can correct for possible interference with the 14C-DIC signal (used for groundwater age). This is a challenge however, as the carbon content for some of these samples is extremely low.
During this two-week visit, we not only learned about the 14C preparation methods and operation of Accelerator Mass Spectrometry (AMS), but also discussed and exchanged ideas with Isotoptech AMS C-14 group scientists. Preliminary 14C results indicate that 14C depleted DIC is observed closer to the sediment-water interface for cores with anticipated SGD. This can be explained by the advective upwards transport of older groundwater. The discrepancy between the TIC and TOC 14C content at similar core depths was found to be very large, indicating that these carbon pools are affected by different processes. This mismatch might be a result of the precipitation of authigenic carbonates or microbial activity.
Report Summary: The heavy halogens are excellent tracers for volatile transport processes in the Earth’s mantle. Our understanding of their budget and distribution is, however, very limited due to their extremely low abundances in the most abundant upper mantle minerals and a lack of well-defined partition coefficients that describe their behaviour during partial melting of the Earth’s mantle.
In this project, we analysed the bromine concentration in minerals and melts of samples, which were produced during high-P-T experiments that simulated partial melting of the Earth’s mantle at Mid-Ocean-Ridge-Basalt and Ocean-Island-Basalt source regions. For this, the neutron irradiation technique was applied, which produced 80,82Kr from 79,81Br. This technique results in unmatched detection limits below the ppm-level for the determination of bromine concentrations in nominally anhydrous minerals. During the analysis, regions of interest in the respective samples were ablated with a UV-VIS-Laser at a 10s of micrometer scale. Afterwards, the noble gases were separated and analysed with the “Albatros” mass spectrometer at ETH Zürich. This allowed us to determine bromine concentrations in the melt and in individual olivine and orthopyroxene crystals.First results show that bromine indeed behaves very incompatible with first estimates of bromine partition coefficients between minerals and melt being well below 10-3. In addition, olivine seems to be the main carrier for the heavy halogens in the Earth’s upper mantle.
Report Summary: The goal of the 2022 visit was to study and measure the electron-impact induced emission from dissociation and/or ionization of CO and CO2 between 0 – 100 eV electron energy. These experiments are part of a longer-term plan to characterize the electron-impact-induced emission features of oxygen-containing molecules found in cometary environments. These data are expected to be used in future modelling and analyses of data acquired in situ during the Rosetta mission to comet 67P/Churyumov-Gerasimenko. We aim to understand the conditions in the inner coma and how electron-impact-induced emission features can probe the physical and chemical processes occurring in the near-nucleus coma environment.
During the first half of the visit, we measured electron-impact spectra of CO2 gas at multiple electron energies. Electron impact of CO2 can give rise to emission from CO, CO+, CO2+, and excited states of C and O atoms. Since the probabilities of the different reaction channels depend strongly on the collision energy, these spectral features offer a way to diagnose the conditions of plasmas containing CO2. The collected spectra and threshold measurements are in reasonable agreement with the limited data in the literature. During the second half of the visit, we measured electron-impact spectra of CO gas at numerous electron energies. Many of the spectral features for neutral CO, CO+, and atomic C and O were characterized, as a function of electron energy, for the first time. Given the time-consuming nature of the measurements, data analysis and additional measurements will continue remotely.
Full Scientific Report on the TNA visit
Dissociative electron impact excitation reactions can provide a remote diagnostic of neutral gases and the physical environment of atmospheres around planets and small bodies in our solar system. The spectral signatures of the excited collision products are unique to each species and span the UV, visible, and infrared ranges. Previous experiments on electron impact of H2O (Bodewits et al 2019) showed clear spectral differences between photo-excitation, photodissociation, and electron impact collisions with water vapour. The efficiency of the electron impact dissociative & ionizing excitation, determined by the energy-dependent cross section, provides a remote diagnostic of the emitters in astrophysical plasmas. This process and its unique spectral signatures have been used to confirm a tenuous O2 atmosphere around Callisto, in the near-nucleus coma of comet 67P/Churyumov-Gerasimenko, and the atmosphere of Ganymede (Roth et al. 2021).
In electron impact, CO2 produces strong emission from its cation, CO2+ (Ajello 1971b), and both CO and CO2 produce strong emission from the “Comet Tail Bands” of CO+ (Ajello 1971a). At lower collision energies beneath the threshold of CO+formation, the Cameron bands of CO (ultraviolet wavelengths) are excited, and electron impact collisions have been inferred from UV observations of the Cameron bands in the atmosphere of Mars (Ajello et al 2019). In most comets, CO2 and CO are second in abundance to water vapour. Both CO and CO2 have lower sublimation temperatures compared to H2O, and can sublimate from cometary nuclei at large heliocentric distances. The threshold of the strongest electron-induced emission of these species (either CO2+ from CO2, or CO+ from CO) are relatively low and can be excited in the comae of comets at large heliocentric distances. Compared to their neutral counterparts, these cations emit in wavelength ranges that are accessible from ground-based observatories. Thus, these species are of particular interest to planetary and cometary science.
During our visit to the EIF lab at Comenius University, we focused on measuring (1) the electron-impact induced emission spectra of the gases CO and CO2 and the excited collision fragments, and (2) the emission cross sections for the important spectral features. For (1), we set a fixed electron beam energy and scanned the CCD camera across the spectral range of interest. A sample of our collected spectra is shown in Figures 1 & 2, which show the electron-impact spectra of CO2 and CO at 50 eV electron energy. At 50 eV, almost every feature in the CO2 data can be identified as bands of the cation CO2+. In the CO spectrum (Fig. 2), the strongest features are from the cation CO+. We also measured the spectra at multiple electron beam energies below and above known thresholds (e.g. the threshold for CO+ formation, ~17 eV, 100 eV), and we identified emission bands of neutral CO. These bands are well-characterized in the ultraviolet beneath ~300 nm, but many of the emission cross sections for features at visible/near-IR wavelengths are not available. In many cases, cross sections are limited to a single value, typically 100 eV electron beam energy. The spectra also show emission lines of atomic O and atomic C in the near-IR.
For (2), measuring absolute cross sections, we adopted a systematic procedure. Using the overview spectra, we deduced the most probable identifications of the spectral features. With the photon detector set at a fixed wavelength, we scan the electron beam energy to measure relative cross sections, which will later be normalized and scaled to precisely known emission cross sections in literature. Interestingly, many of the molecular bands in the spectra have multiple thresholds, as shown as by the measured relative cross section of the CO2+ feature (Figure 3). In a similar measurement of a CO+ Comet Tail band (455 nm, Figure 4), our measured thresholds are consistent with data available in literature. For both sets of experiments (CO and CO2), the spectra were far richer in features than anticipated. While we are able to identify many features by comparison to theoretical models and other experiments, the cross section measurements for every feature could not be completed in a single visit. We will continue to collaborate with the EIF laboratory remotely to measure the remainder of the cross sections. It is expected that a manuscript detailing our cross section measurements on CO and CO2 will be submitted to the Astrophysical Journal Supplement Series in the coming year.
M. Ajello, 1971a, The Journal of Chemical Physics, 53, 7.
M. Ajello, 1971b, The Journal of Chemical Physics, 53, 7.
Ajello et al 2019, Journal of Geophysical Research: Space Physics, 124, 2954-2977
Figure 1: Measured electron impact-induced emission spectrum of CO2 gas at 50 eV electron energy with a 100 micron slit size. Faint atomic features are visible in the near-IR. The emission between 280 and 500 nanometers is primarily from the cation CO2+.
Figure 2: Measured electron impact-induced emission spectrum of CO gas at 50 eV electron energy with a 400 micron slit size. Faint atomic features are visible in the near-IR. The emission between 300 and 650 nanometers is primarily from the cation CO+.
Figure 3: Measured relative emission cross section of the blended CO2+ / CO+ band at 428.3 nm from electron impact of CO2 gas. Multiple thresholds are visible in the cross section as a function of collision energy, indicating that the feature is a likely blend of CO2+ and CO+ emission bands. The thresholds are consistent with theoretical values calculated from the known dissociation and excitation energies.
Figure 4: Relative emission cross section of a CO+ comet tail band (455 nm) from electron impact of CO gas. The threshold of CO+ emission (16.74 eV) is consistent with the value in the literature within the experimental uncertainties.
Visiting postdoc Steve Bromley and PhD student Barbora Stachova discussing the electron impact spectrum of CO gas at 100 eV electron beam energy. Credit: S Bromley
Figure 5: Visiting postdoc Steve Bromley and PhD student Barbora Stachova discussing the electron impact spectrum of CO gas at 100 eV electron beam energy.
20-EPN-060: Characterise UV-Optical emission by conducting electron impact reactions on molecules relevant to the atmospheres of small bodies in our solar system
Report Summary: Auroral emissions from electron impact processes provide the opportunity to remotely characterize the physical properties of plasma and neutral gases surrounding small bodies. Surprisingly, Rosetta found that outside 2 AU, atomic and molecular emission features in the inner coma were predominantly caused by dissociative electron impact excitation. These emission features provide a wealth of information on local plasma conditions and through excited fragment species, it can allow for the measurement of chemical abundances of species that may otherwise not be easily detected remotely (CO2, O2).
We conducted electron impact experiments at the electron induced fluorescence laboratory at Comenius University (Bratislava, Slovak Republic) to characterize electron-impact induced emission of fragment species in the neutral gas surrounding comets and other small bodies in our solar system. For this project, we studied collisions between electrons up to 100 eV and CO2 and CO molecules. We measured velocity-dependent emission cross sections, determine activation thresholds of relevant reactions, and construct a spectral atlas that will aid observers and astrophysical modelers.
Report Summary: Different studies reported the endurance of cyanobacteria to Mars-like conditions; however, little is known about the cellular and molecular mechanisms responsible for this resistance. The further combination of Martian UV fluxes and perchlorate ions at concentrations found on the surface of Mars increases the challenges for survival. Under this context, this study aimed to investigate the adaptability and cellular responses of metabolically active biofilms of Chroococcidiopsis CCMEE 029 to Martian surface-like conditions combined with perchlorate ions.
Biofilms obtained from cells mixed with two different Martian regolith analogs and 2.4 mM of perchlorate ions on top of an agarized regolith-based medium were exposed to unprotected Mars-like conditions for 3 days. Parameters consisted of a Mars-like atmosphere (95% CO2, 4% N2, 1% O2) constant pressure of 700 Pa, periodic photosynthetically active radiation (PAR, 400-700nm, 3W/ m²/s) and UV (4W/m²/s) irradiation for 16 h followed by 8 h of dark with diurnal cycling of relative humidity and temperature from 75% to 0% and +15ºC to -50ºC respectively. The photosynthetic yield was followed during the exposure with the Mini-PAM analyzer integrated into the Martian simulation chamber. Post-exposure analyses of cell-viability assessment, CFU capacity, and pigment autofluorescence and morphology will be performed. Proteomics analyses are ongoing in collaboration with Dr. Peter Lasch from the Robert Koch Institute, Berlin (Doellinger et al. 2020).
Overall, this study will contribute to extending our appreciation of the limits of life as we know it, from the habitability of Mars to future management of Life Support and In-Situ Resource Utilization systems.
Report Summary: Carbonaceous chondrites are likely derived from dark (C-class) asteroids. Sample return missions to dark asteroids (JAXA Hayabusa-2, OSIRIS-REx) will allow us to link specific meteorites to these possible parent bodies. The compositions of the sample return target asteroids (Ryugu and Bennu) are currently unknown, as are the compositions of other dark asteroids. Dark asteroids are important scientific targets because they may have delivered prebiotic organic molecules to the early Earth.To help address how we can determine the compositions of dark asteroids, particularly whether they are primitive, aqueously-altered, and/or heated, we conducted a series of experiments at PSL designed to address this.
Specifically, we performed heating experiments, in vacuum, on clay minerals present in carbonaceous chondrite meteorites, and measured their subsequent spectral reflectance properties, as well as on samples heated in previous experiments (clays, carbonaceous chondrites, carbonaceous chondrite analogues), focusing on the most diagnostic spectral feature relevant to dark asteroids – the 3 micron region hydroxyl/water absorption band. The results are still being analysed, but it appears that heating in vacuum and exposure to vacuum cause changes in the depth and shape of this absorption feature, as well as the albedo, spectral slope, and appearance of additional absorption features. The results of this study will provide important constraints into the composition and history of dark asteroids.
In the TA call 2 of the Europlanet 2024 framework, both hemispherical and bidirectional reflectance spectra were collected on a total of 13 meteorites. For each meteorite, spectral data were recorded between 0.2 μm and 25 μm.
The analysed meteorite samples included carbonaceous chondrites as well as non- carbonaceous chondrites that contain carbonaceous clasts and phases. The meteorites were measured as bulk, and the same 2 mm diameter for the incoming beam aperture was used. These measurements and their results will provide additional insights on the infrared spectra of meteorites and their carbon content, which will help us better understand and constrain the composition of their respective parent asteroids.
Report Summary: The Antarctic cryptoendolithic communities are microbial ecosystems that dominate the biology of most ice-free areas in Continental Antarctica and described for the first time in the McMurdo Dry Valleys, the largest ice-free area of the continent. The Dry Valleys are a nearly pristine environment largely undisturbed and uncontaminated by humans and show remarkable peculiarities, representing an important analogue for the conditions of ancient Earth and Mars and a model environment for astrobiological studies.
These ice-free areas are dominated mostly by oligotrophic mineral soil and rocky outcrops and, for the harshest conditions in this area, the biology is dominated by cryptic microbial life-forms dwelling inside rocks. These cryptoendolithic communities are complex and self-supporting assemblages of phototrophic and heterotrophic microorganisms, including Bacteria, Chlorophyta and both free-living and lichen-forming fungi.
Despite the recent molecular studies to investigate the biodiversity and community composition, the interaction microbes-microbes and microbes-rock matrix, the spatial organization, rock microstructure (e.g. porosity, pore size and connectivity) are totally unexplored.
We, herein, are proposing to build an interactions network map, on colonized and not colonized sandstone, resolving the contributions of the different microorganisms and the relationships established among them and between microbial cells and the lithic substrate.
20-EPN2-108: Ultrastructure and nano-geochemistry of organic materials in 3.4-billion-year-old stromatolites: windows into biogeochemical cycling on the early Earth (and Noachian Mars?)
Report Summary: This TA visit used the facilities of the Korea Basic Science Institute at Daejeon (analytical transmission electron microscopy) and Busan (nano-scale secondary ion microscopy) to analyses samples of siliciclastic-hosted microbial mats from the Mesoarchaean of Western Australia.
Using NanoSIMS, we performed ion mapping of the bio-essential elements C, N and S, and determined the isotopic fractionations of these elements in order to assess whether preserved elemental cycles reflected abiotic or biotic networks; if biotic, these fractionations can inform us of the type of ecosystem present in the rocks at the time of microbial mat formation. Using analytical TEM, we performed imaging, high-resolution imaging and elemental mapping of ultrathin focussed ion beam-milled sections of microbial mats in order to characterise the ultrastructure of the mats, identify the types of carbonaceous materials present, and determine organic material–mineral relationships at sub-micron resolutions.
The results of the visit will be integrated with datasets obtained at my home institution (e.g. optical microscopy, SEM-EDX and Fourier transform infrared microspectroscopy) to provide a comprehensive analysis of these microbial mats. We will propose analogies between this ancient ecosystem and potential ecosystems in habitable siliciclastic settings on Mars. Overall, the visit was highly successful, during which we analysed more samples than expected and we hope that this will mark the beginning of a longer-term collaboration on the application of nanoscience approaches to planetary science and astrobiology questions.
Report Summary: The ten days virtual visit permitted the successful acquisition of trace and rare earth element composition as well as Sr-Nd isotopic composition of 16 clay size terrigenous samples from core MD12-3396Q from the Indian sector of the Southern Ocean and East of the Kerguelen Plateau. Blank levels as well as MAG-1 geostandard composition are consistent with previous analyses on this sediment core carried out in 2018 by the project leader.
The new data confirm a general trend during the last glacial period: an important increase of the contribution of material from Antarctica during the Heinrich Stadial (HS) 1 and from the HS 3 to the HS 2 due to enhanced equatorward export of AntArctic Bottom Water (AABW) likely caused by increased AABW formation. During other intervals of the last glacial period, sedimentation was dominated by particles from the Kerguelen Plateau delivered by the Antarctic Circumpolar Current (ACC).
In addition, these new data highlight the occurrence of a third source of particles whose contribution starts during the deglaciation reaching a maximum during the Holocene. This source is possibly Africa, which would imply a more efficient transport of particles from Southern Africa to the Indian Ocean by the Agulhas retroflection and/or a southern migration of the Southern Ocean climatic fronts.
20-EPN-083: Beyond Antarctica: a survey on detection of life in endolithic fossils supporting future space exploration missions
Visit by Federico Biagioli, University of Tuscia (Italy) to TA2.19 Center for Microbial Life Detection, Medical University Graz (Austria). Dates of visit: 14-20 November 2021 (in person visit), 21-26 April 2022 (remote analysis)
Report Summary: Endolithic growth is the ultimate microbial adaptation and the predominant life-form in the far extreme ice-free areas of Antarctic deserts, considered among of the best analogues of the Martian environment on Earth. Although recent molecular studies have started to shed light on the biodiversity, distribution and composition of crypto-endolithic communities in visibly colonized rock samples, fossilized or apparently not colonized endolithic communities remain largely unexplored. Amplicon-sequencing analysis of fungal and prokaryotic domains on both not colonized and fossil samples were here performed to gain information about preservation of extinct life traces within rock and evidences of possible life detection also in eventual extra-terrestrial samples. Genomic DNA was extracted and sequenced from 24 fossil and 6 apparently not colonized rocky samples, resulting in a high number of reads and mapped ASVs for fungal (657,626 quality- filtered reads and 161 ASVs), bacterial 16S rDNA (1,296,594 reads mapped into 839 ASVs) and 16S archaeal specific (2,813,402 validated clustered in 3,514 ASVs) datasets. The high number of reads and ASVs achieved allows us to suppose that rocks not only represent a perfect refuge from harsh external environmental conditions, but also an important preservation ark for biosignatures of past life forms.
20-EPN-014: Ancient oceanic crusts as tracers of terrestrial mantle evolution – Ages and mantle source fingerprints from centimetric mantle eclogite xenoliths
Report Summary: Kimberlite-borne eclogite xenoliths with subducted oceanic crustal protoliths were typically affected by multiple processes during metamorphism and extended residence in cratonic lithosphere.
We acquired precise Nd isotope compositions (143Nd/144Nd) from minute amounts of eclogitic garnet and clinopyroxene derived from centimetric pristine and metasomatised eclogite xenoliths from Orapa, Botswana, originally for insights into their origin, ages and later evolution as part of the continental mantle. Though not yielding any pre-entrainment age constraints, the new data provide intriguing insights into the behaviour of Sm and Nd in the main eclogite constituents during mantle metasomatism.
Unradiogenic and isotopically homogeneous Nd in clinopyroxene from metasomatised eclogites correlates strongly with indicators of metasomatism by kimberlite melt, which also lowered its Sm/Nd ratios. In contrast, garnet has Sm/Nd showing no difference between metasomatised and pristine specimens. Clinopyroxene-garnet two-point isochron ages correlate positively with temperature of the eclogites’ last residence in the mantle, and several metasomatised samples give ages that are younger than the timing of entrainment to the surface and cooling.
These seemingly paradoxical observations can be explained when equilibration mechanisms and crystal-chemical controls are taken into consideration. Volume diffusion at high temperature caused slow Nd isotopic exchange, whereas melt-assisted recrystallisation at low temperature facilitated instant equilibration. Moreover, metasomatised eclogites residing at low temperature contain garnet with lower grossular content, both of which impeded the addition of Nd to garnet, which retained high Sm/Nd. Combined with its isotopic homogenisation, garnet with high Sm/Nd causes flattening of the two-point isochron slope, resulting in geologically implausible young ages.
20-EPN-015: Deciphering fluidization of mass flows by metastable volatiles on extra-terrestrial bodies
Project lead: Tjalling de Haas. Visit by Lonneke Roelofs, Utrecht University, the Netherlands to TA2.20 Open University Mars Chamber (UK). Dates of visit: 20 September – 29 October 2021
Report Summary: Martian gullies are alcove-channel-fan systems that have been hypothesized to be formed by the action of liquid water and brines, the effects of sublimating CO2 ice, or a combination of these processes. Recent activity and new flow deposits in these systems have shifted the leading hypothesis from water-based flows to CO2-driven flows, as it is hard to reconcile present activity with the low availability of atmospheric water under present Martian conditions. Direct observations of flows driven by metastable CO2 on the surface of Mars are however nonexistent, and our knowledge of CO2-driven flows under Martian conditions remains limited. For the first time, CO2-driven granular flows were produced in a small-scale flume under Martian atmospheric conditions in the Mars Chamber at the Open University (UK). The experiments were used to quantify the slope threshold and CO2 fraction limits for fluidization. With these experiments, we show that the sublimation of CO2 can fluidize sediment and sustain granular flows under Martian atmospheric conditions. The morphology of the deposits is lobate and depends highly on the CO2-sediment ratio, sediment grain size, and flume angle. The gas-driven granular flows are sustained under low (<20o) flume angles and small volumes of CO2 (around 5% of the entire flow). Pilot experiments with sediment flowing over a layer of CO2 suggest that even smaller percentages of CO2 ice are needed for fluidization. The data further shows that the flow dynamics are complex with surging behavior and complex pressure distribution in the flow, through time and space.
20-EPN-038: The strange behaviour of highly viscous mud in the low pressure environment: why the mixture changes its volume?
Visit by Petr Brož, Institute of Geophysics of the Czech Academy of Science (Czech Republic) to TA2.20 Open University Mars Chamber (UK). Dates of visit: 6-17 December 2021
Report Summary: We performed multiple mud experiments inside a low-pressure chamber to investigate whether the volume of mud changes once exposed to the reduced atmospheric pressure of Mars. Our results show that mud extruded onto the surface under martian environmental conditions increases its volume and hence behaves differently than on Earth. The low atmospheric pressure causes instability of the water present in the mud mixture, leading to the formation of bubbles, which increase the volume of the mud.
These bubbles are then trapped within the mud. The buoyancy of the bubbles is not sufficient to overcome the drag force within the viscous material and rise to the surface. Hence, these bubbles remain trapped and gradually grow up to centimetre scale sizes. During their growth they push the mud out of the container resulting in horizontal and vertical inflation of the mud surface over cm-scales.
This behaviour is not observed at terrestrial mud flows, but it is somewhat similar to volumetric changes associated with degassing of some terrestrial lavas or mud volcano eruptions. Our experimental approach hence shows that viscous mud exposed to reduced atmospheric pressure behaves differently to on Earth.
20-EPN2-074: Titanium and chromium isotopes in individual chondrules and anomalous clasts in chondrite meteorites
Visit by Philip Reger, University of Western Ontario (Canada) to TA2.14 ETH Zurich Geo- and Cosmochemistry Isotope Facility(Switzerland). Dates of visit: 5-22 July 2021
Report Summary: Chondrules, which are sub-millimetre igneous spherules and the main component of chondrites, formed during the first 5 Myr of the Solar System. Both 26Al-26Mg and 207Pb-206Pb ages of individual chondrules have also shown a ~2 Myr age difference between them in single meteorites. To advance our understanding of chondrule formation and the evolution of the protoplanetary disk within its first 5 Myr of existence, we proposed to obtain the mass-independent isotopic compositions of Cr and Ti for 6 selected chondrules and anomalous clasts from H and L ordinary chondrites. During the Europlanet TA visit, the Cr isotope compositions were analyzed by MC-ICP-MS after undergoing Cr and Ti separation by ion-exchange chromatography (awaiting mass spectrometry measurements for Ti). The Cr isotopic analyses are the most precise results from individual chondrules to date and show variability of the Cr isotope composition in individual chondrules, even within the same meteorite. A comparison of ε54Cr with chronological data previously obtained on the same chondrules suggests that the Cr isotope composition of the inner Solar System (NC reservoir) underwent a gradual change during at least the first 2 Myr of the Solar System. This change could potentially reflect thermal processing, a change of infalling molecular cloud material, or the decreasing incorporation of refractory minerals without 54Cr excesses into chondrule precursors.
Report Summary: The hostile current conditions on the surface of Mars entail that, if any form of life exists or ever existed on the planet, it may have adopted survival strategies like those evolved by terrestrial microorganisms inhabiting extremely harsh regions, such as Antarctic deserts. Here, one of the most common strategies observed is the cryptoendolithic growth, defined as the colonisation of the small interstices inside rocks, where microorganisms are protected from external hostile conditions. However, endolithic microorganisms can break down the surrounding rock substratum, thus causing the exfoliation of the external layers of the colonised rocks. Consequently, exposure to wind and saltating sand can cause the dispersal of the shallow rock fragments and endolithic colonies to the environment.
This study aimed to examine the possibility of dispersal of hypothetical rock-dwelling microorganisms on the surface of Mars. To achieve this goal, colonised Antarctic sandstone rocks were exposed to simulated martian and terrestrial windy environments at the Planetary Environment Facility in Aarhus University in four different simulations. Rock, sand and dust samples were collected after each simulation to assess the survival and the variety of dispersed microorganisms in the two scenarios. Although biological data are not available at the moment of the draft of the report, remarkable differences were observed in the dispersal of dust and sand between the different conditions.
Report Summary: The non-equilibrium chemistry driven by the charged particle and photon irradiation processes are responsible for the rich chemistry on the surfaces of icy satellites. Among the icy satellites of the Jovian and Saturnian planetary systems, a few satellites such as Ganymede, Europa, Dione, Rhea, Callisto and Titan that are embedded in their respective planetary magnetospheres were observed to undergo rich chemical processes due to the bombardment of a wide range of energetic atomic and molecular ions that are present in their planet’s magnetospheres, which processes the icy surfaces of satellites by irradiation and implantation. Magnetospheres also help in bringing new species from one satellite to the other. Especially in the Jupiter system of icy satellites, sulfur transfer from Io to the other satellites is quite likely. The sulfur ions from Io are picked up by the magnetosphere and are accelerated towards the other icy satellites; Europa being the closest neighbour to Io will be implanted with sulfur ions. The Jovian satellites, due to the presence of the Jupiter’s magnetosphere, are subjected to highly energetic S ion irradiation which leads to a range of chemical activity on their surfaces. In this project, we have studied the effect of S ion irradiation on Aspartic acid for a range of energies at two different temperatures (100 K, 20 K), where the 100 K experiments are aimed to mimic the conditions of Europa. The irradiated residue was then analysed using an optical microscope, scanning electron microscope and liquid chromatography mass spectrometry.
Report Summary: During this TA visit under Europlanet 2024 RI 2nd call, reflectance VIS-NIR spectra of several ammonium salts were collected at the CSS facility (IPAG laboratory) in Grenoble, France. Different temperature steps were chosen to collect cryogenic data down to 90 K. Samples were characterised by low temperature crystalline phase transitions, and for these reasons, the measurement steps have been increased in the proximity of the expected temperature of mineral transformation. Cooling and heating experiments, using the same cooling/heating rate, were performed to bracket the phase transition T and verify its reversibility. All the spectra were collected with three different grain size (150/125 – 125/80 – 80/32 μm) in the spectral range from 1 to 4.6 μm at low T. Typical absorption features due to overtones and combinations of NH4+ groups were identified in the spectral range investigated. Phase transitions, when detected, show an interesting behaviour with change in shape and position of some (sensitive) absorption bands which could be useful for the identification of these phases at non-ambient T. Moreover, the effect of low T and different granulometry were observed.
It has been proposed that ammonium minerals are present in varying percentages in icy planetary bodies. The availability of these compounds is linked to the upwelling of ammonium salts (NH4+) with ice from the subsurface of possible oceans resulting from cryovolcanism phenomena. The identification of these minerals on the surface can give information about internal composition/dynamics and potential habitability of icy bodies.
