Report Summary: Our experimental campaign aimed to understand sediment transport driven by CO2 ice sublimation condensed inside a porous regolith. To quantify the erosion of sediment associated with the sublimation of CO2 frost in the subsurface of a ~30° slope, we tested various compositions (MGS-1, sand, sand-dust mixtures). While some sediment showed little to no activity over several attempts (sand), others showed significant slope activity (sand + >=10% MGS clay).
The main objective of the project was to study electron impact processes of small organic compounds, using acetone as the first target.
Record and analyse emission spectra of acetone induced by electron impact at several different energies in the range 10 – 100 eV.
Determine emission cross sections corresponding to selected most intensive transitions in range of impact energies (from the thresholds of selected process to 100 eV).
Identify neutral products of electron impact fragmentation of acetone.
Determine reaction kinetics parameters such as threshold energies for selected electron impact excitation reactions of acetone.
During the first half of the visit, we measured electron-impact spectra of acetone at multiple electron energies and generated partial spectral electron energy map which provides the spectral information at various electron energies and thus the efficiency curves (relative emission cross-section curves). During the second half of the visit, the measured data was partially analysed. The emission band in the range of 415 – 445 nm corresponds to the radiation of CH (A2Δ–X2Π) (ν,ν) fragment. Less intensive radiation of CH (B2Σ−–X2Π) (0,0) fragment was identified within 386 – 402 nm. Several emission lines of hydrogen’s Balmer series Hγ – Hη were detected throughout the spectrum as well. Individual rotational transitions from P, Q, R branches of both CH fragments were identified according to LIFBASE 2.1.1 spectroscopy tool, which is software to chart the spectroscopy of diatomic molecules. The rotational temperature of the LIFBASE spectrum was set to ~ 5000 K.
Report Summary: The chemistry of sulphur in icy extra-terrestrial settings such as the dense interstellar medium and the outer Solar System remains poorly constrained. In particular, the chemical routes towards the formation of SO2 ice (and other volatile sulphur-bearing species) is not completely understood, despite the detection of this species in interstellar icy grain mantles, on the surface of Europa, and on comets. We have therefore explored the possibility of forming SO2 ice as a result of the irradiation of oxygen-bearing ices (including O2, CO, CO2, H2O, and CH3OH) deposited on top of pure elemental sulphur layers, both of which are known to exist in the dense interstellar medium and the outer Solar System where radiation chemistry may be engendered by galactic cosmic rays or the solar wind.
Our results demonstrate that SO2 may indeed be produced after the 1 MeV He+ ion irradiation of O2 and CO2 ices deposited on top of elemental sulphur, but not as a result of similar irradiations conducted using CO, H2O, or CH3OH ices. Other volatile radiation product species incorporating sulphur, such as CS2, OCS, and H2SO4, were also detected in different experiments. Our work should therefore contribute to a better understanding of solid-phase sulphur astrochemistry and the role of elemental sulphur in the formation of volatile sulphur-bearing species in icy extra-terrestrial settings.
Report Summary: Over the last decades it became clear that we live in a “molecular universe”. Carbon forms the basis of the majority of the molecular species that so far have been identified in space. Although small carbon-based molecules, like CO and CO2, are some of the most abundant molecules in space, only a small fraction of the carbon is expected to be locked up in such species. It was proposed that a large portion of the interstellar carbon, up to 20%, is built in polycyclic aromatic hydrocarbons (PAHs) and fullerenes. Several laboratory studies were carried out to investigate the effects of vacuum ultraviolet photolysis on PAH:H2O ices. However, data about interaction energetic ions with PAH ices are very scare.
We therefore studied the radiolysis of the pure pyrene ice and mixed pyrene- water ices at different concentrations at 20 K with 200 keV and 2 MeV H+ and 2 MeV C2+ beams at Atomki. The preliminary analysis of water-pyrene ices irradiated 200 keV H+ (with pyrene concentration from about 5 to 100% of pyrene) indicates that pyrene is more radio-resistant at high concentrations. The results are preliminary and analysis is ongoing.
Report Summary: We have measured the concentration of halogens in the glasses of chondrules from enstatite chondrites. There is a clear correlation between Chlorine and Bromine abundances, but no clear relationship between Cl or Br and F. Iodine was not measured. In the main S is well correlated with Cl: this trend may have been modified by unintended analysis of micron scale blebs on sulphide. Halogen profiles have been taken across a number of suitable target chondrules, for diffusion modelling, which will be presented and published in due course. The array of data for F/Cl is sub-chondritic while the Br/Cl array is super-chondritic.
Evaporation and condensation may play important roles in controlling halogen behaviour, along with partitioning between other significant reservoirs in chondrites because fluorine is likely to be compatible in a number of silicate minerals. More will be known after diffusion modelling and after the experimental partition coefficients have been determined.
Report Summary: Discontinuity surfaces, associated with seafloor cementation, are hence of primordial importance for fully apprehending the geological record, yet they have received far less attention than the sedimentary rocks surrounding them. Fundamental problems that are still not sufficiently understood concern the lateral change of discontinuities. In this project, we tackle this issue by studying the lateral variation of five distinct discontinuity horizons present in the Middle Jurassic of the High Atlas (Morocco), where outstanding exposures permit to track these surfaces over tens of kilometres. Hence, the purpose of this work is to characterise at a high-resolution the large-scale variation of petrographic and geochemical (C, O and Sr-isotopes) properties of discontinuities (matrix and cement phases) along dip and strike of a Jurassic moderately deepening ramp. δ18O (176 values) and δ13C (105 values) signatures were obtained on twenty-one cements and grain types, including 14 different early calcite cements and fabrics corresponding to dogtooth cements (7), turbid synaxial cements (1) and micritic/microsparitic fabrics (6).
Data confirm that dogtooth cements can precipitate in marine phreatic, meteoric phreatic and shallow burial environments. The highly negative δ18O values of micritic fabrics and turbid synaxial cements, which form in seawater, indicate that they transformed during subsequent diagenesis (i.e during meteoric water circulation or shallow burial). It indicates that they precipitate initially with an unstable mineralogy (aragonite or high-magnesium calcite). δ18O and δ13C data on early cements suggest that a same discontinuity can change laterally from a subaerial exposure surface to a marine surface.
Report summary: The characterisation of dust is paramount in the understanding of Martian climatology. Dust significantly influences Mars global climate, interacting with the incoming solar radiation, altering the atmospheric temperature budget. Local and global dust storms can cover the planet for weeks, influencing the correct functioning of scientific instruments on the surface (The Rover “Opportunity” is the most famous example). The dynamics of dust lifting is strictly related to the wind velocity field, so its characterisation would provide important information on the characteristics of Martian winds.
The proposing team has developed an Optical Particle Counter (OPC) aimed at providing direct measurements of grain concentration and size distribution on Mars, which would be the first ever accomplished outside of Earth. The instrument is able to detect dust grains in the 0.4-20 μm diameter range. Both the breadboard and the flight model versions of the instrument have been tested in Martian environment, showing good performances.
The trip to the Planetary Environment Facilities at the University of Aarhus has allowed the verification that the instrument is correctly able to sample dust grains in its upper sensible range (up to 20 µm in grain diameter) also in presence of winds up to 20 m/s. A sandbed with embedded dust has also been created inside the Martian wind tunnel, allowing the simulation of natural saltation conditions. The instrument has been able to retrieve dust grains in all simulated conditions, both for monodispersed calibrated dust samples and for polydisperse samples.
20-EPN-054: Understanding large aeolian ripples on Mars through wind tunnel experiments
Visit by Simone Silvestro, INAF Osservatorio Astronomico di Capodimonte (Italy), and Hezi Yizhaq, Midreshet Ben-Gurion (Israel), to TA2.4 Planetary Environment Facilities (PEF), AU (Denmark) Dates of visit: 04-08 April 2022
Report summary: In our experiments in the Planetary Environment Facility in Aarhus we obtained, for the first time, two superimposed ripple patterns on monodisperse sand beads in CO2 air.
The presence of two distinct sets of aeolian sand ripples in unimodal sand suggests two formational mechanisms. Morphological characteristics such as straight crests and regular spacing point toward an impact mechanism to be responsible for the formation of the smaller (cm-scale) ripples. Conversely, the higher sinuosity of the larger (decimeter) ripples suggest a different type instability (hydrodynamic) at work. We also detect an increase in sizes for the ripples with decreasing pressure which is currently under investigation.
Collectively, our work seem to confirm the hydrodynamic nature hypothesised for the large Martian ripples.
Report summary: Thanks to the collaboration between the University of Geneva and the University of Aarhus through the Europlanet Research program we performed a set of experiments on the remobilisation of volcanic particles. Since removal processes of volcanic particles are relatively poorly characterised, these experiments represent a unique opportunity to study the dynamics of aeolian processes. The obtained results provide valuable information on the threshold friction velocities (i.e. wind friction velocity above which particles start to detach from deposits) of different ash compositions, fundamental for modelling and forecasting remobilisation events.
A total of 32 experiments were performed by using a setup composed of a sample plate (i.e., bed of volcanic ash exposed to gradually increasing wind friction velocities) from which particles were removed by wind and imaged using various techniques simultaneously (i.e. microscopes, and webcam)). These direct observations were combined with multiple particle collection methods to study the characteristics of remobilised particles (i.e. sediment traps and adhesive papers). A complete set of half-phi grainsize classes (from 0 to 500 μm) from 4 volcanoes were analysed.
Preliminary results show a relation between the threshold friction velocity and the grainsize, in agreement with erosion theories. In addition, these experiments illustrate variations in threshold friction velocities as a function of magma composition: lighter particles (i.e. rhyolite) are easier to remobilise than denser particles (i.e. basalt). These results are pioneering, systematically quantifying threshold friction velocities of volcanic ash for wide grainsize and composition ranges for the first time.
The set of experiments within the 20-EPN-053 project represents a preliminary step towards the characterisation of the electrical properties of volcanic ash in a collaboration between the University of Geneva and the Aarhus University. This topic is fundamental to better understand aggregates formation in a volcanic eruption and improve model forecasting.
The main setup consists of a horizontal wind tunnel where a recirculating flow allows volcanic ash of different sizes (e.g. from 1 μm to 500 μm, sieved in intervals of half-phi on the Krumbein scale) and compositions (e.g. from basaltic to andesitic) to be resuspended and collide together. Single particles and aggregates are filmed during their motion in the wind tunnel by means of a High Speed Camera (HSC) placed crosswise to the main flow direction. In addition to this, a set of four Optical Particle Counters (OPCs) are located at different heights downwind to the flow (i.e. 5 cm, 10 cm, 25 cm, 50 cm) with the goal of capturing differences in particle population for very fine ash (i.e. <40μm) due to electrostatic phenomena.
The primary goal is to detected particle trajectories that will be later used to quantify the bulk charge carried by single particles by means of an inversion of the equation of motion. The secondary goal is to understand if OPCs can be used combined with the wind tunnel facility to reveal a change in particle population on the recorded histograms that can be associated with aggregation processes due to the electrostatic force.
Report Summary: The traditional approach of measuring the isotopic compositions of mid-ocean ridge basalts (MORB) is problematic because MORB is homogenised prior to eruption, and therefore does not record the full heterogeneity of the mantle source. To overcome this problem, we developed low- concentration coupled Pb-Nd isotope analysis of minerals at high spatial resolution to assess the isotopic heterogeneity of melts delivered to Earth’s oceanic crust and hence that of the depleted upper mantle. We acquired small volume Pb and Nd isotope analyses from minerals in gabbroic cumulates from fast-spreading oceanic crust at Hess Deep using the Thermo Scientific TRITON Plus at the Vrije Universiteit in Amsterdam. We measured minerals from 27 samples (Nd from 25 cpx and 19 plag, Pb from 18 plag) covering the full stratigraphic depth (4350 m to 25 m) of the Hess Deep oceanic crust. Our study reveals that Pb isotopes from primitive plagioclase domains show greater heterogeneity than Nd isotopes from plagioclase and clinopyroxene, validating the new coupled Pb-Nd isotopic approach. The Pb data do not vary systematically with depth but do show a departure in 207Pb/204Pb away from the NHRL and across the main trend of East Pacific Rise MORB that may indicate cumulate-melt mixing throughout the crust or the involvement of an exotic mantle source.
Report Summary: ‘Fibrous’ diamonds, a fast-growing form of diamonds that often encapsulate carbon- and water-rich (C-O-H) fluid microinclusions, are a primary target for studies of C-O-H mantle fluids and how these fluids influence deep mantle processes. However, only a small amount of diamond (normally <1 mg) and even smaller amounts of C-O-H fluid microinclusions can be sampled and analyzed using conventional laser ablation approaches and mass spectrometry measurements. In the present project, we implemented a novel diamond-in-liquid laser ablation technique that was developed to overcome the sample size limitation, combined with ultra-low blank column chromatography and 1013 Ohm resistor TIMS analyses, to provide the first high-precision Sr-Nd-Pb isotopic compositions of C-O-H mantle fluids in diamonds from the Kaapvaal Craton in southern Africa. We successfully processed and analyzed 12 samples from De Beers Pool, 5 from Finsch and 6 from Koffiefontein mines, as well as standards and blanks. We finished processing the collected data which show exciting Sr-Nd-Pb relationships that vary between diamonds carrying different C-O-H fluids and micro-mineral inclusions. We still need to complete some data processing and calculations, as well as correlate the isotopic ratios with trace element compositions to fully understand the results and their geological significance. Nonetheless, we are certain that the outcome of this Europlanet project will have a major impact on our understanding of the origin and evolution of C-O-H mantle fluids, the transport of mobile components between different mantle (and crustal) reservoirs, and the role of deep C-O-H fluids in the global circulation of volatiles through Earths’ history.
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 fluidisation. 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 fluidisation. The data further shows that the flow dynamics are complex with surging behavior and complex pressure distribution in the flow, through time and space.
Report Summary: Chondrites are the most primitive agglomerates formed in the solar system. In this project, we want to develop a thermometer based on Al-in-olivine/spinel equilibrium to calculate the temperature of formation of chondrites. or this project, we have performed a large number of new low- to high-pressure (1 atm – 10 GPa) experiments relevant to chondrule formation at the KU Leuven.
Experiments were run at high temperature (1200-1800°C), under variable oxygen fugacity conditions (IW+1 to IW+5, IW = iron-wustite). From 18-22 October 2021, Thomas van Gerve and Kat Shepherd (KU Leuven) worked with the Cameca IMS 1270 E7 ion probe at CRPG, Nancy, under the supervision of Dr. Johan Villeneuve and M. Nordine Bouden. We have measured the following masses: 12C, 16O1H, 18O, 19F, 27Al, 30Si, 32S and 35Cl in olivine, glass and glass inclusions. During our analytical session, we measured ~ 150 points in olivine and glass in addition to the standards. Results are extremely reproducible and show a trend of slightly increasing Al content in olivine as a function of the Fo content (molar Mg/(Mg+Fe)) of olivine. Using our new SIMS results, we are in the process of developing a thermodynamically rooted model taking into account major components in spinel and olivine.
Report Summary: In this project different bright areas of Haulani crater (e.g. Southern floor, i.e. ROI3 and North-east crater wall, i.e. ROI4) on Ceres have been studied by arranging different analogue mixtures and comparing them with Dawn VIR data. The end-members have been identified based on previous studies (Tosi et al. 2018, 2019) and the analogue mixtures have been produced with grain size 50-100µm for two bright crater regions. The two initial mixtures have been acquired in the VIS-NIR spectral range (0.35-4.5µm) at low temperature, i.e. from 200K to 300K similar to Haulani by using Cold Spectroscopy Facility (CSS) (IPAG, France).
By comparing the spectral parameters (Band Center, Band Depth and FWHM of absorption bands at 2.7, 3.1, 3.4µm, spectral slope in the 1.2-1.9µm range and reflectance level at 2.1µm) with the obtained spectra of mixtures and VIR data, the best candidate to reproduce Haulani’ bright areas is the mixture A3-8. That mixture exhibits values for the 2.7BD (Antigorite, Illite), 3.1BD (NH4-Montmorillonite), 3.4 BD (NaCO3) and the 3.1 µm FWHM very close to Haulani ROI3 and ROI4. In order to better reproduce Haulani areas some improvements may be performed in the next future, e.g., by changing the dark component with a mixture of graphite plus magnetite to better reproduce the spectral slope of Haulani or by adding hydrous natrite in low percentage to the mixture, e.g. 2-8% to assess the role of this component found in Haulani bright areas and how is the contribution to 2.7 µm spectral band.
Report Summary: In the frame of the Europlanet 2024 1st TA call, reflectance VIS-NIR spectra were collected. Ten different temperature steps were chosen to collect cryogenic data: 270-245-220-180-160-140-120-100-90-270 up K.
For the samples characterized by a low temperature phase transitions (mascagnite (NH4)2SO4, sal-ammoniac NH4Cl, ammonium phosphate (NH4)H2PO4, tschermigite (NH4)Al(SO4)2·12(H2O) and ammonium nitrate NH4NO3), 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 break the phase transition T. In particular, mascagnite, sal-amoniac and ammonium phosphate monobasic samples showed clear and very interesting spectral bands variations during cooling, indicating that a phase transition occurred. Spectra were collected with three different grain size (150/125 – 125/80 – 80/32 μm) in the spectral range from 1 to 4.8 μm.
The collected data will help on the interpretation of VIR remote spectra from Europa, Pluto’s moons, Enceladus and other icy celestial bodies surface where NH4 minerals have been supposed to occur. Moreover, the study of ammonium bearing minerals and their behavior at very low temperature might give information on how the phase transition affects the bands position and shapes inside the reflectance spectra. Overtones and combinations of NH4 bands are in the 1-3 μm range, whereas fundamental vibrational modes (ν1 and ν3) are present in the ~3 μm area.