I24-Microfocus Macromolecular Crystallography
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Diamond Proposal Number(s):
[31420]
Open Access
Abstract: A 1494 Dalton hemoglycin space polymer of Glycine18 Hydroxy-glycine4 Fe2O4 termed the “core unit” is part of a polymer of Glycine, Si, Fe and O that forms tubes, vesicles and a lattice structure. It has been isolated from four different CV3 meteorites and characterized by mass spectrometry, FIB/SIMS and X-ray analysis. In quantum calculations (HF and DF wB97X-D 6-31G) the polymer has an absorption at 480 nm that is dependent on rectus “R” (= dextro D) chirality in a hydroxy glycine residue whose C-terminus is bonded to an iron atom. The absorption originates in the Fe II state as a consequence of chiral symmetry breaking. In confirmation of theory, measurements at Diamond Light Source UK, on crystals of hemoglycin derived from Acfer-086 and Sutter’s Mill meteorites have shown a strong 483 ± 3 nm absorption that confirms the proposed location of hydroxy glycine residues within the polymer. A high 483 nm to 580 nm absorption ratio points to an “R” chirality excess in hemoglycin, suggesting that 480 nm photons could have provided the energy for its replication in the protoplanetary disc.
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Sep 2022
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I18-Microfocus Spectroscopy
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Diamond Proposal Number(s):
[31641]
Open Access
Abstract: The rapidly recovered Winchcombe CM chondrite regolith breccia fall gives the opportunity to analyse the secondary alteration phases of this meteorite type in great detail, without the effects of terrestrial contamination. A key part of determining the record of parent body water-rock reactions is studying the mineralogy of phyllosilicates with SEM, (S)TEM-EDX and XAS to determine their structure and cation site occupancies including Fe2+/Fe3+. Linked to the secondary alteration and phyllosilicate mineralogy is the redistribution of sulphur, a process which has been linked to the extent of hydrous alteration [1]. Here we consider the identity and assemblages of secondary S-bearing phases - serpentines and tochilinite - in a polished section of Winchcombe in order to better understand the alteration histories of CM chondrites and the nature of their serpentine-like phases. We are also studying these phases of interest in a set of other fresh CM meteorites including the recent fall Aguas Zarcas. As part of the Winchcombe analytical team, we have analysed clast and matrix in the section P30543 [1] at the University of Leicester Advanced Microscopy Facility. An initial investigation identified various locations of interest for further FIB-TEM analysis and XAS. FIB lift-out sections measuring up to 15 × 8 µm were extracted using a FEI Quanta 200 3D FIB-SEM, and thinned to ~100 nm attached to TEM Cu-grids for TEM analysis. High-resolution TEM imaging and STEM EDX was performed using JEOL 2100 TEM’s. Fe K XANES and EXAFS were performed at Beamline I18 of Diamond Light Source on P30543 using the techniques described in [3,4] to quantify Fe3+/SFe. Although the hydrated sulphide tochilinite is present in small amounts as needle-like crystalline patches in this section, the dominant S-bearing low temperature phase is a S-bearing 1:1 structure serpentine. This can be distinguished from the tochilinite in composition, as tochilinite is ~43 wt% SO3 whereas the Sserpentine is typically ~6-10 wt% SO3. The S-bearing serpentine can in turn also be distinguished from Spoor serpentine in the same section by d001 spacings which are 0.62-0.70 and 0.70-0.74 nm respectively. The relatively scarce tochilinite has d-spacings of 0.54 nm. The S-poor and S-rich serpentine phases are both ferric, having Fe3+/SFe 0.5-0.75. In contrast the tochilinite is more ferrous. We are studying the relative abundances and textural characteristics of S-bearing serpentine compared to bona fide tochilinite in Winchcombe and other CM’s in order to provide fresh insights into the record of progressive waterrock reactions in their parent bodies. [1] Suttle M. et al. 2022 MAPS in prep. [2] Daly L. et al. 2022 MAPS in prep. [3] Hicks L. J. et al. (2020) MAPS 55, 2599–2618. [4] Piercy J.D., Bridges J.C. and Hicks L.J. (2022) GCA 326: 97-118.
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Jun 2022
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Open Access
Abstract: The structure of a new polymorph of MgSO4·6H2O, a potentially important mineral on the surface of Europa, one of Jupiter’s icy moons, was reported by Maynard-Casely et al. [Maynard-Casely, H. E.; Brand, H. E.; Wilson, S. A.; Wallwork, K. S. Mineral Diversity on Europa: Exploration of Phases Formed in the MgSO4–H2SO4–H2O Ternary. ACS Earth Space Chem. 2021, 5 (7), 1716−1725. DOI: 10.1021/acsearthspacechem.1c00073]. The reported structure is unambiguously incorrect because the stoichiometry is wrong; the formula unit contains only half of the SO42– oxyanions required. We highlight where this error could have been detected at various stages of the analysis, writeup, and submission process and make recommendations to avoid repetition of the mistake.
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Apr 2022
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I14-Hard X-ray Nanoprobe
I18-Microfocus Spectroscopy
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Abstract: New mineralogical studies of Lafayette reveal that it contains a notably variable abundance of martian carbonate. Four percent was identified in mesostasis (3.2%) and olivine-hosted (0.8%) fractures in one polished section, but only 0.2% of both textural types in another. The Lafayette carbonates are Mg0.0-2.0Cc13.2-38.6Sd17.7-81.9Rh3.1-42.9. They have undergone variable but extensive amounts of dissolution and replacement as the nakhlite secondary fluid evolved, associated with the precipitation of ferric saponite in olivine fractures and a serpentine-like phyllosilicate in the mesostasis. The mesostasis carbonate has undergone the highest degree of corrosion and replacement. TEM analysis has shown the presence of Fe-(hydr)oxide (likely ferrihydrite) nanoparticles on olivine-hosted carbonates which can be linked to the cessation of more extensive carbonate dissolution at those sites. The mesostasis serpentine-like mineral has been described here on the basis of WDS and EDX analyses, HRTEM and Fe-K XANES, as odinite, a ferric, 0.7 nm d001-spacings phyllosilicate mineral with a characteristic 1:1 serpentine-like structure. The carbonate dissolution stage and then formation of Fe-(hydr)oxide nanoparticles occurred under circumneutral-alkaline conditions 7 < pH < 10. This range of pH is also where the general dissolution mechanism switched from a proton-promoted, to a water hydrolysis reaction associated with a reduction in the dissolution rates. As dissolution rates were reduced and the fluid had cooled to ≤50°C, the precipitation of the ferric saponite and odinite, a phyllosilicate associated with temperatures of ∼25°C, dominated over the carbonate dissolution. The extensive dissolution of such crustal carbonate across the upper martian crust, producing bicarbonate and carbon dioxide, and the coupled formation of ferric phyllosilicates, would lead to the formation of CH4 in substantial amounts via a Fischer-Tropsch type reaction. The results of our study illustrate a process to explain the relatively low abundance of detected carbonate on Mars and a likely source for some of the methane on Mars.
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Feb 2022
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I08-Scanning X-ray Microscopy beamline (SXM)
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A.
Steele
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L. G
Benning
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R.
Writh
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A.
Schreiber
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T.
Araki
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F. M.
Mccubbin
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M. R.
Fries
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L. R.
Nittler
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J.
Wang
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L. J.
Hallis
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P. G.
Conrad
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C.
Conley
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S.
Vitale
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A. C.
O'Brien
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V.
Riggi
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K.
Rogers
Diamond Proposal Number(s):
[2444]
Abstract: Water-rock interactions are relevant to planetary habitability, influencing mineralogical diversity and the production of organic molecules. We examine carbonates and silicates in the martian meteorite Allan Hills 84001 (ALH 84001), using colocated nanoscale analyses, to characterize the nature of water-rock reactions on early Mars. We find complex refractory organic material associated with mineral assemblages that formed by mineral carbonation and serpentinization reactions. The organic molecules are colocated with nanophase magnetite; both formed in situ during water-rock interactions on Mars. Two potentially distinct mechanisms of abiotic organic synthesis operated on early Mars during the late Noachian period (3.9 to 4.1 billion years ago).
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Jan 2022
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I14-Hard X-ray Nanoprobe
I18-Microfocus Spectroscopy
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Abstract: This thesis focuses on the mineralogical study of altered martian meteorites and the development of a novel wet-chemistry instrument. X-ray spectroscopy and electron microscopy have been used to investigate the secondary mineralogy of martian meteorites and their associated fluids. Martian analogue brines were investigated with transmission spectroscopy in order to address the technique’s capabilities for detecting dilute, astrobiologically significant fluids.
The newly-found martian shergottite, Northwest Africa (NWA) 10416, bears a distinctive colouration in its olivine megacrysts which is suggestive of hydrous alteration. The meteorite has been petrographically characterised and the origin of its alteration has been determined as terrestrial. Oxygen isotope analysis and the observation of secondary phases within shock features using Transmission Electron Microscopy (TEM) have indicated a terrestrial fluid. Synchrotron X-ray Absorption Spectroscopy (XAS), X-ray Diffraction (XRD) and Electron Probe Micro-Analysis (EPMA) have allowed its characterisation as a low-temperature, possibly acidic, fluid.
Analysis of the martian nakhlite, Lafayette, has been performed in order to assess the extent of carbonate dissolution by a hydrothermal martian fluid. Textures determined by Scanning Electron Microscopy (SEM) and TEM, and compositions determined by EPMA and XAS have displayed the variable nature of this dissolution and allowed the identification of the mesostasis phyllosilicate as odinite. This work has illustrated a process in which martian crustal fluids can dissolve carbonates and produce substantial amounts of methane, informing our understanding of martian atmospheric methane.
The capabilities of transmission spectroscopy when detecting organic martian analogue brines have been assessed to further the development of the wet-chemistry instrument, ASPIRE. Transmission spectroscopy was unsuccessful in detecting the likely low organic concentrations (ppb) expected in potentially habitable martian aqueous environments. However, future avenues of research have been suggested for consideration, including investigation into the potential of reflectance spectroscopy and calibration of ASPIRE to mineralogical-free regions within the infrared region.
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Dec 2021
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I11-High Resolution Powder Diffraction
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Diamond Proposal Number(s):
[10025]
Open Access
Abstract: The precipitation of hydrated phases from a chondrite-like Na–Mg–Ca–SO4–Cl solution is studied using in situ synchrotron X-ray powder diffraction, under rapid- (360 K h−1, T = 250–80 K, t = 3 h) and ultra-slow-freezing (0.3 K day−1, T = 273–245 K, t = 242 days) conditions. The precipitation sequence under slow cooling initially follows the predictions of equilibrium thermodynamics models. However, after ∼50 days at 245 K, the formation of the highly hydrated sulfate phase Na2Mg(SO4)2·16H2O, a relatively recent discovery in the Na2Mg(SO4)2–H2O system, was observed. Rapid freezing, on the other hand, produced an assemblage of multiple phases which formed within a very short timescale (≤4 min, ΔT = 2 K) and, although remaining present throughout, varied in their relative proportions with decreasing temperature. Mirabilite and meridianiite were the major phases, with pentahydrite, epsomite, hydrohalite, gypsum, blödite, konyaite and loweite also observed. Na2Mg(SO4)2·16H2O was again found to be present and increased in proportion relative to other phases as the temperature decreased. The results are discussed in relation to possible implications for life on Europa and application to other icy ocean worlds
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Oct 2021
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B18-Core EXAFS
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Diamond Proposal Number(s):
[7314, 8372, 9050]
Abstract: Jarosite is a common mineral on the surface of Mars, but relatively rare on Earth. Since the Opportunity rover reported widespread jarosite at Meridiani Planum in 2004, the mineral has been repeatedly identified on Mars. On Earth, jarosite forms through the weathering of iron-bearing minerals in water-limited settings. However, scientists have struggled to understand how the mineral may have formed on Mars. An international group of researchers have therefore studied whether glaciers played a role in the precipitation of jarosite on Mars in its geologic past.
The ‘ice-weathering model’ suggests that the precipitation of jarosite on Mars could be related to the presence of massive ice deposits developed during ancient glacial ages. To test this hypothesis, the researchers investigated the properties of deep Antarctic ice, as an Earth analogue for paleo-ice deposits on Mars.
Diamond Light Source’s B18 beamline is dedicated to X-ray Absorption Spectroscopy. This technique can characterise geochemical and mineralogical properties, even on tiny mineral dust samples extracted from Antarctic ice. The team measured more than 50 samples retrieved from the Antarctic Talos Dome ice core. They observed jarosite present in deep ice and depicted a coherent scenario to describe the formation of this mineral. Their scenario is consistent with the ice-weathering model, supporting the hypothesis that glaciers had a fundamental role in shaping the geologic and geochemical past of Mars.
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Jul 2021
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E01-JEM ARM 200CF
E02-JEM ARM 300CF
I14-Hard X-ray Nanoprobe
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Abstract: Introduction: Airless planetary bodies with surfaces exposed to the space environment are bombarded by electrons and protons from the solar wind and cosmic rays, as well as micrometeorites, resulting in space weathering [1]. Features of space weathering include partially amorphised grain surface rims, measuring up to
~100 nm thick, containing nanophase Fe metal (npFe0) particles, vesicular blistering, and solar flare tracks [1,2].
Space weathered samples collected by the JAXA Hayabusa spacecraft from asteroid Itokawa have previously been analysed using the I14 X-ray nanoprobe beamline at Diamond Light Source synchrotron, measuring Fe-K
X-ray absorption near-edge spectroscopy (XANES), and revealing an increased ferric-ferrous ratio (Fe3+/ΣFe) relative to their respective host grain mineralogy [3].
In this study, we seek to better understand the formation of space weathered lunar surface soil samples collected during the Apollo 17 mission, investigating the Fe-redox variations observed in the dominant silicate phase and the nano-grains of the space weathered rims using Fe-K XANES and EELS, with high-resolution STEM imaging.
Methods/Materials: The lunar sample number is 78481,29 - a surface sample collected from the top 1 cm of trench soils at Station 8 of Apollo 17 [4]. Three FIB lift-out sections have been extracted successfully from lunar grains identified to have space weathered surfaces. Two of the lunar grains were augite pyroxene, En81Fs16 and En85Fs12, and one olivine, Fa39.
Using the I14 X-ray Nanoprobe Beamline at Diamond, Fe-Kα XAS spectra are obtained from a series of XRF maps over the samples, with energies typically in the range 7000-7300 eV, with a higher energy resolution range over the XANES features (~7100-7150 eV). The XANES maps are processed using Mantis 2.3.02 [5], and isolated spectra normalized in Athena 0.8.056 [6]. By observing increasing shifts in the 1s→3d transition pre- absorption-edge peak centroid energy positions, the Fe-redox variations can be estimated between the sample host mineralogy and the space weathered zone, when compared to reference minerals of known ferric-ferrous
ratio (Fe3+/ΣFe).
A JEOL ARM200CF and JEOL JEM-ARM300CF instrument was used for EELS analyses and high-resolution STEM imaging respectively, at ePSIC in Diamond. EELS are performed using an accelerating voltage of 200 keV, current 15 μA, and 0.25eV/ch with a 5 mm EELS aperture, measuring linescans from the host to the space weathered zones to provide verification of the Fe-redox variation by observing the shifts in the Fe-Lα peaks.
Results: HR-STEM imaging confirmed the expected partial amorphisation and npFe0 particles (Fe0 metal confirmed observing lattice fringe spacings of ~2.06 Å) in the space weathered zones of all three lunar samples.
XANES mapping was able to identify the space weathered zone separate from the host grain mineralogy, and analyses of the XANES spectra from each revealed a consistent positive shift in the 1s→3d pre-edge centroid energy positions for the space weathered zone when compared to the host. Increases of up to ~0.23 eV in the space weathered (SW) zone, compared to the substrate host mineralogy of augite or olivine, suggests an
increase in ferric content in the space weathered zones up to ΔFe3+/ΣFe ~0.14 ±0.03. Positive shifts in the absorption edge positions for SW zones also support these results.
A total of 18 EELS linescans measured, at various locations along the space weathered rims in all three lunar samples, also shows a consistent increased shift in the Fe-L peak energy position. A positive shift in the EELS Fe-L peak position is indicative of increased ferric content, as shown by reference minerals measured including
Fe-rich olivine (Fe3+/ΣFe = 0.00) and magnetite (Fe3+/ΣFe = 0.67) with average EELS Fe-L peak positions of ~712.1 eV and ~713.6 eV respectively.
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Jul 2021
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Abstract: Seismic studies are essential for accurate characterisation of planetary interior structures, but are dependent on modelling for interpretation, requiring data on the elastic properties of likely constituent minerals. With the potential deployment of seismic stations on icy worlds such as Europa and Titan envisioned for the near future, a campaign of study into the elasticity of potential icy ocean world minerals is of paramount importance.
In the paper we assess the role of first-principles computer simulations to this problem, in particular focussing on the application of recent advances in simulating dispersion forces in loosely-bonded molecular solids, likely to be the main constituents of icy ocean worlds. This is of particular interest for these kinds of materials, since the complex sample handling, phase transitions and the difficulty of obtaining single crystals often greatly complicates the experimental determination of the full elastic tensor.
We focus on CO2, C6H6, MgSO4·7H2O and CaSO4·2H2O as they allow us to benchmark the performance over a wide range of chemical space, structural topologies, crystal symmetries and bonding types, and moreover have accurate experimentally determined unit-cell dimensions, bulk moduli and full elastic tensors for benchmarking purposes.
We demonstrate that the dispersion corrected approaches indeed perform superior in modelling the experimental density profiles (mean unsigned differences of merely 0.04 g/cm3 (CO2), 0.02 g/cm3 (C6H6), 0.003 g/cm3 (MgSO4·7H2O) and 0.013 g/cm3 (CaSO4·2H2O)) and may find application in exploring the compressive parameters of candidate materials, which could then be used in rheological models of icy ocean worlds.
Moreover, we have assessed if the elastic constants computed by dispersion corrected density functional theory are accurate enough to be used in a reference data base for the seismic exploration of icy ocean worlds. Despite one approach having demonstrated good accuracy compared with the experimental values in modelling the elasticity of CO2, we instead find average differences from expected P and S wave velocities of around 10 to 25% for the elastically more complex title compounds. In part these differences are due to the large temperature difference between the experimental elasticity data (typically near 300 K) and our calculations, which were performed in the athermal limit.
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Jul 2021
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