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  • JOURNAL ARTICLE
    Davison TM, Derrick JG, Collins GS, Bland PA, Rutherford ME, Chapman DJ, Eakins DEet al.,

    Impact-induced compaction of primitive solar system solids: The need for mesoscale modelling and experiments

    , Procedia Engineering, ISSN: 1877-7058

    Primitive solar system solids were accreted as highly porous bimodal mixtures of mm-sized chondrules and sub-μm matrix grains. To understand the compaction and lithification of these materials by shock, it is necessary to investigate the process at the mesoscale; i.e., the scale of individual chondrules. Here we document simulations of hypervelocity compaction of primitive materials using the iSALE shock physics model. We compare the numerical methods employed here with shock compaction experiments involving bimodal mixtures of glass beads and silica powder and find good agreement in bulk material response between the experiments and models. The heterogeneous response to shock of bimodal porous mixtures with a composition more appropriate for primitive solids was subsequently investigated: strong temperature dichotomies between the chondrules and matrix were observed (non-porous chondrules remained largely cold, while the porous matrix saw temperature increases of 100’s K). Matrix compaction was heterogeneous, and post-shock porosity was found to be lower on the lee-side of chondrules. The strain in the matrix was shown to be higher near the chondrule rims, in agreement with observations from meteorites. Chondrule flattening in the direction of the shock increases with increasing impact velocity, with flattened chondrules oriented with their semi-minor axis parallel to the shock direction.

  • CONFERENCE PAPER
    Shah J, Muxworthy AR, Almeida T, Kovacs A, Russell SS, Genge M, Dunin-Borkowski REet al.,

    Electron Holography of Chondrule Dusty Olivine (poster)

    , Meteorites and Solar System formation workshop
  • JOURNAL ARTICLE
    Watters WA, Hundal CB, Radford A, Collins GS, Tornabene LLet al.,

    Dependence of secondary crater characteristics on downrange distance: high-resolution morphometry and simulations

    , Journal of Geophysical Research: Planets, ISSN: 2169-9097
  • JOURNAL ARTICLE
    Collins GS, Collins GS, 2017,

    Moon formation: Punch combo or knock-out blow?

    , Nature Geoscience, Vol: 10, Pages: 72-73, ISSN: 1752-0894
  • JOURNAL ARTICLE
    Collins GS, Lynch E, Mcadam R, Davison TM, Collins GS, Lynch E, McAdam R, Davison TM, Collins GS, Lynch E, McAdam R, Davison TMet al., 2017,

    A numerical assessment of simple airblast models of impact airbursts

    , Meteoritics and Planetary Science, ISSN: 1086-9379

    © 2017 The Meteoritical Society. Asteroids and comets 10-100 m in size that collide with Earth disrupt dramatically in the atmosphere with an explosive transfer of energy, caused by extreme air drag. Such airbursts produce a strong blastwave that radiates from the meteoroid's trajectory and can cause damage on the surface. An established technique for predicting airburst blastwave damage is to treat the airburst as a static source of energy and to extrapolate empirical results of nuclear explosion tests using an energy-based scaling approach. Here we compare this approach to two more complex models using the iSALE shock physics code. We consider a moving-source airburst model where the meteoroid's energy is partitioned as two-thirds internal energy and one-third kinetic energy at the burst altitude, and a model in which energy is deposited into the atmosphere along the meteoroid's trajectory based on the pancake model of meteoroid disruption. To justify use of the pancake model, we show that it provides a good fit to the inferred energy release of the 2013 Chelyabinsk fireball. Predicted overpressures from all three models are broadly consistent at radial distances from ground zero that exceed three times the burst height. At smaller radial distances, the moving-source model predicts overpressures two times greater than the static-source model, whereas the cylindrical line-source model based on the pancake model predicts overpressures two times lower than the static-source model. Given other uncertainties associated with airblast damage predictions, the static-source approach provides an adequate approximation of the azimuthally averaged airblast for probabilistic hazard assessment.

  • JOURNAL ARTICLE
    Forman LV, Bland PA, Timms NE, Daly L, Benedix GK, Trimby PW, Collins GS, Davison TM, Forman LV, Bland PA, Timms NE, Daly L, Benedix GK, Trimby PW, Collins GS, Davison TM, Forman LV, Bland PA, Timms NE, Daly L, Benedix GK, Trimby PW, Collins GS, Davison TM, Forman LV, Bland PA, Timms NE, Daly L, Benedix GK, Trimby PW, Collins GS, Davison TMet al., 2017,

    Defining the mechanism for compaction of the CV chondrite parent body

    , GEOLOGY, Vol: 45, Pages: 559-562, ISSN: 0091-7613

    © 2017 Geological Society of America. The Allende meteorite, a relatively unaltered member of the CV carbonaceous chondrite group, contains primitive crystallographic textures that can inform our understanding of early Solar System planetary compaction. To test between models of porosity reduction on the CV parent body, complex microstructures within ~0.5-mm-diameter chondrules and ~10-μm-long matrix olivine grains were analyzed by electron backscatter diffraction (EBSD) techniques. The large area map presented is one of the most extensive EBSD maps to have been collected in application to extraterrestrial materials. Chondrule margins preferentially exhibit limited intragrain crystallographic misorientation due to localized crystal-plastic deformation. Crystallographic preferred orientations (CPOs) preserved by matrix olivine grains are strongly coupled to grain shape, most pronounced in shortest dimension < a > , yet are locally variable in orientation and strength. Lithostatic pressure within plausible chondritic model asteroids is not sufficient to drive compaction or create the observed microstructures if the aggregate was cold. Significant local variability in the orientation and intensity of compaction is also inconsistent with a global process. Detailed microstructures indicative of crystal-plastic deformation are consistent with brief heating events that were small in magnitude. When combined with a lack of sintered grains and the spatially heterogeneous CPO, ubiquitous hot isostatic pressing is unlikely to be responsible. Furthermore, Allende is the most metamorphosed CV chondrite, so if sintering occurred at all on the CV parent body it would be evident here. We conclude that the crystallographic textures observed reflect impact compaction and indicate shock-wave directionality. We therefore present some of the first significant evidence for shock compaction of the CV parent body.

  • JOURNAL ARTICLE
    Jourdan F, Timms NE, Eroglu E, Mayers C, Free A, Bland PA, Collins G, Davison T, Abe M, Yada Tet al., 2017,

    Collisional history of asteroid Itokawa

    , Geology, ISSN: 1943-2682

    In situ extrate rrestrial samples returned for study (e.g., from the Moon) are crucial in understanding the origin and evolution of the Solar System as, contrary to meteorites, they provide a known geological context for the samples and their analyses. Asteroid 25143 Itokawa is a rubble pile asteroid consisting of reaccumulated fragments from a catastrophically disrupted monolithic parent asteroid, and from which regolith dust particles have been recovered by the Hayabusa space probe. We analyzed two dust particles using Electron Backscatter Diffraction (EBSD) and 40 Ar/39 Ar dating techniques. One of the grains showing signs of 15–25 GPa impact shock pressure, yielded a 40 Ar/Ar plateau age of 2.3 ± 0.1 Ga. We develop a novel temperature -pressure-porosity model, coupled with diffusion models to show that the relatively low pressure and high temperature involved in the impact process can be reconciled only if the asteroid was already made of porous material at ~2.3 Ga and thus, if asteroid Itokawa was already formed, thereby providing a minimum age for catastrophic asteroid breakup. A second particle shows no sign of deformation indicating shock pressure of ˂ 10 GPa and a calculated maximum temperature of ~200 °C. This low temperature estimate is compatible with a lack of isotopic resetting for this particle. This suggests that the breakup of Itokawa’s parent was a relatively low-temperature process at the scale of the asteroid, and occurred on a pre-shattered parent body.

  • JOURNAL ARTICLE
    Johnson BC, Blair DM, Collins GS, Melosh HJ, Freed AM, Taylor GJ, Head JW, Wieczorek MA, Andrews-Hanna JC, Nimmo F, Keane JT, Miljkovic K, Soderblom JM, Zuber MT, Johnson BC, Blair DM, Collins GS, Melosh HJ, Freed AM, Taylor GJ, Head JW, Wieczorek MA, Andrews-Hanna JC, Nimmo F, Keane JT, Miljković K, Soderblom JM, Zuber MT, Johnson BC, Blair DM, Collins GS, Melosh HJ, Freed AM, Taylor GJ, Head JW, Wieczorek MA, Andrews-Hanna JC, Nimmo F, Keane JT, Miljković K, Soderblom JM, Zuber MT, Johnson BC, Blair DM, Collins GS, Melosh HJ, Freed AM, Taylor GJ, Head JW, Wieczorek MA, Andrews-Hanna JC, Nimmo F, Keane JT, Miljković K, Soderblom JM, Zuber MT, Johnson BC, Blair DM, Collins GS, Melosh HJ, Freed AM, Taylor GJ, Head JW, Wieczorek MA, Andrews-Hanna JC, Nimmo F, Keane JT, Miljkovi K, Soderblom JM, Zuber MT, Johnson BC, Blair DM, Collins GSet al., 2016,

    Formation of the Orientale lunar multiring basin

    , SCIENCE, Vol: 354, Pages: 441-444, ISSN: 0036-8075

    Multiring basins, large impact craters characterized by multiple concentric topographic rings, dominate the stratigraphy, tectonics, and crustal structure of the Moon. Using a hydrocode, we simulated the formation of the Orientale multiring basin, producing a subsurface structure consistent with high-resolution gravity data from the Gravity Recovery and Interior Laboratory (GRAIL) spacecraft. The simulated impact produced a transient crater, ~390 kilometers in diameter, that was not maintained because of subsequent gravitational collapse. Our simulations indicate that the flow of warm weak material at depth was crucial to the formation of the basin's outer rings, which are large normal faults that formed at different times during the collapse stage. The key parameters controlling ring location and spacing are impactor diameter and lunar thermal gradients.

  • JOURNAL ARTICLE
    Kring DA, Kramer GY, Collins GS, Potter RWK, Chandnani M, Kring DA, Kramer GY, Collins GS, Potter RWK, Chandnani M, Kring DA, Kramer GY, Collins GS, Potter RWK, Chandnani M, Kring DA, Kramer GY, Collins GS, Potter RWK, Chandnani M, Kring DA, Kramer GY, Collins GS, Potter RWK, Chandnani M, Kring DA, Kramer GY, Collins GS, Potter RWK, Chandnani Met al., 2016,

    Peak-ring structure and kinematics from a multi-disciplinary study of the Schrodinger impact basin

    , NATURE COMMUNICATIONS, Vol: 7, Pages: 13161-13161, ISSN: 2041-1723

    The Schrödinger basin on the lunar farside is ∼320 km in diameter and the best-preserved peak-ring basin of its size in the Earth-Moon system. Here we present spectral and photogeologic analyses of data from the Moon Mineralogy Mapper instrument on the Chandrayaan-1 spacecraft and the Lunar Reconnaissance Orbiter Camera (LROC) on the LRO spacecraft, which indicates the peak ring is composed of anorthositic, noritic and troctolitic lithologies that were juxtaposed by several cross-cutting faults during peak-ring formation. Hydrocode simulations indicate the lithologies were uplifted from depths up to 30 km, representing the crust of the lunar farside. Through combining geological and remote-sensing observations with numerical modelling, we show that a Displaced Structural Uplift model is best for peak rings, including that in the K-T Chicxulub impact crater on Earth. These results may help guide sample selection in lunar sample return missions that are being studied for the multi-agency International Space Exploration Coordination Group.

  • JOURNAL ARTICLE
    Morgan JV, Gulick SPS, Bralower T, Chenot E, Christeson G, Claeys P, Cockell CS, Collins GS, Coolen MJL, Ferriere L, Gebhardt C, Goto K, Jones H, Kring DA, Le Ber E, Lofi J, Long X, Lowery C, Mellett C, Ocampo-Torres R, Osinski GR, Perez-Cruz L, Pickersgill A, Poelchau M, Rae A, Rasmussen C, Rebolledo-Vieyra M, Riller U, Sato H, Schmitt DR, Smit J, Tikoo S, Tomioka N, Urrutia-Fucugauchi J, Whalen M, Wittmann A, Yamaguchi KE, Zylberman W, Morgan JV, Gulick SPS, Bralower T, Chenot E, Christeson G, Claeys P, Cockell C, Collins GS, Coolen MJL, Ferrière L, Gebhardt C, Goto K, Jones H, Kring DA, Le Ber E, Lofi J, Long X, Lowery C, Mellett C, Ocampo-Torres R, Osinski GR, Perez-Cruz L, Pickersgill A, Poelchau M, Rae A, Rasmussen C, Rebolledo-Vieyra M, Riller U, Sato H, Schmitt DR, Smit J, Tikoo S, Tomioka N, Urrutia-Fucugauchi J, Whalen M, Wittmann A, Yamaguchi KE, Zylberman W, Morgan JV, Gulick SPS, Bralower T, Chenot E, Christeson G, Claeys P, Cockell C, Collins GS, Coolen MJL, Ferrière L, Gebhardt C, Goto K, Jones H, Kring DA, Le Ber E, Lofi J, Long X, Lowery C, Mellett C, Ocampo-Torres R, Osinski GR, Perez-Cruz L, Pickersgill A, Poelchau M, Rae A, Rasmussen C, Rebolledo-Vieyra M, Riller U, Sato H, Schmitt DR, Smit J, Tikoo S, Tomioka N, Urrutia-Fucugauchi J, Whalen M, Wittmann A, Yamaguchi KE, Zylberman W, Morgan JV, Gulick SPS, Bralower T, Chenot E, Christeson G, Claeys P, Cockell C, Collins GS, Coolen MJL, Ferrière L, Gebhardt C, Goto K, Jones H, Kring DA, Le Ber E, Lofi J, Long X, Lowery C, Mellett C, Ocampo-Torres R, Osinski GR, Perez-Cruz L, Pickersgill A, Poelchau M, Rae A, Rasmussen C, Rebolledo-Vieyra M, Riller U, Sato H, Schmitt DR, Smit J, Tikoo S, Tomioka N, Urrutia-Fucugauchi J, Whalen M, Wittmann A, Yamaguchi KE, Zylberman W, Morgan JV, Gulick SPS, Bralower T, Chenot E, Christeson G, Claeys P, Cockell C, Collins GS, Coolen MJL, Ferrière L, Gebhardt C, Goto K, Jones H, Kring DA, Le Ber E, Lofi J, Long X, Lowery C, Mellett C, Ocampo-Torres R, Osinski GR, Pereet al., 2016,

    The formation of peak rings in large impact craters

    , SCIENCE, Vol: 354, Pages: 878-882, ISSN: 0036-8075

    Large impacts provide a mechanism for resurfacing planets through mixing near-surface rocks with deeper material. Central peaks are formed from the dynamic uplift of rocks during crater formation. As crater size increases, central peaks transition to peak rings. Without samples, debate surrounds the mechanics of peak-ring formation and their depth of origin. Chicxulub is the only known impact structure on Earth with an unequivocal peak ring, but it is buried and only accessible through drilling. Expedition 364 sampled the Chicxulub peak ring, which we found was formed from uplifted, fractured, shocked, felsic basement rocks. The peak-ring rocks are cross-cut by dikes and shear zones and have an unusually low density and seismic velocity. Large impacts therefore generate vertical fluxes and increase porosity in planetary crust.

  • CONFERENCE PAPER
    Penny C, Muxworthy AR, Fabian K, 2016,

    The Curie temperature of magnetite nanoparticles (poster)

    , 15th Castle Meeting
  • CONFERENCE PAPER
    Penny C, Muxworthy AR, Fabian K, 2016,

    The Curie temperature of magnetite nanoparticles (poster)

    , EMRS Fall 2016
  • CONFERENCE PAPER
    Shah J, Bates H, Muxworthy AR, Russell SS, Genge MJet al., 2016,

    A micro-CT conglomerate test (poster)

    , 15th Castle Meeting
  • CONFERENCE PAPER
    Shah J, Muxworthy AR, Almeida T, Kovacs A, Russell SS, Genge M, Dunin-Borkowski Ret al., 2016,

    Hot Holography: Magnetic recording fidelity of dusty olivine (poster)

    , 13th UK Planetary Forum Early Career Scientists’ Meeting
  • CONFERENCE PAPER
    Shah J, Muxworthy AR, Almeida TP, Kovacs A, Russell SS, Genge M, Dunin-Borkowski Ret al., 2016,

    In-situ heating holography of chondrule dusty olivine

    , Magnetic Interactions
  • CONFERENCE PAPER
    Shah J, Muxworthy AR, Almeida TP, Kovacs A, Russell SS, Genge M, Williams W, Dunin-Borkowski REet al., 2016,

    Determining the magnetic recording fidelity of chondrule dusty olivine

    , 15th Castle Meeting
  • JOURNAL ARTICLE
    Abubakar R, Muxworthy AR, Sephton MA, Southern P, Watson JS, Fraser AJ, Almeida TP, Abubakar R, Muxworthy AR, Sephton MA, Southern P, Watson JS, Fraser AJ, Almeida TP, Abubakar R, Muxworthy AR, Sephton MA, Southern P, Watson JS, Fraser AJ, Almeida TP, Abubakar R, Muxworthy AR, Southern P, Watson JS, Fraser AJ, Almeida TP, Sephton MA, Abubakar R, Muxworthy AR, Sephton MA, Fraser Aet al., 2015,

    Formation of magnetic minerals at hydrocarbon-generation conditions

    , MARINE AND PETROLEUM GEOLOGY, Vol: 68, Pages: 509-519, ISSN: 0264-8172

    © 2015 The Authors. In this paper, we report the pyrolysis and formation of magnetic minerals in three source rock samples from the Wessex Basin in Dorset, southern England. The experimental conditions in the laboratory recreated the catagenesis environment of oil source rocks. Magnetic analysis of both the heated and the unheated samples at room temperature and at very low-temperatures (5 K), coupled with transmission electron-microscopy imaging and X-ray analysis, revealed the formation of nanometre-sized ( < 10 nm), magnetic particles that varied across the rock samples analysed, but more importantly across the pyrolysis temperature range. Magnetic measurements demonstrated the formation of these magnetic minerals peaked at 250 °C for all rock samples and then decreased at 300 °C before rising again at 320 °C. The newly formed magnetic minerals are suggested to be primarily pyrrhotite, though magnetite and greigite are also thought to be present. The sizes of the magnetic minerals formed suggest a propensity to migrate together with oil potentially explaining the magnetic anomalies observed above and within oil fields.

  • JOURNAL ARTICLE
    Jacobs CT, Goldin TJ, Collins GS, Piggott MD, Kramer SC, Melosh HJ, Wilson CRG, Allison PA, Jacobs CT, Goldin TJ, Collins GS, Piggott MD, Kramer SC, Melosh HJ, Wilson CRG, Allison PA, Jacobs CT, Goldin TJ, Collins GS, Piggott MD, Kramer SC, Melosh HJ, Wilson CRG, Allison PAet al., 2015,

    An improved quantitative measure of the tendency for volcanic ash plumes to form in water: implications for the deposition of marine ash beds

    , JOURNAL OF VOLCANOLOGY AND GEOTHERMAL RESEARCH, Vol: 290, Pages: 114-124, ISSN: 0377-0273

    © 2014. Laboratory experiments and numerical simulations have shown that volcanic ash particles immersed in water can either settle slowly and individually, or rapidly and collectively as particle-laden plumes. The ratio of timescales for individual and collective settling, in the form of analytical expressions, provides a dimensionless quantitative measure of the tendency for such plumes to grow and persist which has important implications for determining particle residence times and deposition rates. However, existing measures in the literature assume that collective settling obeys Stokes' law and is therefore controlled by the balance between gravitational forces and viscous drag, despite plume development actually being controlled by the balance between gravitational forces and inertial drag even in the absence of turbulence during early times. This paper presents a new measure for plume onset which takes into account the inertial drag-controlled (rather than viscous drag-controlled) nature of plume growth and descent. A parameter study comprising a set of numerical simulations of small-scale volcanic ash particle settling experiments highlights the effectiveness of the new measure and, by comparison with an existing measure in the literature, also demonstrates that the timescale of collective settling is grossly under-estimated when assuming that plume development is slowed by viscous drag. Furthermore, the formulation of the new measure means that the tendency for plumes to form can be estimated from the thickness and concentration of the final deposit; the magnitude and duration of particle flux across the water's surface do not need to be known. The measure therefore permits the residence times of particles in a large body of water to be more accurately and practically determined, and allows the improved interpretation of layers of volcaniclastic material deposited at the seabed.

  • JOURNAL ARTICLE
    Miljkovic K, Wieczorek MA, Collins GS, Solomon SC, Smith DE, Zuber MT, Miljković K, Wieczorek MA, Collins GS, Solomon SC, Smith DE, Zuber MT, Miljković K, Wieczorek MA, Collins GS, Solomon SC, Smith DE, Zuber MTet al., 2015,

    Excavation of the lunar mantle by basin-forming impact events on the Moon

    , EARTH AND PLANETARY SCIENCE LETTERS, Vol: 409, Pages: 243-251, ISSN: 0012-821X

    © 2014 Elsevier B.V. Global maps of crustal thickness on the Moon, derived from gravity measurements obtained by NASA's Gravity Recovery and Interior Laboratory (GRAIL) mission, have shown that the lunar crust is thinner than previously thought. Hyperspectral data obtained by the Kaguya mission have also documented areas rich in olivine that have been interpreted as material excavated from the mantle by some of the largest lunar impact events. Numerical simulations were performed with the iSALE-2D hydrocode to investigate the conditions under which mantle material may have been excavated during large impact events and where such material should be found. The results show that excavation of the mantle could have occurred during formation of the several largest impact basins on the nearside hemisphere as well as the Moscoviense basin on the farside hemisphere. Even though large areas in the central portions of these basins were later covered by mare basaltic lava flows, surficial lunar mantle deposits are predicted in areas external to these maria. Our results support the interpretation that the high olivine abundances detected by Kaguya spacecraft could indeed be derived from the lunar mantle.

  • CONFERENCE PAPER
    Montgomery W, Sephton MA, Watson JS, Zeng H, Montgomery W, Sephton MA, Watson JS, Zeng H, Montgomery W, Sephton MA, Watson J, Zeng Het al., 2015,

    The Effects of Minerals on Heavy-Oil and Bitumen Chemistry When Recovered by Steam-Assisted Methods

    , SPE Heavy Oil Conference-Canada, Publisher: SPE-SOC PETROLEUM ENGINEERS, CANADA, Pages: 15-17, ISSN: 0021-9487

    Copyright © (2014) by the Society of Petroleum Engineers All rights reserved. The production of gaseous sulfur-containing species during the steam-assisted recovery of heavy oil and bitumen have important consequences for both economics and safety. Factors such as the effects of mineral matrices require laboratory data to produce accurate models. To study mineral effects on gas production we studied a well-characterized oil-containing core and the isolated crude oil from that core. The samples were run at 250-300°C in the continued presence of liquid water for 24 hours. The reaction products of all experiments include gases, oil flotate, oil sinkate, water-soluble products, and water- insoluble residues. All reaction products were studied with a variety of analytical techniques, including FTIR spectroscopy, chromatographic fractionation (SARA analysis), GC-MS, pyrolysis GCMS and GC-FPD/TCD. These techniques were applied to whole oil, maltenes and asphaltene fractions. Physical properties including viscosity and density were also measured. Our data provide insights into the physical and chemical consequences of steam assisted recovery of heavy oils and bituments from sedimentary rock reservoirs and reveal that geological and geochemical context is an essential consideration.

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