| 1. |
- Arnadottir, Anna, et al.
(författare)
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The Meridian S01E02 : Impact Craters on Culture Night
- 2021
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Konstnärligt arbete (övrigt vetenskapligt/konstnärligt)abstract
- In this second episode of the podcast Nic and Rebecca invite Josefin Martell to the mic and chat to her about Impact Craters. Thereafter they take a closer look at one of their favourite astronomical objects: Dimidium.
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| 2. |
- Herrmann, Maria, et al.
(författare)
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The first U–Pb age for shocked zircon from the Mien impact structure, Sweden, and implications for metamictization-induced zircon texture formed during impact events
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Ingår i: Meteoritics and Planetary Science. - 1086-9379.
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Tidskriftsartikel (refereegranskat)abstract
- Shocked zircon from impactites from the Mien impact structure, Sweden, has been investigated with the aim to date the impact event and correlate the degree of U–Pb age resetting with shock-related microtextures. In situ U–Pb spot isotope analyses of granular and microporous–granular zircon grains from the impact melt rocks give an age of 120.0 ± 1.0 Ma. This essentially confirms the previous best estimate age of 122.4 ± 2.3 Ma, while also increasing precision on the Mien impact age. U–Pb isotope mapping shows that radiation damage likely explains the similar U–Pb age reset associated with different shock-related microtextures. Microporous and some of the granular and microporous–granular domains yield higher U concentrations along with younger 238U/206Pb dates. Lower U contents with older 238U/206Pb dates are predominately observed in pristine domains. Due to the U-decay, the zircon lattice is damaged, a process through which Pb can be lost. This would result in younger 238U/206Pb dates, as observed for the high U domains. As the zircon crystal lattices were locally weakened, metamictization possibly facilitated the development of microporous and granular textures during the impact event. Analyses of unshocked Mien zircon confirm that radiation damage already existed before impact. Lead loss from granular domains occurred through recrystallization and from microporous domains through Pb leaching by hydrothermal fluids. In addition, our study demonstrates the utility of combined U–Pb isotope mapping and spot analysis in unraveling the link between U–Pb resetting and shock-related microtextures, the formation of which was in this case likely promoted by pre-existing radiation damage.
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| 3. |
- Martell, Josefin
(författare)
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Leave no trace: A non-destructive correlative approach providing new insights into impactites and meteorites
- 2022
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Doktorsavhandling (övrigt vetenskapligt/konstnärligt)abstract
- Impact cratering is today recognized as a fundamental geological process on all rocky bodies in the solar system. On Earth, however, processes such as plate tectonics and erosion have eradicated most craters from the geological record, or they may be buried under sediments, oceans, and vegetation. The formation of a hypervelocity impact crater involves extreme pressures and temperatures that induce permanent changes in the target rocks, so-called shock-metamorphic effects, which can be used to identify and confirm impact structures. The research in this thesis focuses on the impact cratering process, both during the formation, and post-impact. A number of terrestrial impactites and meteorites were analyzed using a multi-modal approach, including correlative non-destructive neutron and X-ray imaging, and detailed 2D analysis using scanning electron microscopy and electron backscatter diffraction. The material encompasses (1) impactites from the Mien impact structure, (2) a sample of the Martian Miller Range (MIL) 03346 meteorite, (3) a Chicxulub drill core sample, (4) a sample of Libyan Desert Glass, and (5) a sample of impact melt rock from the Luizi impact structure. The first study investigated shock deformation in zircon grains from the Mien impact structure in Sweden, using electron backscatter diffraction (EBSD). The results show that several of these grains contain evidence of the former presence of a high-pressure phase that is only known from impact structures. These grains would be suitable candidates for refining the age of the impact event. In paper II, combined NCT and XCT were employed to investigate the three-dimensional distribution of hydrogen-rich material in MIL 03346, by utilizing the neutrons’ sensitivity to hydrogen. The results revealed that the hydrogen-rich material occurs in localized clusters, with limited interconnectivity between clusters. This suggests that the fluid source could be small patches of sub-surface ice and that the alteration event likely was short-lived, meaning that the source terrain of this sample was likely not habitable. In Paper III we combined XCT and NCT to test if these methods can be used to locate projectile material in impactites. After careful investigations of the 3D images, an iron-nickel silicide spherule could be pin-pointed in the Libyan Desert glass. The sample was then polished for detailed analysis using scanning electron microscopy. Overall, the non-destructive nature of XCT and NCT makes these methods highly relevant for studying rare samples, such as meteorites and returned samples.
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| 4. |
- Martell, Josefin, et al.
(författare)
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Shock deformation in zircon grains from the Mien impact structure, Sweden
- 2021
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Ingår i: Meteoritics and Planetary Science. - : Wiley. - 1086-9379 .- 1945-5100. ; 56:2, s. 362-378
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Tidskriftsartikel (refereegranskat)abstract
- Recognition of impact-induced deformation of minerals is crucial for the identification and confirmation of impact structures as well as for the understanding of shock wave behavior and crater formation. Shock deformed mineral grains from impact structures can also serve as important geochronometers, precisely dating the impact event. We investigated zircon grains from the Mien impact structure in southern Sweden with the aim of characterizing shock deformation. The grains were found in two samples of impact melt rock with varying clast content, and in one sample of suevitic breccia. We report the first documentation of so-called “FRIGN zircon” (former reidite in granular neoblastic zircon) from Mien (pre-erosion diameter 9 km), which confirms that this is an important impact signature also in relatively small impact structures. Furthermore, the majority of investigated zircon grains contain other shock-related microtextures, most notably granular and microporous textures, that occur more frequently in grains found in the impact melt than in the suevitic breccia. Our findings show that zircon grains that are prime candidates for establishing a new and improved age refinement of the Mien impact structure are present in the impact melt.
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| 5. |
- Martell, Josefin, et al.
(författare)
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The scale of a martian hydrothermal system explored using combined neutron and x-ray tomography
- 2022
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Ingår i: Science Advances. - : American Association for the Advancement of Science (AAAS). - 2375-2548. ; 8:19
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Tidskriftsartikel (refereegranskat)abstract
- Nakhlite meteorites are igneous rocks from Mars that were aqueously altered ~630 million years ago. Hydrothermal systems on Earth are known to provide microhabitats; knowledge of the extent and duration of these systems is crucial to establish whether they could sustain life elsewhere in the Solar System. Here, we explore the three-dimensional distribution of hydrous phases within the Miller Range 03346 nakhlite meteorite using nondestructive neutron and x-ray tomography to determine whether alteration is interconnected and pervasive. The results reveal discrete clusters of hydrous phases within and surrounding olivine grains, with limited interconnectivity between clusters. This implies that the fluid was localized and originated from the melting of local subsurface ice following an impact event. Consequently, the duration of the hydrous alteration was likely short, meaning that the martian crust sampled by the nakhlites could not have provided habitable environments that could harbor any life on Mars during the Amazonian.
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