| 1. |
- 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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| 2. |
- Drobyshev, Igor, et al.
(författare)
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Lifespan and mortality of old oaks - combining empirical and modelling approaches to support their management in Southern Sweden
- 2008
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Ingår i: Annals of Forest Science. - : Springer Science and Business Media LLC. - 1286-4560 .- 1297-966X. ; 65:4, s. 401-401
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Tidskriftsartikel (refereegranskat)abstract
- Old oaks (Quercus robur L.) play an important role in the southern Scandinavian landscape by providing habitat for a wide range of species, a large proportion of them being currently on the National Redlists. To provide support for the management of these trees, we review data on oak mortality and formulate a mortality-driven stochastic model analysing interactions between mortality rate, oak recruitment rate into 100-150 age class, and amount of oaks older than 200 years. Empirical annual mortality rates varied between 0 and 13% with average 1.68%. Trees older 200 years had an average mortality rate of 1.1%. Oaks in the high density forests showed higher mortality (3.2%) as compared to the trees growing in the low density forests (1.2%). A 400-year long modelling exercises indicated that under current mortality rates (regular mortality being centred around 1% annually; and irregular mortality 7% with average return time of 13 years) the long-term maintenance of 20 trees older than 200 years per ha would require an input rate of 1 to 5 trees x year(-1) x ha(-1) into the 100-150 years old class. The modelling highlighted the importance of initial oak abundance affecting amount of old trees at the end of shorter (100 years) simulation period.
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| 3. |
- Martell, J., et al.
(författare)
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Combined Neutron and X-Ray Tomography-A Versatile and Non-Destructive Tool in Planetary Geosciences
- 2024
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Ingår i: Journal of Geophysical Research - Planets. - : American Geophysical Union (AGU). - 2169-9097 .- 2169-9100. ; 129:2
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Forskningsöversikt (refereegranskat)abstract
- With several upcoming sample return missions, such as the Mars Sample Return Campaign, non-destructive methods will be key to maximizing their scientific output. In this study, we demonstrate that the combination of neutron and X-ray tomography provides an important tool for the characterization of such valuable samples. These methods allow quantitative analyses of internal sample features and also provide a guide for further destructive analyses with little to no sample treatment, which maintains sample integrity, including minimizing the risk of potential contamination. Here, we present and review the results from four case studies of terrestrial impactites and meteorites along with their analytical setup. Using combined X-ray and neutron tomography, a Ni-Fe silicide spherule, that is, projectile material, was located within a Libyan Desert Glass sample and the distribution of hydrous phases was pinpointed in selected impactite samples from the Chicxulub IODP-ICDP Expedition 364 drill core and the Luizi impact structure, as well as in the Miller Range 03346 Martian meteorite. Neutron and X-ray tomography give complementary three-dimensional information about the distribution of different phases within a geologic sample. We demonstrate that these two methods can be successfully used to locate meteoritic material (i.e., from the impacting object) and hydrous components in terrestrial impactites and meteorites. This can help shed light on aqueous processes in the Solar System as well as the impact cratering process. Non-destructive methods like these will be important for up-coming sample return missions to characterize the returned samples and guide further destructive analyses. Combined neutron and X-ray imaging was used to locate projectile material and hydrous phases in meteorites and terrestrial impactites Locating and identifying projectile material can shed light on the impact cratering process Combined neutron/X-ray tomography can serve as a fundamental method for the characterization of material from (future) sample return missions
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