5 research outputs found
Compositional Heterogeneity of Impact Melt Rocks at the Haughton Impact Structure, Canada: Implications for Planetary Processes and Remote Sensing
Connecting the surface expression of impact craterârelated lithologies to planetary or regional subsurface compositions requires an understanding of material transport during crater formation. Here, we use imaging spectroscopy of six clastârich impact melt rock outcrops within the wellâpreserved 23.5âMa, 23âkm diameter Haughton impact structure, Canada, to determine melt rock composition and spatial heterogeneity. We compare results from outcrop to outcrop, using clasts, groundmass, and integrated clastâgroundmass compositions as tracers of transport during craterâfill melt rock formation and cooling. Supporting laboratory imaging spectroscopy analyses of 91 meltâbearing breccia and clast samples and microscopic Xâray fluorescence elemental mapping of cut samples paired with spectroscopy of identical surfaces validate outcropâscale lithological determinations. Results show different clastârich impact melt rock compositions at three sites kilometers apart and an inverse correlation between silicaârich (sandstone, gneiss, and phyllosilicateârich shales) and gypsumârich rocks that suggests differences in source depth with location. In the target stratigraphy, gypsum is primarily sourced from ~1âkm depth, while gneiss is from >1.8âkm depth, sandstone from >1.3 km, and shales from ~1.6â1.7 km. Observed heterogeneities likely result from different excavation depths coupled with rapid quenching of the melt due to high content of cool clasts. Results provide quantitative constraints for numerical models of impact structure formation and give new details on melt rock heterogeneity important in interpreting mission data and planning sample return of impactites, particularly for bodies with impacts into sedimentary and volatileâbearing targets, e.g., Mars and Ceres
Pre-Mission Input Requirements to Enable Successful Sample Collection by a Remote Field/EVA Team
We used a field excursion to the West Clearwater Lake Impact structure as an opportunity to test factors that contribute to the decisions a remote field team (for example, astronauts conducting extravehicular activities (EVA) on planetary surfaces) makes while collecting samples for return to Earth. We found that detailed background on the analytical purpose of the samples, provided to the field team, enables them to identify and collect samples that meet specific analytical objectives. However, such samples are not always identifiable during field reconnaissance activities, and may only be recognized after outcrop characterization and interpretation by crew and/or science team members. We therefore recommend that specific time be allocated in astronaut timeline planning to collect specialized samples, that this time follow human or robotic reconnaissance of the geologic setting, and that crew member training should include exposure to the laboratory techniques and analyses that will be used on the samples upon their return to terrestrial laboratories
Compositional Heterogeneity of Impact Melt Rocks at the Haughton Impact Structure, Canada: Implications for Planetary Processes and Remote Sensing
Connecting the surface expression of impact craterârelated lithologies to planetary or regional subsurface compositions requires an understanding of material transport during crater formation. Here, we use imaging spectroscopy of six clastârich impact melt rock outcrops within the wellâpreserved 23.5âMa, 23âkm diameter Haughton impact structure, Canada, to determine melt rock composition and spatial heterogeneity. We compare results from outcrop to outcrop, using clasts, groundmass, and integrated clastâgroundmass compositions as tracers of transport during craterâfill melt rock formation and cooling. Supporting laboratory imaging spectroscopy analyses of 91 meltâbearing breccia and clast samples and microscopic Xâray fluorescence elemental mapping of cut samples paired with spectroscopy of identical surfaces validate outcropâscale lithological determinations. Results show different clastârich impact melt rock compositions at three sites kilometers apart and an inverse correlation between silicaârich (sandstone, gneiss, and phyllosilicateârich shales) and gypsumârich rocks that suggests differences in source depth with location. In the target stratigraphy, gypsum is primarily sourced from ~1âkm depth, while gneiss is from >1.8âkm depth, sandstone from >1.3 km, and shales from ~1.6â1.7 km. Observed heterogeneities likely result from different excavation depths coupled with rapid quenching of the melt due to high content of cool clasts. Results provide quantitative constraints for numerical models of impact structure formation and give new details on melt rock heterogeneity important in interpreting mission data and planning sample return of impactites, particularly for bodies with impacts into sedimentary and volatileâbearing targets, e.g., Mars and Ceres