Geology Research Works
Permanent URI for this collectionhttp://hdl.handle.net/1903/1594
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Item Active Seismic Exploration of Planetary Subsurfaces via Compressive Sensing(2025) Wang, Jingchuan; Schmerr, Nicholas; Lekic, VedranThe software supports the following study: We present a method for improving seismic data collection on planetary surfaces such as the Moon and Mars. This approach is based on recent advances in compressive sensing technology to reduce the number of data collection points required compared to conventional methods without sacrificing the quality of the resulting subsurface images. We demonstrate its effectiveness using both synthetic and field data from locations with similarities to planetary surface environments. The method is then applied to reanalyze seismic data collected by the crew of the Apollo 14 and 16 missions. Our study has implications for mission planning, as this method can make space missions more efficient by reducing the equipment and time to collect geophysical data on planetary surfaces. It also makes it possible to reconstruct missing or damaged data, improving the quality of imagery and enhancing our understanding of the interior of other worlds.Item Dataset for Constraining Wetland and Landfill Methane Emission Signatures Through Atmospheric Methane Clumped Isotopologue Measurements" [Paper #2024JG008249-T](2025) Sun, Jiayang; Farquhar, JamesFrom Primary Paper: Microbial methane emissions are associated with a wide range of isotopic signatures, providing information about the sources and sinks of methane. Methods of directly sampling methane from environments such as wetlands may fail to capture the temporal and spatial variations in emissions at a specific site and time. The Keeling plot method is commonly used to infer the overarching isotopic signatures of methane sources. In this study, we have expanded the application of the Keeling plot from conventional stable isotope ratios to include novel clumped isotopologue compositions of methane. This advancement aims to provide more robust constraints on regional methane emission signatures. We analyzed methane isotopologue compositions from air samples collected above wetlands and landfills across Maryland, USA, and determined the endmember compositions for background air, wetland, and landfill sources. Our findings indicate that the isotopologue compositions of methane from regional wetland emissions exhibit seasonal variations — δ13C and δD values become less positive as winter approaches, reflecting changes in methane oxidation and production rates. The continuous monitoring of air methane isotopologue signatures will deepen our understanding of the seasonal patterns in methane emissions and contribute to refining the global methane budget, as valuable insights can be extracted from these measurements.Item A Better Understanding of Atmospheric Methane Sources Using 13CH3D and 12CH2D2 Clumped Isotopes(2024-09) Haghnegahdar, Mojhgan A.We evaluate the use of clumped isotopes of methane (CH4) to fingerprint local atmospheric sources of methane. We focus on a regenerative stormwater conveyance (RSC) stream wetland site running through the University of Maryland campus, which emits methane due to its engineering. Air samples in the RSC were collected at different heights above the surface and at different times of the day including both early in the morning, after methane accumulated below the nocturnal boundary layer, and late in the afternoon when convection mixed air to the cloud layer. Measured Δ12CH2D2 values of air samples record mixing between locally produced methane with low D/H and ambient air. The Δ12CH2D2 of the near surface air collected at the RSC during the early morning ranges from ~+23‰ to ~+35‰ which is lower than the ~+50‰ values of tropospheric air. Mixing between background air (with Δ12CH2D2 ~+50‰) and methane captured from chamber and bubble samples, as well as produced in incubation (all with negative Δ12CH2D2), explains the observed values of Δ12CH2D2 and Δ13CH3D of near surface RSC air samples. The effect of mixing with biogenic sources on Δ13CH3D is much smaller. The findings demonstrate how methane isotopologues can be used as a tool not only to fingerprint local contributions to these greenhouse gas emissions but also to identify sources of near-surface methane hot spots.Item Snowfall Replenishes Groundwater Loss in the Great Basin of the Western United States, but Cannot Compensate for Increasing Aridification(Wiley, 2024-03-20) Hall, Dorothy K.; Loomis, Bryant D.; DiGirolamo, Nicolo E.; Forman, Barton A.There has been an acceleration of groundwater loss in the Great Basin (GB) of the western U.S. as determined from total water storage (TWS) measurements from the GRACE/FO satellite missions. From 2002 to 2023, there was a loss of TWS in the GB of ∼68.7 km3 which is more than six times the current volume of the Lake Mead Reservoir. In this arid/semi-arid region, groundwater is the primary factor contributing to the decade-scale decline in TWS. Stronger declining trends are found in the western versus the eastern GB. Snow loading is the major cause of seasonal fluctuations of TWS in the GB. Despite annual replenishment of groundwater by snow, the downward trend persists even in notable snow years. Likely causes include declining snow mass, upstream water diversions and increased evaporation/sublimation due to increasing temperatures. Dire consequences for humans and wildlife are associated with this large loss of groundwater.Item Chemical and genetic characterization of the ungrouped pallasite Lieksa(Wiley, 2023-11-03) Chiappe, Emily M.; Ash, Richard D.; Luttinen, Arto; Lukkari, Sari; Kuva, Jukka; Hilton, Connor D.; Walker, Richard J.The meteorite Lieksa was found in 2017 in Löpönvaara, Finland, and later donated to the Finnish Museum of Natural History. Here, we report siderophile element concentrations, genetic isotopic data, and a metal–silicate segregation age for the meteorite. The ~280 g Lieksa is ~80% metal and ~20% silicate and oxide inclusions by volume, with the inclusions consisting primarily of Fe-rich olivine. Due to Lieksa's silicate content, coupled with a texture characterized by metal enclosing the silicates, it has been classified as a pallasite. Lieksa's olivine and bulk chemical characteristics are distinct from those of the known pallasite and iron meteorite groups, consistent with its classification as ungrouped. The meteorite exhibits a flat, chondrite-normalized highly siderophile element pattern, consistent with an origin as an early crystallization product from a metallic melt with chondritic relative abundances. Molybdenum, Ru, and 183W isotopic data indicate that Lieksa formed in the non-carbonaceous (NC) domain of the solar nebula. Radiogenic 182W abundances for Lieksa yield a model metal–silicate segregation age of 1.5 ± 0.8 Myr after calcium-aluminum-rich inclusion formation, which is within the range established for other NC-type pallasite and iron meteorite parent bodies.Item The Hunga Tonga-Hunga Ha'apai Volcanic Eruption as Seen in Satellite Microwave Observations and MiRS Temperature Retrievals(Wiley, 2023-12-06) Lee, Yong-Keun; Hindley, Neil; Grassotti, Christopher; Liu, QuanhuaThe strongest volcanic eruption since the 19th century occurred on 15 January 2022 at Hunga Tonga-Hunga Ha'apai, generating unprecedented atmospheric waves not seen before in observations. We used satellite microwave observations from (a) Advanced Technology Microwave Sounder (ATMS) on board the National Oceanic and Atmospheric Administration (NOAA)-20 and the Suomi-National Polar-orbiting Partnership (SNPP) and (b) Advanced Microwave Sounding Unit (AMSU)-A on board Meteorological operational satellite (MetOp)-B/MetOp-C to study these waves in the stratosphere immediately after the eruption. The NOAA Microwave Integrated Retrieval System (MiRS) was applied to these microwave observations to produce atmospheric temperature profiles. The atmospheric Lamb wave and fast-traveling gravity waves are clearly revealed in both the brightness temperatures and the MiRS retrieved temperatures, revealing their vertical phase structures. This study is the first attempt to perform a detailed analysis of the stratospheric impact of the Tonga eruption on operational satellite microwave observations and the corresponding MiRS retrievals.Item Oxygen Fugacity of Global Ocean Island Basalts(Wiley, 2024-01-27) Willhite, Lori N.; Arevalo, Ricardo Jr.; Piccoli, Philip; Lassiter, John C.; Rand, Devin; Jackson, Matthew G.; Day, James M. D.; Nicklas, Robert W.; Locmelis, Marek; Ireland, Thomas J.; Puchtel, Igor S.Mantle plumes contain heterogenous chemical components and sample variable depths of the mantle, enabling glimpses into the compositional structure of Earth's interior. In this study, we evaluated ocean island basalts (OIB) from nine plume locations to provide a global and systematic assessment of the relationship between fO2 and He-Sr-Nd-Pb-W-Os isotopic compositions. Ocean island basalts from the Pacific (Austral Islands, Hawaii, Mangaia, Samoa, Pitcairn), Atlantic (Azores, Canary Islands, St. Helena), and Indian Oceans (La Réunion) reveal that fO2 in OIB is heterogeneous both within and among hotspots. Taken together with previous studies, global OIB have elevated and heterogenous fO2 (average = +0.5 ∆FMQ; 2SD = 1.5) relative to prior estimates of global mid-ocean ridge basalts (MORB; average = −0.1 ∆FMQ; 2SD = 0.6), though many individual OIB overlap MORB. Specific mantle components, such as HIMU and enriched mantle 2 (EM2), defined by radiogenic Pb and Sr isotopic compositions compared to other OIB, respectively, have distinctly high fO2 based on statistical analysis. Elevated fO2 in OIB samples of these components is associated with higher whole-rock CaO/Al2O3 and olivine CaO content, which may be linked to recycled carbonated oceanic crust. EM1-type and geochemically depleted OIB are generally not as oxidized, possibly due to limited oxidizing potential of the recycled material in the enriched mantle 1 (EM1) component (e.g., sediment) or lack of recycled materials in geochemically depleted OIB. Despite systematic offset of the fO2 among EM1-, EM2-, and HIMU-type OIB, geochemical indices of lithospheric recycling, such as Sr-Nd-Pb-Os isotopic systems, generally do not correlate with fO2.Item Characterization of Regolith And Trace Economic Resources (CRATER): An Orbitrap-based laser desorption mass spectrometry instrument for in situ exploration of the Moon(Wiley, 2024-02-11) Ray, Soumya; Arevalo, Ricardo Jr.; Southard, Adrian; Willhite, Lori; Bardyn, Anais; Ni, Ziqin; Danell, Ryan; Grubisic, Andrej; Gundersen, Cynthia; Llano, Julie; Yu, Anthony; Fahey, Molly; Hernandez, Emanuel; Graham, Jacob; Lee, Jane; Ersahin, Akif; Briois, Christelle; Thirkell, Laurent; Colin, Fabrice; Makarov, AlexanderRationale Characterization of Regolith And Trace Economic Resources (CRATER), an Orbitrap™-based laser desorption mass spectrometry instrument designed to conduct high-precision, spatially resolved analyses of planetary materials, is capable of answering outstanding science questions about the Moon's formation and the subsequent processes that have modified its (sub)surface. Methods Here, we describe the baseline design of the CRATER flight model, which requires <20 000 cm3 volume, <10 kg mass, and <60 W peak power. The analytical capabilities and performance metrics of a prototype that meets the full functionality of the flight model are demonstrated. Results The instrument comprises a high-power, solid-state, pulsed ultraviolet (213 nm) laser source to ablate the surface of the lunar sample, a custom ion optical interface to accelerate and collimate the ions produced at the ablation site, and an Orbitrap mass analyzer capable of discriminating competing isobars via ultrahigh mass resolution and high mass accuracy. The CRATER instrument can measure elemental and isotopic abundances and characterize the organic content of lunar surface samples, as well as identify economically valuable resources for future exploration. Conclusion An engineering test unit of the flight model is currently in development to serve as a pathfinder for near-term mission opportunities.Item Stabilizing Effect of High Pore Fluid Pressure on Fault Growth During Drained Deformation(Wiley, 2023-07-21) Zega, Zachary; Zhu, WenluDilatant hardening is an accepted model for the stabilizing effect of high pore fluid pressure on fault slip and operates when deformation is undrained. To test whether high pore fluid pressure impedes fault propagation under drained conditions, we deformed highly permeable Darley Dale sandstone using strain rates of 10−4 s−1, 10−5 s−1, and 10−6 s−1, respectively. For each strain rate, we compared the inelastic behaviors and faulting styles among rocks deformed under different pore fluid pressures (Pf) (2–180 MPa). The confining pressure (Pc) was attuned to the pore fluid pressure throughout deformation to maintain a constant differential pressure (Pc − Pf) of 10 MPa. In samples deformed at 10−4 s−1 and 10−5 s−1, faulting behaviors were similar regardless of the magnitude of pore fluid pressure. However, when the strain rate was lowered to 10−6 s−1, we observed prolonged stress drops and slower slip velocities in samples deformed under high pore fluid pressures. In samples deformed at 10−6 s−1, we demonstrate that chemically assisted subcritical crack growth played an important role during faulting. A quantitative microstructural analysis revealed that slow faulting at slow strain rates was accompanied by pervasive microcracking and diffuse shear bands, which suggests pervasive subcritical cracking enabled slow faulting under drained conditions at the sample length scale. High pore fluid pressure may have facilitated slow faulting chemically by increasing the rate of subcritical cracking, mechanically via localized dilatant hardening, or both. Our results provide insight into the mechanics of faulting in natural settings where subcritical cracking is prevalent.Item 182W and HSE constraints from 2.7 Ga komatiites on the heterogeneous nature of the Archen mantle(Elsevier, 2018-03-02) Puchtel, I.S.; Blichert-Toft, J.; Touboul, M.; Walker, Richard J.While the isotopically heterogeneous nature of the terrestrial mantle has long been established, the origin, scale, and longevity of the heterogeneities for different elements and isotopic systems are still debated. Here, we report Nd, Hf, W, and Os isotopic and highly siderophile element (HSE) abundance data for the Boston Creek komatiitic basalt lava flow (BCF) in the 2.7 Ga Abitibi greenstone belt, Canada. This lava flow is characterized by strong depletions in Al and heavy rare earth elements (REE), enrichments in light REE, and initial e143Nd = +2.5 ± 0.2 and initial e176Hf = +4.2 ± 0.9 indicative of derivation from a deep mantle source with time-integrated suprachondritic Sm/Nd and Lu/Hf ratios. The data plot on the terrestrial Nd-Hf array suggesting minimal involvement of early magma ocean processes in the fractionation of lithophile trace elements in the mantle source. This conclusion is supported by a mean mu142Nd = -3.8 ± 2.8 that is unresolvable from terrestrial standards. By contrast, the BCF exhibits a positive 182W anomaly (mu182W = +11.7 ± 4.5), yet is characterized by chondritic initial g187Os = +0.1 ± 0.3 and low inferred source HSE abundances (35 ± 5% of those estimated for the present-day Bulk Silicate Earth, BSE). Collectively, these characteristics are unique among Archean komatiite systems studied so far. The deficit in the HSE, coupled with the chondritic Os isotopic composition, but a positive 182W anomaly, are best explained by derivation of the parental BCF magma from a mantle domain characterized by a predominance of HSE-deficient, differentiated late accreted material. According to the model presented here, the mantle domain that gave rise to the BCF received only ~35% of the present-day HSE complement in the BSE before becoming isolated from the rest of the convecting mantle until the time of komatiite emplacement at 2.72 Ga. These new data provide strong evidence for a highly heterogeneous Archean mantle in terms of absolute HSE abundances and W isotopic composition, and also indicate slow mixing, on a timescale of at least 1.8 billion years. Additionally, the data are consistent with a stagnant-lid plate tectonic regime in the Hadean and Archean, prior to the onset of modern-style plate tectonics.