Humidity-induced phase transitions of ferric sulfate minerals studied by in situ and ex situ X-ray diffraction

Phases encountered in the hydration of monoclinic and trigonal anhydrous Fe2(SO4)3 and evaporation of Fe2(SO4)3 solutions at room temperature were determined using in situ and ex situ X-ray diffraction (XRD) under dynamic relative humidity (RH) control at room temperature (22–25 °C). Both monoclinic and trigonal forms of Fe2(SO4)3 remain anhydrous at 11% RH or below, and undergo the following phase evolution sequence: anhydrous Fe2(SO4)3 → (ferricopiapite, rhomboclase) → kornelite → paracoquimbite at RH between 33 and 53% as a function of time. Evaporation of aqueous Fe2(SO4)3 solutions at 40% < RH < 60% results in precipitation of ferricopiapite and rhomboclase during evaporation, followed by a transition to kornelite and then paracoquimbite. Evaporation at RH < 33% produced an amorphous ferric-sulfate phase. The presence of some iron sulfate hydrates and their stability under varying RH are not only determined by the final humidity level, but also the intermediate stages and hydration history (i.e., either ferricopiapite or paracoquimbite can be a stable phase at 62% RH depending on the hydration history). The sensitivity to humidity change and path-dependent transitions of ferric sulfates make them potentially valuable indicators of paleo-environmental conditions and past water activity on Mars. The phase relationships reported herein can help in understanding the diagenesis of ferric sulfate minerals, and are applicable to geochemical modeling of mineral solubility in multi-component systems, an endeavor hindered by the need for fundamental laboratory studies of iron sulfate hydrates

Sulfate Deposition in Regolith Exposed in Trenches on the Plains Between the Spirit Landing Site and Columbia Hills in Gusev Crater, Mars

During its exploration within Gusev crater between sol 01 and sol 158, the Spirit rover dug three trenches (Fig. 1) to expose the subsurface regolith [1, 2, 9]. Laguna trench (approx. 6 cm deep, approx.203 m from the rim of Bonneville crater) was dug in Laguna Hollow at the boundary of the impact ejecta from Bonneville crater and the surrounding plains. The Big Hole trench (approx. 6-7 cm deep) and The Boroughs trench (approx. 11 cm deep) were dug in the plains between the Bonneville crater and the Columbia Hills (approx.556 m and approx.1698 m from the rim of Bonneville crater respectively). The top, wall and floor regolith of the three trenches were investigated using the entire set of Athena scientific instruments [10]

Study of the possible usage of infrared photographic mapping to evaluate cultivated areas in Jardinopolis, SP

There are no author-identified significant results in this report

In-Situ and Experimental Evidence for Acidic Weathering of Rocks and Soils on Mars

Experimental data for alteration of synthetic Martian basalts at pH=0-1 indicate that chemical fractionations at low pH are vastly different from those observed during terrestrial weathering. Rock analyses from Gusev crater are well described by the relationships apparent from low pH experimental alteration data. A model for rock surface alteration is developed which indicates that a leached alteration zone is present on rock surfaces at Gusev. This zone is not chemically fractionated to a large degree from the underlying rock interior, indicating that the rock surface alteration process has occurred at low fluid-to-rock ratio. The geochemistry of natural rock surfaces analyzed by APXS is consistent with a mixture between adhering soil/dust and the leached alteration zone. The chemistry of rock surfaces analyzed after brushing with the RAT is largely representative of the leached alteration zone. The chemistry of rock surfaces analyzed after grinding with the RAT is largely representative of the interior of the rock, relatively unaffected by the alteration process occurring at the rock surface. Elemental measurements from the Spirit, Opportunity, Pathfinder and Viking 1 landing sites indicate that soil chemistry from widely separated locations is consistent with the low-pH, low fluid to rock ratio alteration relationships developed for Gusev rocks. Soils are affected principally by mobility of FeO and MgO, consistent with alteration of olivine-bearing basalt and subsequent precipitation of FeO and MgO bearing secondary minerals as the primary control on soil geochemistry

Human-Computer Interaction and the Future ofWork

Advances in computing technology, changing policies, and slow crises are rapidly changing the way we work. Human-computer interaction (HCI) is a critical aspect of these trends, to understand how workers contend with emerging technologies and how design might support workers and their values and aspirations amidst technological change. This SIG invites HCI researchers across diverse domains to reflect on the range of approaches to future of work research, recognize connections and gaps, and consider how HCI can support workers and their wellbeing in the future

Stratigraphic evolution of the Neoproterozoic Callison Lake Formation: Linking the break-up of Rodinia to the Islay carbon isotope excursion

The ∼780 to 540 Ma Windermere Supergroup of western North America records the protracted development of the western Laurentian passive margin and provides insights into the nature, timing, and kinematics of Rodinia's fragmentation. Here we present a refined tectono- and chemo-stratigraphic model for circa 780 to 720 Ma sedimentation in NW Canada through a study of the Callison Lake Formation (formalized herein) of the Mount Harper Group, spectacularly exposed in the Coal Creek and Hart River inliers of the Ogilvie Mountains of Yukon, Canada. Twenty-one stratigraphic sections are integrated with geological mapping, facies analysis, carbon and oxygen isotope chemostratigraphy, and Re-Os geochronology to provide a depositional reconstruction for the Callison Lake Formation. Mixed siliciclastic, carbonate, and evaporite sediments accumulated in marginal marine embayments formed in discrete hangingwall depocenters of a prominent Windermere extensional fault zone. Deposition of the Windermere Supergroup in NW Canada post dates the eruption of the circa 780 Ma Gunbarrel Large Igneous Province by ∼30 million years, is locally associated with compressional or transpressional tectonism, and predates the successful rift-drift transition by ∼200 million years. In order to accommodate evidence for coeval extensional and compressional tectonism, abrupt facies change, and Neoproterozoic fault geometries, we propose that NW Laurentia experienced strike-slip deformation during the ∼740 to 660 Ma early fragmentation of the supercontinent Rodinia. Sequence stratigraphic data from the Callison Lake Formation and other basal Windermere successions in the northern Canadian Cordillera delineate three distinct depositional sequences, or transgressive-regressive (T-R) cycles, that are coeval with similar stratigraphic packages in the ∼780 to 720 Ma Chuar-Uinta Mountain-Pahrump basins of the western United States. The global circa 735 Ma Islay carbon isotope excursion is consistently present in carbonate strata of the third T-R cycle and is interpreted to represent a primary perturbation to the global carbon cycle, possibly driven by the uplift and weathering of extensive shallow epicontinental seaways and evaporite basins.Earth and Planetary Science

Sulfate deposition in subsurface regolith in Gusev crater, Mars

Excavating into the shallow Martian subsurface has the potential to expose stratigraphic layers and mature regolith, which may hold a record of more ancient aqueous interactions than those expected under current Martian surface conditions. During the Spirit rover&rsquo;s exploration of Gusev crater, rover wheels were used to dig three trenches into the subsurface regolith down to 6&ndash;11 cm depth: Road Cut, the Big Hole, and The Boroughs. A high oxidation state of Fe and high concentrations of Mg, S, Cl, and Br were found in the subsurface regolith within the two trenches on the plains, between the Bonneville crater and the foot of Columbia Hills. Data analyses on the basis of geochemistry and mineralogy observations suggest the deposition of sulfate minerals within the subsurface regolith, mainly Mg-sulfates accompanied by minor Ca-sulfates and perhaps Fe-sulfates. An increase of Fe2O3, an excess of SiO2, and a minor decrease in the olivine proportion relative to surface materials are also inferred. Three hypotheses are proposed to explain the geochemical trends observed in trenches: (1) multiple episodes of acidic fluid infiltration, accompanied by in situ interaction with igneous minerals and salt deposition; (2) an open hydrologic system characterized by ion transportation in the fluid, subsequent evaporation of the fluid, and salt deposition; and (3) emplacement and mixing of impact ejecta of variable composition. While all three may have plausibly contributed to the current state of the subsurface regolith, the geochemical data are most consistent with ion transportation by fluids and salt deposition as a result of open-system hydrologic behavior. Although sulfates make up &gt;20 wt.% of the regolith in the wall of The Boroughs trench, a higher hydrated sulfate than kieserite within The Boroughs or a greater abundance of sulfates elsewhere than is seen in The Boroughs wall regolith would be needed to hold the structural water indicated by the water-equivalent hydrogen concentration observed by the Gamma-Ray Spectrometer on Odyssey in the Gusev region

Severe leukocytoclastic vasculitis secondary to the use of a naproxen and requiring amputation: a case report

<p>Abstract</p> <p>Introduction</p> <p>Leukocytoclastic vasculitis (also known as hypersensitivity vasculitis and cutaneous necrotizing vasculitis) can present with various manifestations, which often delays the diagnosis and treatment. In order to show the importance of the early recognition of leukocytoclastic vasculitis, we present a case which occurred secondary to the use of a common pharmaceutical, naproxen. We were unable to find a case of leukocytoclastic vasculitis secondary to naproxen in the literature.</p> <p>Case presentation</p> <p>We present the case of a 33-year-old African American woman with below the knee and bilateral digital gangrene from hypersensitivity vasculitis secondary to the non-steroidal anti-inflammatory medication naproxen.</p> <p>Conclusion</p> <p>This is an original case report focusing on the rheumatologic management of leukocytoclastic vasculitis. However, other specialties, such as internal medicine, dermatology, infectious disease, general surgery and pathology, can gain valuable information by reviewing this case report. Reporting a case of leukocytoclastic vasculitis secondary to treatment with naproxen will advance our understanding of this disease etiology by adding yet another non-steroidal anti-inflammatory drug to the list of potential causes of leukocytoclastic vasculitis.</p

Using the Abitibi Greenstone Belt to Understand Martian Hydrothermal Systems and the Potential for Biosignature Preservation in High Temperature Aqueous Environments

Metabolic bone diseases like osteoporosis result from the disruption of normal bone mineral balance (BMB) resulting in bone loss. During spaceflight astronauts lose substantial bone. Bed rest provides an analog to simulate some of the effects of spaceflight; including bone and calcium loss and provides the opportunity to evaluate new methods to monitor BMB in healthy individuals undergoing environmentally induced-bone loss. Previous research showed that natural variations in the Ca isotope ratio occur because bone formation depletes soft tissue of light Ca isotopes while bone resorption releases that isotopically light Ca back into soft tissue (Skulan et al, 2007). Using a bed rest model, we demonstrate that the Ca isotope ratio of urine shifts in a direction consistent with bone loss after just 7 days of bed rest, long before detectable changes in bone mineral density (BMD) occur. The Ca isotope variations tracks changes observed in urinary N-teleopeptide, a bone resorption biomarker. Bone specific alkaline phosphatase, a bone formation biomarker, is unchanged. The established relationship between Ca isotopes and BMB can be used to quantitatively translate the changes in the Ca isotope ratio to changes in BMD using a simple mathematical model. This model predicts that subjects lost 0.25 +/- 0.07% (+/- SD) of their bone mass from day 7 to day 30 of bed rest. Given the rapid signal observed using Ca isotope measurements and the potential to quantitatively assess bone loss; this technique is well suited to study the short-term dynamics of bone metabolism