skip to main content
US FlagAn official website of the United States government
dot gov icon
Official websites use .gov
A .gov website belongs to an official government organization in the United States.
https lock icon
Secure .gov websites use HTTPS
A lock ( lock ) or https:// means you've safely connected to the .gov website. Share sensitive information only on official, secure websites.

Explore Research Products in the PAR
It may take a few hours for recently added research products to appear in PAR search results.


Title: A Multi-Technique Analysis of Surface Materials From Blood Falls, Antarctica
Aperiodic discharge of brine at Blood Falls forms a red-tinged fan at the terminus of Taylor Glacier, Antarctica. Samples from this discharge provide an opportunity for mineralogical study at a Martian analogue study site. Environmental samples were collected in the field and analyzed in the laboratory using Fourier transform infrared, Raman, visible to near-infrared, and Mössbauer spectroscopies. Samples were further characterized using microprobe and inductively coupled plasma optical emission spectroscopy for chemistry, and x-ray diffraction, scanning electron microscopy, and transmission electron microscopy for mineralogy, crystallography, and chemistry. The mineralogy of these samples is dominated by the carbonate minerals calcite and aragonite, accompanied by quartz, feldspar, halide, and clay minerals. There is no strong evidence for crystalline iron oxide/hydroxide phases, but compositionally and morphologically diverse iron- and chlorine-rich amorphous nanospheres are found in many of the samples. These results showcase the strengths and weaknesses of different analytical methods and underscore the need for multiple complementary techniques to inform the complicated mineralogy at this locale. These analyses suggest that the red color at Blood Falls arises from oxidation of dissolved Fe 2+ in the subglacial fluid that transforms upon exposure to air to form nanospheres of amorphous hydroxylated mixed-valent iron-containing material, with color also influenced by other ions in those structures. Finally, the results provide a comprehensive mineralogical analysis previously missing from the literature for an analogue site with a well-studied sub-ice microbial community. Thus, this mineral assemblage could indicate a habitable environment if found elsewhere in the Solar System.  more » « less
Award ID(s):
1643687
PAR ID:
10347293
Author(s) / Creator(s):
; ; ; ; ;
Date Published:
Journal Name:
Frontiers in Astronomy and Space Sciences
Volume:
9
ISSN:
2296-987X
Format(s):
Medium: X
Sponsoring Org:
National Science Foundation
More Like this
  1. ; ; ; ; ; ; (, Geosciences)
    Understanding the mineralogy and geochemistry of the subsurface is key when assessing and exploring for mineral deposits. To achieve this goal, rapid acquisition and accurate interpretation of drill core data are essential. Hyperspectral shortwave infrared imaging is a rapid and non-destructive analytical method widely used in the minerals industry to map minerals with diagnostic features in core samples. In this paper, we present an automated method to interpret hyperspectral shortwave infrared data on drill core to decipher major felsic rock-forming minerals using supervised machine learning techniques for processing, masking, and extracting mineralogical and textural information. This study utilizes a co-registered training dataset that integrates hyperspectral data with quantitative scanning electron microscopy data instead of spectrum matching using a spectral library. Our methodology overcomes previous limitations in hyperspectral data interpretation for the full mineralogy (i.e., quartz and feldspar) caused by the need to identify spectral features of minerals; in particular, it detects the presence of minerals that are considered invisible in traditional shortwave infrared hyperspectral analysis. 
    more » « less
  2. ; (, Minerals)
    Climate change induced changes in river flow dynamics have the potential to change the composition of suspended sediments in crucial tropical river ecosystems, possibly affecting their resiliency. This study investigates how changes in river discharge and bedrock lithology affected the physiochemical nature of river suspended sediments over a typical year in three Puerto-Rican rivers. Suspended sediment samples were collected on filter membranes in 2006 from three watersheds of differing lithology (quartz-diorite, volcaniclastic, and mixed lithology) in the Luquillo Mountains, Puerto-Rico. By monitoring changes in suspended sediment mineralogical composition (determined by XRD and SEM) as a function of discharge, we determined how sediment loads responded to changes in hydrological input in a typical year. Results showed that bedrock lithology influenced river suspended sediment mineralogy, with the fraction of crystalline versus amorphous material strongly influenced by the dominant lithology of the watershed. Crystalline phases were associated with granodiorite bedrock compared to amorphous material dominating the volcaniclastic watersheds. Thus, the mineralogy of suspended sediments in the river systems was controlled by secondary minerals. Mineralogical results showed that, bearing quantitative changes upon hydrological events, suspended sediments in all three watersheds returned to baseline composition post storm events, suggesting that the three watersheds are resilient to the events recorded that year. While the long-term mineralogical analysis of the evolution of suspended material in the studied rivers provided insights into river response to hydrologic events, it also proved technically challenging as materials in suspension in such pristine rivers are sparse and poorly crystalline. 
    more » « less
  3. ; ; ; ; ; (, The Planetary Science Journal)
    Abstract The Chemistry and Mineralogy X-ray diffraction (XRD) instrument aboard the Curiosity rover consistently identifies amorphous material at Gale Crater, which is compositionally variable, but often includes elevated sulfur and iron, suggesting that amorphous ferric sulfate (AFS) may be present. Understanding how desiccating ferric sulfate brines affect the spectra of Martian material analogs is necessary for interpreting complex/realistic reaction assemblages. Visible and near-infrared reflectance (VNIR), mid-infrared attenuated total reflectance (MIR, FTIR-ATR), and Raman spectra, along with XRD data are presented for basaltic glass, hematite, gypsum, nontronite, and magnesite, each at three grain sizes (<25, 25–63, and 63–180μm), mixed with ferric sulfate (+/−NaCl), deliquesced, then rapidly desiccated in 11% relative humidity or via vacuum. All desiccated products are partially or completely XRD amorphous; crystalline phases include starting materials and trace precipitates, leaving the bulk of the ferric sulfate in the amorphous fraction. Due to considerable spectral masking, AFS detectability is highly dependent on spectroscopic technique and minerals present. This has strong implications for remote and in situ observations of Martian samples that include an amorphous component. AFS is only identifiable in VNIR spectra for magnesite, nontronite, and gypsum samples; hematite and basaltic glass samples appear similar to pure materials. Sulfate features dominate Raman spectra for nontronite and basaltic glass samples; the analog material dominates Raman spectra of hematite and gypsum samples. MIR data are least affected by masking, but basaltic glass is almost undetectable in MIR spectra of those mixtures. NaCl produces similar FTIR-ATR and Raman features, regardless of analog material. 
    more » « less
  4. ; ; (, Proceedings of the International Ocean Discovery Program)
    null (Ed.)
    International Ocean Discovery Program Expedition 369 recovered a volcanic sequence (Lithostratigraphic Unit VI) at Site U1513 on the eastern Naturaliste Plateau, offshore southwest Australia. We report here the mineralogical composition of the 82.2 m thick volcanic sequence cored in Holes U1513D (24 samples) and U1513E (20 samples) based on X-ray diffraction analysis. The primary minerals preserved in basalt flows and dolerite dikes are plagioclase feldspar and pyroxene, whereas the original olivines have been mostly transformed into secondary phases. Increasing alteration intensity is accompanied by higher amounts of clay minerals (chlorite, kaolinite, interstratified smectite-chlorite, and smectite), iron oxides (magnetite, hematite, and goethite), and likely other secondary minerals associated with serpentinization and sericitization processes. The fine-grained matrix of the volcaniclastic beds contains abundant clay minerals (mainly kaolinite) accompanied by intense hematization. 
    more » « less
  5. ; ; (, Environmental Data Initiative)
    In the Baltimore urban long-term ecological research (LTER) project, (Baltimore Ecosystem Study, BES) we use the watershed approach to evaluate integrated ecosystem function. The LTER research is centered on the Gwynns Falls watershed, a 17,150 ha catchment that traverses a gradient from the urban core of Baltimore, through older urban residential (1900 - 1950) and suburban (1950- 1980) zones, rapidly suburbanizing areas and a rural/suburban fringe. Our long-term sampling network includes four longitudinal sampling sites along the Gwynns Falls as well as several small (40 - 100 ha) watersheds located within or near to the Gwynns Falls. The longitudinal sites provide data on water and nutrient fluxes in the different land use zones of the watershed (rural/suburban, rapidly suburbanizing, old suburban, urban core) and the small watersheds provide more focused data on specific land use areas (forest, agriculture, rural/suburban, urban). Each of the gaging sites is continuously monitored for discharge and is sampled weekly for chemistry. Additional chemical sampling is carried out in a supplemental set of sites to provide a greater range of land use. Weekly analyses includes nitrate, phosphate, total nitrogen, total phosphorus, chloride and sulfate, total suspended solids, turbidity, fecal coliforms, temperature, dissolved oxygen and pH. Cations, dissolved organic carbon and nitrogen and metals are measured on selected samples. This dataset presents stream chemistry from the Upper Gwynns Falls tributaries. From April 1999 to August 2000 Johns Hopkins University graduate student Mark Colosimo sampled a group of sites in the Upper Gwynns Falls (Red Run, Horsehead Branch, Scotts Level Branch, Holly Branch). There were two sites in the Red Run drainage. This watershed drains approximately 19 km2 and has been rapidly suburbanizing since the early 1990s. Percent impervious surface was approximately 10% as of 2002. Sampling station Red Run 1 (RR1) was approximately 35 m upstream of the crossing of Painters Mill Bridge Road, and 350 m upstream of the confluence with the Gwynns Falls. Sampling station Red Run 2 (RR2) was farther upstream, between the Pleasant Hill and Dolfield road crossings. There were two sites along Scotts Level Branch, an older suburban watershed which was approximately 25% impervious surface in 1970. Site SL1 drains approximately 11 km2 and is located at the outlet of the sub-watershed, just above the confluence with Gwynns Falls. Site SL2 is at the McDonogh Rd. bridge crossing. The Horsehead Branch (HH) sampling site was located at the McDonogh Road crossing. It drains approximately 5 km2 that has undergone rapid urbanization since the mid 1980s. As of 1997 percent impervious surface was approximately 12%. The Holly Bank (HB) sampling site was located just upstream of Gwynnbrook Ave. Seventy percent of land in this drainage is classified residential. The Gwynns Falls at McDonogh (GF5) site was located at the McDonogh school / McDonogh road crossing of the Gwynns Falls and samples a drainage area of approximately 51 km2, with approximately 20% impervious surface. 
    more » « less
  • Citation Formats
  • MLA
  • APA
  • Chicago
  • BibTeX
  • Save / Share this Record
  • Send to Email