Kathryn S. Kierein-Young

Late-stage formation of Martian chloride salts through ponding and evaporation

Small deposits of chloride salts have been documented at hundreds of locations on Mars through the use of multispectral orbital data. Given the small spatial extent of these deposits, their formation mechanisms, timing, and relation to other aqueous processes in Mars’ history are presently poorly constrained. Here we detail one of the chloride deposits near Meridiani Planum, the location of the Opportunity rover. This chloride deposit likely formed from fluviolacustrine processes, implying an active hydrologic cycle. Late-stage activity led to valley incision in the surrounding highlands and ponding of water to form a lake in a local basin. The lake level eventually rose and breached the drainage divide, leading to significant outflow. The remaining water evaporated and eventually precipitated the chlorides at the lowest levels. Through digital terrain models, the lake and salt flat volumes were used to calculate the salinity of the lake, which at full lake extent was ∼8% of the salinity of Earth’s oceans. Crater density measurements on the terrain cross-cut by the outlet valley constrain the maximum age to 3.60 Ga. This hydrological episode occurred after regional widespread fluvial incision and also post-dates formation of the sulfate bedrock being investigated by Opportunity. We conclude that this and other similar chloride deposits represent some of the last vestiges of habitable surface water on Mars as recorded in the mineralogical record.

The extraction of soil dielectric properties from AIRSAR data

Abstract Complex dielectric constants determined by inversion of the polarized returns of radar images acquired in wet conditions clearly delineate the distribution of saline soils in the Tragowel Plains Irrigation Area of Victoria, Australia. There is good agreement between the areas delineated as having anomalous dielectric constants by the radar backscatter inversion techniques with saline areas as defined by geophysics and as inferred from dielectric constants determined in the field. The radar-determined complex dielectric constants are significantly smaller than might be expected from the known moisture contents of the soils at the time of image acquisition. The magnitudes of P-band radar-delermined dielectric constants most closely approach those expected from field determinations although the distribution of L-band-determined dielectric constants give the best discrimination between saline and non-saline areas as seen at the surface. Modification of the inversion algorithm to allow for the effects...

1999 AIG/HyVista HyMap group shoot: commercial hyperspectral sensing is here

A hyperspectral “group shoot” was conducted during September 1999 by Analytical Imaging and Geophysics (AIG) in cooperation with HyVista Corporation, Sydney, Australia, utilizing HyMap, an advanced 126-band hyperspectral sensor covering the 0.4 - 2.5 micrometer region with 3-10 m spatial resolution. The purpose of this effort was to make high-quality hyperspectral data commercially available to customers for their sites of interest across the United States. Over 200 flightlines of HyMap data were collected throughout the United States for government, academic, and commercial customers. The standard product delivered by AIG/Hy Vista was fully-calibrated radiance data along with precision-geocoded, apparent reflectance spectral image data. This marks the first time that commercial hyperspectral data has been delivered in a standard map-referenced, reflectance-corrected, ready-to-use form. Preliminary work with these datasets has demonstrated unprecedented spectral mapping capabilities for a variety of disciplines, including geology, vegetation studies, environmental assessment, near-shore marine mapping, and military applications. Data were also acquired in support of data simulation efforts the proposed Warfighter and the Australian ARIES hyperspectral satellites. Examples of the 1999 data, a description of the production processing flow, and scientific analysis results are discussed here.

Coiviparison of Landsat Thematic Mapper and Geophysical and Environmental Research Jmaging Spectrometer Data for the Cuprite Mining District, Esmeralda and Nye Counties, Nevada

Landsat TM images and Geophysical and Environmental Research Imaging Spectrometer (GERIS) data were analyzed for the Cuprite mining district and compared to available geologic and alteration maps of the area. The TM data, with 30 m resolution and 6 broadbands, allowed discrimination of general mineral groups. Clay minerals, playa deposits, and unaltered rocks were mapped as discrete spectral units using the TM data, but specific minerals were not determined, and definition of the individual alteration zones was not possible. The GERIS, with 15 m spatial resolution and 63 spectral bands, permitted construction of complete spectra and identification of specific minerals. Detailed spectra extracted from the images provided the ability to identify the minerals alunite, kaolinite, hematite, and buddingtonite by their spectral characteristics. The GERIS data show a roughly concentrically zoned hydrothermal system. The mineralogy mapped with the aircraft system conforms to previous field and multispectral image mapping. However, identification of individual minerals and spatial display of the dominant mineralogy add information that can be used to help determine the morphology and genetic origin of the hydrothermal system.

Extraction of soil dielectric properties from AIRSAR and SIR-C imagery

Complex dielectric constants determined by inversion of the polarized returns of AIRSAR radar images acquired in wet conditions clearly delineate the distribution of saline soils in the Tragowel Plains irrigation area of Victoria, Australia. There is good agreement between the areas delineated as having anomalous dielectric constants by the radar inversion techniques with saline areas as defined by geophysics and determined in the field. The radar-determined complex dielectric constants are significantly smaller than might be expected from the known moisture contents of the soils at the time of image acquisition. The magnitudes of P band radar-determined dielectric constants most closely approach those expected from field determinations although the distribution of L band-determined dielectric constants give the best discrimination between saline and non-saline areas. Modification of the inversion algorithm to allow for the effects of vegetation produces complex dielectric constant magnitudes in the saline regions that are closer to expected values. Variations in the complex dielectric constant derived by inversion of SIR-C imagery acquired under dry conditions is largely a function of soil moisture content. This is closely related to the local recent irrigation history. Inversion of imagery acquired at small incidence angles does not yield meaningful results and it is inferred that this is because the small perturbation model does not apply. The results support the belief that incipient soil salinity can be mapped and monitored by polarimetric radar.