Color-ratio Images Research Articles

Io Hot Spot Distribution Detected by Juno/JIRAM

AbstractIn this work, we present the most updated catalog of Io hot spots based on Juno/JIRAM data. We find 242 hot spots, including 23 previously undetected. Over the half of the new hot spots identified, are located at high northern and southern latitudes (>70°). We observe a latitudinal variability and a larger concentration of hot spots in the polar regions, in particular in the North. The comparison between JIRAM and the most recent Io hot spot catalogs listing power output (Veeder et al., 2015, https://doi.org/10.1016/j.icarus.2014.07.028; de Kleer, de Pater, et al., 2019, https://doi.org/10.3847/1538-3881/ab2380), shows JIRAM detected 63% and 88% of the total number of hot spots, respectively. Furthermore, JIRAM observed 16 of the 34 faint hot spots previously identified. JIRAM data revealed thermal emission from 5 dark pateræ inferred to be active from color ratio images, thus confirming that these are hot spots.

Geologic mapping of the Urvara and Yalode Quadrangles of Ceres

We conducted geologic mapping of the Urvara (Ac-13) and Yalode (Ac-14) Quadrangles (21–66°S, 180–360°E) of the dwarf planet Ceres utilizing morphologic, topographic, and compositional information acquired by NASA's Dawn mission. The geologic characteristics of the two large impact basins Urvara (170 km diameter) and Yalode (260 km diameter) and their surroundings were investigated using Dawn Framing Camera datasets, including Survey (415 m/pixel), HAMO (140 m/pixel), and LAMO (35 m/pixel) images and mosaics, color and color ratio images, and DTMs derived from stereo-photogrammetry. Geologic mapping demonstrates that impact cratering has dominated the geologic history of the Urvara and Yalode Quadrangles, with early cratered terrain formation followed by formation of the large basins and widespread emplacement of basin-related smooth material. Impact craters display a wide range of preservation states from nearly completely buried/degraded forms to more recent pristine craters with terraced inner walls and lobate ejecta deposits. Cross-cutting relationships and morphologic signatures show that the Urvara impact followed the Yalode impact, consistent with ages derived from crater size-frequency distributions (580 ± 40 Ma for Yalode and 550 ± 50 Ma for Urvara). Observed differences in basin materials and rim morphology suggest heterogeneities in the substrate excavated by impact. Smooth deposits that cover large areas of the quadrangles, including the basin floors, rims, and exterior zones, are interpreted to be dominated by Urvara ejecta but Yalode ejecta and localized ice-rich flow material may be minor components. Geologic mapping results and simulations of ejecta emplacement suggest that Urvara and Yalode ejecta deposits extend for large distances (more than two crater diameters from the basin centers) and may serve as important stratigraphic markers for the geologic record of Ceres.

Phase-ratio imaging as applied to desert sands for tracking human presence.

The phase function is a measure of the light-scattered intensity, or radiance, as a function of scattering angle θ. A phase ratio is the ratio of two values of the phase function measured at different scattering angles and relates to the slope of the phase function. By taking the ratio of two images acquired at different illumination or observation conditions, a phase-ratio image can be constructed. Such images accentuate differences in the phase curves, rather than their intensities, and are more sensitive to microtopography than to material properties. We produce phase-ratio images from intensity images acquired at different observation times and locations in the desert environment of White Sands National Monument. Because of the lack of surface features, coregistration of the images is challenging, especially for images acquired from different observation locations. However, we do demonstrate that phase-ratio images can be used to identify disturbed sands. We also produce polarimetric and color-ratio images. These latter images do not suggest the possibility of identifying topographical differences due to human presence.

Integration of Geological Mapping and Remote Sensed Studies for the Discovery of Iron–Ore Mineralization in Mutomo–Ikutha Area, SE Kenya

This research integrates geology with remote sensing techniques to establish characteristic features that can be used to discover iron ore mineralization within the Neoproterozoic rocks of Mutomo - Ikutha area in south eastern Kenya. The association of hornblende gneiss and shearing as well as alteration processes near the mineralized regions appear to play an important role in the distribution and localization of the iron mineralization The methods used in this research include Image processing techniques applied on the digital subset ETM+ data that cover Mutomo - Ikutha area and geological field mapping. These techniques generated several products of enhanced satellite imagery, such as colour composite images, ratio images and principal component images. These techniques have been successfully used in the lithological discrimination of iron ore bearing sheared hornblende gneisses. The capabilities of remote sensing data to characterize the iron ore bearing gneisses, in addition to characterization and mapping the hydrothermal alteration zones helped in identification of iron mineralization regions. Extensive field geologic and geochemical investigations to the pronounced zones delineated by the image processing technique, led to discovery of four locations of high iron anomalies with some iron mineralization, mainly connected to the studied Neoproterozoic hornblende gneisses. Chemical studies were carried out using atomic absorption spectrophotometer (AAS) and X-Ray florescence, for some selected mineralized samples. Petrographic analysis and physical properties of the iron minerals were carried out as well. These investigations confirm the present iron mineral to be magnetite ore enriched with phosphates. The magnetite is found in close association with apatite chalcopyrite, quartz, and chlorite. Relics of corroded magnetite grains are occur along the Tiva river bed as well as along the road sides.

Digital Image Processing and Analysis Techniques for Detection of Hydrothermal Alteration Zones: A Case Study in Siah-Jangal Area, North of Taftan Volcano, Southeastern Iran

Hydrothermal alteration zones have significant role in prospecting of porphyry mineral deposits. In this research, Image processing techniques were applied on the digital subset ETM + data covered the Siah-Jangal area. These techniques generated several products of enhanced satellite imagery, such as colour composite images, ratio images and principal component analysis images. These techniques have been successfully used in mapping of hydrothermal alteration and mineralization zones in the study area. The colour composite and band ratio methods show very clearly the hydrothermal altered zones of clay minerals and iron oxides in and around the Siah-Jangal area. The principal component analysis using the Crosta technique also enabled us to represent undoubtedly the altered hydroxyl and iron-oxide mineral zones as well. The Crosta method has been used on selected 6 (standard method of PCA), 4 and 3 bands. There is no significant difference of the hydroxyl images in the Band ratio and PC methods. But the best results, in terms of mapping the distribution of iron oxide alteration, were obtained using the band ratio and Crosta methods on 3 bands. The results indicate that methods is promising for identifying alteration zones and can assist exploration geologists to find new prospects of porphyry copper and gold deposits in the other virgin regions before costly detailed ground investigations.

Geologic mapping of ejecta deposits in Oppia Quadrangle, Asteroid (4) Vesta

Oppia Quadrangle Av-10 (288–360°E, ±22°) is a junction of key geologic features that preserve a rough history of Asteroid (4) Vesta and serves as a case study of using geologic mapping to define a relative geologic timescale. Clear filter images, stereo-derived topography, slope maps, and multispectral color-ratio images from the Framing Camera on NASA’s Dawn spacecraft served as basemaps to create a geologic map and investigate the spatial and temporal relationships of the local stratigraphy. Geologic mapping reveals the oldest map unit within Av-10 is the cratered highlands terrain which possibly represents original crustal material on Vesta that was then excavated by one or more impacts to form the basin Feralia Planitia. Saturnalia Fossae and Divalia Fossae ridge and trough terrains intersect the wall of Feralia Planitia indicating that this impact basin is older than both the Veneneia and Rheasilvia impact structures, representing Pre-Veneneian crustal material. Two of the youngest geologic features in Av-10 are Lepida (∼45km diameter) and Oppia (∼40km diameter) impact craters that formed on the northern and southern wall of Feralia Planitia and each cross-cuts a trough terrain. The ejecta blanket of Oppia is mapped as ‘dark mantle’ material because it appears dark orange in the Framing Camera ‘Clementine-type’ color-ratio image and has a diffuse, gradational contact distributed to the south across the rim of Rheasilvia. Mapping of surface material that appears light orange in color in the Framing Camera ‘Clementine-type’ color-ratio image as ‘light mantle material’ supports previous interpretations of an impact ejecta origin. Some light mantle deposits are easily traced to nearby source craters, but other deposits may represent distal ejecta deposits (emplaced >5 crater radii away) in a microgravity environment.

Io: Heat flow from small volcanic features

We identify nine new faint thermal sources on Io via color ratio images constructed from relatively high spatial resolution Galileo NIMS data acquired late in the mission. All of these identifications are associated with small dark paterae. We utilize NIMS data to quantify their volcanic thermal emission as ∼0.53×1012W (or ∼0.5% of Io’s total heat flow). In addition, we refine our previous estimates of the thermal emission from 47 hot spots and highlight several hot spots within the Amirani flow field.Small dark paterae still out-number faint (close to the limit of detection) hot spots identified in high spatial resolution multi-wavelength NIMS data. In particular, we point out 24 small dark paterae that were scanned by NIMS (at resolutions down to ∼17km/pixel) but had no detectable volcanic thermal emission. All dark paterae are expected to have some volcanic thermal emission, but the small size and finite number of detectable faint sources limit their contribution to the total heat flow on Io. Compared to small paterae, small dark flows are more numerous but must have significantly lower surface temperatures.Finally, we update and summarize our results for the global heat flow on Io due to 242 recently active volcanic features including other dark paterae as well as large dark flows. The volcanic thermal emission from known hot spots, undetected (scanned) dark patera and outbursts can account for only ∼56.2×1012W (or ∼54%) of Io’s total heat flow. Approximately 49×1012W (or ∼46%) of Io’s heat flow remains an enigma.

Alteration mineral mapping with ASTER data by integration of coded spectral ratio imaging and SOM neural network model

This study applied coded spectral ratio imaging and a self-organizing map (SOM) neural network model for subpixel classification of Advanced Spaceborne Thermal Emission and Reflection Radiometer (ASTER) data to map alteration minerals of the Masahim volcano, SE Iran. Spectra of samples were measured using a FieldSpec spectroradiometer, and were interpreted for finding key alteration minerals. Key minerals including sericite and kaolinite were selected. Thirty-six nonreciprocal spectral ratios of 9 ASTER reflective bands were created. Each spectral parameter (of 9 spectral bands and 36 spectral ratios) for the field and library mineral spectra was divided into deciles. Each decile of spectral bands or ratios was labeled from 9 for the highest down to 0 for the lowest decile. Spectral ratio code signature patterns of field samples were then compared to the US Geological Survey (USGS) spectral library to find 3 spectral ratio images for each key mineral. Based on these 3 ratio images, color ratio images were created and training areas were selected by a geographic information systems (GIS) overlay approach and were used to train the SOM model. This model was applied to the 5, 15, and 36 ratio image data sets as chemical composition images, and the results were compared using confusion matrices and coefficient of determination (R2). The results of SOM applied to 15 and 36 ratio image data sets showed good identification of key minerals. We achieved overall accuracies of 87% for SOM applied to the 36 ratio images, 86% for 15, and 85% for 5 ratio image data sets. The R2 produced from 15 ratio image data sets for sericite and kaolinite were 0.35 and 0.52, whereas they were 0.64 and 0.68, for 36 ratio image data sets. It was concluded that using SOM applied to ratio images could, therefore, be useful in alteration mapping of a volcano.

Olivine or impact melt: Nature of the “Orange” material on Vesta from Dawn

NASA’s Dawn mission observed a great variety of colored terrains on asteroid (4) Vesta during its survey with the Framing Camera (FC). Here we present a detailed study of the orange material on Vesta, which was first observed in color ratio images obtained by the FC and presents a red spectral slope. The orange material deposits can be classified into three types: (a) diffuse ejecta deposited by recent medium-size impact craters (such as Oppia), (b) lobate patches with well-defined edges (nicknamed “pumpkin patches”), and (c) ejecta rays from fresh-looking impact craters. The location of the orange diffuse ejecta from Oppia corresponds to the olivine spot nicknamed “Leslie feature” first identified by Gaffey (Gaffey, M.J. [1997]. Icarus 127, 130–157) from ground-based spectral observations. The distribution of the orange material in the FC mosaic is concentrated on the equatorial region and almost exclusively outside the Rheasilvia basin. Our in-depth analysis of the composition of this material uses complementary observations from FC, the visible and infrared spectrometer (VIR), and the Gamma Ray and Neutron Detector (GRaND). Several possible options for the composition of the orange material are investigated including, cumulate eucrite layer exposed during impact, metal delivered by impactor, olivine–orthopyroxene mixture and impact melt. Based on our analysis, the orange material on Vesta is unlikely to be metal or olivine (originally proposed by Gaffey (Gaffey, M.J. [1997]. Icarus 127, 130–157)). Analysis of the elemental composition of Oppia ejecta blanket with GRaND suggests that its orange material has ∼25% cumulate eucrite component in a howarditic mixture, whereas two other craters with orange material in their ejecta, Octavia and Arruntia, show no sign of cumulate eucrites. Morphology and topography of the orange material in Oppia and Octavia ejecta and orange patches suggests an impact melt origin. A majority of the orange patches appear to be related to the formation of the Rheasilvia basin. Combining the interpretations from the topography, geomorphology, color and spectral parameters, and elemental abundances, the most probable analog for the orange material on Vesta is impact melt.

Spectral heterogeneity on Phobos and Deimos: HiRISE observations and comparisons to Mars Pathfinder results

The High-Resolution Imaging Science Experiment (HiRISE) onboard Mars Reconnaissance Orbiter (MRO) has been used to observe Phobos and Deimos at spatial scales of around 6 and 20m/px, respectively. HiRISE (McEwen et al., JGR, 112, CiteID E05S02, DOI: 10.1029/2005JE002605, 2007) has provided, for the first time, high-resolution colour images of the surfaces of the Martian moons. When processed, by the production of colour ratio images for example, the data show considerable small-scale heterogeneity, which might be attributable to fresh impacts exposing different materials otherwise largely hidden by a homogenous regolith. The bluer material that is draped over the south-eastern rim of the largest crater on Phobos, Stickney, has been perforated by an impact to reveal redder material and must therefore be relatively thin. A fresh impact with dark crater rays has been identified. Previously identified mass-wasting features in Stickney and Limtoc craters stand out strongly in colour. The interior deposits in Stickney appear more inhomogeneous than previously suspected. Several other local colour variations are also evident.Deimos is more uniform in colour but does show some small-scale inhomogeneity. The bright “streamers” (Thomas et al., Icarus, 123, 536–556,1996) are relatively blue. One crater to the south-west of Voltaire and its surroundings appear quite strongly reddened with respect to the rest of the surface. The reddening of the surroundings may be the result of ejecta from this impact.The spectral gradients at optical wavelengths observed for both Phobos and Deimos are quantitatively in good agreement with those found by unresolved photometric observations made by the Imager for Mars Pathfinder (IMP; Thomas et al., JGR, 104, 9055–9068, 1999). The spectral gradients of the blue and red units on Phobos bracket the results from IMP.

Interpretation and processing of ASTER data for geological mapping and granitoids detection in the Saghro massif (eastern Anti-Atlas, Morocco)

Satellite remote sensing analysis is extensively used for geological mapping in arid regions. However, it is not considered readily applicable to the mapping of metamorphic and igneous terrains, where lithological contacts are less predictable. In this work, ASTER (Advanced Spaceborne Thermal Emission and Reflection Radiometer) data were used to clarify the geological framework of the Precambrian basement in the Saghro massif (eastern Anti-Atlas, Morocco). The Saghro basement is composed of low-grade metasedimentary sequences of the Saghro Group (Cryogenian), intruded by calc-alkaline plutons of late Cryogenian age. These rocks are unconformably covered by volcanic to volcaniclastic series of Ediacaran age that are broadly coeval with granitoid plutons. All of these units are cut by a complex network of faults associated with hydrothermal fluid flows, which developed during and shortly after the emplacement of the volcanic rocks. The geological mapping of the Precambrian units was challenging in particular for the Edicaran granitoid bodies, because they are characterized by very similar compositions and a widespread desert varnish coating. For this reason, a two-stage approach has been adopted. In the first step, false color composites, band ratios, and principal components analyses on visible and near infrared (VNIR) and shortwave infrared (SWIR) bands were chosen and interpreted on the basis of the field and petrographic knowledge of the lithologies in order to detect major lithological contacts and mineralized faults. In the second step, a major effort was dedicated to the detection of granitoid plutons using both thermal infrared (TIR) and VNIR/SWIR data. The ASTER TIR bands were used to evaluate Reststrahlen and Christiansen effects in the granitoid rocks spectra, whereas VNIR/SWIR false color composite and ratio images were chosen directly on the basis of the granitoid spectra (derived from both spectrophotometric analyses of samples and selected sites in the ASTER image). Finally, spectral angle mapper (SAM) and supervised maximum-likelihood classifications (MLL) were carried out on VNIR/SWIR data, mainly to evaluate their potential for discriminating granitoid rocks. The results have further demonstrated the value of ASTER data for geological mapping of basement units, particularly if the processing has been based on a detailed knowledge of the rock mineral assemblages. In addition, the analytical comparison of ASTER TIR and VNIR/SWIR data has demonstrated that the latter are very effective in the distinction of granitoids with very similar silica content, because they can be recognized by secondary effects related to their hydrothermal and surface alterations (K-feldspar kaolinitization, plagioclase saussiritization, substitution of mafic minerals with oxides, inhomogeneous desert varnish coating, and clay/oxide proportions).

Multispectral polarimetry as a tool to investigate texture and chemistry of lunar regolith particles

We report results of telescope polarimetric imaging of the Moon with a CCD LineScan Camera at large phase angles, near 88°. This allows measurements of the polarization degree with an absolute accuracy better than 0.3% and detection of features with polarization contrast as small as 0.1%. The measurements are carried out in two spectral bands centered near 0.65 and 0.42 μm. We suggest characterizing the lunar regolith with the parameter ( P max ) a A , where P max , A , and a are the degree of maximum polarization, albedo, and the parameter describing the linear regression of the correlation P max – A . The parameter bears significant information on the particle characteristic size and packing density of the lunar regolith. We also suggest characterizing the lunar regolith with color-ratio images obtained with a polarization filter at large phase angles. We here consider the color-ratios C | | ( 0.65 / 0.42 μm ) and C ⊥ ( 0.65 / 0.42 μm ) . Using light scattering model calculations we show that the color-ratio images obtained with a polarization filter at large phase angles suggest a new tool to study the lunar surface. In particular, it turns out that the color-ratios C | | ( 0.65 / 0.42 μm ) and C ⊥ ( 0.65 / 0.42 μm ) are sensitive to somewhat different thicknesses of the surfaces of regolith particles. We consider the applicability of the Hubble Space Telescope, the Very Large Telescope (ESO), and a spacecraft on a lunar polar orbit for polarimetric observations of the lunar surface.

Compositional Variability of the Serenitatis/Tranquillitatis Region of the Moon from Telescopic Multispectral Imaging and Spectroscopy

We present results from a combined CCD multispectral imaging and near-IR spectroscopic study of a region near the border between the Mare Serenitatis and Mare Tranquillitatis lunar impact basins. We have detected and spatially mapped variations in mare TiO2 abundance, in the degree of spectral maturity of impact craters and their ejecta blankets, and in the level of fresh highlands contamination within mare units. Techniques employed include color ratio images, image-oriented linear mixing models, and spectral band analyses. Specific findings include the detection of relatively fresh highlands materials in the craters Tacquet and Sulpicius Gallus and in the central peak and floor of the crater Plinius, the detection of low-TiO2 Serenitatis-like mare materials in a confined region of the ejecta from the crater Dawes, and the determination of immaturity rather than composition as the origin of the high albedo in the rectangular deposit surrounding Dawes. The combination of high spatial resolution imaging and high spectral resolution spectroscopy and the use of synthesizing techniques such as mixture modeling will provide valuable tools to optimize the scientific return from telescopic, Galileo, Clementine, and other future lunar data sets.

Discriminating rock and surface types with multispectral satellite data in the Richtersveld, NW Cape Province, South Africa

Abstract Thematic Mapper (TM) digital data were processed to produce false colour composites (FCCs), ratio images and Colour Ratio Composites (CRCs), Principal Component (PC) false colour composites, and classified images, and these were compared for their geological information content. Classification by Bayes’ Maximum Likelihood method was investigated, and the best results came from using a summer image and recalculating data to reflectance values. A shadow class was used to improve the quality of the spectral signatures, and it was found that the chosen value of the standard deviation of the band variance was important to the usefulness of the classification. A comparison of TM and SPOT images (for the two test areas) emphasised the superiority of TM in the spectral domain, and of SPOT in resolution and stereoscopy. The TM FCC of Bands 145 were much more informative than the SPOT FCC, and the SPOT Principal Components did not differentiate rock types as well as TM PCs. However, the superior resolution...

Color heterogeneity of the surface of Phobos: Relationships to geologic features and comparison to meteorite analogs

Multispectral observations of Phobos by the VSK (Videospectrometric) TV cameras and KRFM (Combined Radiometer and Photometer for Mars) UV‐visible spectrometer on Phobos 2 have provided new determinations of the satellite's spectral reflectance properties, at greater spatial and spectral resolutions and over a greater geographic range than have previously been available. Images of the ratio of visible and NIR reflectances covering the longitude range 30°–250°W were constructed from 0.40–0.56 μm and 0.78–1.1 μm VSK images. Eight‐channel 0.3–0.6 μm spectra obtained by the KRFM instrument package were used to provide greater spectral resolution of parts of these images. The data were calibrated using instrumental parameters measured on‐ground and in‐flight, and the calibrations were refined and tested using previous spectral measurements of Phobos and telescopic spectra of Mars, which is visible in the background in both data sets. The average color ratio of Phobos was found to be ∼0.97±0.14, consistent with previously obtained measurements. However, the surface is heterogeneous, with at least four recognizable spectral units whose absolute color ratios were determined to within ∼10%: a “red” unit with a color ratio of 0.7–0.8, a “reddish gray” unit with a color ratio of 0.8–1.0, a “bluish gray” unit with a color ratio of 1.0–1.1, and a “blue” unit with a color ratio of 1.1–1.4. The “red” unit occurs in the interiors of several dark‐floored craters and as adjacent patches. The “blue” unit composes the interior of Stickney, as well as a lobate deposit superposed on the crater's rim and extending to the southwest. The “blue” lobe is surrounded by a broad “bluish gray” aureole that breaks up into patchy outliers in its distal portions. Intervening surfaces are “reddish gray.” The “red,” “reddish gray,” and “bluish gray” units were sampled by the KRFM spectrometer, and the “bluish gray” unit was found to have a distinct 0.3–0.6 μm spectrum. The spatial distributions of the color ratio units and their reflectance systematics are inconsistent with Mars shine or particle size differences alone being responsible for color variations, but lateral optical or compositional heterogeneity is supported by the units' different UV‐visible spectra. The redder and bluer color units are interpreted to have been excavated by impacts, from an optically and/or compositionally heterogeneous interior overlain by a “reddish gray” surficial layer. The location of the “blue” lobe emanating from Stickney correlates with the location of one of the morphologic classes of grooves, as predicted by ejecta reimpact models of groove origin. The large color ratio of “blue” material is inconsistent with a carbonaceous chondrite composition but is comparable to that of an assemblage of mafic minerals like that forming black chondrites. Qualitative and quantitative comparison of the color ratio and UV‐visible spectral properties of “bluish gray” material with those of meteorites indicates that black chondrites are this material's closest spectral analog. The UV‐visible spectra of “reddish gray” and “red” materials most resemble spectra of black chondrites but are also comparable to spectra of some carbonaceous chondrites.

Endogenic modification of impact craters on Mercury

Surface resolution of Mercury from Mariner-10 images is insufficient for identifying volcanic forms analogous to most of those on the moon. Consequently, other criteria must be used in order to assess the possibility of Mercurian volcanism. One criterion is the presence of internally modified impact craters similar to floor-fractured and mare-filled craters on the moon. Such craters typically occur near or within the lunar maria and exhibit features (fractures, shallow floors, dark-haloed craters, mare units) that either are resolvable at Mariner-10 resolutions or are detectable by indirect means, e.g., albedo and color contrasts. Mariner-10 images reveal several plausible examples, which, as on the moon, most commonly occur near plains-filled basins. The color-ratio images by Hapke, Danielson, Klaasen and Wilson indicate that some of the Mercurian craters exhibit red plains materials on their floors. Such distinctive units may correspond either to lavas analogous to mare basalts within certain lunar craters or to compositionally distinct subsurface material retained in the impact crater. Indicators used to recognize crater modification also can be used to recognize basin modification. Specifically, several basins exhibit photometric contrasts between basin-filling plains and basin exterior; moreover, several impact craters superposed on the interior plains exhibit dark haloes suggesting excavation of compositionally distinct material. Despite the generally poor surface resolution, possible endogenic features are recognized, including irregular rimless depressions. Mercurian volcanism may have occurred and in certain regions may resemble that of the Mare Australe region on the moon.

Detection of naturally heavy-metal-poisoned areas by LANDSAT-1 digital data

Natural poisoning of soil and vegetation due to heavy metals originating from sulphide deposits in the bedrock has been demonstrated at several locations in Norway. At some of these, the features of poisoning are rather widespread, suggesting that the recognition of such naturally poisoned areas by means of satellite imagery and satellite digital tapes might be possible. An occurrence of natural Cu poisoning near Karasjok, northern Norway, was selected as a training area. LANDSAT-1 computer compatible tapes were used to prepare enhanced colour ratio images and to calculate ratios of calibrated channel reflectances. Ground reflectance measurements were also carried out using radiometers with band passes equivalent to those on the LANDSAT multispectral scanner system. Compared with the surroundings the LANDSAT data over the training area showed unique spectral characteristics. These are also indicated on the enhanced ratio images, and the digital data can be utilized in supervised discriminant analysis and unsupervised “cluster” analysis. In particular, the area of the natural Cu poisoning shows low values in the band 7/band 5 reflectance ratio. At present, a detailed, precise numerical correlation between the ground and satellite reflectance data is not possible due to differences in resolution, although spatial correlation of spectral trends can be established. It appears that features of natural heavy metal poisoning can be located with the 0.45-hectare resolution of the LANDSAT multispectral scanner system. The search for such features might therefore be used as a tool in mineral exploration. The current resolution limitation can be overcome by utilizing scanners at aircraft altitudes.