USGS Digital Spectral Library splib05a

Clark, R. N.; Swayze, Gregg A.; Wise, Richard K.; Livo, Eric; Hoefen, Todd M.; Kokaly, Raymond F.; Sutley, S.J.

doi:10.3133/ofr03395

Cited by 174 publications

(208 citation statements)

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“…We identified ferric oxide and some clay minerals by analyzing reflectance spectra using the Material Identification and Characterization Algorithm (MICA), a module of the PRISM software system (Kokaly, 2011), which uses continuum removal to isolate diagnostic absorption features and linear regression to compare spectral features. In this way, the spectra of Bodélé samples are compared with reference spectra of minerals and other materials (Clark et al, 2007). In this study, we are interested in the iron-bearing minerals with electronic absorption features centered primarily in the visible and near-infrared wavelengths (0.4 to 1.0 μm).…”

Section: Reflectance Spectroscopymentioning

confidence: 99%

“…We also determined the type of ferric oxide mineral, whether primarily hematite (-Fe 2 O 3 ) or goethite (-FeOOH), which are the two most common forms in desert soils and surfaces (hereafter collectively referred to as iron oxides or ferric oxides), and which have different optical properties. Reflectance spectroscopy can be used to identify different ferric oxide minerals (e.g., Clark et al, 2007), as can certain magnetic methods (Maher et al, 2004;Guyodo et al, 2006;Carter-Stiglitz et al, 2006;Liu et al, 2006;Maher, 2011). Mössbauer spectroscopy was also employed to identify with high specificity various iron phases, including amounts of hematite and goethite as well as the fraction that occur as nanoparticles, in a sample.…”

Section: Introductionmentioning

confidence: 99%

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Iron oxide minerals in dust-source sediments from the Bodélé Depression, Chad: Implications for radiative properties and Fe bioavailability of dust plumes from the Sahara

et al. 2016

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Atmospheric mineral dust can influence climate and biogeochemical cycles. An important component of mineral dust is ferric oxide minerals (hematite and goethite) which have been shown to influence strongly the optical properties of dust plumes and thus affect the radiative forcing of global dust. Here we report on the iron mineralogy of dust-source samples from the Bodélé Depression (Chad, north-central Africa), which is estimated to be Earth's most prolific dust producer and may be a key contributor to the global radiative budget of the atmosphere as well as to long-range nutrient transport to the Amazon Basin. By using a combination of magnetic property measurements, Mössbauer spectroscopy, reflectance spectroscopy, chemical analysis, and scanning electron microscopy, we document the abundance and relative amounts of goethite, hematite, and magnetite in dust-source samples from the Bodélé Depression. The partition between hematite and goethite is important to know to improve models for the radiative effects of ferric oxide minerals in mineral dust aerosols. The combination of methods shows (1) the dominance of goethite over hematite in the source sediments, (2) the abundance and occurrences of their nanosize components, and (3) the ubiquity of magnetite, albeit in small amounts. Dominant goethite and subordinate hematite together compose about 2% of yellowreddish dust-source sediments from the Bodélé Depression and contribute strongly to diminution of reflectance in bulk samples. These observations imply that dust plumes from the Bodélé Depression that are derived from goethite-dominated sediments strongly absorb solar radiation. The presence of ubiquitous magnetite (0.002-0.57 wt. %) is also noteworthy for its potentially higher solubility relative to ferric oxide and for its small sizes, including PM<0.1m. For all examined samples, the average iron apportionment is estimated at about 33% in ferric oxide minerals, 1.4 % in magnetite, and 65% in ferric silicates. Structural iron in clay minerals may account for much of the iron in the ferric silicates. We estimate that the mean ferric oxides flux exported from the Bodélé Depression is 0.9 Tg/yr with greater than 50% exported as ferric oxide nanoparticles (<0.1m). The high surface-to-volume ratios of ferric oxide nanoparticles once entrained into dust plumes may facilitate increased atmospheric chemical and physical processing and affect iron solubility and bioavailability to marine and terrestrial ecosystems.

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Section: Reflectance Spectroscopymentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

Iron oxide minerals in dust-source sediments from the Bodélé Depression, Chad: Implications for radiative properties and Fe bioavailability of dust plumes from the Sahara

et al. 2016

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“…In this work, we expand the knowledge base by building a spectral database of 137 microorganisms from 0.35 to 2.5 μm (currently data for three such organisms are available in the literature; see ref. 4). There are several advantages of choosing this wavelength range.…”

Section: Discussionmentioning

confidence: 99%

“…Although there is a considerable knowledge base of the spectral properties of land plants (4,5), very little information is present in the literature on the reflectance properties of microorganisms. Land plants are widespread on present-day Earth and are easily detected from high-resolution spacecraft observations (6).…”

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confidence: 99%

Surface biosignatures of exo-Earths: Remote detection of extraterrestrial life

Hegde

Paulino-Lima

Kent

et al. 2015

Proc. Natl. Acad. Sci. U.S.A.

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Exoplanet discovery has made remarkable progress, with the first rocky planets having been detected in the central star's liquid water habitable zone. The remote sensing techniques used to characterize such planets for potential habitability and life rely solely on our understanding of life on Earth. The vegetation red edge from terrestrial land plants is often used as a direct signature of life, but it occupies only a small niche in the environmental parameter space that binds life on present-day Earth and has been widespread for only about 460 My. To more fully exploit the diversity of the one example of life known, we measured the spectral characteristics of 137 microorganisms containing a range of pigments, including ones isolated from Earth's most extreme environments. Our database covers the visible and near-infrared to the short-wavelength infrared (0.35-2.5 μm) portions of the electromagnetic spectrum and is made freely available from biosignatures. astro.cornell.edu. Our results show how the reflectance properties are dominated by the absorption of light by pigments in the visible portion and by strong absorptions by the cellular water of hydration in the infrared (up to 2.5 μm) portion of the spectrum. Our spectral library provides a broader and more realistic guide based on Earth life for the search for surface features of extraterrestrial life. The library, when used as inputs for modeling disk-integrated spectra of exoplanets, in preparation for the next generation of space-and ground-based instruments, will increase the chances of detecting life.biosignatures | spectral library | reflectivity | extremophiles | pigments I n the last decade, the field of exoplanet research has transitioned rapidly from detection to detection and characterization, with the first rocky exoplanets detected in the central star's liquid water habitable zone. Much of the excitement of this research in both the astrobiology community and the general public is motivated by the quest to discover a second genesis of life. The great distances that separate us from even the most nearby stars dictate that all measurements of the exoplanet must be made through remote sensing techniques for the foreseeable future. Thus, it is critical for us to determine the types of biosignatures that we should be looking for when designing the next generation of ground-and space-based instruments that will observe these planets at high spectral and possibly spatial resolutions.Since the mid-1960s a primary life-searching strategy has been to look for a specific combination of an oxidizing and a reducing gas in the exoplanetary atmosphere, such as the O 2 and CH 4 in our atmosphere, because this is a thermodynamically unstable situation suggesting that an active agent such as life is responsible for the chemical disequilibrium (1, 2). Of particular interest, both from an observational and modeling perspective, is to complement those indirect life detection studies with surface features that are direct properties of the organisms themselves (3).Alt...

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“…Hyperspectral endmember-spectra are randomly chosen from a spectral library measured from 0.4 to 2.5 µm with 420 wavelengths and compiled by the United States Geological Survey (USGS) [14]. The number of endmembers is varied from 2 to 10 in our tests.…”

Section: Tested Data and Experiments Designmentioning

confidence: 99%

A new multiplicative nonnegative matrix factorization method for unmixing hyperspectral images combined with multispectral data

Benkouider

Karoui

ville

et al. 2017

2017 25th European Signal Processing Conference (EUSIPCO)

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In these investigations, a novel algorithm is proposed for linearly unmixing hyperspectral images combined with multispectral data. This algorithm, which is used to unmix the considered hyperspectral image, is founded on nonnegative matrix factorization. It minimizes, with new multiplicative update rules, a novel cost function, which includes multispectral data and a spectral degradation model between these data and hyperspectral ones. The considered multispectral variables are also used to initialize the proposed algorithm. Tests, using synthetic data, are carried out to assess the performance of our algorithm and its robustness to spectral variability between the processed data. The obtained results are compared to those of state of the art methods. These tests prove that the proposed algorithm outperforms all other used approaches.Index Terms-Hyper/multispectral imaging, linear unmixing, multiplicative update rule, nonnegative matrix factorization, spectral degradation model

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USGS Digital Spectral Library splib05a

Cited by 174 publications

References 0 publications

Iron oxide minerals in dust-source sediments from the Bodélé Depression, Chad: Implications for radiative properties and Fe bioavailability of dust plumes from the Sahara

Iron oxide minerals in dust-source sediments from the Bodélé Depression, Chad: Implications for radiative properties and Fe bioavailability of dust plumes from the Sahara

Surface biosignatures of exo-Earths: Remote detection of extraterrestrial life

A new multiplicative nonnegative matrix factorization method for unmixing hyperspectral images combined with multispectral data

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