Mineral Mapping and Applications of Imaging Spectroscopy

Spectroscopy is a tool that has been used for decades to identify, understand, and quantify solid, liquid, or gaseous materials, especially in the laboratory. In disciplines ranging from astronomy to chemistry, spectroscopic measurements are used to detect absorption and emission features due to specific chemical bonds, and detailed analyses are used to determine the abundance and physical state of the detected absorbing/emitting species. Spectroscopic measurements have a long history in the study of the Earth and planets. Up to the 1990s remote spectroscopic measurements of Earth and planets were dominated by multispectral imaging experiments that collect high-quality images in a few, usually broad, spectral bands or with point spectrometers that obtained good spectral resolution but at only a few spatial positions. However, a new generation of sensors is now available that combines imaging with spectroscopy to create the new discipline of imaging spectroscopy. Imaging spectrometers acquire data with enough spectral range, resolution, and sampling at every pixel in a raster image so that individual absorption features can be identified and spatially mapped (Goetz et al., 1985).

I. INTRODUCTION

Planetary surfaces are complex and the Earth's surface is probably the most complex in our solar system, showing varied geology, oceans, ice caps, abundant life and anthropogenic influences. Other planets have different geology and different surface compositions. In order to understand our own planet as well as others, we produce maps of materials and other measurable quantities. Maps of the Earth's surface can depict many themes, including those in geology, ecosystems, environmental hazards, land management and global change. Geologic mapping can include the depiction of geologic formations (thus providing information on ages and placements of units through geologic time), soils, mineral occurrences, faults, mineralized zones and aggregate for building materials. Environmental applications can include acid-rock drainage, oil or toxic waste spills, water quality and other distributions. Geologic hazards maps can include volcanic eruption potential, swelling clays, fault zones and landslide hazards. The need for accurate and more detailed maps has never been greater, which drives the requirement for more advanced information such as that from imaging spectrometers.