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D. Blaney (NASA Jet Propulsion Laboratory, California Insitute of Technology)
Since reaching the Columbia Hills, Spirit has investigated their composition and structure with the Athena payload. Two remote sensing instruments collected spectral information at visible (PanCam) and at thermal infrared (Mini-TES) wavelengths. Observations were coordinated and targeted to determine the mineralogical diversity and identify lithologies for investigation with the rest of the payload. Spirit has measured a wide range of targets including outcrop, rocks, and disturbed soils. While there is variation within classes, materials observed fell into five rock types and two soil types. Class names derive from their general location and a representative example target. Gusev plains rocks (e.g. Adirondack) have an olivine feature in the long wavelength part of the spectrum and are the dominant rocks on the plains. While initially very rare in the Columbia hills, plains basalts have become more common as the rover has climbed into the hills. West Spur rocks (e.g. Palenque) are highly altered. Lower Husband Hill I rocks (e.g. Wishstone) are dominated spectrally by intermediate plagioclase feldspar while Lower Husband Hills II rocks (e.g. Peace) show spectral evidence for bound water. Upon reaching the ``Cumberland Ridge", two types of materials were identified. The ``Watchtower" and ``Jibsheet" outcrops represent the next class, characterized by steep slope from 700 cm-1 to 400 cm-1. Finally, the ``Methuselah" outcrop shares many of the same spectral characteristics as Lower Husband Hill I (e.g. Wishstone). Disturbed soils all have similar characteristics, except for Huron (near Paso Robles), which shows evidence for water at Mini-TES wavelengths and is significantly less ``red" than other materials measured at visible wavelengths. The complex mixture of rock types indicate that multiple processes have been at work in the formation and evolution of the Columbia Hills. This work was carried out at the Jet Propulsion Laboratory, California Institute of Technology, under contract to NASA.
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Bulletin of the American Astronomical Society, 37 #3
© 2004. The American Astronomical Soceity.