[1] Hematite-bearing deposits in the Terra Meridiani region of Mars constitute the top stratum of a partially eroded layered complex that covers dissected Noachian-aged cratered terrain. The hematite unit consists of dark plains and dunes covering a bright substrate. This substrate is fully exposed beyond the borders of the hematite-bearing deposit and consists of polygonal ground separated by ridges or valleys, together with layered deposits that have been eroded into a variety of landforms. The complex is partially covered by a regional-scale aeolian mantle that thickens toward the north. The hematite-bearing stratum exhibits low albedoes, pulse widths, and intermediate thermal inertias, whereas the underlying unit exhibits high values of these parameters. Both units have spectral emissivity signatures similar to those for the low albedo cratered terrain to the south, with the addition of hematite for the top stratum. The complex is interpreted to consist of extensive plains-forming lava flows and tephra deposits emplaced during an extensional regime and at least partially buried by an aeolian mantle. Aeolian stripping of the mantle exposed much of the complex and differentially eroded the deposits to produce the landforms existent today. Exploration of the hematite-bearing deposits by the 2003 Mars Exploration Rover, ''Opportunity,'' will allow testing of the hypotheses presented since this stratum has been locally reworked into dunes that only partially cover the underlying brighter portion of the complex. In particular, the rover-based measurements will allow us to test the extent to which the unusual remote-sensing properties of the units indicate aqueous alteration.

[1] Rover mast-based stereo imaging, reflectance or emission spectra, and laser-induced breakdown spectroscopy (LIBS) provide powerful synergistic data sets for rapidly determining geologic setting, mineralogy, and elemental composition for rock and soil targets. We report results from hand specimen examination, multiple spectral reflectance (VISIR, 0.4-2.5 mm), and remote LIBS measurements for representative samples (basalt, iron oxides, altered rhyolite, and dolostone) collected during the May 2000 rover trials at Black Rock Summit, Nevada. Major findings are (1) reflectance data indicate the presence of olivine and montmorillonite for the basaltic sample, whereas LIBS data show variations with depth as an alumino-silicate coating is ablated and a basaltic composition is revealed beneath; (2) iron oxide reflectance data are dominated by goethite and hematite with the additional detection of hydrated cryptocrystalline SiO 2 (an interpretation fully supported by the LIBS data); (3) VISIR reflectance data for rhyolite show significant alteration to kaolinite, an inference that would be difficult to make from LIBS data alone; (4) dolostone reflectance data show dominantly dolomite with minor iron oxides, inferences confirmed through analyses of LIBS data; and (5) LIBS data acquired for samples as a function of depth and spatial location significantly aid in understanding the extent of sample coatings and compositional and mineralogical diversity. Given the hand specimen examination and results from joint analysis of the two rapid-acquisition spectral techniques, a scenario for acquisition and analysis of mast-based imaging reflectance or emission spectroscopy and LIBS is presented within the context of the scientific objectives for the Mars Exploration Program.

Acquisition downtime resulting from bad weather is often a significant factor in the cost of marine seismic surveys. In the North Sea, for instance, seismic data are acquired mostly during the summer, and weather downtime can still amount to 40% of the survey time.Our approach to reducing weather downtime is based on the following concepts:• During multiple acquisition passes, seismic signal is repeatable; bad weather noise is not. •Filtering algorithms are applied to reduce swell noise. •Imaging with least-squares inversion algorithms is less sensitive to noise-edited data than conventional imaging. To test these concepts we acquired multiple pass data covering the same areas in good and bad weather. A survey was made from the Barents sea and the acquisition was performed with a vessel equipped for standard 3D surveys.Commercial 3D data provide a reference for quantitative comparison of seismic images and of attributes derived from the seismic data. The results obtained so far are encouraging, and we expect opportunities for cost-effective reduction of bad weather downtime (10% to 20%) without compromising quality requirements.