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The Mystery of Mars is a beautiful and informative book, aimed at young readers ages 8 to 12. The child in your life (if he or she is any kind of “space cadet”) will enjoy looking at this intelligent, comprehensive, and colorful introduction to Mars. The book wisely capitalizes on two aspects of our human nature: our love of exploration and our inability to resist a mystery Human beings of all ages love to explore, and in spite of the recent setbacks in Mars exploration, the lure of other planetary frontiers has never been stronger.

Updated radiometric calibration and systematic processing procedures for Galileo solid-state imaging (SSI) data from the first (1990) Earth-Moon encounter are presented. These procedures were applied to a whole-disk imaging sequence of the Moon centered near Mare Orientale, called Lunmap 14 (L14). Processing of L14 data included radiometric calibration, subpixel coregistration, scattered light removal, geometric control and reprojection, photometric normalization, and calibration to Earth-based spectra. Coregistration and scattered-light removal procedures are improvements over the initial calibration of the SSI mosaics. The effects of scattered light correction are best seen using a whole-Moon view such as L14; resolution of the debated amounts of light scattering from within or outside the camera field of view is not necessary. Scattered light removal particularly affects the 1-μm spectral region and has implications for interpretation of mafic mineral signatures in mare deposits of the lunar limb and farside. Recalibrated spectra indicate that mare ponds of the limb show moderately deep 1-μm absorptions, and thus mafic mineral contents, comparable to those of other nearside basalts. Mafic mineral contents of Schiller-Shickard cryptomaria are higher than previously thought and are similar to some low-Ti nearside basalts. Many of the recalibrated spectra from South Pole/Aitken are similar to those of Schiller-Schickard cryptomaria, suggesting that many of these soils represent a mixed mare/highland lithology. The hypothesis that there is an olivine enrichment in southern South Pole/Aitken basin is not supported strongly by spectra shown here.

The Galileo spacecraft imaged parts of the western limb and far side of the Moon in December 1990. Ratios of 0.41/0.56 gin filter images from the Solid State hnaging (SSI) experiment provided information on the titanium content of mare deposits' ratios of the 0.76/0.99 gm images indicated 1 gin absorptions associated with Fe 2+ in mafic minerals. Mare ages were derived froin crater statistics obtained from Lunar Orbiter images. Results on mare coinpositions in western Oceanus Procellarum and the Humorurn basin are consistent with previous Earth-based observations, thus providing confidence in the use of Galileo data to extract compositional information. Mare units in the Grimaldi and Riccioli basins range in age froin 3.25 to 3.48 Ga and consist of medium- to medium-high titanium (

Copernican-age craters are among the most conspicuous features seen on the far side and western limb of the Moon in the Galileo multispectral images acquired in December 1990. Among the new morphologic observations of far-side craters are bright rays, continuous ejecta deposits, and dark rings associated with probable impact-melt veneers. These observations suggest that the mapped age assignments of several large far-side craters (Ohm, Robertson, and possibly Lowell and Lenz) need revision. New crater size-frequency measurements on Lunar Orbiter images suggest the following age reassignments: Hausen (170 km diameter), Pythagoras (120 km), and Bullialdus (61 km) from Eratosthenian to Upper Imbrian, and Carpenter (60 km) and Harpalus (39 km) from Copernican to Eratosthenian. Colors and albedos of craters (away from impact-melt veneers) are correlated with their geologic emplacement ages as determined from counts of superposed craters; these age-color relations are used to estimate the emplacement age (time since impact event) for other Copernican-age craters. These age-color relations indicate a probable Copernican age for 27 far-side or western limb craters larger than 10 km diameter that were not previously mapped as Copernican. The apparent deficiency of Copernican craters on the far side compared with the near side in published geologic maps is not present in our data. Age-color trends differ between mare and highland regions and between the interiors and continuous ejecta of the craters. Similar trends are established for color and albedo versus soil-maturity indices for the returned lunar samples, with distinct trends for mare and highland soils. However, the mare versus highland offsets are reversed in the two comparisons. These relations can be explained by variations in regolith thicknesses and rates of mixing with relatively fresh, crystalline ejecta. Therefore, the soil-maturity trends represent longer geologic time periods in regions with thinner regoliths, such as the maria.

Data on the distribution of impact craters on Venus are analyzed in relation to the geologic history of Venus and the effects of high ambient pressures and temperatures on the cratering process itself. The cratering record of Venus is discussed in terms of size, number, spatial distribution, and state of preservation of craters. The morphology of Venusian craters is examined as a function of the diameter, and features unique to these craters are discussed. Attention is also given to several craters that illustrate important features of Venusian crater; surface 'splotches' that are closely related in origin to impact craters; and implications of the distribution of severely modified craters for Venus' recent geologic history.

Analyses of imaging radar data of volcanic terranes on Earth and Venus have emphasized the need for a clearer understanding of how these data can be most effectively used to accomplish important volcanological goals, including the interpretation of eruptive styles and the characterization of the geologic history of volcanic centers. The second Shuttle Imaging Radar experiment (SIR-B) obtained two digital images over the summit caldera and the Southwest Rift Zone of Kilauea Volcano in 1984. Our geologic analyses of these images indicate that SIR-B data are particularly useful for delineating the distribution and surface textural variations of a9a lava flows, for mapping large-scale topographic features with radar-facing slopes, and for identifying an areally extensive pyroclastic deposit. Analyses of the SIR-B data of Kilauea, however, do not permit unambiguous identification of landforms such as pahoehoe lava flows, cinder cones, and fissures. Although separation of low-return units such as pahoehoe lava flows and adjacent pyroclastic ash is not greatly improved using standard image-enhancement techniques, the texture-analysis technique applied here did facilitate discrimination of such smooth-surfaced volcanic deposits. Although analyses of the SIR-B data permit a generally accurate interpretation of the eruptive history of Kilauea, the inability to distinguish low-return pahoehoe flows results in misinterpretation of several aspects of Kilauea volcanism, suggesting that caution should be exercised in the interpretation of SAR data of volcanic terranes.

Reflectance spectra from several regional lunar pyroclastic deposits are presented in support of the theory that mantling units have a unique spectral signature indicative of the presence of a significant, Fe-bearing volcanic glass component. The Rime Bode region discussed is illustrative of an area in which several types of remote sensing data were used to reconstruct the geologic events associated with the emplacement of a regional pyroclastic mantling deposit. Five new areas are identified on the basis of the present data which may represent higher albedo regional pyroclastic deposits.

The Imager for Mars Pathfinder (IMP) acquired more than 16,000 images and provided panoramic views of the surface of Mars at the Mars Pathfinder landing site in Ares Vallis. This paper describes the stereoscopic, multispectral IMP imaging sequences and focuses on their use for digital mapping of the landing site and for deriving cartographic products to support science applications of these data. Two-dimensional cartographic processing of IMP data, as performed via techniques and specialized software developed for ISIS (the U.S. Geological Survey image processing software package), is emphasized. Cartographic processing of IMP data includes ingestion, radiometric correction, establishment of geometric control, coregistration of multiple bands, reprojection, and mosaicking. Photogrammetric processing, an integral part of this cartographic work which utilizes the three-dimensional character of the IMP data, supplements standard processing with geometric control and topographic information [Kirk et al., this issue]. Both cartographic and photogrammetric processing are required for producing seamless image mosaics and for coregistering the multispectral IMP data. Final, controlled IMP cartographic products include spectral cubes, panoramic (360° azimuthal coverage) and planimetric (top view) maps, and topographic data, to be archived on four CD-ROM volumes. Uncontrolled and semicontrolled versions of these products were used to support geologic characterization of the landing site during the nominal and extended missions. Controlled products have allowed determination of the topography of the landing site and environs out to ∼60 m, and these data have been used to unravel the history of large- and small-scale geologic processes which shaped the observed landing site. We conclude by summarizing several lessons learned from cartographic processing of IMP data.

A new kind of ocean surface feature has been observed on Seasat synthetic aperture radar (SAR) images of the Mississippi River Birdfoot Delta and adjacent Gulf of Mexico waters. Although ocean surface wave patterns have been detected by Seasat SAR in several coastal areas, their origin was attributed to the interaction between oceanic currents and bottom topography. In contrast, we find no such correlation between surface wave patterns and bathymetry at the Mississippi Delta, where the morphometry and distribution of the detected waveforms suggest a river discharge origin. Although contemporaneous data from the Landsat D Thematic Mapper are not available, visible and infrared images acquired at other times generally support this hypothesis; the boundaries of the turbid, cooler river water correspond well to those of the surface wave patterns detected by the Seasat SAR.