S>fflk+.SmSt> i 0 0,\g gN l r g t^l,-^:,g. 'X @W0-';D4:* -W u iA 27. P. de Loriol, Paleontologie Fran,aise, ou Description des Fossiles de la France, Serie 1, Animaux Invertebr6s. Terrain Jurassique (Masson, Paris, 1882-1889. 28. Because of incomplete preservation, most species have at least some missing character data. In this analysis used the species in each genus with the fewest missing characters. 29. Because unordered characters cannot be averaged, first ordinated species using principal-coordinates analysis [J. C. Gower, Biometrika 53, 325 (1966)] on the between-species morphological distance matrix (10). Twenty principal coordinates were used because interspecies distances based on this number of coordinates correlate well with distances based on the raw character data. Similar results are obtained if other numbers of principal coordinates are used. 30. S. J. Gould and C. B. Calloway, Paleobiology 6, 383 (1980). 31. D. L. Meyer and D. B. Macurda Jr., ibid. 3, 74 (1977). 32. E. S. Pearson, Biometrika 18, 173 (1926); M. Foote, Paleobiology 18, 1 (1992). 33. M. Slatkin, Paleobiology 7, 421 (1981); J. W. Valentine et al., ibid. 20, 131 (1994). 34. N. G. Lane, J. Paleontol. 37, 917 (1963); J. C. Brower, ibid. 40, 613 (1966); ibid. 61, 999 (1987); A. Breimer, Proc. K. Ned. Akad. Wet. Ser. B 72, 139 (1969); and G. D. Webster, ibid. 78, 149 (1975); D. L. Meyer, Mar. Biol. 22, 105 (1973); in Echinoderm Nutrition, M. Jangoux and J. M. Lawrence, Eds. (Balkema, Rotterdam, 1983), pp. 25-42; M. Roux, Geobios (Lyon) 11, 213 (1978); A. Breimer and N. G. Lane, in Treatise on Invertebrate Paleontology, part T, Echinodermata 2, R. C. Moore and C. Teichert, Eds. (Geological Society of America, Boulder, CO, and University of Kansas, Lawrence, KS, 1978), pp. 316-347; G. Ubaghs, ibid., pp. 58-216; W. I. Ausich, J. Paleontol. 54, 273 (1980); ibid. 57, 31 (1983); ibid. 62, 906 (1988); C. E. Brett, Lethaia 14, 343 (1981); S. K. Donovan, ibid. 21, 169 (1988); ibid. 23, 291 (1990); T. W. Kammer, J. Paleontol. 59, 551 (1985); and W. I. Ausich, Paleobiology 13, 379 (1987 using laser illumination of a particle suspension (13,14). A high ratio of same sense to opposite sense polarization and high reflectivity has been detected by radar observations of the Galilean satellites of Jupiter (15,16,17) to observe from the Earth. Radar can identify deposits of frozen volatiles because, under certain conditions, they produce a unique radar signature (6). However, such radar observations may not be conclusive depending on the quantity of volatiles present, the nature of the surface, and the sensitivity of the measurements. Frozen volatiles have much lower transmission loss than silicate rocks, producing a higher average radar reflectivity than silicate rocks. Total internal reflection also preserves the transmitted circular polarization sense in the scattered signal. An opposition surge or coherent backscatter opposition effect (CBOE) (7-12) may also be observed as the phase, or bistatic angle 1 (Fig. 1), approaches 0. The CBOE requir...

In the course of 71 days in lunar orbit, from 19 February to 3 May 1994, the Clementine spacecraft acquired just under two million digital images of the moon at visible and infrared wavelengths. These data are enabling the global mapping of the rock types of the lunar crust and the first detailed investigation of the geology of the lunar polar regions and the lunar far side. In addition, laser-ranging measurements provided the first view of the global topographic figure of the moon. The topography of many ancient impact basins has been measured, and a global map of the thickness of the lunar crust has been derived from the topography and gravity.

[1] We present new polarimetric radar data for the surface of the north pole of the Moon acquired with the Mini-SAR experiment onboard India's Chandrayaan-1 spacecraft. Between mid-February and mid-April, 2009, Mini-SAR mapped more than 95% of the areas polewards of 80°latitude at a resolution of 150 meters. The north polar region displays backscatter properties typical for the Moon, with circular polarization ratio (CPR) values in the range of 0.1-0.3, increasing to over 1.0 for young primary impact craters. These higher CPR values likely reflect surface roughness associated with these fresh features. In contrast, some craters in this region show elevated CPR in their interiors, but not exterior to their rims. Almost all of these features are in permanent sun shadow and correlate with proposed locations of polar ice modeled on the basis of Lunar Prospector neutron data. These relations are consistent with deposits of water ice in these craters.

Abstract. In order to investigate the feasibility of ice deposits at the lunar south pole, we have integrated all relevant lunar polar data sets. These include illumination data, Arecibo ground-based monostatic radar data, newly processed Clementine bistatic radar data, and Lunar Prospector neutron spectrometer measurements. The possibility that the lunar poles harbor ice deposits has important implications not only as a natural resource for future human lunar activity but also as a record of inner solar system volatiles (e.g., comets and asteroids) over the past billion years or more. We find that the epithermal neutron flux anomalies, measured by Lunar Prospector, are coincident with permanently shadowed regions at the lunar south pole, particularly those associated with Shackleton crater. Furthermore, these areas also correlate with the • = 0 circular polarization ratio (CPR) enhancements revealed by new processing of Clementine bistatic radar echoes, which in turn are colocated with areas of anomalous high CPR observed by Arecibo Observatory on the lower, Sun-shadowed wall of Shackleton crater. Estimates of the extent of high CPR from Arecibo Observatory and Clementine bistatic radar data independently suggest that •10 km 2 of ice may be present on the inner Earth-facing wall of Shackleton crater. None of the experiments that obtained the data presented here were ideally suited for definitively identifying ice in lunar polar regions. By assessing the relative merits of all available data, we find that it is plausible that ice does occur in cold traps at the lunar south pole and that future missions with instruments specifically designed to investigate these anomalies are worthy. IntroductionThe lunar poles have long been theorized to harbor ice deposits in permanently shadowed regions because these regions can act to cold trap volatile compounds, including water introduced into the lunar environment [Watson et al., 1961]. This is a fascinating possibility both because such deposits would serve as a natural resource for future human lunar activity and because the plausible sources of lunar water (e.g., comets and asteroids) are of inherent interest. In fact, modeling the temperatures of shadowed craters near the poles [Ingersoll et al., 1992;Salvail and Fanale, 1994; Vasavada, 1998] shows temperatures low enough to cold trap materials substantially more volatile than water ice. Studies of the transport and retention of water ice and other volatiles also support the possibility of water ice being present at the pole [Butler, 1997; Morgan and Shemansky, 1991 ]. The latter work suggested that sputtering was rapid enough to destroy slow continuous deposits of water ice, for example, from micrometeorite water, or water produced from reduction of lunar surface materials to produce water from solar wind hydrogen but that thick deposits of ice introduced by comets or large "wet" asteroids might survive by sequestering of ice by regolith overturn.•Naval Research Laboratory, Washington, D.C. No conclusive evidence of w...

The Miniature Radio Frequency (Mini-RF) system is manifested on the Lunar Reconnaissance Orbiter (LRO) as a technology demonstration and an extended mission science instrument. Mini-RF represents a significant step forward in spaceborne RF technology and architecture. It combines synthetic aperture radar (SAR) at two wavelengths (S-band and X-band) and two resolutions (150 m and 30 m) with interferometric and communications functionality in one lightweight (16 kg) package. Previous radar observations (Earth-based, and one bistatic data set from Clementine) of the permanently shadowed regions of the lunar poles seem to indicate areas of high circular polarization ratio (CPR) consistent with volume scattering from volatile deposits (e.g. water ice) buried at shallow (0.1-1 m) depth, but only at unfavorable viewing geometries, and with inconclusive results. The LRO Mini-RF utilizes new wideband hybrid polarization architecture to measure the Stokes parameters of the reflected signal. These data will help to differentiate "true" volumetric ice reflections from "false" returns due to angular surface regolith. Additional lunar science investigations (e.g. pyroclastic deposit characterization) will also be attempted during the LRO extended mission. LRO's lunar operations will be contemporaneous with India's Chandrayaan-1, which carries the Forerunner Mini-SAR (S-band wavelength and 150-m resolution), and bistatic radar (S-Band) measurements may be possible. On orbit calibration, procedures for LRO