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Half a century after the moon landings, what counts as cultural property in space, how should it be protected--and who should do the protecting? A recent international accord provides some [...]

The latest science news, in brief. The latest science news, in brief., Author Affiliations: Vaccines and Delta, Moon volcanism and an NIH departure A health worker gives a COVID-19 vaccine in Hanoi. Credit: Nhac Nguyen/AFP/Getty A man surrounded my medical workers in [...]

Diviner Lunar Radiometer Experiment surface-temperature maps reveal the existence of widespread surface and near-surface cryogenic regions that extend beyond the boundaries of persistent shadow. The Lunar Crater Observation and Sensing Satellite (LCROSS) struck one of the coldest of these regions, where subsurface temperatures are estimated to be 38 kelvin. Large areas of the Lunar polar regions are currently cold enough to cold-trap water ice as well as a range of both more volatile and less volatile species. The diverse mixture of water and high-volatility compounds detected in the LCROSS ejecta plume is strong evidence for the impact delivery and cold-trapping of volatiles derived from primitive outer solar system bodies. 10.1126/science.1187726

Three concepts for the shelters on the moon are presented here. It is envisaged that the first robots will land on the moon and start preparing sites for advanced bases and also for future human presence. These robots will encounter severe radiation and micrometeor hits when they are exposed to the lunar atmosphere. During the period of intense solar radiation these robots have to be temporarily sheltered, since shielding on the robots may not be adequate to protect the instruments. The construction of these shelters has to be performed with very little equipment support. This paper presents concepts and their feasibility analysis for the fabrication of shelters under such stringent constraints. DOI: 10.1061/(ASCE)0893-1321(2009)22:4(396) CE Database subject headings: Moon; Composite materials; Conceptual design; Space structures.

Observations of the subsurface geology of the Moon help advance our understanding of lunar origin and evolution. Radar sounding from the Kaguya spacecraft has revealed subsurface layers at an apparent depth of several hundred meters in nearside maria. Comparison with the surface geology in the Serenitatis basin implies tflat the prominent echoes are probably from buried regolith layers accumulated during the depositional hiatus of mare basalts. The stratification indicates a tectonic quiescence between 3.55 and 2.84 billion years ago; mare ridges were formed subsequently. The basalts that accumulated during this quiet period have a total thickness of only a few hundred meters. These observations suggest that mascon loading did not produce the tectonics in Serenitatis after 3.55 billion years ago. Global cooling probably dominated the tectonics after 2.84 billion years ago.

Everyone has seen the visible face of the Moon, but have you ever wondered what the other side looks like? In October 1959, the Soviet spacecraft Luna 3 snapped the [...]

To link to full-text access for this article, visit this link: http://dx.doi.org/10.1016/j.icarus.2006.08.011 Byline: Colin M. Dundas, Alfred S. McEwen Keywords: Cratering; Moon; Impact processes Abstract: The large, fresh crater Tycho in the nearside lunar highlands has an extensive system of bright rays covering approximately 560,000 km.sup.2, containing dense clusters of secondary craters. Examination of crater densities in several clusters shows that Tycho produced almost 10.sup.6 secondary craters larger than 63 m diameter. This is a lower limit, because small crater densities are reduced, most likely by mass wasting. We estimate a crater erasure rate of 2-6 cm/Myr, varying with crater size, and consistent with previous results. This process has removed many small craters, and it is probable that the original number of secondary craters formed by Tycho was higher. Also, we can only identify distant secondaries of Tycho where they occur in bright rays. Craters on Mars and Europa also formed large numbers of secondaries, but under possibly ideal conditions for spallation as a mechanism to produce high-velocity ejecta fragments. The results from Tycho show that large numbers of such fragments can be produced even from impact into a heavily fragmented target on which spallation is expected to be less important. Author Affiliation: Department of Planetary Sciences, Lunar and Planetary Laboratory, University of Arizona, Tucson, AZ 85721, USA Article History: Received 20 February 2006; Revised 28 July 2006

To link to full-text access for this article, visit this link: http://dx.doi.org/10.1016/j.icarus.2006.08.024 Byline: Edgar L Andreas Keywords: Ices; Meteorology; Moon; Moon; surface; Regoliths Abstract: The strong hydrogen signal that the Lunar Prospector saw at the Moon's poles suggests that water ice may be present near the surface of the lunar regolith. A robotic mission to obtain in situ samples and to quantify the amount of this valuable resource must be designed carefully to avoid dissipating too much heat in the regolith during coring or drilling and, thus, causing the ice to sublimate before it is processed. Here I use new results for the saturation vapor pressure of water ice to extend previous estimates of its sublimation rate down to a temperature of 40 K, typical of the permanently shaded craters near the lunar poles where the water ice is presumed to be trapped. I find that, for temperatures below 70 K, the sublimation rate of an exposed ice surface is much less than one molecule of water vapor lost per square centimeter of surface per hour. But even if a small ice sample ([approximately equal to]4 ng) were heated to 150 K, it could exist for over two hours without sublimating a significant fraction of its mass. Hence, carefully designed sampling and sample handling should be able to preserve water ice obtained near the lunar poles for an accurate measurement of its in situ concentration. Author Affiliation: U.S. Army Cold Regions Research and Engineering Laboratory, 72 Lyme Road, Hanover, NH 03755-1290, USA Article History: Received 6 April 2006; Revised 18 August 2006

To link to full-text access for this article, visit this link: http://dx.doi.org/10.1016/j.icarus.2005.08.007 Byline: Athena Coustenis (a), Alberto Negrao (a)(d)(f), Alberto Salama (c), Bernhard Schulz (b), Emmanuel Lellouch (a), Pascal Rannou (d), Pierre Drossart (a), Therese Encrenaz (a), Bernard Schmitt (e), Vincent Boudon (g), Andrei Nikitin (h) Keywords: Titan; Satellites of Saturn; Surfaces; Satellite; Infrared observations; ISO Abstract: The near-infrared spectrum of Titan, Saturn's largest moon and one of the Cassini/Huygens' space mission primary targets, covers the 0.8 to 5 micron region in which it shows several weak CH.sub.4 absorption regions, and in particular one centered near 2.75 micron. Due to the interference of telluric absorption, only part of this window region (2.9-3.1 [mu]m) has previously been observed from the ground [Noll, K.S., Geballe, T.R., Knacke, R., Pendleton, F., Yvonne, J., 1996. Icarus 124, 625-631; Griffith, C.A., Owen, T., Miller, G.A., Geballe, T., 1998. Nature 395, 575-578; Griffith, C.A., Owen, T., Geballe, T.R., Rayner, J., Rannou, P., 2003. Science 300, 628-630; Geballe, T.R., Kim, S.J., Noll, K.S., Griffith, C.A., 2003. Astrophys. J. 583, L39-L42]. We report here on the first spectroscopic observations of Titan covering the whole 2.4-4.9 [mu]m region by two instruments on board the Infrared Space Observatory (ISO) in 1997. These observations show the 2.75-[mu]m window in its complete extent for the first time. In this study we have also used a high-resolution Titan spectrum in the 2.9-3.6 [mu]m region taken with the Keck [Geballe, T.R., Kim, S.J., Noll, K.S., Griffith, C.A., 2003. Astrophys. J. 583, L39-L42; Kim, S.J., Geballe, T.R., Noll, K.S., Courtin, R., 2005. Icarus 173, 522-532] to infer information on the atmospheric parameters (haze extinction, single scattering albedo, methane abundance, etc.) by fitting the methane bands with a detailed microphysical model of Titan's atmosphere (updated from Rannou, P., McKay, C.P., Lorenz, R.D., 2003. Planet. Space Sci. 51, 963-976). We have included in this study an updated version of a database for the CH.sub.4 absorption coefficients [STDS, Wenger, Ch., Champion, J.-P., 1998. J. Quant. Spectrosc. Radiat. Transfer 59, 471-480. See also http://www.u-bourgogne.fr/LPUB/TSM/sTDS.html for latest updates; Boudon, V., Champion, J.-P., Gabard, T., LoA'te, M., Michelot, F., Pierre, G., Rotger, M., Wenger, Ch., Rey, M., 2004. J. Mol. Spectrosc. 228, 620-634]. For the atmosphere we find that (a) the haze extinction profile that best matches the data is one with higher (by 40%) extinction in the atmosphere with respect to Rannou et al. (2003) down to about 30 km where a complete cut-off occurs; (b) the methane mixing ratio at Titan's surface cannot exceed 3% on a disk-average basis, yielding a maximum CH.sub.4 column abundance of 2.27 km-am in Titan's atmosphere. From the derived surface albedo spectrum in the 2.7-3.08 micron region, we bring some constraints on Titan's surface composition. The albedo in the center of the methane window varies from 0.01 to 0.08. These values, compared to others reported in the other methane windows, show a strong compatibility with the water ice spectrum in the near-infrared. Without confirming its existence from this work alone, our data then appear to be compatible with water ice. A variety of other ices, such as CO.sub.2, NH.sub.3, tholin material or hydrocarbon liquid cannot be excluded from our data, but an additional unidentified component with a signature around 2.74 micron is required to satisfy the data. Author Affiliation: (a) LESIA, Observatoire de Paris-Meudon, 5, place Jules Jannsen, F-92195 Meudon Cedex, France (b) California Institute of Technology, Mail Code 100-22, 770 South Wilson Avenue, Pasadena, CA 91125, USA (c) ISO Data Centre, European Space Agency, Villafranca del Castillo, P.O. Box 50727, 28080 Madrid, Spain (d) Service d'Aeronomie/CNRS, Universite de Paris 6-Universite de Versailles, France (e) Laboratoire de Planetologie de Grenoble, 38041 Grenoble Cedex 9, France (f) Observatorio Astronomico and Faculdade de CiA*ncias da Universidade de Lisboa, 1749-016 Lisboa, Portugal (g) Laboratoire de Physique de l'Universite de Bourgogne (LPUB)-CNRS UMR 5027, 9 Av. A. Savary, BP 47870, F-21078 Dijon Cedex, France (h) Laboratory of Theoretical Spectroscopy, Institute of Atmospheric Optics, Russian Academy of Sciences, 634055 Tomsk, Russia Article History: Received 24 March 2005; Revised 31 July 2005

The south polar region of the Moon contains areas permanently shadowed from solar illumination, which may provide cold traps for volatiles such as water ice. Previous radar studies have emphasized the search for diagnostic polarization signatures of thick ice in areas close to the pole, but near-surface regolith properties and regional geology are also important to upcoming orbital studies of the shadowed terrain. To study regional regolith variations, we collected 70-cm wavelength, 450-m resolution, dual-circular polarization radar data for latitudes 60-90[degrees] S using the Arecibo and Greenbank telescopes. The circular polarization ratio, [[micro].sub.c], is sensitive to differences in rock abundance at the surface and up to tens of m below the surface, depending upon the regolith loss tangent. We observe significant variations in [[micro].sub.c], attributed to changes in the surface and subsurface rock population, across the south polar highlands. Concentric haloes of low polarization ratio surrounding Hausen, Moretus, and other young craters represent rock-poor ejecta layers. Values of [[micro].sub.c] up to ~1 occur in the floors and near-rim deposits of Eratosthenian and Copernican craters, consistent with abundant rocky ejecta and/or fractured impact melt. Enhanced [[micro].sub.c] values also correspond to areas mapped as Orientale-derived, plains-forming material [Wilhelms, D.E., Howard, K.A., Wilshire, H.G., 1979. USGS Map I-1162], and similar polarization properties characterize the permanently shadowed floors of craters Faustini and Shoemaker. Small areas of very high (> 1.5) circular polarization ratio occur on shadowed and seasonally sunlit terrain, and appear to be associated with small craters. We suggest that regolith in low-lying areas near the south pole is characterized by a significant impact melt component from Orientale, which provides a source for excavation of the block-rich ejecta around small craters observed in this and earlier radar studies. The lower portion of the interior wall of Shackleton crater, permanently shadowed from the sun but visible from Earth, is not significantly different in 70-cm scattering properties from diurnally/seasonally sunlit areas of craters with similar morphology. Keywords: Moon; Radar; Regoliths

Following the tracing of jets emanating from Comet Wild-2 to depressions in the ice by Brownlee et al. [2004. The Stardust--A successful encounter with the remarkable Comet Wild 2. Lunar Planet. Sci. 35. Abstract 1981], we demonstrated experimentally the formation of depressions and chaotic terrain on comet analogs when gas is released from underlying ice pockets. We also demonstrated experimentally the ejection of ice grains into the experimental cometary 'coma.' Keywords: Comets; Comets composition: Comets dynamics; Surfaces comets

We report on observations of the full Moon brightness temperature covering the frequency range of 300-950 GHz, and also on observations of the lunar eclipse of July 16, 2000, though only covering the frequency range of 165-365 GHz due to poor atmospheric transmission at higher frequencies. All observations were performed from the summit of Mauna Kea (HI) using a Fourier Transform Spectrometer mounted on the Caltech Submillimeter Observatory and supplemented by measurements of the atmospheric opacity using a 183 GHz Water Vapor Monitor. The telescope was pointed to the center of the lunar disk (with a footprint of ~45-15 km on the Moon at 300 through 900 GHz). In order to obtain the correct values of the Moon brightness temperatures at all frequencies we carefully corrected for the atmospheric absorption, which varies across the submillimeter domain. This correction is fully described. The measured pre-eclipse brightness temperature is around 337 K in the 165-365 GHz range. This temperature slightly increases with frequency to reach ~353 K at 950 GHz, according to previous broader band data. The magnitude of the temperature drop observed during the eclipse at 265 GHz (central frequency of the band covered) was about ~70 K, in very good agreement with previous millimeter-wave measurements of other lunar eclipses. We detected, in addition, a clear frequency trend in the temperature drop that has been compared to a thermal and microwave emission model of the lunar regolith, with the result of a good match of the relative flux drop at different frequencies between model and measurements. Keywords: Moon, surface; Radio observations; Data reduction techniques

Meteorite impact on the lunar surface produces a consistent, broadly graded soil. In this note, the geotechnical and geological systems are compared to characterize lunar soil. In terms, the lunar soil particle size distribution is described as sandy silt/silty sand, well-graded. In geologic terms, it is described as very fine sand, very poorly sorted, nearly symmetrical, and mesokurtic. Because of its broad particle size distribution, lunar soil may be internally erodible. CE Database subject headings: Soils; Particle size distribution; Classification; Silts; Sand.

Differential scanning calorimetry indicates that adsorbed water and goethite, a product of hydrated ilmenite, are thermally stable over geologic time in the lunar polar regions. Adsorbed water can undergo burial as a result of several mechanisms, thereby achieving protection from sputtering or Lyman [alpha] radiation losses. Adsorbed, subsurface water layers on lunar dust, and any hydrated minerals present, could account for a majority of the hydrogen at the north lunar pole as well as account for a portion of that found at the south pole, particularly in small ( Key Words: Moon; Moon, surface; ices.

Optical flashes observed on the night side of the Moon during the 1999 Leonid meteor shower have attracted the interest of astronomers. These flashes are attributed to high-velocity impacts of Leonid meteoroids on the lunar surface. Here, we report five lunar flashes detected over a 5.8-h observation period centered at 11:25 UT on Nov. 18, 1999, in Japan. The flashes are characterized by an abrupt brightening. Three flashes exhibited afterglows that remained visible for at least 50 ms, which is longer than the duration predicted for radiation from an impact-generated plasma cloud. We show that thermal radiation from hot droplets ejected from the lunar surface during high-velocity impacts could be the cause of the afterglows. Key Words: cratering; impact processes; meteoroids; meteors; Moon, surface.

Optical and near-IR signatures of water ice on the Moon's surface were sought in the permanently shadowed regions near its poles. Significant amounts of multiply-scattered radiation partly illuminate primary shadows cast by craters and other features. If there is water ice in the permanently shadowed regions of the Moon's surface, its spectral signature should appear in this multiply-scattered light. This investigation can be done most effectively with observations obtained by spacecraft, because most selenocentric positions occupied by the Earth will also be occupied by the Sun at some point in time, and because the lunar poles are seen only obliquely to a terrestrial observer. Images obtained by Clementine are particularly well-suited to this task, because the spacecraft's polar orbit allowed images of the poles to be acquired on nearly every orbit, resulting in literally thousands of images taken within a few degrees of each pole, and because the filters on the ultraviolet-visual camera (UVVIS) and the near infrared camera (NIR) occur at major absorption bands or within important continuum features of water ice. Approximately 5800 images obtained by the UVVIS camera and 1800 images obtained by the NIR camera were calibrated and combined into coadded mosaics to create multispectral maps of the lunar poles with the highest possible signal-to-noise. Unfortunately, analysis of our UVVIS mosaics indicates that any possible signal from multiply-scattered light in primary shadows was overwhelmed by instrumental stray light. For the NIR camera, we were able to determine the normalized reflectance of several regions that were identified by Margot et al. (1999, Science 284, 1658-1660) as permanent shadows. We have identified one permanently shadowed crater with a 1.5-[micro]m band spectral signature indicative of between 2.5 and 21% fractional coverage of H20 frost. However, the same region shows a 2.0 [micro]m spectral signature that is inconsistent with the presence of any water. Key Words: Moon; Moon, surface; ices.

This paper deals with the problem of water permanence on the surface of the Moon. Possible zones where water ice can survive are called cold traps (K. Watson, B. C. Murray, and H. Brown 1961, J. Geophys. Res. 66, 3033-3045). These are zones of the Moon permanently obscured where the temperatures are low enough to preserve ice for billions of years. In this work we developed a model for the topographic temperatures of complex craters whose shape was approximated by a capsized frustum of a circular right cone. Double-shaded areas were simulated by embedding a small hemispherical crater in the shadowed part of the previous one. Their temperatures were calculated using the R. R. Hodges, Jr. (1980, Proc. Lunar Planet. Sci. Conf. 11th, 2463-2477) model. First we verified that our results were in agreement with those of previous models. Our results confirm those obtained by J. R. Salvail and E P. Fanale (1994, Icarus 111, 441-445), and in agreement with Hodges (1980), we found that the lowest temperatures are reached by Tycho-like craters that are the larger and shallower among the examined cases. When small craters are embedded in the shaded area of larger ones, their temperatures are low enough to preserve other volatiles like CO2 (Hodges 1980). In particular, if we consider double-shaded areas in Biot-like craters, the temperatures are lower than 103 K in a shell of almost 20o around the poles, thus allowing the preservation of ices. For geometrical reasons a hemispherical crater embedded in the bottom of a Biot-like crater cold remain in the shadowed area for latitude values lower than those reached by an analogous crater embedded in Sosigene or Tycho-like craters. Therefore the latitudinal radius of polar frost caps could be greater than that predicted by previous models that did not consider double-shaded areas. However, double shielding occurs in only a fraction of the secondary craters; therefore, in this case eventual deposits of ice would be of smaller dimensions compared with the case of primary shielding. Analysis of the Clementine radar data (S. Nozette, C. L. Lichtenberg, P. Spudis, R. Bonner, W. Ort, E. Malaret, M. Robinson, and E. M. Shoemaker 1996, Science 274, 5292-5300) and the Lunar Prospector neutron spectrometer data seems to be consistent with the presence of water ice in very low concentrations across a significant number of craters, thus confirming the old hypothesis of Watson et al. Key Words: Moon; Moon surface; ices.

We present a multispectral photometric study of the Moon between solar phase angles of 0 and 85 degrees. Using Clementine images obtained between 0.4 and 1.0 (mu)m, we produce a comprehensive study of the lunar surface containing the following results: (1) empirical photometric functions for the spectral range and viewing and illumination geometries mentioned, (2) photometric modeling that derives the physical properties of the upper regolith and includes a detailed study of the causes for the lunar opposition surge, (3) an absolute calibration of the Clementine UV/Vis camera. The calibration procedure given on the Clementine calibration web site produces reflectances relative to a halon standard and further appear significantly higher than those seen in groundbased observations. By comparing Clementine observations with prior groundbased observations of 15 sites on the Moon we have determined a good absolute calibration of the Clementine UV/Vis camera. A correction factor of 0.532 has been determined to convert the web site (www.planetary.brown.edu/clementine/calibration.html) reflectances to absolute values. From the calibrated data, we calculate empirical phase functions useful for performing photometric corrections to observations of the Moon between solar phase angles of 0 and 85 degrees and in the spectral range 0.4 to 1.0 (mu)m. Finally, the calibrated data is used to fit a version of Hapke's photometric model modified to incorporate a new formulation, developed in this paper, of the lunar opposition surge which includes coherent backscatter. Recent studies of the lunar opposition effect have yielded contradictory results as to the mechanism responsible: shadow hiding, coherent backscatter, or both. We find that most of the surge can be explained by shadow hiding with a halfwidth of approximately 8 degrees. However, for the brightest regions (the highlands at 0.75-1.0 (mu)m) a small additional narrow component (halfwidth of Key Words: Moon; Moon, surface; photometry.

In order to assess the thermal stability of polar ice deposits, we present model calculated temperatures of flat surfaces and surfaces within bowl-shaped and flat-floored polar impact craters on Mercury and the Moon. Our model includes appropriate insolation cycles, realistic crater shapes, multiple scattering of sunlight and infrared radiation, and depth- and temperature-dependent regolith thermophysical properties. Unshaded water ice deposits on the surface of either body are rapidly lost to thermal sublimation. A subsurface water ice deposit is stable within 2 degrees latitude of the Moon's poles. Meter-thick water ice deposits require billions of years to sublime if located in the permanently shaded portions of flat-floored craters within 10 degrees latitude of the poles of Mercury and 13 degrees latitude of the poles of the Moon. Results for craters associated with radar features on Mercury are consistent with the presence of stable water ice deposits if a thin regolith layer thermally insulates deposits at lower latitudes and within smaller craters. A regolith cover would also reduce losses from diffusion, ion sputtering, impact vaporization, and H Ly(alpha) and is implied independently by the radar observations. Permanently shaded areas near the Moon's poles are generally colder than those near Mercury's poles, but the Moon's obliquity history, its orbit through Earth's magnetospheric tail, and its radar-opaque regolith may limit the volume and radar detectability of ice deposits there.

Altimetric profiles from the Clementine LIDAR are used to calculate the depths of 29 large craters and basins on the Moon. Plotting the depths of the best preserved structures together with values for simple and complex craters measured in pre-Clementine studies reveals an inflection in the depth/diameter (d/D) curve in addition to the one revealed by pre-Clementine data. This inflection occurs in the diameter range that corresponds to the morphologic transition from complex crater to basin. The best empirical power law fit for basin depths is [log.sub.10]0(d) = 0.41 x [[[log.sub.10](D)].sup.0.57]. This relationship is characterized by a lower slope than that for complex craters, demonstrating that this morphologic transition corresponds to a further decrease in the depth of an impact structure relative to its diameter with increasing size. Qualitative consideration of possible causes for the second inflection leads to the conclusion that it is most likely a consequence of a short-term modification mechanism that influences fundamental crater morphology, such as the increasing influence of gravity with diameter. Thicknesses of maria in the major basins are calculated by assuming that their unfilled depths would follow the d/d relation. Results are compared with previous estimates and yield thicknesses that are generally greater than those determined by studies of flooded craters and less than those obtained from analysis of gravity. Key Words: moon; moon surface; cratering; impact processes; collisional physics.

The rate at which cratering events currently occur on the Moon is considered inlight of their influence on the use of the Moon as a radiometric standard. Theradiometric effect of small impact events is determined empirically from the studyof Clementine images. Events that would change the integral brightness of the moonby 1% are expected once per 1.4 Gyr. Events that cause a 1% shift in one pixel forlow Earth-orbiting instruments with a 1-km nadir field of view are expectedapproximately once each 43 Myr. Events discernible at 1% radiometric resolutionwith a 5 arc-sec telescope resolution correspond to crater diameters ofapproximately 210 m and are expected once every 200 years. These rates areuncertain by a factor of two. For a fixed illumination and observation geometry,the Moon can be considered photometrically stable to 1 x [10.sup.-8] per annumfor irradiance, and 1 x [10.sup.-7] per annum for radiance at a resolution commonfor spacecraft imaging instruments, exceeding reasonable instrument goals by sixorders of magnitude.

The first results of an ongoing effort to search for new species in the lunar atmosphere are presented. The observations in terms of the degree to which atomic metal abundances in the lunar atmosphere are stoichiometric, that is, proportional to surface abundances (as the Na:K ratio is), are discussed. Na and K are the only atmospheric constituents to have been observed from Earth, but Apollo sample returns established that a variety of species are more abundant in the lunar surface than either Na or K. Simple stoichiometric arguments (i.e., assuming atmospheric production proportional to surface abundance) predict that relatively abundant lunar surface constituents such as Si, Al, Ca, Mg, Fe, and Ti should be more abundant in the lunar atmosphere than either Na or K. The 2.7-m coude and 2.1-m cassegrain echelle spectrographs at the University of Texas McDonald Observatory were used to investigate this hypothesis by searching for solar resonant scattering lines of nine metallic species between 3700 and 9700 [Angstrom]. Spectra were taken 20 arcsec above the apparent subsolar limb of the Moon near quarter phase on 30 July 1994 and 10-12 March 1995. Upper limits were obtained for the first time for the abundant lunar surface species Si, Al, Ca, Fe, and Ti, as well as Ba and the alkalis Li, Rb, and Cs. In the cases of Si, Ca, Fe, and Ti, the derived upper limits are more than an order of magnitude lower than the simple stoichiometric model predicts. The upper limits for Li and Al are less constraining. The Ba, Rb, and Cs upper limits lead to the conclusion that those species are not stoichiometrically overabundant above the detection threshold in the atmosphere. It is concluded that the stoichiometric Na:K ratio is peculiar in that the mechanism(s) that produce the lunar Na and K atmosphere somehow favor those atomic species over many more or comparably abundant lunar surface species.

During the Clementine 1 mission, a bistatic radar experiment measured the magnitude and polarization of the radar echo versus bistatic angle, β, for selected lunar areas. Observations of the lunar south pole yield a same-sense polarization enhancement around β = 0. Analysis shows that the observed enhancement is localized to the permanently shadowed regions of the lunar south pole. Radar observations of periodically solar-illuminated lunar surfaces, including the north pole, yielded no such enhancement. A probable explanation for these differences is the presence of low-loss volume scatterers, such as water ice, in the permanently shadowed region at the south pole., The possibility of ice on the moon was suggested in 1961 (1). Volatiles degassed from the primitive moon or deposited on the lunar surface by cometary and asteroidal impacts might [...]

Many floor-fractured craters on the Moon show surface deformation like that seen over terrestrial laccoliths. Consequently, terrestrial laccoliths provide one model for such crater modification. This model directly relates surface deformation to the growth of a shallow, crater-centered intrusion, and it estimates intrusion size and magma pressure. It also yields a minimum estimate for intrusion depth. Maximum intrusion depths cannot be directly constrained, but a range of likely intrusion depths can be derived with additional assumptions. When the model is applied to the crater Taruntius, the surface record indicates an intrusion [approximately]30 km across and 1900 m thick. The calculated excess magma pressure is [approximately]9 MPa (90 bar), and the estimated intrusion depths range from [approximately]1 to [approximately]5 km. If magma pressure reflects a hydrostatic magma column beneath Taruntius, these values suggest a total magma column length of [approximately]65 km during crater modification.

Some researchers have asserted that atmospheric absorption distorts lunar emission spectra obtained with a balloon-borne telescope. This has led to the scrapping of the Christiansen emission peak, which had been used by earlier researchers to interpret compositional differences in the moon's surface. However, further study reveals that atmospheric absorption does not distort lunar emission spectra, proving the effectiveness of the Christiansen emission peak in interpreting the lunar surface.