Observations of water vapor ions at the lunar surface

The Apollo 14 Suprathermal Ion Detector Experiment observed a series of bursts of 48.6 eV water vapor ions at the lunar surface during a 14-h period on March 7, 1971. The maximum flux observed was 10⁸ ions cm^–2 s^–1 sr^–1. These ions were also observed at Apollo 12, 183 km to the west. Evaluation of specific artificial sources including the Apollo missions and the Russian Lunokhod leads to the conclusion that the water vapor did not come from a man-made source. Natural sources exogenous to the Moon such as comets and the solar wind are also found to be inadequate to explain the observed fluxes. Consequently, these water vapor ions appear to be of lunar origin.Paper dedicated to Prof. Harold C. Urey on the occasion of his 80th birthday on 29 April 1973.     

Sulfates on Mars: A systematic Raman spectroscopic study of hydration states of magnesium sulfates

The martian orbital and landed surface missions, OMEGA on Mar Express and the two Mars Explorations Rovers, respectively, have yielded evidence pointing to the presence of magnesium sulfates on the martian surface. In situ identification of the hydration states of magnesium sulfates, as well as the hydration states of other Ca- and Fe- sulfates, will be crucial in future landed missions on Mars in order to advance our knowledge of the hydrologic history of Mars as well as the potential for hosting life on Mars. Raman spectroscopy is a technique well-suited for landed missions on the martian surface. In this paper, we report a systematic study of the Raman spectra of the hydrates of magnesium sulfate. Characteristic and distinct Raman spectral patterns were observed for each of the 11 distinct hydrates of magnesium sulfates, crystalline and non-crystalline. The unique Raman spectral features along with the general tendency of the shift of the position of the sulfate ν₁ band towards higher wavenumbers with a decrease in the degree of hydration allow in situ identification of these hydrated magnesium sulfates from the raw Raman spectra of mixtures. Using these Raman spectral features, we have started the study of the stability field of hydrated magnesium sulfates and the pathways of their transformations at various temperature and relative humidity conditions. In particular we report on the Raman spectrum of an amorphous hydrate of magnesium sulfate (MgSO₄·2H₂O) that may have specific relevance for the martian surface.     

Timing of diagenetic haematite growth in red pelagic limestones from Gubbio (Italy)

Magnetite, haematite, and to a minor extent maghaemite are recognised in the Cretaceous and Paleocene red pelagic limestones at Gubbio. The magnetite is detrital (or biological), whereas the haematite grew during diagenesis from a goethitic precursor. Thermal and AF demagnetization of samples collected from close to reversal boundaries indicate that the various magnetization components do not record the polarity reversal at exactly the same stratigraphic level. In the few tens of centimetersbelow a recorded geomagnetic reversal, defined by the magnetite magnetization, some of the haematite grains are magnetized in the post-reversal field. The blocking temperature spectra of this haematite fraction (with post-reversal magnetization) are found to shift toward higher temperatures as the reversal boundary is approached. The blocking temperature spectra reflect the grain size spectra of the haematite, which we interpret as arising by the continual nucleation of grains down to a certain burial depth where the conditions are no longer conducive to further haematite growth. The depth below reversal boundaries to which haematite with post-reversal magnetization can occur, is estimated to be about 60 cm (after compaction), and is equivalent to a time of about 10⁵ years for these particular sediments. A detailed study of the magnetization components at reversal boundaries indicates that the first diagenetic growth of haematite through the single-domain critical volume occurs prior to the mechanical fixation of the detrital (or biological) magnetite. Subsequently the diagenetic haematite grains do not rotate in response to the ambient geomagnetic field polarity as easily as the magnetite, because of their occurrence as pigmentary coatings on larger non-magnetic grains.     

A case study considering the comparability of mass and volumetric suspended sediment data

Contemporary real-time instruments that advance suspended sediment monitoring capabilities often provide results in units (e.g. volumetric) that are not easily comparable to traditional mass (e.g. gravimetric) methods. A Midwest case study was initiated to assess the accuracy of three methods commonly used to convert volumetric data to mass. Water samples from rural, suburban, and urban stream reaches were analyzed for suspended sediment concentration using laser diffraction and wet sieving methods, resulting in paired volumetric (μl/l) and mass (mg/l) suspended sediment concentrations. Observed volumetric data were converted to mass using an assumed particle density (Pd) of 2.65 g/cm³, a calculated Pd, and linear regression. Using the assumed Pd, estimated mass data differed from observed mass data by as much as 60 %. Dividing mass concentration (mg/l) by the volumetric concentration (μl/l) resulted in site-specific average suspended sediment particle densities ranging from 2.17, 1.99, 1.76 g/cm³ for different land use types. Using a calculated Pd, estimated mass data differed from observed mass data by as much as 45 %. Paired sample t tests showed observed and estimated mass values to be significantly different (p < 0.01). R ² values for regression equations ranged from 0.82 to 0.88. Conversion difficulties likely result from temporal and spatial variations of Pd. The results illustrate the imprecision of conversion methods and highlight possible estimation errors assuming idealized conditions. Continued work is necessary to improve quantitative relationship(s) between mass and volumetric suspended sediment data and the utility of both types of information for science and land management practices.     

南极格罗夫山火星陨石GRV 99027的宇宙射线暴露年龄

中国第16次南极考察队回收的GRV 99027的宇宙成因核素10Be和26Al的含量分别为(14.1±0.6)和(67.5±3.4) dpm/kg, 从10Be的含量计算出GRV 99027的宇宙线暴露年龄为(4.4±0.6) Ma, 而其过高的26Al的含量表明来自太阳射线的影响. 幔源火星陨石GRV 99027, LEW 88516, Y-793605, NWA 1950和ALHA77005具有非常相近的宇宙线暴露年龄, 再加上极为相似的矿物学和地球化学特征, 说明它们极有可能来自火星上的同一次撞击事件.