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The first unambiguous global distribution of Ca on the Moon has been revealed by the Kaguya Gamma-Ray Spectrometer. The observation of the 3737 keV gamma rays from 40 Ca with a high energy resolution Ge detector, corrected for fast neutrons, improved greatly our confidence in these remote sensing data. While the derived Ca abundance generally confirms the mare-highland dichotomy, we found that the eastern mare regions such as Crisium, Nectaris, and Fecunditatis exhibit unexpected high Ca abundances. This may be explained by regional concentrations of high-Ca clinopyroxene. Our Ca map also shows that the lowest CaO abundance found in the returned samples (∼8 wt%) may actually be common in Oceanus Procellarum, suggesting the possible sampling bias of Apollo and Luna missions. These observational results on Ca serve as a complementary criterion for better characterization of mare regions on the Moon.

Kaguya gamma-ray spectrometer measured thorium (Th) distribution on the lunar farside with the highest sensitivity among past gamma-ray remote sensing missions. The newly obtained Th map has revealed that two regions near the equator on the farside have the lowest Th abundances. We found that the variation of the Th abundance perfectly correlates with the crustal thickness in the farside and the southern nearside, and it could be a result of the crystallization of the lunar magma ocean.

The Miniaturised Mossbauer Spectrometers MIMOS II on board the two Mars Exploration Rovers (MER) have now been collecting valuable scientific data for more than five years. Mossbauer Spectrometers are part of two future missions: Phobos Grunt (Russian Space Agency) and a joint ESA—NASA Rover in 2018. The new advanced MIMOS IIA instrument described in this paper uses Silicon Drift Detectors (SDD) allowing also X-ray fluorescence chemical analysis (XRF) simultaneously to Mossbauer acquisitions. This paper highlights the features and technological improvements of the new spectrometer MIMOS IIA.

The high precision gamma-ray spectrometer (GRS) is scheduled to be launched on the lunar polar orbiter of the SELENE mission in 2007. The GRS consists of a large Ge crystal as a main detector and massive bismuth germanate crystals as an anticoincidence detector. A Stirling cryocooler was adopted in cooling the Ge detector. The flight model of SELENE GRS has been completed and an energy resolution of 3.0 keV (FWHM) at 1.332 MeV has been achieved. The spectrometer aims to observe nuclear line gamma rays emitted from the lunar surface in a wide energy range from 100 keV to 12 MeV for one year and more to obtain chemical composition on the entire lunar surface. The gamma-ray data enable us to study lunar geoscience problems including crust and mantle composition, and volatile reservoirs at polar regions.

High-purity germanium (HPGe) detectors used in space for gamma-ray spectroscopy in astrophysics and planetary exploration are known to be damaged by energetic particles. For interplanetary missions close to the Sun such as Messenger or BepiColombo to explore planet Mercury, solar protons represent an important source of damage. In this work, irradiation tests were performed on two large-volume coaxial n-type HPGe detectors with mono-energetic beams of 50-60 MeV protons. One of the detectors, designed for spatial applications, was incrementally exposed to a proton fluence up to 7.5 x 1010 p/cm2 and the other to a unique fluence of 10(10) p/cm(2.) The results showed that the degradation of the energy resolution appeared for fluences higher than 5 x 108 p/cm(2). Moreover, a loss in detection efficiency was observed for fluences above 1010 p/cm(2). Annealings above 80 degrees C allowed the recovery of the initial resolution but not the initial efficiency. By extrapolating the results beyond the experimental conditions, this study also establishes the limits for the use of spaceborne HPGc detectors in harsh low-energy proton environment. (c) 2006 Elsevier B.V. All rights reserved.

Neutron spectroscopy is a new way to study planetary bodies that have sufficiently thin atmospheres. This technique was demonstrated for the first time with Lunar Prospector around the Moon. Here, we report results for moderated neutrons having energies from 0 to 500 keV that were measured using the anti-coincidence shield (ACS) of the gamma-ray spectrometer. We describe the detection method, followed by data reduction with an emphasis on each data processing step; most steps rely on in-flight calibrations. The behavior of the ACS is well known regarding the measurement of moderated neutrons. We present a map of 0– 500 keV neutrons over the whole Moon with a spatial resolution of ∼60 km . Statistical errors per pixel are less than 2%. The resulting map includes information about the hydrogen content, concentrations of Fe, Ti, traces of Sm and Gd, and the atomic mass of the regolith. These data complement other neutron products of Lunar Prospector, namely thermal (0– 0.4 eV ), epithermal (0.4– 100 eV ) and fast (0.5– 8 MeV ) neutrons. The previous unexplored region between 100 eV and 500 keV reveals several high counting rate regions that are also visible in epithermal neutron data.

The Japanese lunar polar orbiter SELENE carries a gamma-ray spectrometer which uses a high-purity Ge detector cooled to 80-90 K by a Stirling mechanical cooler. The Gamma-Ray Spectrometer (GRS) consists of a large volume n-type Ge detector (252 cc) as the main detector and bismuth-germanate (BGO) and plastic scintillators as an active shielding. The engineering model still maintains excellent energy resolution even after severe vibration testing. The Gamma-Ray Spectrometer will globally map of the Moon for the major elements of O, Mg, Al, Si, Ti, Fe, etc. and natural radioisotopes of K, Th and U with a high precision. The energy resolution of the GRS is such that it would identify prompt gamma-ray line from hydrogen and the location and the amount of ice, if it exists at the polar regions.

We review the current status of the development of Gamma-Ray Spectrometer (GRS) for the Lunar mission SELENE. The GRS instrument will measure gamma-rays in the energy range from 100 keV to 9 MeV. The instrument is a high-purity Ge detector surrounded by BGO and plastic scintillators which are operated as an anticoincidence shield, and is cooled by a Stirling cycle cryocooler. The primary objective is to provide global maps of the lunar composition. Measurements are anticipated for Fe, Ti, U, Th, K, Si, Mg, Al, O, Ca and Na over the entire lunar surface. The abundance of water ice in the permanently shaded craters at both the lunar poles will be measured with this instrument.

The MGS MAG/ER investigation provides vector measurements of the magnetic field and the ionospheric electron density near periapsis. The instrumentation consists of twin triaxial fluxgate magnetometers and a “top hat” electrostatic analyzer of electrons in the energy range of 1 eV to 20 keV. Results include extensive mapping of the detached bow shock wave in the solar wind, the nature and structure of the ionopause and magnetic pile-up boundaries. The most surprising result is the discovery of localized magnetic fields of planetary origin, presumably due to remanent crustal magnetization. Maximum fields measured while below the ionosphere exceed 300 nT. We present an initial study of one of these very localized fields and extrapolations to the Martian surface in the Acidalia planitia.

Several upstream ion distributions having a gyrating signature have been identified with the 3DP/PESA-High analyser on board the WIND spacecraft. These distributions are observed at distances greater than 20 R E from the Earth's bow shock. The distributions are observed in association with low frequency waves propagating quasi-parallel to the background magnetic field. By estimating the bulk velocity of the gyrating ions, we have found that the waves resonate with the particles. The observation of gyrating ions at large distances from the shock suggests their local production, probably from field-aligned beam disruption.

Two and six keV electron and proton data obtained by the FVA detector onboard ISEE 1 and 2 in the upstream region near apogee are analyzed. Tracing back electron and ion fluxes shows that electrons are present in a region of space near the boundary inside the foreshock, and that diffuse and intermediate ions do not directly issue from the bow shock surface. Using the assumptions that they result from the scattering of an initial population with no magnetic moment (μ=0), and that their mean energy is conserved through a diffusion process, we get a clear organisation of the data. Protons are present in a broad region of space inside the foreshock but appear at greater distances from the boundary when the spacecraft is near apogee. It is thought that these protons have their origin in the scattered beam-like distributions produced at the shock surface.