Analysis of MESSENGER Gamma-Ray Spectrometer data from the Mercury flybys

Rhodes, E. A.; Evans, L. G.; Nittler, L. R.; Starr, R.; Sprague, A. L.; Lawrence, D. J.; McCoy, Timothy J.; Stockstill-Cahill, K. R.; Goldsten, J.; Peplowski, P. N.; Hamara, D.; Boynton, W. V.; Solomon, Sean C.

doi:10.1016/j.pss.2011.07.018

Cited by 18 publications

(17 citation statements)

References 16 publications

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“…Peak areas are limited to the full-energy photopeaks, with the exception of the 6129-keV oxygen data, which include counts from the first-and secondescape peaks. abundance of K with Mercury flyby GRS data were published by Rhodes et al [2011], and their results (870 AE 360 ppm) are consistent with the elemental abundances derived in this work for comparable regions.…”

Section: Abundance Mappingsupporting

confidence: 90%

Variations in the abundances of potassium and thorium on the surface of Mercury: Results from the MESSENGER Gamma‐Ray Spectrometer

et al. 2012

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A technique for converting gamma‐ray count rates measured by the Gamma‐Ray Spectrometer on the MESSENGER spacecraft to spatially resolved maps of the gamma‐ray emission from the surface of Mercury is utilized to map the surface distributions of the elements Si, O, and K over the planet's northern hemisphere. Conversion of the K gamma‐ray count rates to elemental abundances on the surface reveals variations from 300 to 2400 ppm. A comparison of these abundances with models for the maximum surface temperature suggests the possibility that a temperature‐related process is controlling the K abundances on the surface as well as providing K to the exosphere. The abundances of K and Th have been determined for several geologically distinct regions, including Mercury's northern smooth plains and the plains interior to the Caloris basin. The lack of a significant variation in the measured Th abundances suggests that there may be considerable variability in the K/Th abundance ratio over the mapped regions.

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Section: Abundance Mappingsupporting

confidence: 90%

Variations in the abundances of potassium and thorium on the surface of Mercury: Results from the MESSENGER Gamma‐Ray Spectrometer

et al. 2012

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“…On the basis of MESSENGER XRS measurements that indicate low Ti abundances (<1 wt%) on the surface of Mercury [Nittler et al, 2011], the 983-keV Ti peak meets the requirement of C N ≫ C P and was therefore used to determine the background amplification factor (1.49 AE 0.10) derived by Peplowski et al [2012] and utilized by Evans et al [2012] to determine the abundances of stable elements on the surface of Mercury. Amplification factors are altitude dependent, and the Ti-derived amplification factor was determined using an elevation cutoff for the low-altitude data of 2000 km, which differs from the cutoff of 2500 km utilized by Rhodes et al [2011] to derive their amplification factor of $2. The difference in the two altitude cutoffs suggests that the divergence between the two amplification factors is larger than suggested by a simple comparison of the two values.…”

Section: Results and Implicationsmentioning

confidence: 99%

“…The difference in the two altitude cutoffs suggests that the divergence between the two amplification factors is larger than suggested by a simple comparison of the two values. As a result, the background corrections of Rhodes et al [2011] overestimate the low-altitude backgrounds and therefore underestimate the planetary signal for the flyby measurements. Later publications on the analysis of orbital data [Peplowski et al, 2011b[Peplowski et al, , 2012Evans et al, 2012] should be referenced for accurate abundances.…”

Section: Results and Implicationsmentioning

confidence: 99%

Aluminum abundance on the surface of Mercury: Application of a new background‐reduction technique for the analysis of gamma‐ray spectroscopy data

et al. 2012

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[1] A new technique has been developed for characterizing gamma-ray emission from a planetary surface in the presence of large background signals generated in a spacecraft. This technique is applied to the analysis of Al gamma rays measured by the MESSENGER Gamma-Ray Spectrometer to determine the abundance of Al on the surface of Mercury. The result (Al/Si = 0.29 À0.13 +0.05 ) is consistent with Al/Si ratios derived from the MESSENGER X-Ray Spectrometer and confirms the finding of low Al abundances. The measured abundance rules out a global, lunar-like feldspar-rich crust and is consistent with previously suggested analogs for surface material on Mercury, including terrestrial komatiites, low-iron basalts, partial melts of CB chondrites, and partial melts of enstatite chondrites. Additional applications of this technique include the measurement of other elements on Mercury's surface as well as the analysis of data from other planetary gamma-ray spectrometer experiments.

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“…The color contrast among different geological units is much less obvious than that for the lunar surface partly because the colors of the volcanic deposits are brighter than their lunar counterparts (i.e., mare basalt) due to the lower amount of iron (Lucey et al, 2006;Nittler et al, 2011;Rhodes et al, 2011). In addition, geological activity on Mercury has been apparently dormant since the Late Heavy Bombardment, leaving a large percentage of the surface ancient ( > 3.8 Ga) (Strom, 1979) and saturated with impact craters; without geological activity, the long-lasting impact cratering process can deform old terrains and mix the volcanic materials (e.g., Arvidson et al, 1975;Schultz, 1989), which may have resulted in the relatively homogeneous color of Mercury's surface.…”

Section: Mercurymentioning

confidence: 99%

“…Mercury exhibits relatively homogeneous gray color and is known to be covered with basaltic materials with common sulfur-and magnesium-rich characteristics (Nittler et al, 2011, Rhodes et al, 2011. At a closer look, there are both smooth plains and heavily cratered regions.…”

Section: Mercurymentioning

confidence: 99%

Geology and Photometric Variation of Solar System Bodies with Minor Atmospheres: Implications for Solid Exoplanets

Fujii

Kimura²,

Dohm³

et al. 2014

Astrobiology

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A reasonable basis for future astronomical investigations of exoplanets lies in our best knowledge of the planets and satellites in the Solar System. Solar System bodies exhibit a wide variety of surface environments, even including potential habitable conditions beyond Earth, and it is essential to know how they can be characterized from outside the Solar System. In this study, we provide an overview of geological features of major Solar System solid bodies with minor atmospheres (i.e., the terrestrial Moon, Mercury, the Galilean moons, and Mars) that affect surface albedo at local to global scale, and we survey how they influence pointsource photometry in the UV/visible/near IR (i.e., the reflection-dominant range). We simulate them based on recent mapping products and also compile observed light curves where available. We show a 5-50% peak-totrough variation amplitude in one spin rotation associated with various geological processes including heterogeneous surface compositions due to igneous activities, interaction with surrounding energetic particles, and distribution of grained materials. Some indications of these processes are provided by the amplitude and wavelength dependence of variation in combinations of the time-averaged spectra. We also estimate the photometric precision needed to detect their spin rotation rates through periodogram analysis. Our survey illustrates realistic possibilities for inferring the detailed properties of solid exoplanets with future direct imaging observations.

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Analysis of MESSENGER Gamma-Ray Spectrometer data from the Mercury flybys

Cited by 18 publications

References 16 publications

Variations in the abundances of potassium and thorium on the surface of Mercury: Results from the MESSENGER Gamma‐Ray Spectrometer

Variations in the abundances of potassium and thorium on the surface of Mercury: Results from the MESSENGER Gamma‐Ray Spectrometer

Aluminum abundance on the surface of Mercury: Application of a new background‐reduction technique for the analysis of gamma‐ray spectroscopy data

Geology and Photometric Variation of Solar System Bodies with Minor Atmospheres: Implications for Solid Exoplanets

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