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

Edgar A. Rhodes, Larry G. Evans, Larry R. Nittler, Richard D. Starr, Ann L. Sprague, David J. Lawrence, Timothy J. McCoy, Karen R. Stockstill-Cahill, John O. Goldsten, Patrick N. Peplowski, David K. Hamara, William V. Boynton, Sean C. Solomon

Research output: Contribution to journalArticle

11 Citations (Scopus)

Abstract

During its three flybys of Mercury, the MESSENGER spacecraft made the first detection of gamma-ray emission from the planets surface. With a closest approach distance of ∼200 km, the flybys provided an opportunity to measure elemental abundances of Mercurys near-equatorial regions, which will not be visited at low altitude during MESSENGERs orbital mission phase. Despite being limited by low planetary photon flux, sufficient counts were accumulated during the first two flybys to estimate bounds on abundances for some elements having relatively strong gamma-ray spectral peaks, including Si, Fe, Ti, K, and Th. Only for Si is the standard deviation σ sufficiently small to conclude that this element was detected with 99% confidence. Iron and potassium are detected at the 2-σ (95% confidence) level, whereas only upper bounds on Ti and Th can be determined. Relative to a Si abundance assumed to be 18 weight percent (wt%), 2-σ upper bounds have been estimated as 9.7 wt% for Fe, 7.0 wt% for Ti, 0.087 wt% for K, and 2.2 ppm for Th. The relatively low upper bound on K rules out some previously suggested models for surface composition for the regions sampled. Upper bounds on Fe/Si and Ti/Si ratios are generally consistent with Ti and Fe abundances estimated from the analysis of measurements by the MESSENGER Neutron Spectrometer during the flybys but are also permissive of much lower concentrations.

Original languageEnglish (US)
Pages (from-to)1829-1841
Number of pages13
JournalPlanetary and Space Science
Volume59
Issue number15
DOIs
StatePublished - Dec 2011

Fingerprint

MESSENGER (spacecraft)
gamma ray spectrometers
spectrometer
confidence
gamma rays
neutron spectrometers
equatorial regions
low altitude
planets
low concentrations
standard deviation
potassium
spacecraft
planet
iron
orbitals
analysis
mercury
photons
estimates

Keywords

  • Elemental abundances
  • Gamma-ray spectrometry
  • Mercury
  • MESSENGER

ASJC Scopus subject areas

  • Space and Planetary Science
  • Astronomy and Astrophysics

Cite this

Rhodes, E. A., Evans, L. G., Nittler, L. R., Starr, R. D., Sprague, A. L., Lawrence, D. J., ... Solomon, S. C. (2011). Analysis of MESSENGER Gamma-Ray Spectrometer data from the Mercury flybys. Planetary and Space Science, 59(15), 1829-1841. https://doi.org/10.1016/j.pss.2011.07.018

Analysis of MESSENGER Gamma-Ray Spectrometer data from the Mercury flybys. / Rhodes, Edgar A.; Evans, Larry G.; Nittler, Larry R.; Starr, Richard D.; Sprague, Ann L.; Lawrence, David J.; McCoy, Timothy J.; Stockstill-Cahill, Karen R.; Goldsten, John O.; Peplowski, Patrick N.; Hamara, David K.; Boynton, William V.; Solomon, Sean C.

In: Planetary and Space Science, Vol. 59, No. 15, 12.2011, p. 1829-1841.

Research output: Contribution to journalArticle

Rhodes, EA, Evans, LG, Nittler, LR, Starr, RD, Sprague, AL, Lawrence, DJ, McCoy, TJ, Stockstill-Cahill, KR, Goldsten, JO, Peplowski, PN, Hamara, DK, Boynton, WV & Solomon, SC 2011, 'Analysis of MESSENGER Gamma-Ray Spectrometer data from the Mercury flybys', Planetary and Space Science, vol. 59, no. 15, pp. 1829-1841. https://doi.org/10.1016/j.pss.2011.07.018
Rhodes EA, Evans LG, Nittler LR, Starr RD, Sprague AL, Lawrence DJ et al. Analysis of MESSENGER Gamma-Ray Spectrometer data from the Mercury flybys. Planetary and Space Science. 2011 Dec;59(15):1829-1841. https://doi.org/10.1016/j.pss.2011.07.018
Rhodes, Edgar A. ; Evans, Larry G. ; Nittler, Larry R. ; Starr, Richard D. ; Sprague, Ann L. ; Lawrence, David J. ; McCoy, Timothy J. ; Stockstill-Cahill, Karen R. ; Goldsten, John O. ; Peplowski, Patrick N. ; Hamara, David K. ; Boynton, William V. ; Solomon, Sean C. / Analysis of MESSENGER Gamma-Ray Spectrometer data from the Mercury flybys. In: Planetary and Space Science. 2011 ; Vol. 59, No. 15. pp. 1829-1841.
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