Bulk composition and early differentiation of Mars

G. Jeffrey Taylor, William V. Boynton, J. Brückner, H. Wänke, G. Dreibus, Kristopher E. Kerry, John M. Keller, Robert C. Reedy, Larry G. Evans, Richard D. Starr, Steven W. Squyres, Suniti Karunatillake, Olivier Gasnault, S. Maurice, C. d'Uston, P. Englert, James M. Dohm, Victor Baker, Dave Hamara, Daniel M. JanesAnn L. Sprague, Kyeong J. Kim, D. Drake

Research output: Contribution to journalArticle

73 Citations (Scopus)

Abstract

We report the concentrations of K, Th, and Fe on the Martian surface, as determined by the gamma ray spectrometer onboard the 2001 Mars Odyssey spacecraft. K and Th are not uniformly distributed on Mars. K ranges from 2000 to 6000 ppm; Th ranges from 0.2 to 1 ppm. The K/Th ratio varies from 3000 to 9000, but over 95% of the surface has K/Th between 4000 and 7000. Concentrations of K and Th are generally higher than those in basaltic Martian meteorites (K = 200-2600 ppm; Th = 0.1-0.7 ppm), indicating that Martian meteorites are not representative of the bulk crust. The average K/Th in the crust is 5300, consistent with the Wänke-Dreibus model composition for bulk silicate Mars. Fe concentrations support the idea that bulk Mars is enriched in FeO compared to Earth. The differences in K/Th and FeO between Earth and Mars are consistent with the planets accreting from narrow feeding zones. The concentration of Th on Mars does not vary as much as it does on the Moon (where it ranges from 0.1 to 12 ppm), suggesting that the primary differentiation of Mars differed 'from that of the Moon. If the average Th concentration (0.6 ppm) of the surface is equal to the average of the entire crust, the crust cannot be thicker than about 118 km. If the crust is about 57 km thick, as suggested by geophysical studies, then about half the Th is concentrated in the crust.

Original languageEnglish (US)
Article numberE03S10
JournalJournal of Geophysical Research: Space Physics
Volume112
Issue number3
DOIs
StatePublished - Mar 20 2007

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mars
Meteorites
Mars
crusts
Moon
crust
Earth (planet)
Chemical analysis
Gamma ray spectrometers
SNC meteorites
Silicates
Martian meteorite
Planets
moon
Spacecraft
2001 Mars Odyssey
gamma ray spectrometers
planets
silicates
spacecraft

ASJC Scopus subject areas

  • Oceanography
  • Astronomy and Astrophysics
  • Atmospheric Science
  • Space and Planetary Science
  • Earth and Planetary Sciences (miscellaneous)
  • Geophysics
  • Geochemistry and Petrology

Cite this

Taylor, G. J., Boynton, W. V., Brückner, J., Wänke, H., Dreibus, G., Kerry, K. E., ... Drake, D. (2007). Bulk composition and early differentiation of Mars. Journal of Geophysical Research: Space Physics, 112(3), [E03S10]. https://doi.org/10.1029/2005JE002645

Bulk composition and early differentiation of Mars. / Taylor, G. Jeffrey; Boynton, William V.; Brückner, J.; Wänke, H.; Dreibus, G.; Kerry, Kristopher E.; Keller, John M.; Reedy, Robert C.; Evans, Larry G.; Starr, Richard D.; Squyres, Steven W.; Karunatillake, Suniti; Gasnault, Olivier; Maurice, S.; d'Uston, C.; Englert, P.; Dohm, James M.; Baker, Victor; Hamara, Dave; Janes, Daniel M.; Sprague, Ann L.; Kim, Kyeong J.; Drake, D.

In: Journal of Geophysical Research: Space Physics, Vol. 112, No. 3, E03S10, 20.03.2007.

Research output: Contribution to journalArticle

Taylor, GJ, Boynton, WV, Brückner, J, Wänke, H, Dreibus, G, Kerry, KE, Keller, JM, Reedy, RC, Evans, LG, Starr, RD, Squyres, SW, Karunatillake, S, Gasnault, O, Maurice, S, d'Uston, C, Englert, P, Dohm, JM, Baker, V, Hamara, D, Janes, DM, Sprague, AL, Kim, KJ & Drake, D 2007, 'Bulk composition and early differentiation of Mars', Journal of Geophysical Research: Space Physics, vol. 112, no. 3, E03S10. https://doi.org/10.1029/2005JE002645
Taylor, G. Jeffrey ; Boynton, William V. ; Brückner, J. ; Wänke, H. ; Dreibus, G. ; Kerry, Kristopher E. ; Keller, John M. ; Reedy, Robert C. ; Evans, Larry G. ; Starr, Richard D. ; Squyres, Steven W. ; Karunatillake, Suniti ; Gasnault, Olivier ; Maurice, S. ; d'Uston, C. ; Englert, P. ; Dohm, James M. ; Baker, Victor ; Hamara, Dave ; Janes, Daniel M. ; Sprague, Ann L. ; Kim, Kyeong J. ; Drake, D. / Bulk composition and early differentiation of Mars. In: Journal of Geophysical Research: Space Physics. 2007 ; Vol. 112, No. 3.
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N2 - We report the concentrations of K, Th, and Fe on the Martian surface, as determined by the gamma ray spectrometer onboard the 2001 Mars Odyssey spacecraft. K and Th are not uniformly distributed on Mars. K ranges from 2000 to 6000 ppm; Th ranges from 0.2 to 1 ppm. The K/Th ratio varies from 3000 to 9000, but over 95% of the surface has K/Th between 4000 and 7000. Concentrations of K and Th are generally higher than those in basaltic Martian meteorites (K = 200-2600 ppm; Th = 0.1-0.7 ppm), indicating that Martian meteorites are not representative of the bulk crust. The average K/Th in the crust is 5300, consistent with the Wänke-Dreibus model composition for bulk silicate Mars. Fe concentrations support the idea that bulk Mars is enriched in FeO compared to Earth. The differences in K/Th and FeO between Earth and Mars are consistent with the planets accreting from narrow feeding zones. The concentration of Th on Mars does not vary as much as it does on the Moon (where it ranges from 0.1 to 12 ppm), suggesting that the primary differentiation of Mars differed 'from that of the Moon. If the average Th concentration (0.6 ppm) of the surface is equal to the average of the entire crust, the crust cannot be thicker than about 118 km. If the crust is about 57 km thick, as suggested by geophysical studies, then about half the Th is concentrated in the crust.

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