Sarah Noble



Volcanology Paper Topic

Andesite in the Northern Plains?:
Implications for the Volcanic History of Mars

Abstract

Intro
- What is TES?
- What is the evidence for andesite?
- What are the issues surrounding the interpretation of andesite?
- How does this evidence relate to the Pathfinder data (the "sulfur-free rock")

Implications if it is Andesite
- Are Plate Tectonics required?
- Could hydrothermally altered crust cause andesites to evolve
- Implications for the size and duration of a possible ocean
- Are their other ways of producing andesite in such volumes?

Glass
- The TES team used deconvolution to determine that their andesite endmember is ~30-40% obsidian-like glass (i.e. very high silica), but that obsidian is the only glass in their spectral library at this time.
- How unique is the spectrum of obsidian? Could the glass component be of lower silica content?
- I am in the process of gathering spectra of a wide range of glass compositions ­ everything from lunar soil agglutinates and other lunar glasses to maskelynite to the Moroz et al JSC Mars 1 simulant glasses (see LPSC31 ab)
- I may measure additional glass spectra of other compositions as well in the Nicolet FTIR spectrometer in RELAB
- I can then compare those spectra to the TES spectral library¹s obsidian to see how strongly glass spectra are controlled by composition

Other possible explanations for TES results
- Could the TES data be satisfactorily explained by other mechanisms?
- A more mafic glass component?
- A concentration of glass due to weathering?
- What implications do these other possibilities have for Mars¹ history?

Conclusions


Refs (partial list):

Bandfield J.L, V.E. Hamilton, and P.R. Christensen (2000) A global View of Martian Surface Compositions from MGS-TES. Science, 287, 1626-1630.

Crisp J., A.B. Kahle, and E.A. Abbott (1990) Thermal Infrared Spectral Character of Hawaiian Basaltic Glasses. Journal of Geophysical Research, 95, B13, 21657-21669.

Christensen P.R., J.L. Bandfield, M.D. Smith, and V.E. Hamilton (2000) Identification of a basaltic component on the Martian surface from Thermal Emission Spectrometer Data. Submitted to Journal of Geophysical Research.

Hamilton V.E and M.B. Wyatt (1999) Thermal Emission Spectroscopy of Synthetic Igneous Glasses. Abstracts to the 5th International Mars Conf.

Nash D.B. and J.W. Salisbury (1991) Infrared Reflectance Spectra (2.2-15mm) of Plagioclase Feldspars. Geophysical Research Letters, 18, 1151-1154.

Sleep N.H. (1994) Martian Plate Tectonics. Journal of Geophysical Research, 99, E3, 5639-5655.

Smith M.D., J. L. Bandfield and P.R. Christensen (2000) Separation of atmospheric and surface spectral features in Mars Global Surveyor Thermal Emission Spectrometer (TES) spectra. Submitted to Journal of Geophysical Research

Wood C.A. and P.W. Francis (1982) Absence of Silicic Volcanism on Mars: Implications for Crustal Composition and Volatile Abundances. Journal of Geophysical Research, 87, B12, 9881-9889.