For those interested in San Antonio....

SwIm Seminar
May 5, 2003
2:00pm CST
Bldg. 178
Conference Room 2

Igneous and Aqueous Processes on Mars: Evidence from Measurements of K and
Th by the Mars Odyssey Gamma-Ray Spectrometer

Presented by:

G. Jeffrey Taylor
Hawai`i Institute of Geophysics and Planetology
University of Hawai`i

The concentrations of potassium and thorium on planetary surfaces reveal
much of the story of crustal evolution. They are both incompatible
elements, so they concentrate in magma. During igneous processing, the
ratio of K to Th stays approximately constant, so K/Th in igneous rocks
reflects that ratio in the bulk silicate planet. However, aqueous
processes can fractionate K from Th, in principle giving us a way to
investigate the extent of aqueous alteration of a planetary surface. I
will report preliminary measurements of the concentrations of K and Th on
Mars. Concentrations of K and Th and the K/Th ratio vary across the
surface. Concentrations are higher than in Martian meteorites, suggesting
that most of the crust formed by partial melting of enriched (or at least
not depleted) mantle. The average Th concentration (1.1 ppm), if
applicable to the entire crust, implies a maximum thickness of about 65
km. The variation in the K/Th ratio suggests that aqueous processes have
affected the chemistry of the surface

Abstract:
G. JEFFREY TAYLOR
Hawai'i Institute for Geophysics and Planetology
University of Hawai'i, Manoa
1680 East-West Rd., Honolulu, HI 96822
gjtaylor@hawaii.edu; www.higp.hawaii.edu/~gjtaylor