St. Catharines 2004
Technical Program

SS19:  Molecules to Planets: Infrared spectroscopy in geochemistry, exploration geochemistry and remote sensing 
Organizers / Organisateurs:  Penny King, Mike Ramsay, Gregg Swayze
Room / Salle:  AS 201

Date:  05/12/2004
Time:  9:00 AM
Presenter:  Michelle C. Goryniuk

The effect of grain size on the thermal infrared reflectance spectra of opal-A from Ohaaki Hot Springs, New Zealand

Goryniuk, M., Rivard, B., and Jones, B. Department of Earth and Atmospheric Sciences, University of Alberta, Edmonton, AB,

The discovery of opal-A on the surface of Mars would be consistent with hydrous activity, and therefore its discovery would have serious implications for those searching for sites hospitable to life. Reflectance values between 0.5-25 ým were collected from a suite of amorphous silicates (opal-A) from the Ohaaki Hot Springs located in the Taupo Volcanic Zone, New Zealand. Spectra were collected from fifteen hand samples and cores, and from crushed material of three different grain sizes (0-74 ým, 74-250 ým, and 250-500 ým). This research has documented the complete spectral signature of opal-A from 0.5-25 ým as observed in two different spectral classes identified from the sample suite. The most obvious spectral features in the TIR were two bands observed at 8 and 9 ým. Two additional bands were detected between 10.05-10.25 ým and 11.25-11.67 ým in fine-grained material. Examining the relative magnitude differences between these four bands was the main criterion for spectra classification. The endmember spectrum of each of the two classes of opal-A are presented and changes in physical properties that alter the opal-A spectral signature are discussed. While limited reflectance spectra of opal-A are available in current literature, this research has examined physical forms of opal-A that would be more compatible with the types of materials that are thought to exist on the surface of Mars.