1. Mineralogy of Siliceous Hot Springs Deposits: Comparing Earth and Mars Intern Vicki Mills Mentor Prof. Jack Farmer

2. (Ruff, 2008) Opaline Silica Deposits (> 90 % Silica )

3. Mini-TES Spectra ( Ruff, S., J. Farmer, W. Calvin et al. 2007. Evidence for possible siliceous sinter at Home Plate in Gusev Crater Eos Transactions, American Geophysical Union, Fall Meeting Suppl, Abstract, P23A-1097 )

4. Transformational Sequence for Silica (SiO 2 ) Polymorphs Opal-A ( SiO 2.n H 2 O ) Opal-C/T Quartz AmorphousParacrystalline Microcrystalline Preservation Potential Low High Decrease in porosity, permeability & structural H 2 0 2-theta peaks: 20-24°2-theta peaks: 20.8° 2-theta curve: centered at 22°

5. Opaline Silica (Opal-A) forms in Hot Spring Environments Study Locations : Excelsior Geyser, Yellowstone National Park, Wyoming

6. Orakei Korako, Orakei Korako, New Zealand New Zealand Steamboat Springs, Nevada Steamboat Springs, Nevada

7. X-Ray Powdered Diffraction (XRPD) Sample Preparation Sample Preparation Mortar & Pestle Mortar & Pestle Sieved 150 μ m Sieved 150 μ m Run Conditions Run Conditions Siemens D-5000 Siemens D-5000 40kV at 30mA 40kV at 30mA CuK α Radiation CuK α Radiation Step size 0.03-0.05° Step size 0.03-0.05° For JADE Analysis Sample Preparation 3g sample + 0.33g ZnO Crushed <20μm w/micronising mill Run Conditions Siemens D-5000 40kV at 30mA CuKα Radiation Step Size 0.0163 For Rock Jock Analysis Sample Preparation

8. New Zealand JADE XRPD Results Yellowstone Steamboat New Zealand Quartz Opal-C/T Amorphous Curve Centered at 22° 2θ Opal-A Clay Profile

9. Rock Jock Results 63.8 61.7 20.022.1 12.311.9

10. Thin Section Analysis Finely laminated sinter Coniform Fabric

11. Characterization of Thin Sections Microbial fossil assemblage (20X) (10X) Calothrix (thermophilic cyanobacterium; filaments are ~30μm in diameter) Phormidium (thermophilic cyanobacterium; filaments are ~5μm in diameter) 35-59°C<35°C

12. Interpretations Similarities between mini-TES spectra of high silica deposits at Home Plate and those of opaline siliceous sinter from hot springs on Earth, suggests a common origin. On earth, siliceous sinters have been shown to preserve a diverse fossil record of microbial life. Similarities between mini-TES spectra of high silica deposits at Home Plate and those of opaline siliceous sinter from hot springs on Earth, suggests a common origin. On earth, siliceous sinters have been shown to preserve a diverse fossil record of microbial life. This interpretation is consistent with the geological setting of Home Plate, which has been interpreted to be an explosive volcanic feature. Two alternative hypotheses have been suggested: Thermal spring deposits, or fumerolic deposits. It is not possible to choose based on current evidence! This interpretation is consistent with the geological setting of Home Plate, which has been interpreted to be an explosive volcanic feature. Two alternative hypotheses have been suggested: Thermal spring deposits, or fumerolic deposits. It is not possible to choose based on current evidence! Other outstanding issues: On Earth, opaline sinters quickly transform to ordered phases, like quartz. However, it appears that even after billions of years on Mars, the high silica deposits at Home Plate have not undergone any significant digenetic transformation. Why? Other outstanding issues: On Earth, opaline sinters quickly transform to ordered phases, like quartz. However, it appears that even after billions of years on Mars, the high silica deposits at Home Plate have not undergone any significant digenetic transformation. Why?