Characterization of Mars Analog Rocks on Kauai and their Potential Applications to Mars

Transcription

1 Proceedings of The National Conference On Undergraduate Research (NCUR) 2012 Weber State University, Ogden, Utah March 29 31, 2012 Characterization of Mars Analog Rocks on Kauai and their Potential Applications to Mars Amanda N. Aguilera Department of Biological Sciences San José State University One Washington Square San Jose, CA Faculty Advisors: Dr. Janice L. Bishop, Dr. Monika Kress, and Dr. Cynthia Phillips Abstract The prospect of life outside the planet Earth has roused interest in humans since the dawn of time. When space exploration began, Mars became the focal point to answering the question, Could there have been life on Mars? The answer lies in what most people know as the ultimate requirement for life: water. Mars is thought to have had liquid water four billion years ago during the Noachian period. Clay minerals are one of the indicators for liquid water on Mars and may provide insights into the surface or subsurface geochemical environment that formed them. Alteration of basaltic material leads to the formation of clays, and this process may have occurred on Mars. Using volcanic rocks collected from Kauai, Hawai i, as an analog, this study involves characterization of altered basaltic material in the hopes of obtaining more information about the alteration of rocks on Mars. Seven samples were collected along the Koke e Trail in Waimea in April In the lab, multiple size fractions were prepared for each sample by either dry-sieving or by grinding and dry-sieving, and reflectance spectroscopy was used to investigate changes in the mineralogy. Spectral analysis included determination of band centers and band depths for multiple features due to iron (Fe), hydroxide (OH), and water (H 2 O) species in the mineral structure. Semi-quantitative analyses were performed to determine the relative abundances of basalt and alteration products in each sample. The samples collected contained olivine, ilmenite, goethite, hematite, maghemite, and phyllosilicates, such as kaolinite and halloysite. These analyses are providing information on how alteration occurred on Kauai, specifically the types of clay minerals present in the Waimea samples. The spectral data generated here will contribute towards understanding the clays observed on Mars by comparing them with spectra taken using CRISM (Compact Reconnaissance Imaging Spectrometer for Mars). CRISM collects visible/near-infrared reflectance spectra at eighteen meters per pixel spatial resolution and is mapping outcrops of clays and other hydrated minerals on Mars. These ancient clay-rich rocks could be indicators for environments where liquid water was once present and that could have been supportive of life. Keywords: Mars, volcanic alteration, reflectance spectroscopy 1.Introduction The composition of Mars has been an intense area of study for planetary scientists for many years, and the most compelling question that they seek to answer is whether or not Mars could have supported life at some point in its history. Through years of research in many fields of science, it has been postulated that Mars supported liquid water on its surface roughly four billion years ago during the Noachian period, the defining element required to sustain life. If this is, in fact, the case, then there may be evidence of this in the mineralogy of the surface of Mars. By inspecting the images taken by CRISM, which collects hyperspectral images of the surface of Mars from the Mars Reconnaissance Orbiter (MRO), and comparing them to spectra acquired from an aqueous, volcanic environment, such as Kauai, this study hopes to determine whether the geologic processes on Mars could have required water.

2 Certain minerals, such as clays, need water in order to form here on Earth, and assuming that Mars has similar geologic processes, if those minerals are present on the surface of Mars, this would strongly support the presence of past water. Confirmation of water on Mars would indicate that the presence of life on Mars would have been possible long before organisms developed on Earth, which could stimulate more missions to Mars in order to collect samples and explore its surface for additional signs of water and life. 2. Methods Seven volcanic basalt samples were collected along the Koke e Trail in Waimea in April 2009 (Fig. 1). These samples were chosen because their volcanic nature in an aqueous environment is similar to that predicted on Mars during the Noachian period, as opposed to previous experiments, which have focused on dry volcanic analogs. JB1082 was collected along the Koke e Trail, and JB1086 was collected along the side of the road out of Waimea Canyon. All samples were collected by Dr. Janice L. Bishop. In the lab, multiple size fractions were prepared for each sample (Fig. 2). Figure 1. Sample collection locations. 865

3 Figure 1. A. Waimea Canyon Koke e Trail map showing the collection locations of samples JB1082 and JB1086. B. Photo of location where JB1082 was collected. C. Photo of location where JB1086 was collected. Each sample that was collected was initially dry-sieved, and then a portion of the largest grain size fraction was ground and dry-sieved again. This allowed the viewing of the external and internal mineralogy of each sample to see if there was a difference. Figure 2. Sample preparation. Figure 2. A. Amanda N. Aguilera grinding samples. B. Aguilera dry-sieving samples. Visible/near-infrared (VNIR) spectroscopy from 0.35 µm to 2.5 µm, and X-ray diffraction (XRD) were used to investigate changes in the mineralogy 2,10,17. Spectral analyses included determination of band centers and band depths for multiple features due to iron (Fe), hydroxide (OH), and water (H 2 O) species in the mineral structure. Semi-quantitative analyses were performed to determine the relative abundances of basalt and alteration products in each sample. 3. Results and Conclusions Spectra are shown in Figure 3A for multiple size fractions of sample JB1082. Differences in the spectra are attributed to differences in mineralogy and grain size. The spectrum of JB1082G (Fig. 3A) exhibited features characteristic of olivine, specifically forsterite (Mg 2 SiO 4 ), that produce three characteristic overlapping bands due to Fe 2+ electronic excitations at 0.84 µm, 1.07 µm, and 1.31 µm 18. The spectrum of JB1082 also included two pairs of doublets at 1.36 µm and 1.40 µm, as well as at 2.17 µm and 2.20 µm, attributed to vibrational modes of OH in the kaolin group of clay minerals 4,6. This spectrum also had a water band near 1.92 µm due to a hydrated mineral 3,4. The phyllosilicate halloysite was consistent with all of these 4,6. The XRD data (Fig. 3B) supported this finding with peaks showing a resemblance to halloysite and forsterite, along with the Fe/Ti-oxide ilmenite. The olivine features are most pronounced in sample JB1082G and are still slightly apparent in JB1082F. However, these features are not observed for the other size fractions. Reflectance spectra of the JB1082 samples were compared to CRISM spectra from image FRT0000A819 collected at Libya Montes (Figs. 3C and 3D), a region on Mars bordering a large impact crater that exhibits ancient fluvial features and contains both mafic minerals and phyllosilicates 12,14. As seen in Figure 3D, the olivine spectral character of JB1082G resembled the olivine character of the Libya Montes spectrum. Both exhibited characteristics of olivines, with a broad band between 1.0 and 1.3 µm and also a steep slope between 1.35 µm and 1.80 µm 18. The Libya Montes spectrum also contained a band near 1.9 µm similar to that of JB1082G, but an Fe/Mg-rich phyllosilicate was present at Libya Montes with a band near 2.3 µm that was different from the Al-OH band observed near 2.2 µm for kaolin group clays. 866

4 A B C D Figure 3. Kauai sample JB1082B analyses. Figure 3. A. JB1082 spectra, showing definite characteristics of olivine (JB1082G) and halloysite. B. XRD of JB1082B showing peaks consistent with forsterite, halloysite, and ilmenite. C. CRISM image taken from FRT0000A819 at Libya Montes, Mars. The image shows olivine in red, pyroxene in grayish tones, and Fe/Mgphyllosilicate in cyan. D. Spectral comparison of JB1082 and CRISM spectra from FRT0000A819. Spectra are shown in Figure 4A for multiple size fractions of sample JB1086. Differences in the spectra are attributed to differences in mineralogy and grain size, as above. The spectra of all JB1086 samples (Fig. 4A) exhibited a strong resemblance to halloysite, specifically the two doublets and the water band mentioned for the JB1082 samples 3,4,6. This was supported by the XRD data (Fig. 4B), which showed a strong resemblance to halloysite, along with maghemite, ilmenite, goethite, and hematite. During lab tests, magnetism was tested for this sample. A weak response was seen in all grain fractions except JB1086G, where the magnet was able to separate out highly magnetic grains that were darker in color than the rest of the sample. Maghemite, a strongly magnetic mineral, could explain the magnetism seen in lab. The presence of maghemite is consistent with aqueous processing of volcanic material, as is seen on Kauai 5,7,9,16. A comparison of the spectra of all JB1086 samples to spectra from Mawrth Vallis, Mars, CRISM image FRT E (Figs. 4C and 4D), showed that both contain a strong kaolin family mineralogy. CRISM analyses of Mawrth Vallis have shown the presence of many phyllosilicates, including kaolin group minerals such as kaolinite 867

5 and halloysite 8,15. Both the spectra for the JB1086 samples and the CRISM spectra showed a doublet at 2.17 µm and 2.20 µm, and a water band at 1.92 µm 3,4,6. The doublet at 1.36 µm and 1.40 µm is often not visible in the CRISM spectra. Spectral features in this area are not captured in any CRISM spectra taken from Mars, most likely due to dust coatings on the surface. A B C D Figure 4. Kauai sample JB1086 analyses. Figure 4. A. JB1086 spectra, showing strong bands characteristic of kaolin group clay minerals. B. XRD of JB1086B showing peak similarities to halloysite, ilmenite, goethite, hematite, and maghemite. C. CRISM image taken from FRT E at Mawrth Vallis, Mars. The image shows basalt caprock in black and dark grey, Fe/Mgphyllosilicate in red and light grey, and Al-phyllosilicates in light blue. D. Spectral comparison of JB1086 and CRISM spectra from FRT E. 4. Future Work Ongoing analyses will further compare the spectra of the JB1082 and JB1086 samples to more CRISM images in order to determine if the hydrated mineral suites observed on Mars are related to those observed on Kauai. Also, compositions of the other five samples will be looked into and compared to CRISM images to see if there are 868

6 similarities. The remaining samples will also be characterized by XRD to confirm the compositions seen in the reflectance spectroscopy. Additionally, these new data will be compared to the results for JB1082 and JB1086 samples in order to determine the relative alteration of each sample, and if their location had an impact on their mineralogy. Ultimately, the results of these data could be used to support the hypothesis that alteration scenarios on Kauai could have occurred on Mars, and support the presence of water and past life on Mars. 5. Acknowledgements The author wishes to express their appreciation to the NASA EPOESS program, and from the Mars Fundamental Research program. This work was funded in part by these grants.the author would also like to thank Dr. T. Bristow from the NPP program at NASA Ames for running and analyzing the XRD patterns. A special thanks to Dr. Monika Kress, Dr. Cynthia Phillips, and Dr. Janice L. Bishop for the support, advice, and education needed in order to accomplish this research. 6. References 1.Bibring J.-P. et al. (2006) Science, 312, pp Bish D. L. (1994) in Quantitative X-Ray Diffraction Analysis of Soil J. Amonette, L. Zelazny, Eds. (Soil Science Society of America) pp Bishop J. L. (2005) in Water on Mars and Life (Advances in Astrobiology and Biogeophysics) T. Tokano, Ed. (Springer, Berlin) pp Bishop J. L. et al. (2007) 44th Annual Mtg Clay Minerals Society. 5. Bishop J. L. et al. (2008) Geophysical Research Abstracts, 10, EGU2008-A Bishop J. L. et al. (2008) Clay Miner., 43, pp Bishop J. L. et al. (2000) Lunar Planet. Sci. XXXI., CD-ROM #1946 (abstr.). 8. Bishop J. L. et al. (2008) Science, 321, doi: /science , pp Bishop J. L. et al. (2007) Clays Clay Minerals, 55, pp Clark R. N. et al. (1990) J. Geophysical Research, 95, pp Crumpler, L.S. & Tanaka K. L. (2003) J. Geophysical Research, 108, doi: /2002je Gaffey S. J. et al. (1993) in Remote Geochemical Analysis: Elemental and Mineralogical Composition C. M. Pieters, P. A. J. Englert, Eds. (Cambridge University Press, Cambridge) pp Jaumann R. et al. (2010) Earth and Planetary Science Letters, 294, pp McKeown N. K. et al. (2009) J. Geophysical Research, 114, E00D10, doi: /2008JE Morris R. V. et al. (2001) Journal of Geophysical Research, 106, pp Murchie S. et al. (2007) Journal of Geophysical Research, 112, doi: /2006je Lane M. D. et al. (2009) Eos Trans. AGU, Fall Meet. Suppl., abs. P23A