SULFATES and MAFIC MINERALS in JUVENTAE CHASMA AS SEEN by CRISM in COORDINATION with OMEGA, HIRISE and CONTEXT IMAGES. J. L. Bishop1, E

Seventh International Conference on Mars 3350.pdf

SULFATES AND MAFIC MINERALS IN JUVENTAE CHASMA AS SEEN BY CRISM IN COORDINATION WITH OMEGA, HIRISE AND CONTEXT IMAGES. J. L. Bishop1, E. Noe Dobrea2,3, S. L. Murchie4, C. M. Weitz3, W. M. Calvin5, L. A. Roach6, S. M. Pelkey6, A. J. Brown1, J. F. Mustard6, J.P. Bibring7, and the MRO CRISM Team, 1SETI Institute/NASA-ARC, Mountain View, CA, 94043 ([email protected]), 2University of Calif., Santa Cruz, CA, 95064, 3Planetary Science Institute, Tucson, AZ, 85719, 4JHU/Applied Physics Lab, Laurel, MD 20723, 5University of Nevada, Reno, NV 89557, 6Dept. of Geol- ogical Sciences, Brown University, Providence, RI 02912, 7Institute d’Astrophysique Spatial (IAS), Orsay, France. Introduction: We are investigating the material was also found in the northern mound and composition of the surface materials in Juventae across the interior region. The distribution of hydrated Chasma, located in northeastern Valles Marineris, material including sulfates is shown in Figure 2, where using hyperspectral visible/near-infrared (VNIR) band depths at 1.9 and 2.13 !m are mapped. The 1.9 CRISM images in coordination with High Resolution !m band depth was determined using points at 1.6, Imaging Science Experiment (HiRISE) and Context 1.936, and 2.1 !m, while the 2.13 !m band depth was Camera (CTX) images. The primary focus is to determined using 1.9, 2.13, and 2.3 !m. characterize the sulfate minerals in the interior layered mounds. The sulfate minerals kieserite and gypsum were identified in the Juventae mounds using Mars Express/OMEGA hyperspectral VNIR images [1,2]. Analyses of MOC and MOLA data infer that subice volcanic eruptions occurred in this region [3], although work by Catling et al. [4] favor lacustrine or airfall deposition. Analyses of HRSC images suggest that interior layered deposits in a northern site within Juventae Chasma are deltaic deposits, while interior layered deposits in a site towards the south of the chasma formed via evaporitic processes [5]. We hope to contribute toward understanding the composition and genesis of this region through ongoing analyses of CRISM and HiRISE images. Image background: Targeted MRO/CRISM images collect 544 wavelengths from 0.36 to 3.9 !m in ~12 km swathes [6]. Images are processed for instrumental effects, converted to I/F and the

atmosphere is removed using a ratio with a CRISM Fig. 1 Context image T01_000875_1765_XI_03S061W_061003 scene of Olympus Mons, scaled to the same column (~20 km across) showing locations of CRISM images density of CO2. A similar atmospheric correction has HRL000028A6 (pink) and HRL0000444C (orange) and been successfully used for OMEGA data [1]. Two HiRISE images TRA_875_1765 (red) and PSP_2590_1765 ~40m/pixel targeted images have been collected in (blue) on the northern mound. Juventae Chasma to date, located at ~3.4°S and 61.6°W as shown in the Context image in Figure 1 [8]. HiRISE images are collected with a spatial resolution as low as ~25 cm/pixel [9] and are acquired in a coordinated manner with CRISM observations. Spectral Background: Gendrin et al. [2] identified gypsum in the interior region of Juventae Chasma, primarily in the southern mound, using bands near 1.4, 1.75, 1.9, and a spectral dropoff at 2.4 !m. Similarly, they used bands near 1.6, 2.1 and 2.4 !m to identify monohydrated sulfate that best corresponded

to the mineral kieserite. Fig. 2 THEMIS IR image overlayed with a mineral map Independent analyses of OMEGA spectra show derived from OMEGA spectra: green indicates the 1.9 !m similar results. The greatest concentration of hydrated band due to H2O and red indicates the 2.13 !m band due to minerals is identified in the southern mound (not yet monohydrated sulfates. (Image credit: THEMIS Science measured by CRISM); however, some hydrated Team/NASA/JPL/ASU) Seventh International Conference on Mars 3350.pdf

Fig. 5 CRISM image HRL000028A6 showing locations of extracted spectra (R 710 nm, G 599 nm, B Fig. 3 CRISM image HRL0000444C showing 533 nm). locations of extracted spectra (R 710 nm, G 599 nm, B 533 nm).

Fig. 4 Subset of HiRISE image PSP_2590_1765 showing the upper portion of CRISM image HRL000444C. Sulfate-bearing spectra were collected from the top edge of the bright feature shown in the left center of this image and pyroxene-bearing spectra were collected from the darker area at the center top of this image as shown in Figure 3. Fig. 6 Subset of HiRISE image TRA_875_1765 showing the central region of CRISM image HRL000028A6 where the dust spectra were collected. Seventh International Conference on Mars 3350.pdf

Observations from CRISM: CRISM images HRL0000444C and HRL000028A6 were analyzed using spectral ratios and band maps. Image HRL0000444C includes the sulfate mound in the center and lower regions, and it contains mafic minerals in the low lying terrain in the upper part of the image (Figures 3 and 4). Image HRL000028A6 covers primarily the sulfate mound (Figures 5 and 6). Band maps of image HRL0000444C are shown in Figure 7 to illustrate the presence of monohydrated sulfates having a band near 2.1 !m. These are examples of how specific mineral features can be isolated in the image. Monohydrated sulfate minerals such as kieserite and szomolnokite exhibit a band near 2.1 !m that can be used to identify these minerals. Fig. 8 CRISM spectra from HRL0000444C. Most More complex equations can also be used to better spectra are an average of two spots that are each a 4x4 express the band shape in addition to the band depth. pixel average. These are shown in black below the smoothed spectra shown in color. Some residual atmospheric features are present, especially near 2 !m.

In Figures 9 and 10 the sulfate spectra are compared with lab spectra of sulfate minerals from larger studies of sulfates associated with Mars [10,11,12]. Formulas for these minerals are listed in Table 1. Monohydrated sulfates exhibit a characteristic band near 2.1 !m in contrast to the ~1.9 !m water band observed for many other minerals. In addition to the ~2.1 !m feature, kieserite has a broad band near 1.6 !m and two weaker bands near 2.4 and 2.5 !m, while szomolnokite has weaker bands near 1.4 and 2.4 !m. Gypsum and starkeyite both have Fig. 7 Two maps of the 2.1 !m band depth. The map features near 1.4 and 2.0 !m that could be contributing on the left was generated using the CRISM parameter to these spectra as well. equations from [9]. The map on the right was made using a more complex band math equation that enables Table 1

mapping of a broad band from 2.07-2.11 !m with Gypsum CaSO4 • 2H2O respect to the continuum at two points on either side of Kieserite MgSO4 • H2O the band. Band Math equation: Starkeyite MgSO4 • 4H2O 2+ 1-(2.072+2.092+2.098+2.111)/(1.847+1.874+2.316+2.435) Szomolnokite Fe SO4 • H2O

Features attributed to sulfates near 1.4, 1.6, 1.75, Image HRL0000444C also has a few small areas 2.1 and 2.4 !m were observed throughout CRISM with spectra that are consistent with olivine and images HRL000028A6 and HRL0000444C. Some of pyroxene. These are shown in Figures 11 and 12 these are difficult to characterize because of residual compared with lab spectra of olivine and pyroxene- atmospheric features. Spectra from images bearing meteorites from Mars. This suggests that HRL0000444C and HRL000028A6 are shown in unaltered material is present here in isolated spots, as Figures 8 to 12. well as the ubiquitous sulfates. Seventh International Conference on Mars 3350.pdf

Fig. 12 Olivine-bearing spectrum from CRISM image HRL0000444C compared to lab reflectance spectra of

Fig. 9 CRISM spectra from HRL0000444C of sulfate- a Martian meteorite (from D. Dyar) and an olivine bearing regions and a plains region compared with lab mineral separate with Fo01 composition (from E. reflectance spectra of sulfate minerals. Approx. band centers Cloutis). are marked for the bands near 1.45, 2.1, 2.4 and 2.52 !m. Summary: Coordinated CRISM, HiRISE and CTX images of the northern mound in the Juventae Chasma interior show evidence of sulfate minerals in many regions of the mound, plus olivine and pyroxene in some lower lying terains just north of the mound. Monohydrated sulfate signatures were observed that are consistent with the presence of kieserite and perhaps also szomolnokite. Hydrated sulfates such as gypsum and starkeyite exhibit bands near 1.45 and 1.9 !m that are consistent with many CRISM spectra in the mound area as well. Analyses of the OMEGA data suggest that a much greater intensity of sulfate

Fig. 10 CRISM spectra from HRL000028A6 of sulfate- minerals exists in the southern mound. We are bearing regions and dust compared with lab reflectance anxiously awaiting the images scheduled for that spectra of sulfate minerals. Each CRISM spectrum is an region. average of two 4x4 pixel spots. These are shown in black behind the smoothed spectra shown in color. References: [1] Bibring J.-P. et al. (2005) Science, 307, 1576-1581. [2] Gendrin A. et al. (2005) Science, 307, 1587-1591. [3] Chapman M. G. et al. (2003) JGR, 108, 5113, doi:10.1029/2002JE002009. [4] Catling, D. C. (2006) Icarus, 181, 26-51. [5] Ori G. G. et al. (2006) LPS XXXVII, Abstract #1247. [6] Murchie S. (2007) LPS XXXVIII, Abstract #1472. [7] Malin, M. C. et al. (2007) LPS XXXVIII, Abstract #2068. [8] McEwen A. S. et al. (2007) JGR, in press. [9] Pelkey, S. M. et al. (2007) JGR, in press. [10] Lane, M. D. et al. (2004) GRL, 31, L19702, doi: Fig. 11 CRISM spectra from HRL0000444C of pyroxene- 1970.11029/12004GRL0 21231. [11] Bishop, J. L. et bearing materials compared to lab reflectance spectra of al. (2005) IJA, 3, 275-285. [12] Lane M. D. et al. Martian meteorites. ALH 84001 (split 271) is dominated by (2007) LPS XXXVIII, Abstract #2176. orthopyroxene, while EETA 79001 (lithology A, split 472) contains both low and high Ca pyroxenes. These CRISM spectra appear to fall in between these two meteorite spectra, Acknowledgments: Lab spectra were measured at suggesting that a combination of both low and high Ca Brown/RELAB. pyroxene could be present here.