1. Composition and Stratigraphy of Acidic or Salty Components at Mawrth Vallis, Mars Janice L. Bishop, Briony Horgan, James J. Wray, Damien Loizeau, Christoph Gross, Patrick C. McGuire, Mario Parente, Frank Seelos, Christina Viviano-Beck and Scott L. Murchie

2. Major phyllosilicate presence at Mawrth Vallis, Mars. -Stratigraphy of ~10-50 m thick upper Al-rich phyllosilicate unit and ~50- 200 m thick lower Fe-rich smectite unit documented in numerous studies (e.g. Poulet et al., 2006; Loizeau et al., 2007, 2010; Bishop et al., 2008, 2013, Wray et al., 2008; McKeown et al., 2009, 2011; Noe Dobrea et al., 2010; Michalsky et al., 2012). Evidence for isolated sulfate outcrops. -Jarosite (Farrand et al., 2010) -Bassanite (Wray et al., 2010). Evidence for unusual “doublet” materials. -Identified by doublet in 2.2-2.3 µm spectral region (Bishop et al., 2013). -Could be consistent with mixture of Al/Si-OH species and Fe-OH species. -Observed in spectra of some sulfates. -Detected in acid alteration products of Fe-rich smectites (Madejova et al., 2009).Introduction 2

3. Location of Mawrth Vallis Situated at boundary of cratered Noachian terrain and northern lowlands, ~25° N, 20° W. Contains abundant Fe/Mg-rich smectites and Al/Si-bearing clays and nanophase materials. 3 HRSC Color Mosaic (McGuire)

4. Phyllosilicate Types at Mawrth Vallis and Their Spectral Character CRISM image FRT0000863E 4 HRSC Color Mosaic (McGuire) c b 5X elevation N 2 km a

5. Phyllosilicate Types at Mawrth Vallis and Their Spectral Character CRISM image FRT00003BFB a b

6. Testing new CRISM MTR3 files In order to better investigate “doublet materials” for the HRL000043EC site in the NW region of Mawrth Vallis, we analyzed spectra in a new MTR3 test image that has improved calibration (new image production led by F. Seelos). MTR3 joined S+L image

7. Testing new CRISM MTR3 files A suite of new spectral parameter products has also been developed to go with the new MTR3 images (Viviano-Beck et al., 2014).

8. Testing new CRISM MTR3 files

9. CRISM Spectra of Doublet Materials 1 2 3 4 5 6 7 HRL000043EC

10. CRISM Spectra Compared to Lab Spectra HRL000043EC

11. CRISM Image HRL00043EC 3D surface view with 5X vertical enhancement showing:  nontronite or Fe/Mg-smectite in red  montmorillonite, allophane or opal in blue  Altered, mixed and Fe 2+ -bearing phases in green

12. CRISM Image HRL00043EC

13. CRISM Image FRT000B141 1 2 3

15. Doublet Materials at Mawrth Vallis Appear to be present at boundary of lower Fe/Mg- smectite unit and upper Al/Si-bearing unit. –Frequently occur in unit labeled in green due to presence of Fe 2+ -bearing phase. –Association of doublet material with Fe 2+ -bearing phase unknown. Spectrally variable throughout single image and across Mawrth Vallis region –Relative intensity of doublet peaks variable. –Band centers of both peaks of doublet shift somewhat, ranging from ~2.22-2.24 µm and ~2.25-2.27 µm. –Pattern of spectral doublet shape not yet found doesn’t appear to be correlated with stratigraphy may be correlated with local geology, still under study

16. Doublet Materials at Mawrth Vallis Not spectrally consistent with one specific mineral or material. –Possible candidates include: jarosite, Ca-sulfate, gibbsite and acid-treated Fe-bearing smectite. –Acid-treated Fe-bearing smectite good candidate because Fe-bearing smectite known to be present and changing degree of acid treatment could produce variability in spectral properties. Implications for geochemistry could be very different depending on which material is responsible for this spectral doublet. –Jarosite and acid-treated smectite imply low pH. –Ca-sulfate and gibbsite imply neutral pH.