Figures for Subsurface Hydrous Chlorides and Oxychlorine Salts (HyCOS) as the Source Materials for Recurring Slope Lineae on Mars Alian Wang1, Z. C. Ling2, Y. C. Yan1, Alfred S. McEwen3, Michael T. Mellon4, Michael D. Smith5, Bradley L. Jolliff1, James Head6 1Dept. Earth and Planetary Sciences and McDonnell Center for Space Sciences, Washington University in St. Louis, St. Louis, Missouri, 63130, USA; 2Shandong Provincial Key Laboratory of Optical Astronomy and Solar-Terrestrial Environment, Institute of Space Sciences, Shandong University, Weihai, 264209, China; 3Lunar and Planetary Laboratory, University of Arizona, Tucson, Arizona, 85721, USA; 4Applied Physics Laboratory, Johns Hopkins University, Laurel, Maryland, 20723, USA; 5NASA Goddard Space Flight Center, Greenbelt, Maryland, 20771, USA; 6Dept. Earth, Environmental and Planetary Sciences, Brown University, Rhode Island, 02912, USA;

Deliquescence a. b. c. d. e. f. g. h. i. Wang et al., 2017 Figure 1. Results of 270 T-RH driven deliquescence-dehydration-rehydration in experiment #1 . An experiment led to deliquescence was marked with orange colored spot; An experiment led to non-change or dehydration or rehydration was marked by a spot of other colors, whose phase identifications were marked and were made by using Raman spectroscopy. Note: the data of FeCl2·4H2O and KMgCl3·6H2O suggest some complicate phase transitions, thus were not included in Figure 4a.

Optical fiber feedthrough Figure2. Experiment #3 set up Sample cup CaCl2 Dry ice (195K) beneath the red foam-cover a CO2 H2O vapor supply b c Dry ice Raman objective d Wang et al., 2017 Raman probe Z stage Electric Feedthrough Rotation stage Motor-hub X stage cold plate Vacuum pump & pressure meter Laser Raman Spectrometer computer PEACh Optical fiber feedthrough feedthrough Quartz window RH meter Needle valve Extra-dry CO2 water bath at 30 C H2O CO2 flow control Extra dry CO2 mix CO2 & H2O supply T-sensor & control Cooling system LN2 Figure3. Laboratory set-up for Experiment #4 Wang et al., 2017

CaCl2·4H2O MgCl2·6H2O FeCl3·6H2O AlCl3·6H2O a. Fe3+-sulfates·9-20H2O Mg-sulfates·7-6 H2O Fe2+-sulfate·7H2O Mg(ClO4)2·6H2O Ca(ClO4)2·4H2O NaClO4·H2O b. Fe2+-sulfates·7H2O Wang et al., 2017 Figure 4. Deliquescence phase boundaries of HyCOS compared with those of hydrous sulfates. The deliquescence phase boundary of each HyCOS was plotted through the middle space between two sets of RH values in T-RH field, where deliquescence was seen at the higher RH values but not seen at the lower RH values. The width of colored bar reflects the uncertainty of phase boundary in RH. Filled orange data points indicate occurrence of deliquescence. Unfilled points indicate non-change or dehydration, both against the deliquescence boundary at the lowest RH (e.g., CaCl2·4H2O for chlorides). Similar deliquescence boundaries for hydrous sulfates were drawn based on data in Figure S1, S2, S3 of supporting document.

Wang et al., 2017 a. MgCl2·6H2O b. CaCl2·4H2O c. FeCl3·6H2O Deliquescence < 4 sols @250K Deliquescence < 60 sols @170K Deliquescence < 1 sol @300K RSL surface Salt-rich subsurface a. MgCl2·6H2O t30% t100% tcenter Deliquescence < 50 sols @250K Deliquescence < 100 sols @ 240K Deliquescence < 2 sol @ 300K b. CaCl2·4H2O Deliquescence < 15 sols @250K Deliquescence < 2 sols @ 300K Deliquescence < 100 sols @ 210 K c. FeCl3·6H2O Wang et al., 2017

Wang et al., 2017 d. AlCl3·6H2O e. Ca(ClO4)2·4H2O f. Mg(ClO4)2·6H2O Deliquescence < 25 sols @250K Deliquescence < 2 sols @ 300K Deliquescence < 100 sols @ 220K RSL surface Salt-rich subsurface d. AlCl3·6H2O deliquescence < 30 sols @ 250K deliquescence < 100 sols @ 230K deliquescence < 1 sol @ 300K e. Ca(ClO4)2·4H2O Deliquescence < 30 sols @250K Deliquescence < 100 sols @230K Deliquescence < 3 sols @300K f. Mg(ClO4)2·6H2O t30% t100% tcenter Wang et al., 2017

Figure 3. of Wang et al., 2017 Deliquescence < 4 sols @ 300K < 100 sols @ 250 K Salt-rich subsurface RSL surface g. NaClO4·H2O t30% t100% tcenter Wang et al., 2017 Figure 5. Time range observed from the macroscopic manifestation of deliquescence of a HyCOS, as the function of T and RH. A symbol (triangle, square, or diamond) marks the time when the full deliquescence (t100%) of tested amount of a HyCOS being reached. The low end of a downward bar from the symbol marks the time when > 30% of starting solid becoming liquid (t30%). The time ranges for deliquescence at different RHs are heavily overlapped. A black dotted line extrapolates through the center (tcenter) of observed time range t of a HyCOS to low temperature. A rectangle with solid red line marks the observed TRSL window. A rectangle with dotted red line marks the modeled T window of salt-rich subsurface [Mellon et al., 2004; Wang et al., 2013]. Purple stars mark the intersections of extrapolation line with the red rectangles, which suggest approximate time (tcenter(T) ) that a HyCOS to reach a macroscopic manifestation of deliquescence at a temperature.

a. Starting phase CaCl2 CaCl2.2H2O CaCl2.4H2O + CaCl2.6H2O CaCl2.2H2O + 3800 3600 3400 3200 3000 Raman Shift (cm-1) b. Starting phase MgCl2 MgCl2.xH2O (x=2, 4, 6, 8, 12) 2800 3550 3500 1000 980 960 940 c. Starting phase NaClO4 NaClO4.xH2O (x=1, 2, more) 3600 3400 3200 3000 Raman Shift (cm-1) 1040 1020 1000 980 960 d. Starting phase Ca(ClO4)2 Ca(ClO4)2 + Ca(ClO4)2.xH2O (x=2, 4) 940 920 3800 Mg(ClO4)2 + Mg(ClO4)2.2H2O + Mg(ClO4)2.6H2O e. Starting phase Mg(ClO4)2 Figure 6. Evidences of HyCOS rehydration at 195 K. (a). Rehydration of CaCl2 at 195 K, revealed by the appearance of H2O Raman peaks (marked by dotted lines); (b) Rehydration of MgCl2 at 195K, revealed by the appearance of H2O Raman peaks; (c). Rehydration of NaClO4 at 195 K, revealed by the appearance of multiple H2O Raman peaks, and by a new Raman peak at 942 cm-1, in addition to 952 cm-1 peak of NaClO4 (both are ClO4 vibrational modes); (d). Rehydration of Ca(ClO4)2 at 195 K, revealed by the appearance of multiple H2O Raman peaks, and by a new Raman peak in 900-1100 cm-1; (e). Rehydration of Mg(ClO4)2 at 195 K, revealed by the appearance of multiple H2O Raman peaks, and by two new Raman peaks in 900-1100 cm-1. Wang et al., 2017

3800 3600 3400 3200 Raman Shift (cm-1) Started as CaCl2 CaCl2·4H2O (4 min 50 s) a. CaCl2 1000 950 900 850 started as Ca(ClO4)2 Ca(ClO4)2 ·4H2O (14 min) Ca(ClO4)2 ·2H2O (10 min) b. Ca(ClO4)2 Wang et al., 2017 Figure 7. Evidence of extremely fast rehydration of chlorides and perchlorates measured at different T and RH in a Mars chamber in experiment #4. (a) rehydration of CaCl2 at 251 K, 23.6 %RH, and 16.4 mbar. The H2O peak (3445 cm-1) of CaCl2·2H2O appeared at 4 minutes 50 seconds after the starting of this experiment. (b). rehydration of Ca(ClO4)2 at 296 K, 4.8 %RH, and 19.7 mbar. The H2O peak (3491 cm-1) of Ca(ClO4)2 ·2H2O and the H2O peak (3550 cm-1) of Ca(ClO4)2·4H2O appeared at 10 and 14 minutes, respectively, after the starting of this experiment.