Ninth International Conference on Mars 2019 (LPI Contrib. No. 2089) 6145.pdf An Overview of Morphological and Compositional investigation of Melas Chasma of Valles Marineris. T. Sivasankari1 and S. Arivazhagan2, 1 2 Centre For Applied Geology, Gandhigram Rural Institute - Deemed to be University, Gandhigram, Dindigul-624302, India ([email protected] and [email protected]).

Introduction Many studies had been carried out by the primarily by aeolian processes in the recent period of time. researchers for various region of Valles Marineris and has Fig. 2. Shows the geology map of the study area. The geolo- revealed evidence for the presence of sulphate deposits gy map of Melas chasma was derived based on the map giv- namely the Interior Layered Deposits (ILD). The present en by Witbeck et al, 1991. The geological features includes study aims at the identification of mafic minerals High Cal- slope materials on the valley walls, dunes, layered materials, cium Pyroxene [HCP] and Phyllosilicate minerals of Melas fractured sediments, ridged plains, floor materials and crater chasma region of Valles Marineris by using CRISM datasets. fill materials. The topography of Chasma was interpreted by The spectra and the mineral distribution maps are derived the contuor map and DEM derived using the MOLA data. using the spectral summary parameters which helps to under- The contour values shows the highest relief of the study area stand the past geologic events ultimately bringing out the is 4000m and the lowest relief is -3800m. From the DEM origin and evolution of Valles Marineris. The Morphological data it is evident that the chasma has almost smooth valley features of Valles Marineris are compared with the CRISM floor with small isolated patches and a rugged topography as well as the HiRiSE Data. The Digital Elevation Model towards the valley wall. The profile of the cross section de- (DEM) is derived using the Mars Orbiter Laser Altimeter rived for the chasma also reveals the same relief values. Fig. (MOLA) data which shows that the depth varies from 3km to 3 shows the Contour map, DEM and the profile graph of the 7km. For the present study, Melas Chasma is taken for geo- cross section derived for the study area. chemical and mineralogical analysis using remote sensing data. The mafic minerals and phyllosilicate mineral distribu- Results and Discussion: Morphology of the Study Area: tion are derived which delineates dominance of pyroxene and Fluvial Channels: the presence Mg-OH phyllosilicates indicating the volcanic Fig. 4.a and 4. b shows the well defined fluvial pattern. Fig. a origin and the processes of low grade metamorphism respec- is the central valley floor of the Melas Chasma which indi- tively. cates that there occurred an extensive flow eroding the either Study Area Valles Marineris lies between -2˚ to -18˚ S sides of the ridge leaving a streamlined texture on the floor. latitude and -26˚ to -108˚W longitude extending about 4000 The origin and the direction of flow is indefinite. Similarly km in length, 200 km in width and 7 km in depth. It has a Fig. 5. b. also shows the fluvial pattern indicating the prima- total areal coverage of about ~ 44, 54, 672 Sq. km, covering ry and secondary order of streams. The flood plain around about 1/5 th of the Martian surface. The formation of the this pattern shows a rough texture due to the deposition of Valles Marineris would have took place in the Noachian to debris. Hesperian age that dates back about ~3.5 bya (Tanaka, 1986). The Valles Marineris province is divided into 11 re- Dune Fields: gions (Fig. 1) of which Melas Chasma is taken for the study. Fig.4. c shows a complex morphology in which the northern Fig. 1 shows the location of Melas Chasma and the various part of the image shows the dune fields that includes both regions of the Valles Maineris province. mega longitudinal dunes and micro level dunes. These dunes may be developed due to the aeolian activity in very recent Geology of the Study Area: The Melas chasma is lo- times since the surface has layered deposits over which the cated at the southern end of the Valles Marineris to the east dunes are present. Below the dune field there occurs a fluvial of Ius Casma and west of Coprates chasma. The Melas channel that shows almost parallel channels of which one chasma acts a bridge connecting the eastern and western major stream in connected to feature that is similar to the flanks of the Valles Marineris province. The Chasma is about water body which may be a paleo lake. 450km in length and 350 km in width covering nearly about approx. 1,44,405 sq. km. and broadens southwards into Sinai Landslide: Planum. It is slightly oblique (NW-SE) to Ius and Coprates Fig. 4. d shows part of the valley wall consisting of a linear Chasmata, with the latter being slightly offset to the south. ridge like feature with smooth texture indicating the presence Melas Chasma is connected to the north with the parallel of fine sediments. In the zoomed image, it is noticed well, Candor and Ophir Chasmata. Melas Chasma displays layered that the occurrence of landslide of the sediment flow can be deposits and provides valuable information about the geolog- noted. There is also a difference in the texture of the area ical history of the canyon system. Because of geology of this surrounding the landslide location. area, it was considered as a high‐priority landing site for MER rovers (Weitz et al., 2003). Based on the literature stu- Mineralogy of the Study Area: Mafic inerals dies the age of the Melas Chasma was estimated to be from The spectra of Pyroxene obtained from CRISM data and the Middle Hesperian (Pelkey and Jakosky, 2002). The geology CRISM spectral library plot of pyroxene is shown in Fig. of western Melas Chasma was studied from Mars Global 5.A). ii and 5.A). iii respectively. The presence of Mafic Surveyor mission (MGS) remote sensing data (Pelkey and minerals like olivine and pyroxene indicates that surface Jakosky, 2002), and the surficial properties were analyzed material is of volcanic origin (Pelkey et al., 2007 & Burns, from Mars Odyssey Thermal Emission Imaging System 1993). (THEMIS) data (Pelkey et al., 2003). Both studies concluded that the Chasma has had a complex history mainly dominated Phyllosilicates:Serpentine show absorption features near 1300 nm due to OH overtones and near 2300 nm due to Al- Ninth International Conference on Mars 2019 (LPI Contrib. No. 2089) 6145.pdf OH. The presence of Serpentine indicates the hydrothermal alteration of ultramaficc rocks (Ehlman et al., 2010). The spectra of serpentine obtained from CRISM data and the CRISM spectral library plot of serpentine is shown in Fig. 5.B). ii and 5.B). iii respectively.

Summary: The MRO HiRiSE data were used to derive the morphological features which has shown evidences for fluvial channels, dunes, and results for landslides. The mor- phological features identified indicates that the fluvial activi- ty aeolian activity had took place actively in the geologic history of mars. The MRO CRISM data Spectral parameter analysis has been used to identify minerals in the Melas chasma. The presence of mafic minerals indicates volcanic originated materials whereas the presence of phyllosilicates indicates low temperature chemical weathering and hydro- Fig. 3: a) Contour map of Melas chasma; b) Profile graph

thermal alteration. showing the cross section of Melas chasma; c) DEM gener- ated using MOLA data corresponding to the cross section. References: [1] Burns, R.G. et al., (1993), Geo-chimica et Cosmochimica Acta, 57, 4555-4574. [2] Ehlmann, B. L. et al., (2009), 40th LPSC, #1787. [3] Ehlmann, B. L. et al., (2009), GRL, 37, 1-5. [4] Gen-drin, A., et al., (2005), Scince, 307, 1587-1591. [5] Pelkey, S. M. et al., (2007), JGR, 112, 1-18. [6] Rampe, E. B. et al., (2011) 42nd LPSC. [7] Rampe, E. B. et al., (2012), Geology, 40, 995-998. [8] Schulte, M., et al (2006), Astrobiology, 6,3764-376. [9] Tana-ka, K. L., (1986), JGR, 91, E139-E158. [10] Viviano- Beck, C. E., et al., (2014), JGR, 119, 1403-1431. Acknowledgement: The authors acknowledge the ISRO, India for financial support from under the MOM-AO research project- ISRO/SSPO/MOM- AO/2016-2017.

Fig. 4: Morphological features identified a) Fluvial channel; b) Fluvial pattern; c).i). Dune field includes mega dunes to micro dunes; ii) Fluvial channels connected to a lake; d) Landslide materials

Fig. 1: Figure showing the location of Melas Chasma

Fig. 5: A) i) location of Spectra; ii)Spectra of Pyroxene obtained from CRISM Data; iii) CRISM Spectra Library Plot of Pyroxene; B) i) location of Spectra; ii) CRISM Spectra Library Plot of Ser pentine; iii)Spectra of Serpentine obtained from CRISM Data;

Fig. 2: Geology map of Melas Chasma