Topographic, spectral and thermal inertia analysis of interior layered deposits in Iani Chaos, Mars

Abstract

a b s t r a c tWe present an analysis of Interior Layered Deposits (ILDs) in Iani Chaos using visible, infrared, hyperspectral and topographic datasets acquired by instruments aboard NASA's Mars Global Surveyor, Mars Odyssey, Mars Reconnaissance Orbiter and ESA's Mars Express spacecraft. We focus on four main regions where ILDs outcrop in Iani Chaos. Deposits span a $2 km range of elevations and exhibit moderate to high albedos, layering at sub-decameter scales, thermal inertias of 300-800 J m À2 K À1 s À1/2 and a range of surface textures. Thermal inertia calculations use slope and azimuth corrections from High Resolution Stereo Camera (HRSC) topography. Spectral features in hyperspectral data acquired by NASA's Compact Reconnaissance Imaging Spectrometer for Mars (CRISM) suggest that gypsum (CaSO 4 Á2H 2 O) and kieserite (MgSO 4 ÁH 2 O) are present in most deposits. We report absorptions typically exhibited by alunite (KAl 3 (SO 4 ) 2 (OH) 6 ) and jarosite KFe 3þ 3 ðOHÞ 6 ðSO 4 Þ 2 as well as a number of features that may be attributable to a wide range of mono-and polyhydrated sulphates and hydroxyl-sulphates bearing a number of cations, including Mg 2+ , Fe 2+ , Fe 3+ and Ca 2+ . Spectral features similar to those of ammonium sulphates may also be present.Analysis of a HiRISE stereo DEM shows planar layering in some ILDs, favouring a sedimentary deposition origin. Stratigraphic mapping of hydration and sulphate spectral features in flat ILDs in central Iani Chaos suggest that specific elevation intervals in the stratigraphic column were subject to different levels of hydration, perhaps during episodes of water table elevation. This is consistent with formation models for ILDs and hydrological modelling. Geomorphic characteristics of deposits in northern and southern Iani Chaos suggest their relatively recent exhumation and significant erosion by aeolian processes. We conclude that any formation theory for ILDs in Iani Chaos should support mechanisms for different hydration states at different stratigraphic elevations and subsequent significant aeolian erosion, burial and reexposure.

Evaporite karst in three interior layered deposits in Iani Chaos, Mars

“…1C) is located toward the head of Ares Vallis in the topographic depressions of lowest elevation in Iani Chaos. These depressions lie 800 m below the start of the main Ares Vallis channel (Sefton-Nash et al, 2012). The ILD has a dome-like morphology, with its longest axis (45 km in length) trending in the NE-SW direction, and its width is about 18 km .…”

“…1D) represents the most extensive ILD in Iani Chaos Sefton-Nash et al, 2012). This ILD displays a terrace-like morphology (Sowe, 2009), with its longest axis (about 100 km in length) trending in the NW-SE direction.…”

“…Further studies of the characteristic spectral absorptions for these deposits revealed details about their mineralogy. The ILDs were found to exhibit a suite of spectral features indicating the presence of mono-and polyhydrated sulphate minerals that display clear signatures of gypsum and kieserite (Sefton-Nash et al, 2012).…”

“…The interior layered deposits (ILDs) of Iani Chaos are characterised by higher thermal inertias than the surrounding terrains (Glotch and Rogers, 2007). Light-toned albedo and layering on multiple scales have been described and partially mapped within these ILDs (Bridges et al, 1913;Sowe, 2009;Guallini et al, 2012;Sefton-Nash et al, 2012). Spectral analyses of the ILDs have revealed the exposure of hydrated sulphate minerals (Gendrin et al, 2005), consistent with their formation by water evaporation (Guallini et al, 2012).…”

“…Spectral analyses of the ILDs have revealed the exposure of hydrated sulphate minerals (Gendrin et al, 2005), consistent with their formation by water evaporation (Guallini et al, 2012). Previous studies of these ILDs described the presence of shallow depression morphologies, generically referred to as pseudokarst topographies (Sefton-Nash et al, 2012), karst-like landforms (Guallini et al, 2012), and grooves or pits (Sowe, 2009). However, to date, no study has analysed these landforms in detail, in terms of their morphologies, possible origins, or significance.…”