Chloride-Bearing Materials in the Southern Highlands of Mars

Abstract

Chlorides commonly precipitate during the evaporation of surface water or groundwater and during volcanic outgassing. Spectrally distinct surface deposits consistent with chloride-bearing materials have been identified and mapped using data from the 2001 Mars Odyssey Thermal Emission Imaging System. These deposits are found throughout regions of low albedo in the southern highlands of Mars. Geomorphologic evidence from orbiting imagery reveals these deposits to be light-toned relative to their surroundings and to be polygonally fractured. The deposits are small (< ∼25 km 2 ) but globally widespread, occurring in middle to late Noachian terrains with a few occurrences in early Hesperian terrains. The identification of chlorides in the ancient southern highlands suggests that near-surface water was available and widespread in early Martian history.

Mineral paragenesis on Mars: The roles of reactive surface area and diffusion

“…In our models the system is open to the atmosphere, and therefore, the loss of water through evaporation is regarded as the main factor inducing supersaturation (as multiple indicators for evaporation have been reported on Mars) [see e.g., Squyres et al ., 2004; Sears and Moore , 2005; Tosca et al ., 2005; Osterloo et al ., 2008; Fairén et al ., 2009; Arvidson et al ., 2014; Toner et al ., 2015; Schwenzer et al ., 2016; Hurowitz et al ., 2017]; and because the system is likewise open at the water‐sediment interface, reactive transport was also considered (Figure 1). In addition, we considered that dissolved volcanic gases (H 2 O, CO 2 , Cl 2 , and SO 2 ) [e.g., Halevy and Head , 2014] are the main anion source to the aqueous solutions, as well as drivers of redox processes and alkalinity, modifying the dissolution kinetics of primary minerals, which, in turn, are largely dependent of pH, temperature, and the reactive surface.…”

“…Provided the existence of an alternative source of anions, mainly derived from volcanic volatiles [ Halevy and Head , 2014], it is expected that these ions would have bonded in evaporites (i.e., sulfates). However, in most localities on Mars, evaporites are commonly absent in clay‐dominated sediments [ Bandfield et al ., 2003; Bishop et al ., 2008; Ehlmann et al ., 2008; Osterloo et al ., 2008]. As a particular example, evaporites in Gale crater are the result of postdepositional fluid migration, in different late‐stage episodes of fluid flow; therefore, clays and evaporites at Gale have very different depositional histories, occurring spatially closely but with deposition times separated by hundreds of millions of years [ Nachon et al ., 2014; Rapin et al ., 2016].…”

The science process for selecting the landing site for the 2011 Mars Science Laboratory

“…The ellipse associated with the putative chloride site south of Meridiani Planum provides access to a small basin near the terminus of a valley network where putative chloride deposits have been identified (Osterloo et al, 2008). The chloride deposits, inferred to have formed via in situ precipitation within a sedimentary sequence, would have required substantial water prior to their emplacement and could comprise a good setting for preservation of any organic materials (Osterloo et al, 2008).…”

“…The chloride deposits, inferred to have formed via in situ precipitation within a sedimentary sequence, would have required substantial water prior to their emplacement and could comprise a good setting for preservation of any organic materials (Osterloo et al, 2008).…”

“…An additional putative chloride site west of Miyamoto crater was proposed to examine the deposits in a small basin based on rationale similar to that given for the previous chloride site south of Meridiani Planum and proposed at the second workshop (Osterloo et al, 2008).…”