Stability of hydrated minerals on Mars

Abstract

[1] The validity of recent identification of various hydrated minerals (kieserite, gypsum, hexahydrite, nontronite, chamosite, and montmorillonite) on Mars was assessed by exposing these minerals to simulated Martian surface conditions of atmospheric composition and pressure, temperature, and ultraviolet light irradiation. When exposed to such conditions the hydrated minerals exhibit in general, greater losses of interlayer H 2 O than structural OH. Minerals such as gypsum that contain structural H 2 O are more resistant to H 2 O loss than phyllosilicates. The partial loss of OH in some of the phyllosilicates is not accompanied by a measurable and systematic change in the wavelength position or intensity of metal-OH absorption bands. The characteristic absorption features that allow for identification of these minerals on Mars may be reduced in intensity, but are nevertheless largely preserved.

The persistence of a chlorophyll spectral biosignature from Martian evaporite and spring analogues under Mars-like conditions

“…When considering these factors, both mineralizing springs, such as those proposed for Arabia Terra (Allen & Oehler 2008), and evaporitic salt deposits are among those Martian paleoenvironments with the highest preservation potential for fossil biosignatures (Farmer & Des Marais 1999;Summons et al 2011). This is also consistent with laboratory data that confirms the stability of many sulphate minerals under present Martian surface conditions (Cloutis et al 2007).…”

“…In addition to providing refuge from harmful UV-radiation, evaporite precipitation can provide preservation from oxidative surface processes (Stivaletta & Barbieri 2009), as well as desiccation due to the fact that gypsum does not dehydrate under Martian conditions (Cloutis et al 2007). It should also be noted that while it has been shown experimentally that Martian levels of UV-irradiation results in a high kill rate, this loss in cell viability does not directly correlate with the destruction of detectable biomolecules, so it may be possible that some biomolecules may remain intact beyond the time of cell death and represent viable biomarkers (Cockell et al 2005).…”

Spectral reflectance properties of carbonaceous chondrites 4: Aqueously altered and thermally metamorphosed meteorites

“…Their samples of ferrihydrite -a common Fe oxyhydroxide in CI chondrites (Buseck and Hua, 1993), montmorillonite, and palagonitic soil all show a decrease in the depth of the 1.9 lm (and 3.0 lm) region H 2 O absorption feature at lower pressures; spectral slopes showed more complex behavior but generally became bluer over the 1.8-2.5 lm interval. Cloutis et al (2007Cloutis et al ( , 2008) exposed a variety of minerals to Mars surface conditions ($660 Pa CO 2 ) followed by the addition of UV irradiation, and then a lower pressure (1 Pa) excursion. Their experiments included smectites (beidellite, nontronite, montmorillonite, saponite), serpentine group phyllosilicates (berthierine, cronstedtite, halloysite, serpentine), as well as some organic materials and goethite.…”

Abundance of minerals in the phyllosilicate-rich units on Mars

“…1A). The surface exposure to the Martian environment and grain size effect have been shown to be unable to account for this reduced spectral contrast (Cloutis et al 2007(Cloutis et al , 2008Cooper & Mustard 1999). Admixture of non-phyllosilicate anhydrous components is therefore required to account for it.…”