The water vapour equilibria over magnesium perchlorate hydrates

Besley, L. M.; Bottomley, G. A.

doi:10.1016/0021-9614(69)90032-9

Cited by 31 publications

(24 citation statements)

References 7 publications

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“…Mg(ClO 4 ) 2 is deliquescent, with a eutectic temperature near 213 K [ Pestova et al , 2005]. Hydrates up to Mg(ClO 4 ) 2 •6H 2 O were identified by Besley and Bottomley [1969], who also found some evidence for an octahydrate. The equilibrium vapor pressure of the hexahydrate‐octahydrate pair, as derived from their phase diagram, falls very near the pseudo vapor pressure curve in Figure 18, at least in the vicinity of 210–200 K.…”

Section: Discussionmentioning

confidence: 99%

Initial results from the thermal and electrical conductivity probe (TECP) on Phoenix

Zent

Hecht

Cobos³

et al. 2010

J. Geophys. Res.

144

138

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The thermal and electrical conductivity probe (TECP), a component of the Microscopy, Electrochemistry, and Conductivity Analyzer (MECA), was included on the Phoenix Lander to conduct in situ measurements of the exchange of heat and water in the Martian polar terrain. TECP measured regolith thermal conductivity, heat capacity, temperature, electrical conductivity, and dielectric permittivity throughout the mission. A relative humidity sensor returned the first in situ humidity measurements from the Martian surface. The dry overburden above the ground ice is a good thermal insulator (average κ = 0.085 W m−1 K−1 and average Cρ = 1.05 × 106 J m−3 K−1). Surface thermal inertia (I) calculated from these values agrees well with daytime orbital determinations, but differences in the spatial and temporal scale of heat transport lead to very different measurements at night. Electrical conductivity was consistent with open circuit throughout the mission; an upper limit conductivity of 2 nS cm−1 is derived. Bulk dielectric permittivity (ɛb) shows several puzzling signals but also a systematic increase overnight in the latter half of the mission, contemporaneous with H2O adsorption. The magnitude of the increase is difficult to reconcile with expected changes in unfrozen water. Atmospheric H2O averages around 1.8 Pa during the day, corresponding to a RH < 5%. At night, much of the H2O disappears from the atmosphere, and RH increases to ∼100%. Temperature and H2O partial pressure data suggest that adsorption on mineral surfaces plays a major role in scrubbing H2O, with a possible contribution from perchlorate salts.

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Section: Discussionmentioning

confidence: 99%

Initial results from the thermal and electrical conductivity probe (TECP) on Phoenix

Zent

Hecht

Cobos³

et al. 2010

J. Geophys. Res.

144

138

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“…Thermal analyses indicate only one transition to the trihydrate phase at around 420–434 K [ Mikuli et al , 1998; Willard and Smith , 1922] or the 4‐hydrate at 409 K [ Dobrynina et al , 1980]. The 2 and 4 hydrates are obtained through dehydration [ Besley and Bottomley , 1969; Krivtsov et al , 1989], or direct precipitation [ Dobrynina et al , 1980].…”

Section: Stability Diagrams and Eutectic Determinationmentioning

confidence: 99%

Stability of perchlorate hydrates and their liquid solutions at the Phoenix landing site, Mars

Chevrier

Hanley

Altheide

2009

Geophysical Research Letters

175

167

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[1] We studied the low-temperature properties of sodium and magnesium perchlorate solutions as potential liquid brines at the Phoenix landing site. We determined their theoretical eutectic values to be 236 ± 1 K for 52 wt% sodium perchlorate and 206 ± 1 K for 44.0 wt% magnesium perchlorate. Evaporation rates of solutions at various concentrations were measured under martian conditions, and range from 0.07 to 0.49 mm h À1 for NaClO 4 and from 0.06 to 0.29 mm h À1 for Mg(ClO 4 ) 2 . The extrapolation to Phoenix landing site conditions using our theoretical treatment shows that perchlorates are liquid during the summer for at least part of the day, and exhibit very low evaporation rates. Moreover, magnesium perchlorate eutectic solutions are thermodynamically stable over vapour and ice during a few hours a day. We conclude that liquid brines may be present and even stable for short periods of time at the Phoenix landing site.

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“…However, many other salts including sulfates and calcium carbonate are also probably present in the soil as suggested by data from previous Mars missions and meteorites [e.g., Rao et al , 2005; Wentworth et al , 2005]. This is important because Mg(ClO 4 ) 2 · n H 2 O and Ca(ClO 4 ) 2 · m H 2 O have freezing temperatures of about 200 K, are extremely deliquescent [ Besley and Bottomley , 1969; Pestova et al , 2005], and mixtures of salts have eutectic temperatures below those of the individual salts [e.g., Seinfeld and Pandis , 2006]. This suggests that the formation of eutectic solutions is possible at the present time on Mars, where ground ice exists near the surface such as at the Phoenix landing site.…”

Section: Formation Of Brines and Salt Layersmentioning

confidence: 99%

Possible physical and thermodynamical evidence for liquid water at the Phoenix landing site

Rennó¹,

Bos²,

Catling³

et al. 2009

J. Geophys. Res.

167

168

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[1] The objective of the Phoenix mission is to determine if Mars' polar region can support life. Since liquid water is a basic ingredient for life, as we know it, an important goal of the mission is to determine if liquid water exists at the landing site. It is believed that a layer of Martian soil preserves ice by forming a barrier against high temperatures and sublimation, but that exposed ice sublimates without the formation of the liquid phase. Here we show possible independent physical and thermodynamical evidence that besides ice, liquid saline water exists in areas disturbed by the Phoenix Lander. Moreover, we show that the thermodynamics of freeze-thaw cycles can lead to the formation of saline solutions with freezing temperatures lower than current summer ground temperatures on the Phoenix landing site on Mars' Arctic. Thus, we hypothesize that liquid saline water might occur where ground ice exists near the Martian surface. The ideas and results presented in this article provide significant new insights into the behavior of water on Mars.

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The water vapour equilibria over magnesium perchlorate hydrates

Cited by 31 publications

References 7 publications

Initial results from the thermal and electrical conductivity probe (TECP) on Phoenix

Initial results from the thermal and electrical conductivity probe (TECP) on Phoenix

Stability of perchlorate hydrates and their liquid solutions at the Phoenix landing site, Mars

Possible physical and thermodynamical evidence for liquid water at the Phoenix landing site

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