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| Titel |
Experimental Demonstration of the Formation of Liquid Brines under Martian Polar Conditions in the Michigan Mars Environmental Chamber |
| VerfasserIn |
Erik Fischer, German Martinez, Harvey Elliott, Caue Borlina, Nilton Renno |
| Konferenz |
EGU General Assembly 2014
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| Medientyp |
Artikel
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| Sprache |
Englisch
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| Digitales Dokument |
PDF |
| Erschienen |
In: GRA - Volume 16 (2014) |
| Datensatznummer |
250093937
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| Publikation (Nr.) |
 EGU/EGU2014-9162.pdf |
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| Zusammenfassung |
| Liquid water is one of the necessary ingredients for the development of life as we know it.
The behavior of various liquid states of H2O such as liquid brine, undercooled liquid
interfacial water, subsurface melt water and ground water [1] needs to be understood in order
to address the potential habitability of Mars for microbes and future human exploration. It has
been shown thermodynamically that liquid brines can exist under Martian polar conditions [2,
3].
We have developed the Michigan Mars Environmental Chamber (MMEC) to simulate the
entire range of Martian surface and shallow subsurface conditions with respect to
temperature, pressure, relative humidity, solar radiation and soil wetness at equatorial
and polar latitudes. Our experiments in the MMEC show that deliquescence of
NaClO4, Mg(ClO4)2 and Ca(ClO4)2 occurs diurnally under the environmental
conditions of the Phoenix landing site when these salts get in contact with water ice.
Since Phoenix detected these salts and water ice at the landing site, including frost
formation, it is extremely likely that deliquescence occurs at the Phoenix landing
site.
By layering NaClO4, Mg(ClO4)2 or Ca(ClO4)2 on top of a pure water ice slab at 800 Pa
and 190 K and raising the temperature stepwise across the eutectic temperature of the
perchlorate salts, we observe distinct changes in the Raman spectra of the samples when
deliquescence occurs. When crossing the eutectic temperatures of NaClO4 (236 K),
Mg(ClO4)2 (205 K) and Ca(ClO4)2 (199 K) [4, 5], the perchlorate band of the Raman
spectrum shows a clear shift from 953 cm-1 to 936 cm-1. Furthermore, the appearance of a
broad O-H vibrational stretching spectrum between 3244 cm-1 and 3580 cm-1 is another
indicator of deliquescence. This process of deliquescence occurs on the order of
seconds when the perchlorate salt is in contact with water ice. On the contrary, when
the perchlorate salt is only subjected to water vapor in the Martian atmosphere,
deliquescence was not observed within the Martian diurnal cycle. This greatly diminishes
the possibility of liquid brine formation without water ice contact and has strong
implications on future robotic and manned missions searching for liquid water on
Mars.
Acknowledgement: This research is supported by a grant from the NASA Astrobiology
Program: Exobiology and Evolutionary Biology. Award #09-EXOB09-0050.
References: [1] Martínez, G. M. and Renno, N. O. (2013), Water and Brines on Mars:
Current Evidence and Implications for MSL, Space Sci. Rev., 175, 29-51. [2] Rennó, N. O.,
et al. (2009), Possible physical and thermodynamical evidence for liquid water
at the Phoenix landing site, J. Geophys. Res., 114, E00E03. [3] Zorzano, M.-P.,
et al., Stability of liquid saline water on present day Mars, Geophys. Res. Lett.,
36, L20201. [4] Hanley, J. et al. (2009), Low Temperature Aqueous Perchlorate
Solutions on the Surface of Mars, Proceedings 40th Lunar and Planetary Sciences
Conference, The Woodlands, TX, USA. [5] Marion, G. M. et al. (2010), Modeling
Aqueous Perchlorate Chemistries with Applications to Mars, Icarus, 207, 675-685. |
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