Justin Filiberto^a, Allan H. Treiman^b, Paul A. Giesting^a,c, Cyrena A. Goodrich^d, Juliane Gross^e

^aSouthern Illinois University, Geology Department, Carbondale, IL 62901, USA
^bLunar and Planetary Institute, Houston, TX 77058, USA
^cIllinois State University, Department of Geography–Geology, Normal, IL 61790-4400, USA
^dPlanetary Science Institute, Tucson, AZ 85719, USA
^eAmerican Museum of Natural History, New York, NY 10024, USA

We report scapolite in a melt inclusion in olivine in Nakhla, which is the first occurrence of Cl-scapolite found in a martian meteorite. Using terrestrial metamorphic experiments and modeling we constrain its origin. Cl-rich scapolite in Nakhla is consistent with formation from either a late stage Cl-rich, water-poor magma or magmatic Cl-rich hydrothermal brine at a minimum temperature of 700 °C. The temperature of hydrothermal activity recorded by the Cl-scapolite is significantly higher than the temperatures recorded by alteration minerals in Nakhla, and the fluid was Cl-rich, not CO₂-rich. Our results demonstrate that high-temperature Cl-rich fluids were present within the martian crust, and any potential biologic activity would have to survive in these high temperatures and saline fluids. Halophiles can thrive in NaCl-rich systems but at significantly lower temperatures than those recorded by the scapolite. During cooling of the fluid, the system could have reached a habitable state for halophiles. Importantly, halophiles can survive the conditions of space if they are encased in salt crystals, and therefore chlorine-rich phases present an opportunity to investigate for extant life both on the surface of Mars and in martian meteorites.

Reference
Filiberto J, Treiman AH, Giesting PA, Goodrich CA and Gross J (2014) High-temperature chlorine-rich fluid in the martian crust: A precursor to habitability.  Earth and Planetary Science Letters 401:110.
[doi:10.1016/j.epsl.2014.06.003]
Copyright Elsevier
Link to Article