“Chemical and isotopic fingerprints of MDRS carbonates” – A quick review
By Roy Naor
Crew Geologist – crew 173
An ongoing study is being conducted in the Weizmann Institute of Science, Israel, aimed at understanding the chemical and isotopic fingerprint of carbonate forming environments on Mars. The research is active in three different areas: Mars in situ observations, lab simulations and comparisons to analogue environments. The MDRS environment is analogous to, for example, a specific type of arid environment that we hypothesise about in our isotopic fractionation models. Therefore, it is important to compare the chemical and isotopic fingerprints of carbonates at MDRS with those anticipated in such an arid environment. This way future studies of Martian geology, for instance by the Mars 2020 rover, will be able to better determine the environment in which the samples were originally formed. In addition, the previous studies on the MDRS environment have laid a number of constraints, which thus make MDRS a very good candidate analogue site to study.
The potential of extraterrestrial life on Mars is well connected to the history, and distribution of water and carbon on the planet. Carbonate minerals are seen as powerful tools with which to explore these fundamental relationships, as they are intimately tied to both the water and the inorganic carbon cycle. Some local deposits of carbonates have been discovered on the surface of Mars and in meteorites. The wide ranging set of observations of carbonate minerals, provided by a series of robotic missions to Mars, not only defined new constraints on the history of Martian climate, but also opened unique windows into primordial Martian aqueous environments. While questions about habitability remain unanswered at this time, we are obtaining more and more information about the environments in which water has existed on the Martian surface. The research frontier is to focus the resolution on the variability of the different mineral forming environments, rather than try to see Mars as a one uniform environment (Niles et al., 2012).
Though it is one of several sampling sites, the MDRS site is a very good one, because there are many constraints inputted by previous intensive MDRS research. The area around MDRS holds several potential types of carbonate forming environments representing varied conditions. Some are newly formed as part of the topsoil under the present conditions. Some are from older formations, representing different conditions relevant to the period when it precipitated as concretion or as a shale component.
The carbonate prospecting field work is focused on locating and sampling carbonate minerals in the topsoil and exhumed formation in the vicinity of MDRS. The procedure is being conducted as follows:
1) A preliminary prospecting work to locate potential sampling sites has been done by reading through previous studies and analyze geological maps of the area. preliminary pinpointing of potential sites leaned on previous work and geological mapping of the area, focusing on carbonate bearing sediments and potential present carbonate forming environment around MDRS.
2) On site locating and verifying carbonates and carbonate bearing assemblage by simple field analysis using HCl 5%.
3) Collecting verified assemblage or suspected outcrop and bringing it back to MDRS, with the intention to retrieve them full to further analysis (making the sampling very rigorous and somewhat analogues to real extraterrestrial field work).
The sampling is carried out using a geological hammer to break small pieces to feet inside the tubes and a garden trowel for soil samples. a meticulous procedure is being conducted to document the samples:
– Marking each sample bag with the date, time, serial number, name of site/outcrop, GPS coordinates.
– Document all of the above procedures by detailed description of the sampled outcrop using a hardcopy waterproof notebook and by taking pictures of the local environment/outcrop (to scale), the sampling area (to scale), the sampled material (to scale) and the sampling procedure.
– Put all of the samples into one box filled with styrofoam mold to protect them during the transport back to Israel, where they will be analyzed extensively at the Weizmann Institute of Science for the carbonates’ chemical and isotopic fingerprint. the samples will go under the procedure of:
– Crystal separation
– Mineral/chemical identification (XRD, EDS, CL)
– Textural analysis (SEM, micro-CT)
– Isotopic analysis (SIMS)
The processed data will be used as an input and as a testing method for the under development model.
The results will be added to our datasets with the intention of publishing them in academic journals.
Niles, P.B., Catling, D.C., Berger, G., Chassefière, E., Ehlmann, B.L., Michalski, J.R., Morris, R., Ruff, S.W., Sutter, B. (2012) Geochemistry of Carbonates on Mars: Implications for Climate History and Nature of Aqueous Environments. Space Sci Rev. DOI 10.1007/s11214-012-9940-y