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Project Progress

Since depositional environment, geology and mineralogy influence the detection of organic matter, soil and rock samples were collected from different topographic units within a single geological unit, the Brushy Basin member. The units chosen included a plain, a region below a cliff and a canyon, see Figure 1. The different topographic units are similar to the topographic units the Mars Science Laboratory will visit in Gale Crater and hence analysis of these samples will be relevant to this mission. Fourier Transform Infra-Red Spectroscopy (FTIR) showed that clays are mostly found in the canyon and base of mountain samples (Figure 2, Table 1). The canyon samples showed the largest abundance of Montmorillonite. Illite was mostly present in the base of mountain samples (Rammos et al. 2013). CNS analysis showed only upper limits for sulfur, and concentrations < 1 % for C and 0.2 % for N, respectively.

Table 1: FT-IR spectra (cm^-1) and corresponding reference minerals. Sample names are indicated with BB-Brushy Basin, and BS-Blue Gate Shale. The topographical units of the samples are indicated with (BM) – Base of Mountain, (Pl)- Plain and©- Canyon.

SEM measurements have been performed indicating a mean grain size of samples in the low micrometer range suitable for quantitative IR spectroscopy, see Figure 3. SEM/EDX analysis is still ongoing in order to determine the elemental composition of the mineralogy. XRD measurements to determine in particular in detail the clay fraction are currently in progress. The combined data will be related to the extraction results on amino acids to investigate the mineral- organic interaction.

Results from the 2009 EuroMoonMars campaign showed that amplification-based methods are an important option for life detection. Whole genome amplification (WGA) methods, in particular strand displacement amplification, have made it possible to detect microbial communities in low biomass environments. WGA methods are a good alternative to PCR (Polymerase Chain Reaction). They are useful not only for the amplification of DNA from low biomass environments but also for life detection investigations, because they are highly sensitive (only small amounts of template DNA are necessary), provide wide genome coverage, do not require previous sequence information and require less energy consumption (no thermal cycling at high temperatures). To examine the extent to which the actual community structure is revealed reliably, possible biases introduced by two different WGA methods were compared. Using a PCR-based method as control, the detection efficacies of two isothermal WGA methods, i.e. one widely used (MDA – Multiple Displacement Amplification) and one new, primer-free method (pWGA – primase-based Whole Genome Amplification), were determined in terms of being biased by species GC content, DNA integrity and fragment size (Direito et al. 2013). MDA was biased towards low GC content species while amplification of low molecular weight DNA was hampered by pWGA (<1.5 kb) Fragmented DNA was less amplified with both WGA methods. The investigations of a new primer free amplification method go beyond what is currently studied in the context of common amplification methods and are of vital importance for future life detection methods, also those including alternative genetic polymers.

References:

P. Ehrenfreund et al. (2011) “Astrobiology and habitability studies in preparation for future Mars missions: trends from investigating minerals, organics and biota”, Intern. Journal of Astrobiology 10/3, 239-254

B. H. Foing et al. & ILEWG EuroGeoMars 2009 team (2011) “Field Astrobiology Research in Moon-Mars analogue environment: Instruments and Methods”, Intern. Journal of Astrobiology 10/3, 141-160

I. Rammos et al. (2013) Field analogue geology and astrobiology in support of Mars Science Laboratory: correlation of organics with topographic units, in preparation

S. Direito, E. Zaura, M. Little, P. Ehrenfreund, H.V. Westerhoff and W. F.M. Röling (2013) Systematic evaluation of bias in microbial community profiles induced by whole genome amplification, PhD thesis and in preparation for Environmental Microbiology