BIOSIGNATURE AND ORGANIC CARBON DETECTION BY REFLECTANCE AND RAMAN SPECTROSCOPY FROM INVERTED FLUVIAL CHANNEL SEDIMENTS. J.M. Stromberg1, A. Parkinson1, M. Morison2, E.A. Cloutis1, N. Casson1, D. Applin1, J. Poitras1, A. Moreras-Marti3, C. Maggiori4, C. Cousins3, L. Whyte4, R. Kruzelecky5, D. Das4, R. Leveille4, K. Berlo4, S. K. Sharma6, T. Acosta-Maeda6, M. Daly7, E., Lalla7. 1Dept. of Geography, Univ. of Winnipeg, Winnipeg, MB, R3B 2E9, Canada. j.stromberg@uwinnipeg.ca, 2Univ. of Waterloo, Waterloo, ON, N2L 3G1, Canada, 3 Univ. of St.Andrews, St Andrews KY16 9AJ, UK, 4 McGill Univ., Ste. Anne de Bellevue, QC, H9X 3V9, Canada, 5 MPB Communications Inc., 151 Hymus Boulevard, Pointe Claire, QC, H9R 1E9, Canada, 6 HIGP, Univ, of Hawaii, 2525 Correa Rd., HIG, Honolulu, HI 96822, USA, 7CRESS, York Univ., 4700 Keele St., Toronto, ON M3J 1P3, Canada.

Introduction: The search for extant life on Mars

hinges on the ability to detect biosignatures using rov-er-mounted instruments. A suite of 11 samples were collected from an inverted fluvial channel near Hanks-ville, Utah, USA as a part of the CanMars Mars Sam-ple Return Analogue Deployment (MSRAD) [1], to assess the presence of organic biosignatures and their detectability at a high-fidelity analogue site. The field site consists of inverted fluvial sediments which repre-sent an anastomosing paleochannel [2,3]. Such features are widely present on Mars from the Noachian through Early Hesperian [4,5,6] and have been proposed to be present in Gale crater [7] and a number of proposed Mars 2020 and ExoMars landing sites [6]. The history of water in these regions is important for past habita-bility but also for the preservation of biomolecules in evaporite minerals (gypsum, calcite, halite) or as endo-lithic communities [7,8,9,10].

The samples were acquired along the CanMars MSRAD rover traverse for detailed off-site analysis with rover-equivalent instruments to assess the ability of different science instruments of future and past Mars Missions (Mars2020, ExoMars, MSL, MER) to detect and characterize various biosignatures.

Methods: An aliquot of each sample was pulver-ized, homogenized, subdivided, and dry sieved to <1 mm and <150 µm, with wet samples first dried at 70°C overnight. Total C value were determined using a Cos-tech Instruments Elemental Analyzer coupled to a Del-taplus XL Continuous Flow Stable Isotope Ratio Mass Spectrometer at the University of Waterloo.

Reflectance Spectra. Reflectance spectra (350-2500nm) were collected at UWinnipeg’ s HOSERlab (psf.uwinnipeg.ca) using an ASD FieldSpec Pro HR spectrometer with ~2-7 nm spectral resolution, and i = 30º and e = 0º using an in-house 150 W quartz-tungsten-halogen collimated light source. A total of 1000 spectra were collected and averaged to improve SNR. Longer wavelength spectra were collected with a Bruker Vertex 70 FTIR spectrometer from 2.0–20.0 µm with a viewing geometry of i = 30° and e = 0°. A total of 1500 spectra were collected at a scanner ve-locity of 40 kHz and were averaged to improve SNR.

Raman Spectroscopy. Raman spectra were acquired from both whole and powdered (<150 µm) samples using a 532nm iRaman system at UWinnipeg. Spectra

were collected from 200-4000 cm-1 with a spectral resolution of ~4 cm-1 with a a ~50mW 532 nm solid state diode laser. The automatic integration time func-tion (which increases integration time incrementally, until the response is close to saturation) was used, yielding an optimal signal-to-noise ratio (SNR).

Powdered samples were also analyzed with a time-resolved standoff Raman spectrometer with 532 nm pulsed excitation (Nd:YAG, 20Hz rep rate, 30mJ/pulse) at the HIGP Raman Systems Laboratory. Integration times range from 1-20 pulses on the ICCD detector (intensified and gated, 1408x1044 pixels, 7x7um pixel, Syntronics) and 1-600 spectra were co-added to improve resolution. Samples were run with an intensifier gain of 95%, gate time of 40ns and a laser power of 10 mJ per pulse.

UV-Raman spectra were acquired from pressed pellets of sample using the 226 nm Raman spectrome-ter at York Univ. The laser excitation was provided by an ALPHALAS diode-pumped solid state Nd:YAG laser with a 0.6 ns pulse width and 1:4 µJ of energy per pulse. Scattered light was focused through a 10 cm telescope into a UV-fiber coupled to an Andor Mechelle spectrometer (+intensified CCD Andor iStar detector cooled to -20°C, measuring 240 to 900 nm.

Results: Total C for the samples were < 0.1% ex-cept in samples with a XRD detectable levels of cal-cite. Chlorophyll and carotenes were detected in sam-ples BC4-S3 and S4 by reflectance and Raman spec-troscopy (Fig 1). There is no evidence of organic C in the FTIR spectra (Fig 1), but there is evidence for car-bonate in samples where is it is below XRD detection limits. The time-resolved Raman spectra are dominated by short-lived luminescence and a minor quartz peak in the endolith bearing sandstone sample (Fig 2).

The UV-Raman SNR was too high in samples BC4-S1,2,9 for peak identification but peaks character-istic of organic carbon were identified in the other 8 samples. These occur at ~1500, 2350, 2600-2700, C-C vibration (1315, 1550), C=O stretching of complex esters (~1730), NH-CH or NH3- (~2320-30) (Fig. 3).

Discussion: The most conclusive organic biosigna-ture observed are the presence of chlorophyll and caro-tene in samples BC4-S3 and S4. This is most likely evidence of present endolithic life, however, their de-tection has implications for Mars as these molecules

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are somewhat stable under Martian surface conditions [5,10]. This stability and preservation potential is de-pendent on their endolithic habitat, and so detection requires a freshly exposed surface [5,10]. The lack of organic carbon in the FTIR spectra, exhibits its limita-tion in low concentration samples (<0.1 wt% C).

Organic C was detected by Raman spectroscopy (532 nm, TR, UV) with variable success in multiple samples. All of the samples exhibit some degree of short-lived luminescence which in itself has been pro-posed as a possible biosignature (Fig.2) [11]. The UV-Raman spectra suffer from low SNR which makes compound-specific identification difficult, however organic C was detected in all samples (Fig.3). The data highlights the exceptionally low detection limits of UV-Raman for organic compounds and begins to ex-plore the breadth of information that can be extracted from UV-Raman data. This approximates the data from the Mars2020 SHERLOC instrument which has the potential to identify reduced carbon compounds, but may not provide sufficient structural information to distinguish between a biological signal and extraterres-trial organic inputs [12].

Fig 1. A. Reflectance (A.) and 532 nm Raman (B) spectra of samples BC4-S3, S7, and S11.

Fig 2. Time resolved Raman spectra of all 11 samples.

Fig 3. UV Raman spectra of samples BC4-S3, S7 and S11. Data offset for clarity. References: [1]Osinski G.R.,, et al., (2017) LPSC XLVIII Abstract #2417 [2]Miall A.D., and Turner-Peterson, C.E., (1989) Sed. Geo., 63. [3]Williams, R.W.E., et al, (2009). Gemorph, 107. [4]Pain, C.F., et al., (2007) Icarus, 190. [5]Newsom , N.E., et al., (2010) Icarus, 205. [6]Balme M., et al., (2015) LPSC XLVI Abstract #1321. [7]Grotzinger, J.P., et al, (2014) Science 24 [8] Summons R.E., et al., (2011) Astrobio., 11. [9]Stromberg J.M., et al., (2014) IJA, 13. [10]Baque, M., et al., (2016) OLEB, 46. [11] Eshelman E., et al., (2015) PSS, 93.[12] Hays L.E., et al., (2017) Astrobio., 17.

Acknowledgements: We thank the Canadian Space Agency, the Natural Sciences and Engineering Research Council of Canada, the Canada Foundation for Innovation, the Manitoba Research Innovation Fund, and UWinnipeg for supporting establishment and continued operation of the Planetary Spectropho-tometer Facility, and this study.

2505.pdf49th Lunar and Planetary Science Conference 2018 (LPI Contrib. No. 2083)