Preservation of organics at Mars' near-surface

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Submitted on 23 Jun 2016

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Preservation of organics at Mars’ near-surface

Caroline Freissinet, Daniel P. Glavin, Arnaud Buch, Cyril Szopa, P. D. Archer Jr., William B. Brinckerhoff, Anna E. Brunner, Jennifer L. Eigenbrode,

Heather B. Franz, S. Kashyap, et al.

To cite this version:

Caroline Freissinet, Daniel P. Glavin, Arnaud Buch, Cyril Szopa, P. D. Archer Jr., et al.. Preser-vation of organics at Mars’ near-surface. Biosignature PreserPreser-vation and Detection in Mars Analog Environments conference, May 2016, Incline Village, NV, United States. �insu-01336824�

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RESERVATION

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C. Freissinet

_{, D. P. Glavin, A. Buch, C. Szopa, P. D. Archer Jr., W. B. Brinckerhoff, A. E. Brunner, J. L.}

Eigenbrode, H. B. Franz, S. Kashyap, C. A. Malespin, M. Millan, K. E. Miller, R. Navarro-Gonzalez, B. D.

Prats, R. E. Summons, S. Teinturier and P. R. Mahaffy

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_{NASA Goddard Space Flight Center, Greenbelt MD,}

_{CRESST, Baltimore MD.}

_{caroline.freissinet@nasa.gov}

Chemical complexification

Biological molecules Prebiotic molecules

Primordial/simple molecules

Gas Chromatograph (GC) – Separates individual compounds from a mix Mass Spectrometer (MS) – Identifies molecules from their mass

Tunable Laser Spectrometer (TLS) – Molecules and Isotopes

GC# MS# TLS# Solid#samples#inlets# 20 15 10 5 0 MS R esp on se (1 0 3 cp s) 1100 1000 900 800 700 600 500 Retention Time (s) SAM Cumberland SAM Cumberland Blank

100 80 60 40 20 0 R el at ive MS R esp on se 1100 1000 900 800 700 600 500 Retention Time (s) Laboratory Breadboard 1, 2-d ich lo ro be nze ne 1, 4-d ich lo ro be nze ne C hl oro be nze ne 102 103 104 105 MS re sp on se (co un ts/ s) 12.4 12.2 12.0 11.8 s x103 20 18 16 14 12 10

Retention Time (minutes)

160 120 80 40 Te mp era tu re C olu mn (° C ) 102 103 104 105 MS R esp on se (co un ts/ s) 12.2 12.0 11.8 11.6 s x103 20 18 16 14 12 10

Retention Time (minutes)

160 120 80 40 Te mp era tu re C olu mn (° C ) 102 103 104 105 MS re sp on se (co un ts/ s) 12.4 12.2 12.0 11.8 s x103 20 18 16 14 12 10

Retention Time (minutes)

160 120 80 40 Te mp era tu re C olu mn (° C ) m/z 105 m/z 281 m/z 229 m/z 323 102 103 104 105 MS re sp on se (co un ts/ s) 12.4 12.2 12.0 11.8 s x103 20 18 16 14 12 10

Retention Time (minutes)

160 120 80 40 Te mp era tu re C olu mn (° C ) a) OD - Sample b) OD - Blank Anderson 2010

Cumberland composition (E. Rampe)

High surface area.

Interlayer charged negatively.

Cation associated with water in the interlayers: retards water flow.

6x104 5 4 3 2 1 0 MS R esp on se (cp s) 300 250 200 150 100 50 0 s 6000 5000 4000 3000 2000 1000 0 1000 900 800 700 600 500 400 300 s 30 20 10 0 x1 0 6 1000 900 800 700 600 500 400 300 3x107 2 1 0 R el at ive MS re sp on se 300 250 200 150 100 50 0 30 20 10 0 x1 0 6 1000 900 800 700 600 500 400 300 Retention Time (s) D ime th yl su lfi de Thiophene 2-me th yl -t hi op he ne 3-me th yl th io ph en e 2, 5-d ime th yl th io ph en e ? 3x107 2 1 0 R el at ive MS re sp on se 300 250 200 150 100 50 0 3x107 2 1 0 R el at ive MS re sp on se 300 250 200 150 100 50 0 3x107 2 1 0 R el at ive MS re sp on se 300 250 200 150 100 50 0 A) SAM CB-7 C) Laboratory Breadboard 6000 5000 4000 3000 2000 1000 0 1000 900 800 700 600 500 400 300 s 6x10 3 B) SAM MJ-1

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technical crew, management and support staff at NASA HQ, JPL, NASA Goddard Space Flight Center, the French Space Agency CNES, Honeybee Robotics, UMBC, USRA and other industry partners for making this mission and these SAM measurements possible.

One of the biggest concerns for the in situ detection of organic molecules on extraterrestrial environment is the preservation potential of the molecules at the surface and subsurface given the harsh radiative environment and oxidants they are exposed to.

The Mars Science Laboratory (MSL) mission hosts Sample Analysis at Mars (SAM), a 40 kg suite of instruments which is devoted to make the inventory of organic and inorganic compounds in Mars’ atmosphere and subsurface, and understanding their processes of preservation.

To date, SAM has detected and identified several organic molecules in the Martian subsuface, such as chloroalkanes, chlorobenzene at various states of chlorination, sulphur-containaing molecules and functionalized aromatic hydrocarbons.

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The presence of organic molecules opens up habitability to another level, where the building blocks of life were available. Understanding their windows of preservation of organics will help in the search for prebiotic or biological signature on Mars.

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Fig. 2: SAM onboard Curiosity: a suite of 3 instruments He#tank# PR# Quadrupole#Mass# Spectrometer################ (2=535#Da)# FR# Hydrocarbon#Trap# (~5#to#300°C)# Gas#Lines########### (135°C)# Sample########### (~50#mg)# GCMS# Mode# Gas#Chromatograph# (MXT#CLP,#30#m)# GC#Split# Gas#Vent# To#Pump# He#flow#~1.5# sccm# ©Danny&Glavin& Cup#in#Oven# (ambient#to# ~880°C#at#35°C/ min,#30#mbar#He)#

Fig. 4: Simplified gas flow diagram for the GCMS mode of SAM

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Fig. 1: From chemistry to b i o l o g y , o n e c a n s e e a complexification of organic molecules. Looking for the whole range will assess the past and present biological potential of Mars.

SAM (Fig. 2) is a suite of three instruments that measure volatiles extracted from solid samples using three primary analytical modes for analysis of organic compounds, including: (1) Evolved gas analysis-quadrupole mass spectrometry (EGA), where solid samples are heated inside a pyrolysis oven up to ~1000°C and the gases released are monitored by quadrupole mass spectrometry (QMS), with portions isolated for gas chromatography mass spectrometry (GCMS) (Fig. 4) and (2) wet chemistry, which consists of an extraction and derivatization with N-methyl-N-tertbutyldimethylsilyl-trifluoroacetamide (MTBSTFA) followed by GCMS anlalysis (Fig. 5)._&

To date, MSL travelled almost 13 km at the surface of Mars and drilled 10 rocks for 9 SAM analyzes. The two samples discussed in this poster are Cumberland (CB), in the Sheepbed mudstone, and Mojave (MJ), Fine-grained sedimentary deposits in Murray Formation of the Pahrump Hills (Fig. 3).

Fig. 3: MSL traverse map and drilling sites

Foil cap Foil cap Outer volume (0.79 cc) Inner volume (0.09 cc) 7 2

Fig. 5: SAM wet chemistry. A) MTBSTFA derivatization reaction. B) SAM carrousel containing 7 MTBSTFA cups (detailed in C))

A)

B) C)

The presence of perchlorates in the soils does not prevent the detection of organic molecules even if it becomes a powerful oxidant when heated!

Lessons learned from SAM derivatization on Mars will feed forward to planning for experiments and wet chemistry on Mars Organic Molecules Analyzer MOMA2020 (ExoMars rover).

SAM data set + lab experiments are consistent with the presence of organic matter in the sample, with a wider diversity than previously recognized.

Organics of martian origin identified in the Sheepbed mudstone and at

Parhump Hills can be preserved in the near-surface over geological times!

SAM data providing important constraints on the types of rock samples (mineralogy, radiation exposition) that should be targeted for future examination and for sample return missions.

Low-temp organics are chlorinated, high-temp organics are not! High-temp. organics are protected from the O₂/Cl released from the decomposition of perchlorates.

Ancient Mars was habitable – was it inhabited?

!  Organics are prone to degradation under cosmic radiations.

Preserved samples would be buried < 2-3 m

MOMA Improvements over SAM:

1)  MOMA samples drilled down to 2 meters deep

2)  N,N-dimethyl-formamide dimethylacetal (DMF-DMA) derivatization will protect the asymmetrical center(s) of derivatized molecule to discriminate and quantify enantiomers (needs enantiomeric preservation studies)

Several organics were identified on Mars, however, the origin (biological vs. abiotic) and the nature of the precursors of the chlorinated organics are unknown (6A).

Sulphur-containing compounds identified at high-temperature in CB and MJ (e.g. thiophene – 6B). Low-temp organics are chlorinated, high-temp

organics are not! High-temp. organics are protected from the O₂/Cl

released from the decomposition of perchlorates. 150-300 ppbv

Pyrolysis-GCMS Derivatization-GCMS

Low temperature cut High temperature cut

Fig. 6: SAM GCMS results. A) Low temperature cut on CB sample (< 450 ºC), identification of chlorohydrocarbons from pyrolysis. B) High temperature cut on CB or MJ samples (> 600 ºC), detection of sulfur-containing, non-chlorinated organics from pyrolysis. C) Derivatization GCMS on high temperature cut of CB sample (> 250 ºC), detection of higher complexity, non-chlorinated organics with tentative identification

A) B) C)

1) Detection of organic molecules indigenous to Mars’ subsurface

2) Origin of the chlorohydrocarbons – effect of perchlorates _{3) Preservation of organics in CB mudstone}

!  Clays are good candidates for accumulating and preserving organics

over geological timescales

CB sample is 65 mm-deep. However, cosmic-ray–produced 3_He, 21_{Ne, and} 36_{Ar yield concordant surface exposure ages of 78 +/- 30 million years}

(Farley et al., Science, 2014). Recently exposed rocks are good targets for preservation. >15&nmol& melli1c& acid& readily( Miller(et(al.,(JGR(2015( Cl O O -O O Cl O O -O O Ca2+# Mg2+# T&>&200°C& Cl Cl Cl Cl Cl Cl Cl Cl Cl Cl Cl Cl 0.1$ 1$ 10$ 100$ 1000$ Alkylth iophe nes$ Alkylbe nzene s$ Benzoic $acid$ Dichloro metha ne$ Chloro benzen e$ Dichloro propa ne$ Dichlo robuta ne*$ Chlor oprop anon e*$ Dichlo roprop anon e*$ Ab un da nc e$( ar bi tra ry $u ni ts )$ Murchison + 50µg Ca Perchlorate Murchison + 500µg Ca Perchlorate Murchison 50µg Ca Perchlorate 500µg Ca Perchlorate * Tentative identification

The chlorohydrocarbons are expected to be formed from the reaction of a non-chlorinated precursor present in the sample and Cl from perchlorate decomposition, in SAM oven even if there presence as such in the sample cannot be totally excluded.

Fig. 7: laboratory experiment show that benzoic, phthalic and mellitic acid, heated in the presence of perchlorate, would form chlorobenzene, dichlorobenzene and trichlorobenzene, and that the abundance of CBZ depends on the initial abundance of the aromatic hydrocarbon.

Laboratory experiments are integral to Mars results. They show that the organics extract of Murchison meteorites, and that functionalized aromatic hydrocarbons, are good candidates for the formation of chlorobenzene in SAM.

Mellitic acids has been shown (Benner et al, P N A S , 2 0 0 0 ) t o b e e n d - p r o d u c t s o f decomposition of living systems molecules, and metastable at Mars’ surface conditions.

Fig. 8: formation of CBZ from Murchison pyrolysed in presence

of perchlorate

Derivatization (6C) preserves chemical structure enabling identification of possible chlorohydrocarbon precursors and other organics of

astrobiological interest (e.g. amino/carboxylic acids) that are not detectable by pyrolysis GCMS alone.

The first detection of reduced organic compounds in martian near surface samples is a significant step toward understanding the preservation of molecules in oxidative/radiative conditions.