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Organic molecules revealed in Mars’s Bagnold Dunes by Curiosity’s derivatization experiment

Abstract

The wet chemistry experiments on the Sample Analysis at Mars instrument on NASA’s Curiosity rover were designed to facilitate gas chromatography mass spectrometry analyses of polar molecules such as amino acids and carboxylic acids. Here we present the results of such a successful wet chemistry experiment on Mars on sand scooped from the Bagnold Dunes with the N-methyl-N-(tert-butyldimethylsilyl) trifluoroacetamide derivatization agent. No amino-acid derivatives were detected. However, chemically derivatized benzoic acid and ammonia were detected. Mass spectra matching derivatized phosphoric acid and phenol were present, as were several nitrogen-bearing molecules and as yet unidentified high-molecular-weight compounds. The origin of these compounds, including those that may be internal to the Sample Analysis at Mars background, is examined. This derivatization experiment on Mars has expanded the inventory of molecules present in Martian samples and demonstrated a powerful tool to further enable the search for polar organic molecules of biotic or prebiotic relevance.

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Fig. 1: The sample acquisition in context.
Fig. 2: Representative traces extracted from the EGA analysis (top) and chromatograms from the MXT-20 (centre) and Chirasil-β Dex (bottom) columns from selected m/z values or bands covering a range of masses1.
Fig. 3: SAM GCMS identification of benzoic acid derivatized compared with the SAM-like GC run of benzoic acid derivatized measured in laboratory.
Fig. 4
Fig. 5: 10 min section (23–33 min) of the chromatogram obtained with the spare Chirasil-β Dex column of the standard mixture of 22 amino acids derivatized with MTBSTFA-DMF.

Data availability

Data from the SAM experiments are archived in the Planetary Data System (pds.nasa.gov). Data from the laboratory experiments can be found at: https://doi.org/10.17632/fbr8tp38gs.1Source data are provided with this paper.

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Acknowledgements

We thank the Mars Science Laboratory and SAM engineering and scientific teams for their support and insightful discussions, F. J. Calef for providing Fig. 1a, R. Sullivan for his advice and contribution to Fig. 1 and P.-Y. Meslin for his insights on phosphorus detections by the ChemCam instrument. M.M. and S.S.J. acknowledge funding from the NASA-GSFC grant NNX17AJ68G: ‘Using Organic Molecule Detections in Mars Analog Environments to Interpret the Results of the SAM Investigation on the MSL Mission’. R.N.-G. acknowledges the Universidad Nacional Autónoma de México (UNAM: PAPIIT IN111619 and PAPIME PE102319) for financial support. We also acknowledge the financial support provided by the Centre National d’Etudes Spatiales (CNES), related to SAM and Mars Science Laboratory.

Author information

Authors and Affiliations

Authors

Contributions

M.M. processed the data, calculated and interpreted GCMS data and wrote most of the manuscript and supplementary material under the supervision of S.S.J. and P.R.M. S.T. and C.A.M. prepared and developed the wet experiment using the SAM Testbed replica located at NASA-Goddard Space Flight Center and performed the SAM flight pyrolysis and derivatization GCMS experiments on Mars. M.M. and A.S. performed SAM-like laboratory analysis in support of flight data. J.C.S. and B.S interpreted EGA data. P.R.M., S.S.J., J.Y.B., A.B., J.P.D., J.L.E., C.F., D.P.G., R.N.-G., C.S., A.J.W., R.H.W. and G.M.W. participated in data processing, discussion and interpretation of results and/or manuscript editing.

Corresponding author

Correspondence to M. Millan.

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Peer review information Nature Astronomy thanks Olivier Forni, Laura Crossey and the other, anonymous, reviewer(s) for their contribution to the peer review of this work.

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Extended data

Extended Data Fig. 1 SAM instrument suite (A), Sample Manipulation System (B), picture of the flight derivatization cup (C) and example of derivatization reaction (D).

(a) SAM suite showing the gas chromatograph (GC), the quadrupole mass spectrometer (MS) and the sample carousel. (b) Sample Manipulation System (SMS) holding the 74 cups in the sample carousel, including both quartz and metal cups. (c) Picture of a flight derivatization metal cup (left) and its outer foil cap (bottom left), and a schematic (right) where the outer reservoir containing the MTBSTFA-DMF and pyrene standard and the inner compartment isolated by a welded metal foil containing the dried DL-3-fluorovaline internal standard are labeled. (D) Example of derivatization reaction of an amino acid with MTBSTFA: the labile hydrogen atom of glycine OH function is substituted by the tert-butyldimethylsilyl group of the MTBSTFA reagent. The products of the reaction are N,O-bis(dimethyl-t-butylsilyl)-glycine (Glycine, di t-BDMS) and 2,2,2-trifluoromethylacetamide (TFMA). Adapted from Mahaffy et al.1.

Source data

Extended Data Fig. 2 Temperature cuts sent to the hydrocarbon trap.

The orange bands highlight the temperature cuts that were sent to the hydrocarbon (HC) trap during pyrolysis. To avoid the saturation of the MTBSTFA-DMF by-products, illustrated here with bi-silylated water (BSW) and N-methyl-2,2,2-trifluoroacetamide (TFMA), 2.5% of the gas was sent from 0–100 °C, 7% from 100–250 °C, and 50% from the remaining portion of the pyrolysis ramp.

Source data

Extended Data Fig. 3 Chromatogram extracted from the pyrolysis–GCMS analysis of the Ogunquit beach sample (OG3).

The two IT flashes: IT 1 and IT 2, are represented by blue arrows at activation times: 0 and 18.3 min, respectively. Bands 4–6 and 8–13 are plotted and correspond to the sum of the ions between the range of given masses (for example, band 4 is the sum of the ions from m/z 45 to 65). The major ion mass fragments of the main chlorohydrocarbons detected have also been extracted to facilitate their identification. The main labeled peaks are: 1) m/z 50: chloromethane, 2) CS2, 3) m/z 84: dichloromethane, 4–5) m/z 90: 1- and 3-chloromethylpropene isomers, 6) m/z 83: trichloromethane, 7) t-BDMS-F, 8) benzene, 9) toluene, 10) TFMA coeluted with Cl-t-BDMS, 11) m/z 112: chlorobenzene, 12) bi-silylated water, and 13) co-elution of all the previous molecules that come out a second time after the second IT flash. SO2 was also detected and co-elutes with chloromethane at 3.2 minutes but is not represented due to the saturation of its peak.

Source data

Extended Data Fig. 4 Dioxygen released from the dry (OG3-red) and wet (OG4-blue) OG sample.

Thermograms of evolved gas from the OG sample comparing the dioxygen released from the dry (OG3-red) and wet (OG4-blue) sample.

Source data

Extended Data Fig. 5 Derivatized ammonia identified by GCMS.

(Top) GCMS identification of derivatized ammonia eluted at 17.3 min in the OG flight chromatogram (a) compared to the laboratory GC analysis of derivatized ammonia analysed in SAM-like operational conditions with the Chirasil-β Dex column (b) detected at 18.8 min. The OG chromatogram is compared to the follow-up analysis from which the signal was increased by 10. The OG follow-up analysis was performed with a 5 °C/min ramp compared to the 10 °C/min ramp of the OG analysis, thus, t-BDMS ammonia eluted at 25.1 min in the follow-up compared to the 17.3 min in the OG analysis. To allow the comparison of both peaks in one figure, the follow-up chromatogram was shifted of 7.8 min to match both flight-retention times. Because the m/z 146 major ion mass fragment of derivatized NH3 was under sampled over the course of the peak elution, its intensity is lower compared to the m/z 188 second major ion mass fragment and what it should be from the NIST spectrum. The m/z 188, second major ion mass fragment of derivatized ammonia, was then chosen and extracted from the TIC for all three chromatograms. (Bottom) Mass spectrum of derivatized ammonia extracted from the SAM chromatogram (red) compared to the mass spectrum extracted from the NIST Mass Spectral Database (blue). A fraction of the m/z 73 and 148 from the SAM mass spectra belong to the mass spectra of bi-silylated water (this is why they have higher intensities in flight compared to the NIST intensities).

Source data

Extended Data Fig. 6 Percentages of the main category of compounds that were extracted relative to the total number of compounds that were extracted from the MXT-20, Chirasil-β Dex and Chirasil-β Dex follow-up analyses.

These percentages are a rough estimation of the compounds that we were able to extract and with co-elutions represent a lower limit of the molecules present in the GCMS chromatogram. This is especially true for the MXT-20 and Chirasil-β Dex columns where the MTBSTFA-DMF saturation plus related by-products are likely obscuring the signal from other molecules.

Source data

Extended Data Fig. 7 Examples of mass spectra of molecules detected in the OG and follow-up analyses.

a. Hexadecamethyl-octasiloxane, a common product from column bleeding was detected in the Chirasil-β Dex chromatogram, b. Dimethylaminoacetonitrile, N-bearing organic detected in the Chirasil-β Dex follow-up analysis, c. 2,2,2-trifluoro-N-methylacetamide, a common MTBSTFA by-product detected in MXT-20, Chirasil-β Dex and follow-up analyses, d. Bis tert-butyldimethylsilyl-ammonia, N-bearing MTBSTFA by-product detected in the Chirasil-β Dex and follow-up analyses.

Extended Data Fig. 8 A 32 min section (23–55 minutes) of the chromatogram of the follow-up analysis obtained with the spare Chirasil-β Dex column where no amino acids were injected.

As shown above, derivatized methionine, serine, threonine, and phenylalanine would be detectable in the first follow-up analysis, and derivatized aspartic acid and hydroxyproline would be detectable in the second follow-up analysis within the standard operating conditions used on Mars for the Chirasil-β Dex column. Derivatized phenylalanine eluting after 49 min of the first follow-up run (represented in red dashed dots) could be detectable if the MS signal continued to be recorded while the column cooled down after the end of the follow-up run. The temperature of the Chirasil-β Dex column is represented in green; it reached ~150 °C at ~56 min of the GC run.

Source data

Supplementary information

Supplementary Information

Supplementary Table 1.

Source data

Source Data Fig. 2

Relevant masses and bands (ranges of masses) exported from Igor 8.

Source Data Fig. 3

Raw Xcalibur GC data and relevant masses exported from Igor 8.

Source Data Fig. 4

Relevant masses and bands (ranges of masses) exported from Igor 8.

Source Data Fig. 5

Raw Xcalibur GC data.

Source Data Extended Data Fig. 1

ChemSketch file used for Extended Data Fig. 1.

Source Data Extended Data Fig. 2

Relevant masses and bands (ranges of masses) exported from Igor 8.

Source Data Extended Data Fig. 3

Relevant masses and bands (ranges of masses) exported from Igor 8.

Source Data Extended Data Fig. 4

Raw EGA data and temperature.

Source Data Extended Data Fig. 5

Raw and processed Xcalibur GC data and relevant masses exported from Igor 8.

Source Data Extended Data Fig. 6

Statistical source data.

Source Data Extended Data Fig. 8

Raw Xcalibur GC data.

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Millan, M., Teinturier, S., Malespin, C.A. et al. Organic molecules revealed in Mars’s Bagnold Dunes by Curiosity’s derivatization experiment. Nat Astron 6, 129–140 (2022). https://doi.org/10.1038/s41550-021-01507-9

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