•We simulated the early Earth's organic chemistry with CO2 as only source of carbon.•We strictly identified the formation of H2O, NH3, N2O and C2N2 in the gaseous phase.•The formation of a solid ...organic phase is also observed.•Possibility for an efficient ionospheric chemistry to provide prebiotic material.
The emergence of life on the Earth has required a prior organic chemistry leading to the formation of prebiotic molecules. The origin and the evolution of the organic matter on the early Earth is not yet firmly understood. Several hypothesis, possibly complementary, are considered. They can be divided in two categories: endogenous and exogenous sources. In this work we investigate the contribution of a specific endogenous source: the organic chemistry occurring in the ionosphere of the early Earth where the significant VUV contribution of the young Sun involved an efficient formation of reactive species. We address the issue whether this chemistry can lead to the formation of complex organic compounds with CO2 as only source of carbon in an early atmosphere made of N2, CO2 and H2, by mimicking experimentally this type of chemistry using a low pressure plasma reactor. By analyzing the gaseous phase composition, we strictly identified the formation of H2O, NH3, N2O and C2N2. The formation of a solid organic phase is also observed, confirming the possibility to trigger organic chemistry in the upper atmosphere of the early Earth. The identification of Nitrogen-bearing chemical functions in the solid highlights the possibility for an efficient ionospheric chemistry to provide prebiotic material on the early Earth.
The Sample Analysis at Mars (SAM) instrument onboard the Curiosity rover and Mars Organic Molecule Analyzer (MOMA) instrument onboard the ExoMars rover are two of the most important instruments used ...for the in-situ search for biosignatures of life on Mars. Tetramethylammonium hydroxide (TMAH) thermochemolysis combined with pyrolysis-gas chromatography and mass spectrometry (Py-GC/MS) has been one of the main techniques utilized by SAM and will be utilized by MOMA. They are both capable of detecting molecular fragments and patterns indicative of life in the Martian near-surface. This study identifies the TMAH thermochemolysis products of targeted nucleotides using flash pyrolysis and SAM-like ramp pyrolysis experiments. Additionally, the optimal TMAH thermochemolysis temperature was determined. Results indicate that the methylated nucleosides can be detected at low abundances when exposed to TMAH thermochemolysis flash pyrolysis at 200 °C. Notably, higher pyrolysis temperatures led to the degradation of nucleosides. Furfuryl methyl ether, one of the degradation products of these nucleosides, was also identified from 200 to 600°C in this study. 300 °C is the optimal temperature for the detection of methylated phosphate under flash pyrolysis of the tested nucleotides with TMAH thermochemolysis. Methylated nucleobases, methyl furfuryl and methyl phosphate are the main products of the tested nucleotides under SAM-like ramp thermochemolysis. Ramped thermochemolysis also resulted in improved performance over flash pyrolysis in the detection of characteristic nucleotide compounds. Uracil and thymine can be detected by both SAM and MOMA if there are nucleotides on Mars; additionally, MOMA will be able to detect adenine. Therefore, methyl furfuryl, methylated phosphate, and the methylated nucleobases uracil, thymine, and adenine are the organic compounds that should be within the SAM and MOMA detection windows if there is DNA/RNA conserved in Martian soil. These experiments will provide a reference for the data collected in-situ by the Curiosity rover and the future ExoMars rover.
•Six nucleotides were analyzed under conditions relevant to Mars’ instrument, dedicated to the search for life.•The methylated nucleosides were detected from nucleotides with TMAH thermochemolysis at SAM-like ramp pyrolysis.•The TMAH thermochemolysis byproducts of six nucleotides were determined.•300 °C is the optimal temperature for the detection of methylated phosphate.•Methyl furfuryl, methylated phosphate, uracil, thymine, and adenine should be within the SAM and MOMA detection windows.
Tetramethylammonium hydroxide (TMAH) is one of the most popular methylation reagents that have been increasingly used for the detection of organic compounds within a wide range of samples, such as ...soil, coal, lacquer, lignin, polymers and for in situ analysis of solid samples by space experiments. The analytical methods and instruments, experimental conditions, and the qualitative and quantitative analysis of organic compounds using TMAH thermochemolysis for the last 10 years were reviewed; additionally, the mechanism of TMAH thermochemolysis and TMAH degradation are overviewed herein. The objective of this paper is to give a broad view of the TMAH thermochemolysis analysis, to demonstrate how the technique can be used for the detection of organics on Mars and other planets, and to promote cooperation between different disciplines which may use thermochemolysis.
•The applications of TMAH thermochemolysis to different matrix and organic compounds were reviewed.•The quantitative methods of organic compounds with TMAH thermochemolysis were summarized.•The mechanism of TMAH thermochemolysis and the degradation of TMAH were reviewed.•New trend in the application of TMAH thermochemolysis in space exploration was outlined.
Tetramethylammonium hydroxide (TMAH) thermochemolysis has been utilized by the Curiosity rover’s Sample Analysis at Mars (SAM) instrument and will be utilized by the ExoMars 2022′s Mars Organic ...Analyzer (MOMA) instrument. TMAH thermochemolysis is one of the main techniques that enables the detection of bioindicators when it is combined with pyrolysis-gas chromatography and mass spectrometry (Py-GC/MS) at the surface of Mars. This study identifies the thermochemolysis products of targeted nucleosides using flash pyrolysis and a SAM-like ramp pyrolysis. Results indicate that the methylated nucleosides can be detected when nucleosides are submitted to TMAH thermochemolysis, which demonstrates that the TMAH thermochemolysis protocol does not result in the decomposition of the nucleosides. To detect the whole structure of each nucleoside, low thermochemolysis temperature is required. 200 °C is the optimal temperature. Methylated nucleobases are the main products of the tested nucleosides when the thermochemolysis temperature is higher than 300 °C. Furfuryl methyl ether, one of the degradation products of these nucleosides, were also identified from 200° to 600°C in this study. These experiments will establish a reference database for interpretation of the data acquired by the SAM and MOMA experiments during operations on Mars.
•Six nucleosides were analyzed under conditions relevant to Mars’ instrument.•The methylated nucleosides were detected first under SAM-like ramp pyrolysis.•The TMAH thermochemolysis byproducts of six nucleosides were determined.•No interaction was found among the nucleoside mixtures.•200 °C is the optimal thermochemolysis temperature for nucleosides and 600 °C for nucleobases.
Establishing the presence and state of organic matter, including its possible biosignatures, in martian materials has been an elusive quest, despite limited reports of the existence of organic matter ...on Mars. We report the in situ detection of organic matter preserved in lacustrine mudstones at the base of the ~3.5-billion-year-old Murray formation at Pahrump Hills, Gale crater, by the Sample Analysis at Mars instrument suite onboard the Curiosity rover. Diverse pyrolysis products, including thiophenic, aromatic, and aliphatic compounds released at high temperatures (500° to 820°C), were directly detected by evolved gas analysis. Thiophenes were also observed by gas chromatography–mass spectrometry. Their presence suggests that sulfurization aided organic matter preservation. At least 50 nanomoles of organic carbon persists, probably as macromolecules containing 5% carbon as organic sulfur molecules.
Sedimentary strata on Mars often contain a mix of sulfates, iron oxides, chlorides, and phyllosilicates, a mineral assemblage that is unique on Earth to acid brine environments. To help characterize ...the astrobiological potential of depositional environments with similar minerals present, samples from four naturally occurring acidic salt lakes and adjacent mudflats/sandflats in the vicinity of Norseman, Western Australia, were collected and analyzed. Lipid biomarkers were extracted and quantified, revealing biomarkers from vascular plants alongside trace microbial lipids. The resilience of lipids from dead organic material in these acid saline sediments through the pervasive stages of early diagenesis lends support to the idea that sulfates, in tandem with phyllosilicates and iron oxides, could be a viable target for biomarkers on Mars. To fully understand the astrobiological potential of these depositional environments, additional investigations of organic preservation in ancient acidic saline sedimentary environments are needed.
Jupiter's moon Europa is a prime target for the search for potential signs of life in the solar system. The Europa Lander Science Definition Team Report outlined investigations and measurement ...requirements on a future Europa Lander and has led us to consider application of powerful techniques such as pyrolysis and derivatization gas chromatography mass spectrometry (GC-MS) and laser desorption mass spectrometry (LD-MS) to elucidate the organic composition of near-surface ice and minerals. Definitive identification of chemical biosignatures using such techniques is strongly enabled by the use of various chemicals, such as perfluorotributylamine (PFTBA) for the MS calibration, α-cyano-hydroxycinnamic acid (CHCA) for matrix-assisted laser desorption and ionization (MALDI) and N,N-dimethylformamide dimethyl acetal (DMF-DMA), N-tert-butyldimethylsilyl-N-methyltrifluoroacetamide (MTBSTFA) and tetramethylammonium hydroxide (TMAH) for wet chemistry GC-MS protocols. The jovian radiation environment is known to represent a uniquely challenging risk to mission performance and lifetime, principally due to high radiation levels. To assess the potential ionizing radiation damage to these important chemicals, we tested their effectiveness following gamma radiation exposure doses up to the anticipated Europa Lander rating requirement of 300 krad(Si). The chemicals were sealed in glass ampules under vacuum (<10 mTorr), to reduce trapped oxygen gas, as the oxidation by O2 may be enhanced in the presence of radiation. We report that all five chemicals exposed to total ionizing doses of 0, 150 and 300 krad(Si) maintained their full effectiveness, and no significant degradation was observed.
•Europa Lander payload radiation was simulated with 150–300 krad of gamma radiation.•Resistance of five experimental reagents to radiation was investigated.•No significant changes in the chemicals' structure or function were observed.•LD-MS and GC-MS are relevant to seek biosignatures in a high radiative environment.
Obtaining carbon isotopic information for organic carbon from Martian sediments has long been a goal of planetary science, as it has the potential to elucidate the origin of such carbon and aspects ...of Martian carbon cycling. Carbon isotopic values (δ
C
) of the methane released during pyrolysis of 24 powder samples at Gale crater, Mars, show a high degree of variation (-137 ± 8‰ to +22 ± 10‰) when measured by the tunable laser spectrometer portion of the Sample Analysis at Mars instrument suite during evolved gas analysis. Included in these data are 10 measured δ
C values less than -70‰ found for six different sampling locations, all potentially associated with a possible paleosurface. There are multiple plausible explanations for the anomalously depleted
C observed in evolved methane, but no single explanation can be accepted without further research. Three possible explanations are the photolysis of biological methane released from the subsurface, photoreduction of atmospheric CO
, and deposition of cosmic dust during passage through a galactic molecular cloud. All three of these scenarios are unconventional, unlike processes common on Earth.
Identifying unequivocal signs of life on Mars is one of the most important objectives for sending missions to the red planet. Here we report Red Stone, a 163-100 My alluvial fan-fan delta that formed ...under arid conditions in the Atacama Desert, rich in hematite and mudstones containing clays such as vermiculite and smectites, and therefore geologically analogous to Mars. We show that Red Stone samples display an important number of microorganisms with an unusual high rate of phylogenetic indeterminacy, what we refer to as "dark microbiome", and a mix of biosignatures from extant and ancient microorganisms that can be barely detected with state-of-the-art laboratory equipment. Our analyses by testbed instruments that are on or will be sent to Mars unveil that although the mineralogy of Red Stone matches that detected by ground-based instruments on the red planet, similarly low levels of organics will be hard, if not impossible to detect in Martian rocks depending on the instrument and technique used. Our results stress the importance in returning samples to Earth for conclusively addressing whether life ever existed on Mars.
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