Mars Instrument Suite Research Articles

Radiation-Driven Destruction of Thiophene and Methyl-Substituted Thiophenes.

Thiophene and two derivatives (2-methylthiophene and 3-methylthiophene) have been detected on the surface of Mars with the Sample Analysis at Mars instrument suite onboard NASA's Curiosity rover. Thiophene could serve as a secondary chemical biosignature since the secondary biosynthesis of thiophene is considered an important production pathway. However, it is critical to understand the abiotic formation and destruction of thiophene and its derivatives since these pathways could affect the molecules' stabilities on planetary surfaces over geological timescales. Here, we present the radiolytic destruction kinetics of thiophene, 2-methylthiophene, and 3-methylthiophene as single-component ices and when diluted in water ice at low temperatures. Using infrared spectroscopy, we determined the destruction rate constants and extrapolated our radiolytic half-lives to the surface of Mars, assuming the measured and modeled surface dose rates. We found that our rate constants strongly depend on temperature and presence of water ice. Based on our determined radiolytic half-life for thiophene under conditions most similar to those of thiophene groups in Martian macromolecules, we expect thiophene to be stable on the surface for significantly longer than the Martian surface exposure age of sites in Gale crater where thiophenes have been detected.

The Curiosity Rover's Exploration of Glen Torridon, Gale Crater, Mars: An Overview of the Campaign and Scientific Results.

The Mars Science Laboratory rover, Curiosity, explored the clay mineral-bearing Glen Torridon region for 1 Martian year between January 2019 and January 2021, including a short campaign onto the Greenheugh pediment. The Glen Torridon campaign sought to characterize the geology of the area, seek evidence of habitable environments, and document the onset of a potentially global climatic transition during the Hesperian era. Curiosity roved 5km in total throughout Glen Torridon, from the Vera Rubin ridge to the northern margin of the Greenheugh pediment. Curiosity acquired samples from 11 drill holes during this campaign and conducted the first Martian thermochemolytic-based organics detection experiment with the Sample Analysis at Mars instrument suite. The lowest elevations within Glen Torridon represent a continuation of lacustrine Murray formation deposits, but overlying widespread cross bedded sandstones indicate an interval of more energetic fluvial environments and prompted the definition of a new stratigraphic formation in the Mount Sharp group called the Carolyn Shoemaker formation. Glen Torridon hosts abundant phyllosilicates yet remains compositionally and mineralogically comparable to the rest of the Mount Sharp group. Glen Torridon samples have a great diversity and abundance of sulfur-bearing organic molecules, which are consistent with the presence of ancient refractory organic matter. The Glen Torridon region experienced heterogeneous diagenesis, with the most striking alteration occurring just below the Siccar Point unconformity at the Greenheugh pediment. Results from the pediment campaign show that the capping sandstone formed within the Stimson Hesperian aeolian sand sea that experienced seasonal variations in wind direction.

Depleted carbon isotope compositions observed at Gale crater, Mars

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 (δ13CVPDB) 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 δ13C 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 13C 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 CO2, and deposition of cosmic dust during passage through a galactic molecular cloud. All three of these scenarios are unconventional, unlike processes common on Earth.

Detection of Reduced Sulfur on Vera Rubin Ridge by Quadratic Discriminant Analysis of Volatiles Observed During Evolved Gas Analysis

AbstractThe Mars Science Laboratory mission investigated Vera Rubin ridge, which bears spectral indications of elevated amounts of hematite and has been hypothesized as having a complex diagenetic history. Martian samples, including three drilled samples from the ridge, were analyzed by the Sample Analysis at Mars instrument suite via evolved gas analysis‐mass spectrometry (EGA‐MS). Here, we report new EGA‐MS data from Martian samples and describe laboratory analogue experiments. Analyses of laboratory analogues help determine the presence of reduced sulfur in Martian solid samples, which could have supported potential microbial life. We used evolved carbonyl sulfide (COS) and carbon disulfide (CS2) to identify Martian samples likely to contain reduced sulfur by applying a quadratic discriminant analysis. While we report results for 24 Martian samples, we focus on Vera Rubin ridge samples and select others for comparison. Our results suggest the presence of reduced sulfur in the Jura member of Vera Rubin ridge, which can support various diagenetic history models, including, as discussed in this work, diagenetic alteration initiated by a mildly reducing, sulfite‐containing groundwater.

Comment on “Evaluation of the Tenax Trap in the Sample Analysis at Mars Instrument Suite on the Curiosity Rover as a Potential Hydrocarbon Source for Chlorinated Organics Detected in Gale Crater” by Miller et al. (2015)

Plain Language SummaryMiller et al. [2015, https://doi.org/10.1002/2015JE004825] described the result of experiments testing the potential of Tenax TA, a polymer used on Sample Analysis at Mars (SAM), as a source of chlorinated benzene. Miller et al. [2015] conclude that the amount of chlorobenzene produced is low and that Tenax TA cannot be the source of the chlorobenzene observed on Mars by SAM. Miller et al. [2015] did not provide the identification of two unknown compounds produced during these pyrolysis experiments, though their abundance is orders of magnitude higher than that of chlorobenzene. Here, we tentatively identify these compounds based on the mass spectra provided by Miller et al. [2015], the most abundant of which is a chlorinated monomer of Tenax TA. This chlorinated monomer is likely to accumulate in the hydrocarbon Tenax trap and in the transfer line between the trap and the mass spectrometer. Further breakdown of these compounds could lead the high background of chlorobenzene observed on Mars.

Reply to Comment by F. Kenig, L. Chou, and D. J. Wardrop on “Evaluation of the Tenax Trap in the Sample Analysis at Mars Instrument Suite on the Curiosity Rover as a Potential Hydrocarbon Source for Chlorinated Organics Detected in Gale Crater” by Miller et al., 2015

AbstractKenig et al. comment on our 2015 reporting of laboratory analog experiments aimed at testing the stability of the hydrocarbon trap material used in the Sample Analysis on Mars (SAM) instrument on board the Curiosity Rover operating in Gale Crater on Mars. They propose chemical structures for some decomposition products of the Tenax TA polymer when it is exposed at high temperatures to the Cl2 and O2 gases formed by the thermal decomposition of perchlorate. Further, Kenig et al. propose that these decomposition products accumulate and then react further in cooler downstream sections of the SAM analytical pipeline to produce the chlorobenzene that was detected in the Cumberland mudstone of Gale Crater. However, numerous experiments conducted in the laboratory show that Tenax TA decomposition products only appear after repeated exposure to much higher levels of Cl2 and O2 than those seen by the flight instrument. Moreover, the sequence of chlorobenzene detections during gas chromatography‐mass spectrometry experiments conducted on Mars cannot be explained by Tenax TA decomposition, nor can the detection of chlorobenzene in Evolved Gas Analysis experiments that involve pathways devoid of Tenax TA. Kenig et al. are incorrect in their assertion that Tenax TA decomposition products can account for the chlorobenzene detected on Mars by SAM.

Identification of Chlorobenzene in the Viking Gas Chromatograph‐Mass Spectrometer Data Sets: Reanalysis of Viking Mission Data Consistent With Aromatic Organic Compounds on Mars

AbstractMotivated by the recent detection of chlorobenzene by the Sample Analysis at Mars instrument suite on the Curiosity rover, and the identification of its carbon source as indigenous to the martian sample, we reexamined the original, microfilm preserved, Viking gas chromatograph‐mass spectrometer data sets. We found evidence for the presence of chlorobenzene in Viking Lander 2 (VL‐2) data at levels corresponding to 0.08–1.0 ppb (relative to sample mass), in runs when the sample was heated to 350°C and 500°C. Additionally, we found a correlation between the temperature dependence of the chlorobenzene signal and the dichloromethane signal originally identified by the Viking gas chromatograph‐mass spectrometer team. We considered possible sources of carbon that may have produced the chlorobenzene signal, by reaction with perchlorate during pyrolysis, including organic carbon indigenous to the martian parent sample and instrument contamination. We conclude that the chlorobenzene signal measured by VL‐2 originated from martian chlorine sources. We show how the carbon source could originate from the martian parent sample, though a carbon source contributed from instrument background cannot yet be ruled out.

Evaluation of the Tenax trap in the Sample Analysis at Mars instrument suite on the Curiosity rover as a potential hydrocarbon source for chlorinated organics detected in Gale Crater

AbstractThe Sample Analysis at Mars (SAM) instrument suite aboard Curiosity has detected chlorinated organic compounds in Martian sediment samples. The chlorine in these molecules is thought to derive from oxychlorine salts in Martian sediments, but the carbon source remains under investigation. To constrain possible carbon sources, we investigated how the composition and concentration of oxychlorine phases in solid samples affect organic molecules released from the Tenax traps on board SAM. We created Mars analogue soils by spiking olivine sand with calcium perchlorate, magnesium perchlorate, or ferric iron chloride and analyzed the volatiles generated during pyrolysis–gas chromatography–mass spectrometry using commercial instruments operated under SAM‐like conditions, with and without a Tenax trap. Benzoic acid, phthalic anhydride, high molecular weight aromatics, and chlorobenzenes are produced from the trap in response to volatiles released during Cl salt pyrolysis. Changes in composition or concentration of oxychlorine phases between samples could thus potentially produce an increase in chlorobenzene, as observed between samples from Rocknest and Cumberland. However, in our experiments benzoic acid, phthalic anhydride, and chlorobenzenes increase in proportion with the amount of HCl sent to the trap, while in Cumberland samples the chlorobenzene increase showed no corresponding increase in HCl. Based on our experiments, the Tenax trap is a possible source of the traces of chlorobenzene observed at Rocknest, John Klein, and Confidence Hills. The order‐of‐magnitude higher chlorobenzene abundances observed at Cumberland cannot be attributed to the Tenax trap. Furthermore, we found no evidence of significant trap degradation after hundreds of experiments with Cl salt‐containing analogue soils.

Analytical techniques for retrieval of atmospheric composition with the quadrupole mass spectrometer of the Sample Analysis at Mars instrument suite on Mars Science Laboratory

The Sample Analysis at Mars (SAM) instrument suite is the largest scientific payload on the Mars Science Laboratory (MSL) Curiosity rover, which landed in Mars׳ Gale Crater in August 2012. As a miniature geochemical laboratory, SAM is well-equipped to address multiple aspects of MSL׳s primary science goal, characterizing the potential past or present habitability of Gale Crater. Atmospheric measurements support this goal through compositional investigations relevant to martian climate evolution. SAM instruments include a quadrupole mass spectrometer, a tunable laser spectrometer, and a gas chromatograph that are used to analyze martian atmospheric gases as well as volatiles released by pyrolysis of solid surface materials (Mahaffy et al., 2012). This report presents analytical methods for retrieving the chemical and isotopic composition of Mars׳ atmosphere from measurements obtained with SAM׳s quadrupole mass spectrometer. It provides empirical calibration constants for computing volume mixing ratios of the most abundant atmospheric species and analytical functions to correct for instrument artifacts and to characterize measurement uncertainties. Finally, we discuss differences in volume mixing ratios of the martian atmosphere as determined by SAM (Mahaffy et al., 2013) and Viking (Owen et al., 1977; Oyama and Berdahl, 1977) from an analytical perspective. Although the focus of this paper is atmospheric observations, much of the material concerning corrections for instrumental effects also applies to reduction of data acquired with SAM from analysis of solid samples.

Volatile, Isotope, and Organic Analysis of Martian Fines with the Mars Curiosity Rover

Samples from the Rocknest aeolian deposit were heated to ~835°C under helium flow and evolved gases analyzed by Curiosity's Sample Analysis at Mars instrument suite. H2O, SO2, CO2, and O2 were the major gases released. Water abundance (1.5 to 3 weight percent) and release temperature suggest that H2O is bound within an amorphous component of the sample. Decomposition of fine-grained Fe or Mg carbonate is the likely source of much of the evolved CO2. Evolved O2 is coincident with the release of Cl, suggesting that oxygen is produced from thermal decomposition of an oxychloride compound. Elevated δD values are consistent with recent atmospheric exchange. Carbon isotopes indicate multiple carbon sources in the fines. Several simple organic compounds were detected, but they are not definitively martian in origin.

Low Upper Limit to Methane Abundance on Mars

By analogy with Earth, methane in the Martian atmosphere is a potential signature of ongoing or past biological activity. During the past decade, Earth-based telescopic observations reported "plumes" of methane of tens of parts per billion by volume (ppbv), and those from Mars orbit showed localized patches, prompting speculation of sources from subsurface bacteria or nonbiological sources. From in situ measurements made with the Tunable Laser Spectrometer (TLS) on Curiosity using a distinctive spectral pattern specific to methane, we report no detection of atmospheric methane with a measured value of 0.18 ± 0.67 ppbv corresponding to an upper limit of only 1.3 ppbv (95% confidence level), which reduces the probability of current methanogenic microbial activity on Mars and limits the recent contribution from extraplanetary and geologic sources.

Collecting Samples in Gale Crater, Mars; an Overview of the Mars Science Laboratory Sample Acquisition, Sample Processing and Handling System

The Mars Science Laboratory Mission (MSL), scheduled to land on Mars in the summer of 2012, consists of a rover and a scientific payload designed to identify and assess the habitability, geological, and environmental histories of Gale crater. Unraveling the geologic history of the region and providing an assessment of present and past habitability requires an evaluation of the physical and chemical characteristics of the landing site; this includes providing an in-depth examination of the chemical and physical properties of Martian regolith and rocks. The MSL Sample Acquisition, Processing, and Handling (SA/SPaH) subsystem will be the first in-situ system designed to acquire interior rock and soil samples from Martian surface materials. These samples are processed and separated into fine particles and distributed to two onboard analytical science instruments SAM (Sample Analysis at Mars Instrument Suite) and CheMin (Chemistry and Mineralogy) or to a sample analysis tray for visual inspection. The SA/SPaH subsystem is also responsible for the placement of the two contact instruments, Alpha Particle X-Ray Spectrometer (APXS), and the Mars Hand Lens Imager (MAHLI), on rock and soil targets. Finally, there is a Dust Removal Tool (DRT) to remove dust particles from rock surfaces for subsequent analysis by the contact and or mast mounted instruments (e.g. Mast Cameras (MastCam) and the Chemistry and Micro-Imaging instruments (ChemCam)).

Exploration of the Habitability of Mars: Development of Analytical Protocols for Measurement of Organic Carbon on the 2009 Mars Science Laboratory

The mission goal of the 2009 Mars Science Laboratory is to assess the habitability of a region on Mars. This large rover incorporates an Analytical Laboratory that contributes to this mission objective by means of a detailed characterization of mineralogy and chemistry. The Sample Analysis at Mars instrument suite in the Analytical Laboratory provides the capability to analyze volatiles released from rocks and soils and gases directly sample from the atmosphere. A primary focus of this suite is the detection and identification of organic molecules. The protocols for the extraction and analysis of organics under development for this mission are described as are experiments carried out on Mars analog samples to evaluate these methods.