Engineering topics

Mahaffy, P. R.

Publications and source records attributed to Mahaffy, P. R..

At least 19 records

NASA NTRS2020

Glen Torridon Mineralogy and the Sedimentary History of the Clay Mineral Bearing Unit

Clay minerals are common in ancient terrains on Mars and their presence at the surface alludes to aqueous processes in the Noachian to Early Hesperian (>3.5 Ga). Gale crater was selected as Curiosity’s landing site largely because of the identification of clay mineral rich strata from orbit. On Earth, the types of clay minerals (i.e., smectites) identified in Gale crater are typically juvenile weathering products that ultimately record the interaction between primary igneous minerals with the hydrosphere, atmosphere, and biosphere. Trioctahedral and dioctahedral smectite were identified by Curiosity in units stratigraphically below the Clay Mineral-Bearing Unit (CBU) identified from orbit. Compositional and sedimentological data suggest the smectite formed via authigenesis in a lake environment and may have been altered during early diagenesis. The CBU is stratigraphically equivalent to a hematite-rich unit to the north and stratigraphically underlies sulfate-rich units to the south, suggesting a dynamic environment and evolving history of water in the ancient Gale crater lake. Targeting these clay mineral rich areas on Mars with rover missions provides an opportunity to explore the aqueous and sedimentary history of the planet.

Thorpe, M. T.↗

NASA NTRS2019

Role of the Tenax® Adsorbent in the Interpretation of the EGA and GC‐MS Analyses Performed With the Sample Analysis at Mars in Gale Crater

The Sample Analysis at Mars (SAM) experiment on the National Aeronautics and Space Administration Curiosity rover seeks evidence of organic compounds on the surface of Mars. Since the beginning of the mission, various organic molecules have been detected and identified. While several have been demonstrated to be indigenous to the Martian soil and rocks analyzed, others appear to have been produced from sources internal to the experiment. The objective of this study is to build an exhaustive molecular database to support the interpretation of SAM results by identifying all the chemical species produced from Tenax® adsorbents, by determining (1) the thermal degradation by‐products of Tenax®, (2) the effect of Tenax® conditioning on the formation of Tenax® by‐products, (3) the impact of MTBSTFA or a mixture of MTBSTFA and DMF on Tenax® decomposition, and (4) the reaction between Tenax® and calcium perchlorate. Our results indicate that the by‐products of the SAM trap are due to the impact of trap heating, the impact of the derivatization reagent (MTBSTFA) and the presence of perchlorate in Martian soil. Some of these by‐products are observed in the SAM gas chromatograph mass spectrometer data from Mars.

Buch, A.↗

NASA NTRS2019

Mineralogical and Geochemical Trends of the Murray Mudstones, Gale Crater: A Combined Sample Analysis at Mars-Evolved Gas Analyzer and Chemistry and Mineralogy Instrument Assessment

The Murray formation is predominantly composed of lacustrine mudstone that forms the basal layer of Aeolis Mons (informally Mt. Sharp) in Gale Crater, Mars. The Murray formation has distinct iron and sulfur mineralogical variation within its stratigraphy detectable by the Chemistry Mineralogy (Che-Min) instrument consisting of magnetite/hematite in the lower Murray and higher hematite, CaSO4, and smectite content in the upper Murray. The objectives of this work were to evaluate the Sample Analysis at Mars Evolved Gas Analyzer (SAM-EGA) data to 1) Determine what SAM-EGA-detectable phases correlate or do not correlate with the Murray mineralogical composition detected by CheMin and 2) Utilize CheMin/SAM results to propose possible formation scenarios for the observed Murray mudstone mineralogy.

Sutter, B.↗

NASA NTRS2019

Evolved Gas Analyses of Mudstones from the Vera Rubin Ridge

The Sample Analysis at Mars (SAM) instrument suite on the Mars Science Laboratory (MSL) rover has been essential in understanding volatile-bearing phases in Gale Crater materials. SAM’s evolved gas analysis mass spectrometry (EGA-MS) has detected H2O, CO2, O2, H2, SO2, H2S, HCl, NO, and other trace gases, including organic fragments, in many samples. The identity and evolution temperature of evolved gases can support CheMin instrument mineral detection and place constraints on trace volatile-bearing phases or phases difficult to characterize with X-ray diffraction (e.g., amorphous phases). For the past ~500 sols, MSL has been exploring the Vera Rubin Ridge (VRR), which exhibits a striking hematite signature in orbital remote sensing data, in order to understand the depositional and diagenetic history recorded in the rocks and how it relates to the underlying Murray Formation. Four rock samples were drilled, one from the Blunts Point Member (Duluth, DU), one from the Pettegrrove Point Member (Stoer, ST), and two from the Jura Member. The Jura Member displays differences in color, summarized as grey and red, and a key goal was to constrain the cause of this color difference and the associated implications for depositional or post-depositional conditions. To investigate, a grey (Highfield, HF) and a red (Rock Hall, RH) Jura sample were drilled. Here we will give an overview of results from SAM EGA-MS analyses of VRR materials, with some comparisons to analyses of samples of the underlying Murray.

McAdam, A. C.↗

NASA NTRS2018

Oxychlorine Detection in Gale Crater, Mars and Implications for past Environmental Conditions

The Sample Analysis at Mars (SAM) instrument on the Mars Science Laboratory (MSL) rover has detected oxychlorine compounds such as perchlorate or chlorate in Gale Crater samples. Two potential pathways for oxychlorine formation on Mars are UV-induced interaction between chlorine and metal oxides or atmospheric oxygen and radiolysis of Cl-containing surface materials by galactic cosmic rays, with the chlorine being volcanically derived in both cases. Oxychlorine compounds are identified by a diagnostic release of O2 at temperatures <600 °C and an HCl release from ~350-850 °C during sample pyrolysis. Of the 16 samples analyzed by SAM as of July 2018, 12 have contained oxychlorine compounds, including all four scooped samples and 8 of the 12 drilled samples.

Archer, P. Douglas, Jr.↗

NASA NTRS2018

NH4-Smectite, a Potential Source of N Compounds (NO) in SAM Analyses

Recent detection of nitrate by Curiosity's Sample Analysis at Mars (SAM) instrument suite in Gale Crater sediments on Mars at abundances up to ~600 mg/kg indicates that nitrogen fixation processes occurred in early Martian history. But little is known about other possible N reservoirs on Mars, including those that may contain reduced forms of fixed N (i.e., NH3, NH4+) in the mantle, crust and sediments. Specifically, fixed nitrogen (i.e. NH3, NH4+, NOx or N that is chemically bound to either inorganic or organic molecules and can be released by hydrolysis to form NH3 or NH4+) is useful to terrestrial living organisms Therefore, understanding whether reduced N compounds such as NH4+ are present in surface materials is important to assess habitability in the Martian environment. While these species generally have short photochemical lifetimes, nitrogen in this form may be sequestered and stabilized in the soil by inclusion of NH4+ in certain phyllosilicates.

Andrejkovičová, S.↗

NASA NTRS2017

Evolved Gas Analyses of Sedimentary Rocks and Eolian Sediment in Gale Crater, Mars: Results of the Curiosity Rover's Sample Analysis at Mars Instrument from Yellowknife Bay to the Namib Dune

The sample analysis at Mars instrument evolved gas analyzer (SAM-EGA) has detected evolved water, H2, SO2, H2S, NO, CO2, CO, O2, and HCl from two eolian sediments and nine sedimentary rocks from Gale Crater, Mars. These evolved gas detections indicate nitrates, organics, oxychlorine phase, and sulfates are widespread with phyllosilicates and carbonates occurring in select Gale Crater materials. Coevolved CO2 (160 +/- 248-2373 +/- 820 μgC(CO2)/g) and CO (11 +/- 3-320 +/- 130 μgC(CO)/g) suggest that organic C is present in Gale Crater materials. Five samples evolved CO2 at temperatures consistent with carbonate (0.32 +/- 0.05-0.70 +/- 0.1 wt % CO3). Evolved NO amounts to 0.002 +/- 0.007-0.06 +/- 0.03 wt % NO3. Evolution of O2 suggests that oxychlorine phases (chlorate/perchlorate) (0.05 +/- 0.025-1.05 +/- 0.44 wt % ClO4) are present, while SO2 evolution indicates the presence of crystalline and/or poorly crystalline Fe and Mg sulfate and possibly sulfide. Evolved H2O (0.9 +/- 0.3-2.5 +/- 1.6 wt % H2O) is consistent with the presence of adsorbed water, hydrated salts, interlayer/structural water from phyllosilicates, and possible inclusion water in mineral/amorphous phases. Evolved H2 and H2S suggest that reduced phases occur despite the presence of oxidized phases (nitrate, oxychlorine, sulfate, and carbonate). SAM results coupled with CheMin mineralogical and Alpha-Particle X-ray Spectrometer elemental analyses indicate that Gale Crater sedimentary rocks have experienced a complex authigenetic/diagenetic history involving fluids with varying pH, redox, and salt composition. The inferred geochemical conditions were favorable for microbial habitability and if life ever existed, there was likely sufficient organic C to support a small microbial population.

Sutter, B.↗

NASA NTRS2017

Nightside Ionosphere of Mars: Composition, Vertical Structure, and Variability

We provide an overview of the composition, vertical structure, and variability of the nightside ionosphere of Mars as observed by Mars Atmosphere and Volatile EvolutioN (MAVEN)'s Neutral Gas and Ion Mass Spectrometer (NGIMS) through 19 months of the MAVEN mission. We show that O+2 is the most abundant ion down to ∼130 km at all nightside solar zenith angles (SZA). However, below 130 km NO+ is the most abundant ion, and NO+ densities increase with decreasing altitude down to at least 120 km. We also show how the densities of the major ions decrease with SZA across the terminator. At lower altitudes the O+2 and CO+2 densities decrease more rapidly with SZA than the NO+ and HCO+ densities, which changes the composition of the ionosphere from being primarily O+2 on the dayside to being a mixture of O+2, NO+, and HCO+ on the nightside. These variations are in accord with the expected ion-neutral chemistry, because both NO+ and HCO+ have long chemical lifetimes. Additionally, we present median ion density profiles from three different nightside SZA ranges, including deep on the nightside at SZAs greater than 150∘ and discuss how they compare to particle precipitation models. Finally, we show that nightside ion densities can vary by nearly an order of magnitude over month long timescales. The largest nightside densities were observed at high northern latitudes during winter and coincided with a major solar energetic particle event.

Mars↗

NASA NTRS2017

Unique, Non-Earthlike, Meteoritic Ion Behavior in Upper Atmosphere of Mars

Abstract Interplanetary dust particles have long been expected to produce permanent ionospheric metal ion layers at Mars, as on Earth, but the two environments are so different that uncertainty existed as to whether terrestrial-established understanding would apply to Mars. The Mars Atmosphere and Volatile EvolutioN (MAVEN) mission made the first in situ detection of the continuous presence of Na+, Mg+, and Fe+ at Mars and indeed revealed non-Earthlike features/processes. There is no separation of the light Mg+ and the heavy Fe+ with increasing altitude as expected for gravity control. The metal ions are well-mixed with the neutral atmosphere at altitudes where no mixing process is expected. Isolated metal ion layers mimicking Earths sporadic E layers occur despite the lack of a strong magnetic field as required at Earth. Further, the metal ion distributions are coherent enough to always show atmospheric gravity wave signatures. All features and processes are unique to Mars.

Meteoritic↗

NASA NTRS2017

Identification of Phyllosilicates in Mudstone Samples Using Water Releases Detected by the Sample Analysis at Mars (SAM) Instrument in Gale Crater, Mars

The Sample Analysis at Mars (SAM) instrument on board the Curiosity Rover has detected high temperature water releases from mud-stones in the areas of Yellowknife Bay, Pahrump Hills, Naukluft Plateau, and Murray Buttes in Gale crater. Dehydroxylation of phyllosilicates may have caused the high temperature water releases observed in these samples. Because each type of phyllosilicate undergoes dehydroxylation at distinct temperatures, these water releases can be used to help constrain the type of phyllosilicate present in each sample.

Hogancamp, J. V. (Clark)↗

NASA NTRS2017

Evolved Gas Analyses of the Murray Formation in Gale Crater, Mars: Results of the Curiosity Rover's Sample Analysis at Mars (SAM) Instrument

The Sample Analysis at Mars (SAM) instrument aboard the Mars Science Laboratory rover has analyzed 13 samples from Gale Crater. All SAM-evolved gas analyses have yielded a multitude of volatiles (e.g., H2O, SO2, H2S, CO2, CO, NO, O2, HCl) [1- 6]. The objectives of this work are to 1) Characterize recent evolved SO2, CO2, O2, and NO gas traces of the Murray formation mudstone, 2) Constrain sediment mineralogy/composition based on SAM evolved gas analysis (SAM-EGA), and 3) Discuss the implications of these results relative to understanding the geological history of Gale Crater.

Sutter, B.↗

NASA NTRS2017

Constraints on the Mineralogy of Gale Crater Mudstones from MSL SAM Evolved Water

The Sample Analysis at Mars (SAM) and Chemistry and Mineralogy (CheMin) instruments on the Mars Science Laboratory (MSL) have analysed more than 150 micron fines from 14 sites at Gale Crater. Here we focus on the mudstone samples. Two were drilled from sites John Klein (JK) and Cumberland (CB) in the Sheepbed mudstone. Six were drilled from Murray Formation mudstone: Confidence Hills (CH), Mojave (MJ), Telegraph Peak (TP), Buckskin (BK), Oudam (OU), Marimba (MB). SAM's evolved gas analysis mass spectrometry (EGA-MS) detected H2O, CO2, O2, H2, SO2, H2S, HCl, NO, and other trace gases, including organic fragments. The identity and evolution temperature of evolved gases can support CheMin mineral detection and place constraints on trace volatile-bearing phases or phases difficult to characterize with X-ray diffraction (e.g., amorphous phases). Here we will focus on SAM H2O data and comparisons to SAM-like analyses of key reference materials.

McAdam, A. C.↗

NASA NTRS2016

Microbial Habitability in Gale Crater: Sample Analysis at Mars (SAM) Instrument Detection of Microbial Essential Carbon and Nitrogen

Chemical analyses of Mars soils and sediments from previous landed missions have demonstrated that Mars surface materials possessed major (e.g., P, K, Ca, Mg, S) and minor (e.g., Fe, Mn, Zn, Ni, Cl) elements essential to support microbial life. However, the detection of microbial essential organic-carbon (C) and nitrate have been more elusive until the Mars Science Laboratory (MSL) rover mission. Nitrate and organic-C in Gale Crater, Mars have been detected by the Sample Analysis at Mars (SAM) instrument onboard the MSL Curiosity rover. Eolian fines and drilled sedimentary rock samples were heated in the SAM oven from approximately 30 to 860 degrees Centigrade where evolved gases (e.g., nitrous oxide (NO) and CO2) were released and analyzed by SAM’s quadrupole mass spectrometer (MS). The temperatures of evolved NO was assigned to nitrate while evolved CO2 was assigned to organic-C and carbonate. The CO2 releases in several samples occurred below 450 degrees Centigrade suggesting organic-C dominated in those samples. As much as 7 micromoles NO3-N per gram and 200 micromoles CO2-C per gram have been detected in the Gale Crater materials. These N and C levels coupled with assumed microbial biomass (9 x 10 (sup -7) micrograms per cell) C (0.5 micrograms C per micrograms cell) and N (0.14 micrograms N per micrograms cell) requirements, suggests that less than 1 percent and less than 10 percent of Gale Crater C and N, respectively, would be required if available, to accommodate biomass requirements of 1 by 10 (sup 5) cells per gram sediment. While nitrogen is the limiting nutrient, the potential exists that sufficient N and organic-C were present to support limited heterotrophic microbial populations that may have existed on ancient Mars.

Sutter, B.↗

NASA NTRS2016

Volatile Analysis by Pyrolysis of Regolith (Vapor) for Planetary Resource Prospecting

Measuring the chemical composition of planetary bodies and their atmospheres is key to understanding the formation of the Solar System and the evolution of the planets and their moons. In situ volatile measurements enable a ground-truth assessment of the distribution and abundance of resources such as water-ice and oxygen, important for a sustained human presence on the Moon and beyond. The Volatile Analysis by Pyrolysis of Regolith (VAPoR) instrument is a compact pyrolysis mass spectrometer designed to detect volatiles released from solid samples that are heated to elevated temperatures and is one technique that should be considered for resource prospecting on the Moon, Mars, and asteroids.

regolith↗

NASA NTRS2016

Cometary Origin of Atmospheric Methane Variations on Mars Unlikely

The detection of methane in the atmosphere of Mars was first reported in 2004. Since then a number of independent observations of methane have been reported, all showing temporal variability. Up until recently, the origin of methane was attributed to sources either indigenous to Mars or exogenous, where methane is a UV degradation byproduct of organics falling on to the surface. Most recently, a new hypothesis has been proposed that argues that the appearance and variation of methane are correlated with specific meteor events at Mars. Indeed, extraplanetary material can be brought to a planet when it passes through a meteoroid stream left behind by cometary bodies orbiting the Sun. This occurs repeatedly at specific times in a planet's year as streams tend to be fairly stable in space. In this paper, we revisit this latest hypothesis by carrying out a complete analysis of all available data on Mars atmospheric methane, including the very recent data not previously published, together with all published predicted meteor events for Mars. Whether we consider the collection of individual data points and predicted meteor events, whether we apply statistical analysis, or whether we consider different time spans between high methane measurements and the occurrence of meteor events, we find no compelling evidence for any correlation between atmospheric methane and predicted meteor events.

methane↗

NASA NTRS2016

In Situ Measurement of Atmospheric Krypton and Xenon on Mars with Mars Science Laboratory

Mars Science Laboratorys Sample Analysis at Mars (SAM) investigation has measured all of the stable isotopes of the heavy noble gases krypton and xenon in the martian atmosphere, in situ, from the Curiosity Rover at Gale Crater, Mars. Previous knowledge of martian atmospheric krypton and xenon isotope ratios has been based upon a combination of the Viking missions krypton and xenon detections and measurements of noble gas isotope ratios in martian meteorites. However, the meteorite measurements reveal an impure mixture of atmospheric, mantle, and spallation contributions. The xenon and krypton isotopic measurements reported here include the complete set of stable isotopes, unmeasured by Viking. The new results generally agree with Mars meteorite measurements but also provide a unique opportunity to identify various non-atmospheric heavy noble gas components in the meteorites. Kr isotopic measurements define a solar-like atmospheric composition, but deviating from the solar wind pattern at 80Kr and 82Kr in a manner consistent with contributions originating from neutron capture in Br. The Xe measurements suggest an intriguing possibility that isotopes lighter than 132Xe have been enriched to varying degrees by spallation and neutron capture products degassed to the atmosphere from the regolith, and a model is constructed to explore this possibility. Such a spallation component, however, is not apparent in atmospheric Xe trapped in the glassy phases of martian meteorites.

Conrad, P. G.↗

NASA NTRS2016

Oxychlorine Detections on Mars: Implications for Cl Cycling

The Sample Analysis at Mars (SAM) instrument has detected evolved O2 and HCl indicating the presence of perchlorate and/or chlorate (oxychlorine) in all 11 sediments analyzed to date. The hyperarid martian climate is believed to have allowed accumulation of oxychlorine and assumed chloride contents similar to those in hyperarid terrestrial settings. The linear correlation of oxychlorine and chloride of Gale Crater sediments is low (r (sup 2) equals 0.64). Correlations present in hyperarid Antarctica and the Atacama Desert are attributed to unaltered atmospheric source coupled with minimal redox cycling by biological activity. Terrestrial semi-arid to arid settings have low correlations similar to Gale Crater and are attributed to additional inputs of Cl minus from sea salt, dust, and/or proximal playa settings, and possible reduction of oxychlorine phases during wetter periods. While microbiological processes could contribute to low oxychlorine/chloride correlations on Mars, several abiotic mechanisms are more likely, such as changing oxychlorine production rates with time and/or post-depositional geochemical redox processes that altered the Gale Crater oxychlorine and chloride contents.

Sutter, B.↗

NASA NTRS2016

In Situ Analysis of Martian Regolith with the SAM Experiment During the First Mars Year of the MSL Mission: Identification of Organic Molecules by Gas Chromatography from Laboratory Measurements

The Sample Analysis at Mars (SAM) instrument onboard the Curiosity rover, is specifically designed for in situ molecular and isotopic analyses of martian surface materials and atmosphere. It contributes to the Mars Science Laboratory (MSL) missions primary scientific goal to characterize the potential past, present or future habitability of Mars. In all of the analyses of solid samples delivered to SAM so far, chlorinated organic compounds have been detected above instrument background levels and identified by gas chromatography coupled to mass spectrometry (GC-MS) (Freissinet et al., 2015; Glavin et al., 2013). While some of these may originate from reactions between oxychlorines and terrestrial organic carbon present in the instrument background (Glavin et al., 2013), others have been demonstrated to originate from indigenous organic carbon present in samples (Freissinet et al., 2015). We present here laboratory calibrations that focused on the analyses performed with the MXT-CLP GC column (SAM GC-5 channel) used for nearly all of the GC-MS analyses of the martian soil samples carried out with SAM to date. Complementary to the mass spectrometric data, gas chromatography allows us to separate and identify the species analyzable in a nominal SAM-GC run time of about 21 min. To characterize the analytical capabilities of this channel within the SAM Flight Model (FM) operating conditions on Mars, and their implications on the detection of organic matter, it is required to perform laboratory experimental tests and calibrations on spare model components. This work assesses the SAM flight GC-5 column efficiency, confirms the identification of the molecules based on their retention time, and enables a better understanding of the behavior of the SAM injection trap (IT) and its release of organic molecules. This work will enable further optimization of the SAM-GC runs for additional samples to be analyzed during the MSL mission.

analysis↗