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Farmer, J. D.

Publications and source records attributed to Farmer, J. D..

At least 19 records
All sourcesNASA NTRSDOE OSTI
NASA NTRS2018

Seeking Signs of Life on Mars: A Strategy for Selecting and Analyzing Returned Samples from Hydrothermal Deposits

Highly promising locales for biosignature prospecting on Mars are ancient hydrothermal deposits, formed by the interaction of surface water with heat from volcanism or impacts. On Earth, they occur throughout the geological record (to at least approx. 3.5 Ga), preserving robust mineralogical, textural and compositional evidence of thermophilic microbial activity. Hydrothermal systems were likely present early in Mars' history, including at two of the three finalist candidate landing sites for M2020, Columbia Hills and NE Syrtis Major. Hydrothermal environments on Earth's surface are varied, constituting subaerial hot spring aprons, mounds and fumaroles; shallow to deep-sea hydrothermal vents (black and white smokers); and vent mounds and hot-spring discharges in lacustrine and fluvial settings. Biological information can be preserved by rapid, spring-sourced mineral precipitation, but also could be altered or destroyed by postdepositional events. Thus, field observations need to be followed by detailed laboratory analysis to verify potential biosignatures. See Attachment

Campbell, K. A.↗
NASA NTRS2018

Seeking Signs of Life on Mars: the Importance of Sedimentary Suites as Part of a Mars Sample Return Campaign

Seeking the signs of life on Mars is often considered the "first among equal" objectives for any potential Mars Sample Return (MSR) campaign. Among the geological settings considered to have the greatest potential for recording evidence of ancient life or its pre-biotic chemistry on Mars are lacustrine (and marine, if ever present) sedimentary depositional environments. This potential, and the possibility of returning samples that could meaningfully address this objective, have been greatly enhanced by investigations of an ancient redox stratified lake system in Gale crater by the Curiosity rover.

Mangold, N.↗
NASA NTRS2017

Mineral Trends in Early Hesperian Lacustrine Mudstone at Gale Crater, Mars

The Mars Science Laboratory Curiosity rover landed in Gale crater in August 2012 to study the layered sediments of lower Aeolis Mons (i.e., Mount Sharp), which have signatures of phyllosilicates, hydrated sulfates, and iron oxides in orbital visible/near-infrared observations. The observed mineralogy within the stratigraphy, from phyllosilicates in lower units to sulfates in higher units, suggests an evolution in the environments in which these secondary phases formed. Curiosity is currently investigating the sedimentary structures, geochemistry, and mineralogy of the Murray formation, the lowest exposed unit of Mount Sharp. The Murray formation is dominated by laminated lacustrine mudstone and is approx.200 m thick. Curiosity previously investigated lacustrine mudstone early in the mission at Yellowknife Bay, which represents the lowest studied stratigraphic unit. Here, we present the minerals identified in lacus-trine mudstone from Yellowknife Bay and the Murray formation. We discuss trends in mineralogy within the stratigraphy and the implications for ancient lacustrine environments, diagenesis, and sediment sources.

Rampe, E. B.↗
NASA NTRS2016

Performing Mineral Hydration Experiments in the CheMin Diffractometer on Mars

Laboratory work is the cornerstone of experimental planetary geochemistry, mineralogy, and petrology, but much is to be gained by "experiments" while on a planet surface. Earth-bound experiments are often limited in ability to control multiple conditions relevant to planetary bodies (e.g. cycles in temperature and vapor pressure of water), but observations on-planet provide a unique opportunity where conditions are native to the planet and those affected by sampling and analysis can be constrained. The CheMin XRD instrument on Mars Science Laboratory has been able to test mineral hydration in samples held for up to 300 Mars days (sols). Clay minerals sampled at Yellowknife Bay early in the mission had both collapsed (10 Å) and expanded (13.2 Å) basal spacing. Collapsed interlayers were expected, but larger spacing was not; it was uncertain whether larger basal spacing would collapse on prolonged exposure to warmer conditions inside CheMin. Observation over several hundred sols showed no collapse, with the conclusion that expanded interlayer spacing was due to partial intercalation by metal-hydroxyl groups that resist dehydration. More recently, a sample of the Murray Formation, Oudam, provided the first XRD detection of gypsum and a chance to observe gypsum stability. Laboratory work suggests gypsum should be stable at Mars surface conditions, and indeed gypsum has been observed from orbit at higher latitudes and in thick veins at Yellowknife Bay by Mastcam reflectance spectra. Laboratory experiments have shown that on dehydration the gypsum would not become X-ray amorphous but would rather transform to a water-deficient bassanite structure. Over a period of 37 sols, it was observed that the Oudam sample in CheMin transformed from an assemblage of gypsum+anhydrite, to gypsum+bassanite+anhydrite, and finally to bassanite+anhydrite. Mg-sulfates were also anticipated but have not been observed in CheMin despite chemical evidence for their presence. Unlike gypsum, hydrated Mg-sulfates can transition to an X-ray amorphous form. Crystalline Mg-sulfates are expected higher in the section on Mount Sharp, where it should be possible to determine whether they persist or are destabilized after sampling, providing further insight into hydrous mineral stability at Mars near-equatorial conditions.

Vaniman, D. T.↗
NASA NTRS2016

Mineralogy of Mudstone at Gale Crater, Mars: Evidence for Dynamic Lacustrine Environments

The Mars Science Laboratory Curiosity rover landed in Gale crater in August 2012 to assess the habitability of sedimentary deposits that show orbital evidence for diverse ancient aqueous environments. Gale crater contains a 5 km high mound of layered sedimentary rocks in its center, informally named Mount Sharp. The lowermost rocks of Mount Sharp contain minerals that are consistent with a dramatic climate change during Mars' early history. During the rover's traverse across the Gale crater plains to the base of Mount Sharp, Curiosity discovered sedimentary rocks consistent with a fluviolacustrine sequence. Curiosity studied ancient lacustrine deposits at Yellowknife Bay on the plains of Gale crater and continues to study ancient lacustrine deposits in the Murray formation, the lowermost unit of Mount Sharp. These investigations include drilling into the mudstone and delivering the sieved less than 150 micrometers fraction to the CheMin XRD/XRF instrument inside the rover. Rietveld refinement of XRD patterns measured by CheMin generates mineral abundances with a detection limit of 1-2 wt.% and refined unit-cell parameters of minerals present in abundances greater than approximately 5 wt.%. FULLPAT analyses of CheMin XRD patterns provide the abundance of X-ray amorphous materials and constrain the identity of these phases (e.g., opal-A vs. opal-CT). At the time of writing, CheMin has analyzed 14 samples, seven of which were drilled from lacustrine deposits. The mineralogy from CheMin, combined with in-situ geochemical measurements and sedimentological observations, suggest an evolution in the lake waters through time, including changes in pH and salinity and transitions between oxic and anoxic conditions. In addition to a geochemically dynamic lake environment, the igneous minerals discovered in the lake sediments indicate changes in source region through time, with input from mafic and silicic igneous sources. The Murray formation is predominantly comprised of lacustrine mudstone and is 150-200 m thick, suggesting long history of lake environments in Gale crater. Curiosity has traversed through the lowermost approximately 30 m of the Murray formation, and each additional sample provides clues about the climate on early Mars.

Rampe, E. B.↗
NASA NTRS2016

Mineralogy of Eolian Sands at Gale Crater

The Mars Science Laboratory rover Curiosity has been exploring outcrop and regolith in Gale crater since August 6, 2012. During this exploration, the mission has collected 10 samples for mineralogical analysis by X-ray diffraction (XRD), using the CheMin instrument. The CheMin (Chemistry and Mineralogy) instrument on the Mars Science Laboratory rover Curiosity uses a CCD detector and a Co-anode tube source to acquire both mineralogy (from the pat-tern of Co diffraction) and chemical information (from energies of fluoresced X-rays). A detailed description of CheMin is provided in [1]. As part of the rover checkout after landing, the first sample selected for analysis was an eolian sand deposit (the Rocknest "sand shadow"). This sample was selected in part to characterize unconsolidated eolian regolith, but primarily to prove performance of the scoop collection system on the rover. The focus of the mission after Rocknest was on the consolidated sediments of Gale crater, so all of the nine subsequent samples were collected by drilling into bedrock com-posed of lithified sedimentary materials, including mudstone and sandstone. No scoop samples have been collected since Rocknest, but at the time this abstract was written the mission stands poised to use the scoop again, to collect active dune sands from the Bagnold dune field. Several abstracts at this conference outline the Bagnold dune campaign and summarize preliminary results from analyses on approach to the Namib dune sampling site. In this abstract we review the mineralogy of Rocknest, contrast that with the mineralogy of local sediments, and anticipate what will be learned by XRD analysis of Bagnold dune sands.

Achilles, C. N.↗
NASA NTRS2016

High-Temperature, Perhaps Silicic, Volcanism on Mars Evidenced by Tridymite Detection in High-SiO2 Sedimentary Rock at Gale Crater, Mars

The Mars Science Laboratory (MSL) rover, Curiosity, has been exploring sedimentary rocks within Gale crater since landing in August, 2012. On the lower slopes of Aeolis Mons (a.k.a. Mount Sharp), drill powder was collected from a high-silica (74 wt% SiO2) outcrop named Buckskin (BK). It was a surprise to find that the Buckskin sample contained significant amounts of the relatively rare silica polymorph tridymite. We describe the setting of the Buckskin sample, the detection of tridymite by the MSL Chemistry and Mineralogy (CheMin) X-ray diffraction instrument, and detection implications. Geologic setting: The Buckskin outcrop is part of the Murray formation exposed in the Marias Pass area. The formation was previously studied by CheMin in the Pahrump Hills member [1] where three samples of drill fines were analyzed (Confidence Hills (CH), Mojave2 (MJ) and Telegraph Peak (TP) [2]). Assuming approximately horizontal bedding, the Buckskin outcrop is approx.15 m stratigraphically above the bottom of the Pahrump Hills member. Mudstone, generally characterized by fine lamination, is the dominant depositional facies [1]. Buckskin Mineralogical and Chemical Composition: The CheMin instrument and XRD pattern analysis procedures have been previously discussed [3-6]. The diffraction pattern used for quantitative XRD analysis (Fig. 1) is the sum of the first 4 of 45 diffraction images. The remaining images are all characterized by both on-ring and off-ring diffraction spots that we attributed to poor grain motion and particle clumping. Coincident with particle clumping was a significant decrease in the intensity of the tridymite diffraction peaks (Fig. 2a). The derived mineralogical composition of the crystalline component (derived from the first 4 diffraction images) is given in Table 1. The tridymite is well-crystalline and its pattern is refined as monoclinic tridymite (Fig 1). Mineral chemical compositions were derived from XRD unit cell parameters or obtained from stoichiometry. The XRD-calculated amorphous component was 50 +/- 15 wt%. We constrained the value to 60 wt% because it is the minimum value necessary to give a positive Al2O3 concentration for the amorphous component using APXS data for the post-sieve dump pile (Table 2). The amorphous component has high SiO2 (approx.77 wt%) and high anion (SO3+P2O5+Cl ~10 wt%) concentrations. Calculation shows that a cation-anion balance is achieved if the cations in the amorphous component except SiO2 and TiO2, which do not readily form salts, are assumed to be present as amorphous mixed-cation sulfates, phosphates, and chlorides (or perchlorates/ chlorates).

Morris, R. V.↗
NASA NTRS2015

Evidence for Acid-Sulfate Alteration in the Pahrump Hills Region, Gale Crater, Mars

The Pahrump Hills region of Gale crater is a approximately 12 millimeter thick section of sedimentary rock in the Murray formation, interpreted as the basal geological unit of Mount Sharp. The Mars Science Laboratory, Curiosity, arrived at the Pahrump Hills in September 2014 and performed a detailed six-month investigation of the sedimentary structures, geochemistry, and mineralogy of the area. During the campaign, Curiosity drilled and delivered three mudstone samples (targets Confidence Hills, Mojave 2, and Telegraph Peak) to its internal instruments, including the CheMin XRD/XRF.

Rampe, E. B.↗
NASA NTRS2015

Mineralogy of the Pahrump Hills Region, Gale Crater, Mars

The Pahrump Hills region of Gale crater is a approximately 12 millimeter thick section of sedimentary rocks in the Murray formation, interpreted as the basal geological unit of Mount Sharp. The Mars Science Laboratory, Curiosity, arrived at the Pahrump Hills in September, 2014, and performed a detailed six-month investigation of the sedimentary structures, geochemistry, and mineralogy of the area. During the campaign, Curiosity drilled and delivered three rock samples to its internal instruments, including the CheMin XRD/XRF. The three targets, Confidence Hills, Mojave 2, and Telegraph Peak, contain variable amounts of plagioclase, pyroxene, iron oxides, jarosite, phyllosilicates, and X-ray amorphous material. Hematite was predicted at the base of Mount Sharp from orbital visible/near-IR spectroscopy, and CheMin confirmed this detection. The presence of jarosite throughout Pahrump Hills suggests the sediments experienced acid-sulfate alteration, either in-situ or within the source region of the sediments. This acidic leaching environment is in stark contrast to the environment preserved within the Sheepbed mudstone on the plains of Gale crater. The minerals within Sheepbed, including Fe-saponite, indicate these sediments were deposited in a shallow lake with circumneutral pH that may have been habitable.

Rampe, E. B.↗
NASA NTRS2015

Update on the Chemical Composition Of Crystalline, Smectite, and Amorphous Components for Rocknest Soil and John Klein and Cumberland Mudstone Drill Fines at Gale Crater, Mars

We have previously calculated the chemical compositions of the X-ray-diffraction (XRD) amorphous component of three solid samples (Rocknest (RN) soil, John Klein (JK) drill fines, and Cumberland (CB) drill fines) using major-element chemistry (APXS), volatile-element chemistry (SAM), and crystalline- phase mineralogy (CheMin) obtained by the Curiosity rover as a part of the ongoing Mars Science Laboratory mission in Gale Crater. According to CheMin analysis, the RN and the JK and CB samples are mineralogically distinct in that RN has no detectable clay minerals and both JK and CB have significant concentrations of high-Fe saponite. The chemical composition of the XRD amorphous component is the composition remaining after mathematical removal of the compositions of crystalline components, including phyllosilicates if present. Subsequent to, we have improved the unit cell parameters for Fe-forsterite, augite, and pigeonite, resulting in revised chemical compositions for the XRD-derived crystalline component (excluding clay minerals). We update here the calculated compositions of amorphous components using these revised mineral compositions.

Morris, R. V.↗
NASA NTRS2015

Crystal-Chemical Analysis Martian Minerals in Gale Crater

The CheMin instrument on the Mars Science Laboratory rover Curiosity performed X-ray diffraction analyses on scooped soil at Rocknest and on drilled rock fines at Yellowknife Bay (John Klein and Cumberland samples), The Kimberley (Windjana sample), and Pahrump (Confidence Hills sample) in Gale crater, Mars. Samples were analyzed with the Rietveld method to determine the unit-cell parameters and abundance of each observed crystalline phase. Unit-cell parameters were used to estimate compositions of the major crystalline phases using crystal-chemical techniques. These phases include olivine, plagioclase and clinopyroxene minerals. Comparison of the CheMin sample unit-cell parameters with those in the literature provides an estimate of the chemical compositions of the major crystalline phases. Preliminary unit-cell parameters, abundances and compositions of crystalline phases found in Rocknest and Yellowknife Bay samples were reported in. Further instrument calibration, development of 2D-to- 1D pattern conversion corrections, and refinement of corrected data allows presentation of improved compositions for the above samples.

Morrison, S. M.↗
NASA NTRS2015

Potential Cement Phases in Sedimentary Rocks Drilled by Curiosity at Gale Crater, Mars

The Mars Science Laboratory rover Curiosity has encountered a variety of sedimentary rocks in Gale crater with different grain sizes, diagenetic features, sedimentary structures, and varying degrees of resistance to erosion. Curiosity has drilled three rocks to date and has analyzed the mineralogy, chemical composition, and textures of the samples with the science payload. The drilled rocks are the Sheepbed mudstone at Yellowknife Bay on the plains of Gale crater (John Klein and Cumberland targets), the Dillinger sandstone at the Kimberley on the plains of Gale crater (Windjana target), and a sedimentary unit in the Pahrump Hills in the lowermost rocks at the base of Mt. Sharp (Confidence Hills target). CheMin is the Xray diffractometer on Curiosity, and its data are used to identify and determine the abundance of mineral phases. Secondary phases can tell us about aqueous alteration processes and, thus, can help to elucidate past aqueous environments. Here, we present the secondary mineralogy of the rocks drilled to date as seen by CheMin and discuss past aqueous environments in Gale crater, the potential cementing agents in each rock, and how amorphous materials may play a role in cementing the sediments.

Rampe, E. B.↗
NASA NTRS2015

Confidence Hills Mineralogy and Chemin Results from Base of Mt. Sharp, Pahrump Hills, Gale Crater, Mars

The Mars Science Laboratory (MSL) rover Curiosity recently completed its fourth drill sampling of sediments on Mars. The Confidence Hills (CH) sample was drilled from a rock located in the Pahrump Hills region at the base of Mt. Sharp in Gale Crater. The CheMin X-ray diffractometer completed five nights of analysis on the sample, more than previously executed for a drill sample, and the data have been analyzed using Rietveld refinement and full-pattern fitting to determine quantitative mineralogy. Confidence Hills mineralogy has several important characteristics: 1) abundant hematite and lesser magnetite; 2) a 10 angstrom phyllosilicate; 3) multiple feldspars including plagioclase and alkali feldspar; 4) mafic silicates including forsterite, orthopyroxene, and two types of clinopyroxene (Ca-rich and Ca-poor), consistent with a basaltic source; and 5) minor contributions from sulfur-bearing species including jarosite.

Cavanagh, P. D.↗
NASA NTRS2014

Mineralogy of Fluvio-Lacustrine Sediments Investigated by Curiosity During the Prime Mission: Implications for Diagenesis

The Mars Science Laboratory rover Curiosity investigated sedimentary rocks that were deposited in a diversity of fluvio-lacustrine settings. The entire science payload was employed to characterize the mineralogy and chemistry of the Sheepbed mudstone at Yellowknife Bay and the Windjana sandstone at the Kimberley. Data from the CheMin instrument, a transmission Xray diffractometer, were used to determine the quantitative mineralogy of both samples. The Sheepbed mudstone contains detrital basaltic minerals, calcium sulfates, iron oxides or hydroxides, iron sulfides, trioctahedral smectite, and amorphous material. The mineral assemblage and chemical data from APXS suggest that the trioctahedral smectite and magnetite formed authigenically as a result of alteration of olivine. The apparent lack of higher-grade phyllosilicates (e.g., illite and chlorite) and the presence of anhydrite indicate diagenesis at ~50- 80 ºC. The mineralogy of the Windjana sandstone is different than the Sheepbed mudstone. Windjana contains significant abundances of K-feldspar, low- and high-Ca pyroxenes, magnetite, phyllosilicates, and amorphous material. At least two distinct phyllosilicate phases exist: a 10 Å phase and a component that is expanded with a peak at ~11.8 Å. The identity of the expanded phase is currently unknown, but could be a smectite with interlayer H2O, and the 10 Å phase could be illite or collapsed smectite. Further work is necessary to characterize the phyllosilicates, but the presence of illite could suggest that Windjana experienced burial diagenesis. Candidates for the cementing agents include fine-grained phyllosilicates, Fe-oxides, and/or amorphous material. Interpretations of CheMin data from the Windjana sandstone are ongoing at the time of writing, but we will present an estimate of the composition of the amorphous material from mass balance calculations using the APXS bulk chemistry and quantitative mineralogy from CheMin.

Rampe, Elizabeth B.↗
NASA NTRS2014

Characterizing the Phyllosilicate Component of the Sheepbed Mudstone in Gale Crater, Mars Using Laboratory XRD and EGA

The Curiosity rover investigated the mineralogy of the Sheepbed mudstone member of the Yellowknife Bay formation in Gale crater. Data from the Chemistry and Mineralogy (CheMin) X-ray diffractometer (XRD) helped identify phyllosilicates in the two drilled samples, John Klein and Cumberland. These patterns showed peaks at low angles, consistent with (001) peaks in 2:1 swelling phyllosilicates [1]. Evolved gas analyses (EGA) by the Sample Analysis at Mars (SAM) instrument of these samples confirmed the presence of phyllosilicates through the release of H2O at high temperatures, consistent with dehydroxylation of octahedral OH in phyllosilicates [2]. CheMin data for the phyllosilicates at John Klein and Cumberland show that they are structurally similar in that their (02l) peaks are near 22.5 deg 2theta, suggesting both samples contain trioctahedral 2:1 phyllosilicates [1]. However, the positions of the (001) peaks differ: the phyllosilicate at John Klein has its (001) peak at 10 Angstroms, whereas the phyllosilicate at Cumberland has an (001) peak at 14 Angstroms. Such differences in (001) dspacings can be ascribed to the type of cation in the interlayer site [3]. For example, large monovalent cations (e.g., K(+)) have low hydration energies and readily lose their H2O of hydration, whereas small divalent cations (e.g., Mg(2+)) have high energies of hydration and retain H2O in the phyllosilicate interlayers [3,4]. The goal of this study is to determine whether differences in the interlayer cation composition can explain the CheMin data from John Klein and Cumberland and to use this knowledge to better understand phyllosilicate formation mechanisms.

Rampe, E. B.↗
NASA NTRS2013

First X-Ray Diffraction Results from Mars Science Laboratory: Mineralogy of Rocknest Aeolian Bedform at Gale Crater

Numerous orbital and landed observations of the martian surface suggest a reasonably uniform martian soil composition, likely as a result of global aeolian mixing [1, 2]. Chemical data for martian soils are abundant [e.g., 2, 3], and phase information has been provided by lander thermal emission and Moessbauer spectroscopic measurements [3, 4, 5, 6]. However, until now no X-ray diffraction (XRD) data were available for martian soil nor has XRD ever been used on another body apart from Earth. XRD is generally considered the most definitive method for determining the crystalline phases in solid samples, and it is the method of choice for determining mineralogy. CheMin s first XRD analysis on Mars coincided with the 100th anniversary of the discovery of X-ray diffraction by von Laue. Curiosity delivered scooped samples of loose, unconsolidated material ("soil") acquired from an aeolian bedform at the Rocknest locality to instruments in the body of the rover (the laboratory). Imaging shows that the soil has a range of particle sizes, of 1-2 mm and smaller, presumably representing contributions from global, regional, and local sources.

Bish, D. L.↗
NASA NTRS2013

Detecting Nanophase Weathering Products with CheMin: Reference Intensity Ratios of Allophane, Aluminosilicate Gel, and Ferrihydrite

X-ray diffraction (XRD) data collected of the Rocknest samples by the CheMin instrument on Mars Science Laboratory suggest the presence of poorly crystalline or amorphous materials [1], such as nanophase weathering products or volcanic and impact glasses. The identification of the type(s) of X-ray amorphous material at Rocknest is important because it can elucidate past aqueous weathering processes. The presence of volcanic and impact glasses would indicate that little chemical weathering has occurred because glass is highly susceptible to aqueous alteration. The presence of nanophase weathering products, such as allophane, nanophase iron-oxides, and/or palagonite, would indicate incipient chemical weathering. Furthermore, the types of weathering products present could help constrain pH conditions and identify which primary phases altered to form the weathering products. Quantitative analysis of phases from CheMin data is achieved through Reference Intensity Ratios (RIRs) and Rietveld refinement. The RIR of a mineral (or mineraloid) that relates the scattering power of that mineral (typically the most intense diffraction line) to the scattering power of a separate mineral standard such as corundum [2]. RIRs can be calculated from XRD patterns measured in the laboratory by mixing a mineral with a standard in known abundances and comparing diffraction line intensities of the mineral to the standard. X-ray amorphous phases (e.g., nanophase weathering products) have broad scattering signatures rather than sharp diffraction lines. Thus, RIRs of X-ray amorphous materials are calculated by comparing the area under one of these broad scattering signals with the area under a diffraction line in the standard. Here, we measured XRD patterns of nanophase weathering products (allophane, aluminosilicate gel, and ferrihydrite) mixed with a mineral standard (beryl) in the CheMinIV laboratory instrument and calculated their RIRs to help constrain the abundances of these phases in the Rocknest samples.

Rampe, E. B.↗