Introduction
Martian geology
In this way, the surface of Mars serves as a time capsule that allows us to examine the geology of a rocky planet early in the history of the solar system. The main goal of this thesis is to understand more deeply this history of the surface and near-surface environments on Mars.
Exploration of Mars
Thesis outline
The Pahrump Hills are ~13 m thick and represent the lowermost 10% of the Murray Formation ( Grotzinger et al., 2015 ). This is due to the H35Cl isobar correction, which dominates the uncertainty for the 36Ar calculation (Farley et al., 2014).
Studies of a Lacustrine-Volcanic Mars Analog Field Site With Mars-2020-Like
Abstract
On the upcoming Mars 2020 rover, two remote sensing instruments, Mastcam-Z and SuperCam, and two microscopic proximity science instruments, SHERLOC and PIXL, will collect compositional (mineralogy, chemistry, and organic) data essential for paleoenvironmental reconstruction. The synergies between and limitations of these instruments were evaluated via investigation of a Mars analog field site in the Mojave Desert using instruments that approximate the data that will be returned to Mars-2020.
Introduction
8 aspects of the composition of the units within a given outcrop and preliminary mapping of these units at a distance. We compare our Mars 2020 analog data and interpretations to the known composition and environmental history of the Mojave outcrop based on previous work (e.g., Hillhouse, 1987; Mason, 1948) and our field verification.
Methods
The green Raman spectra were resampled to the SuperCam resolution of 10 cm-1 (Wiens et al., 2017). 14 textures and patterns that may indicate the presence of potential biosignatures in the rock (Abbey et al., 2017).
Results of Mars-2020 payload simulation
Proximity data from the outcrop locations in (A), collected by simulated SuperCam, show (B-E) RMI images for texture; images are representative and the exact location of spectra is not shown (visible green areas in panel B are chlorophyll-bearing and were avoided in all analyses), (F-I) green Raman spectra for mineralogy and (J-M) LIBS chemistry. LIBS analysis of the clay-rich detrital sediments (sample CR002, unit LD) reveals aluminum-rich compositions with some additional potassium and calcium than what would be expected for pure montmorillonite, likely indicating the presence of minor gypsum, plagioclase, and K-feldspar. illite or muscovite (Table 2-5).
Discussion
This capability would be effective in the context of the more mafic surface mineralogy on Mars. PIXL's capabilities on Mars-2020 will be greater than what is simulated here because of the ability to quantify as well as map.
Conclusions
The coarsening-upward nature of the Pahrump Hills sequence indicates fluvio-deltaic progradation over older lacustrine mud deposits (Grotzinger et al., 2015). 98 sharp mountain, or even the ∼1 km high part of the mound, composed of fluviolacusrine and sulfate layers (Grotzinger et al., 2015).
A Two-Step K-Ar Experiment on Mars: Dating the Diagenetic Formation of
Abstract
The Mojave 2 mudstone, which contains relatively abundant jarosite, showed a young K-Ar total Ga age (1σ precision). A low-temperature step associated with jarosite mixed with K-bearing evaporites and/or phyllosilicates yielded a juvenile K-Ar model of Ga age.
Introduction
54 of Cumberland, as well as the extraordinary abundance of the mineral sanidine with very high argon content (∼20 wt%) in the Windjana sample. The phases present in Mojave 2 are easily clustered by the formation mechanism and argon release temperature: the low-temperature step should provide information about the formation and preservation of water-related minerals in the sample (i.e., secondary constituents). , while the high temperature step should date only the detrital components.
Sample and Methodology
It is possible that the small grain size of the mudstone and/or flood melt associated with volatile bearing minerals in the rock contributes to the release of Ar. After completion of the dynamic mode measurements, a semi-static mode was initiated in which a valve pumping the QMS was almost completely closed to allow a build-up of pressure, increasing sensitivity (Farley et al., 2014).
Results
66 The remaining 45-65% of the K2O in Mojave 2 should be in the amorphous and/or phyllosilicate fractions. Due to the combination of the relatively subtle shifts in peak position between different phyllosilicate species and the width of those peaks, their characterization is difficult using the XRD pattern generated by the CheMin instrument (Vaniman et al., 2014).
Discussion
Phylldosilicate phases are also unlikely to lose significant amounts of argon at 150°C (Evernden et al., 1960). The K-Ar geochronology result on the Cumberland sample (Farley et al., 2014) provides further insight into the issue of Ar retention.
Conclusions
This conclusion suggests that Mount Sharp was largely or completely formed at the start of the Amazonas, consistent with crater counting by (Palucis et al., 2014). 161 less total amount of perchlorate to achieve the same precision, more dilute solutions can actually increase the sensitivity of the measurement (Eiler et al., 2017).
Billion-Year Exposure Ages in Gale Crater Indicate a Pre-Amazonian
Abstract
The erosion rates and mechanisms operating on Mount Sharp can be assessed through experiments performed by the SAM instrument to determine the cosmogenic noble gas content of the new samples Mojave 2 and Quela. Instead, since the surfaces on Mount Sharp have existed for much of Mars' history, the hill must have formed early, probably during the Hesperian.
Introduction
81 Murray, a multilayered sulfate unit forms the upper part of the Mount Sharp Group (Fraeman et al., 2016; Milliken et al., 2010). The Mount Sharp Group is overlain by probable eolian overlying strata that form the upper part of the sedimentary mound (Grotzinger et al., 2015; Milliken et al., 2010).
Materials and methods
Mapping the margin of the covered interval as the Murray-Stimson contact reveals a contact surface that dips slightly to the north. Mastcam image taken from the north side of the Butte River where Quela was sampled.. strata are shown in the red highlighted box indicating the Murray-Stimson contact extends to the base of the Murray Buttes.
Results
Cosmogenic isotope production rate calculations for each isotope depend on the chemical composition of the samples (Tables 4-3 and 4-5 in the Appendix), as described by Farley et al. A detailed description of noble gas quantification for each sample is provided in the Appendix.
Discussion
Like previous workers (Farley et al., 2014; Vasconcelos et al., 2016), we assume that atmospheric noble gases are negligible in these analyses. Unlike the case for Cumberland and Windjana (Farley et al., 2014; Vasconcelos et al., 2016), there is no geochemical reason to favor a scarp retreat model over a vertical denudation model.
Erosion and exposure history of Mount Sharp
Based on nearby exposures of the Murray-Stimson contact, Mojave 2 also appears to be well below the paleosurface (Figure 4-2). Regardless of the formation mechanism of Mount Sharp, these modern erosion rates imply that for the observed landforms in Gale Crater (including Mount Sharp itself) to emerge, the rate of landscape change must have been much greater in the ancient past, consistent with the conclusions of Grotzinger et al.
Conclusions
This insufficient rate can be explained by the slowing of erosion over time due to weathering (Armstrong & Leovy, 2005; Grotzinger et al., 2015; Jakosky et al., 1994), if only the rate, and not the style or the location of the erosion has changed. In addition, crater morphologies at Aeolis Palus show only 20–40 m of post-Hesperian erosion (Grant et al., 2014), reasonably consistent with the derived erosion rate of 20–100 m Ga-1 calculated above.
Appendix
The release of NO in EGAs has been attributed to the breakdown of nitrate in SAM ( Stern et al., 2015 ). 37Cl17O16O3, non-negligible space charge effects are likely to occur in the ion trap, causing changes in instrumental mass fractionation (Eiler et al., 2017).
Reevaluation of Perchlorate in Gale Crater Rocks Suggests Geologically Recent
Abstract
However, the continuously humid paleoenvironment recorded by the sedimentary rocks at Gale Crater was not favorable for the deposition of highly soluble salts. The conclusion that the perchlorate observed in Gale Crater (and possibly Mars in general) is most likely Amazonian means that its effects should not extend into the early history of Mars.
Introduction
107 reinterpreted as consistent with perchlorate based on the presence of chloromethane (Navarro-González et al., 2010), although this interpretation has been challenged (Biemann & Bada, 2011). This interpretation was strongly based on analogy with the results of extremely isotopically 37Cl-depleted perchlorate in the Atacama, fractionated via an unknown mechanism (Böhlke et al., 2005).
Perchlorate in Gale crater
This contrast between Cumberland and John Klein also suggests that late addition of perchlorate by diagenetic fluids is unlikely (Archer et al., 2016). A similar correlation was observed in the first drilled bedrock samples, although a temporal association with HCl (m/z 36 and 38) was also reported (Ming et al., 2014).
Alternative explanations for O 2 release
However, O2 release from sulfate always coincides with that of SO2, which is not observed in O2 releases between 200 and 500°C attributed to perchlorate (Sutter et al., 2017). In the case of thick MnO2 (~100 μm), we found that the onset of O2 release occurs at about 600oC, similar to the results obtained by Hogancamp et al. 2018b) in a MnO2 sample of unspecified grain size.
Modern perchlorate
Conclusions
Unusually 37Cl-depleted and highly variable chlorine isotopes in the Gale Crater bedrock (Farley et al., 2016) support the presence of perchlorate on Mars analogous to observed isotopes in the Atacama Desert on Earth. To date, the only Martian materials suggested to contain ancient perchlorate have been the drilled samples in Gale Crater (Archer et al., 2016).
Appendix
F is the ratio of the reactant concentration divided by the initial concentration (C/Co). Constraints on the origin and evolution of the layered mound in Gale Crater, Mars using Mars Reconnaissance Orbiter data.
A New Method of Isotopic Analysis of Perchlorate Using Electrospray-Orbitrap
Abstract
Isotopic fingerprinting has been demonstrated as an effective means of locating a source of perchlorate (ClO4-) contamination. Existing methods of perchlorate isotope analysis require substantial sample preparation, multiple aliquots, and are unable to determine clumped isotope values.
Introduction
Here we report a new method of measuring the isotopic fingerprint of unfragmented perchlorate ions (ClO4-) with high precision using electrospray orbitrap mass spectrometry (Eiler et al., 2017). We apply this technique to the reduction of perchlorate by Fe0 nanoparticles (Cao et al., 2005) and derive fractionation factors for this reaction, which has not been previously evaluated with respect to its isotopic effects.
Methods
These standards have known values for δ37ClSMOC and δ18OVSMOW and therefore allow direct calculation of the true isotopic ratio for each experimental sample. -5) where R is the isotopic ratio of a species of interest, Ro is the isotopic ratio of the starting material, F is the remaining fraction, and α is the fractionation factor.
Results
Similarly, measurement of the sample taken at 21.8 hours at 50°C returned abnormal isotopic results; δ37ClSMOC and δ18OVSMOW fell more than 3-sigma below the Rayleigh curve. This behavior suggests an error in the measurement compared to a true chemical signal, so this point was also discarded.
Discussion
158 behavior as a sign that the true uncertainty in δ37ClSMOC is underestimated by the standard error of the mean. 165 measurement of primary perchlorate is likely the best interpretation of the Martian data in analogy to the highly depleted 37Cl signals observed in some terrestrial perchlorates (Böhlke et al., 2005; . Farley et al., 2016).
Conclusions
Hurowitz (2017), Sorting compositional trends in sedimentary rocks from the Bradbury Group (Aeolis Palus), Gale Crater, Mars, Journal of Geophysical Research: Planets. Collection of samples in Gale Crater, Mars; an overview of the Mars Science Laboratory sample acquisition, sample processing and handling system.
