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At least 19 records
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NASA NTRS2018

Curiosity's Investigation at Vera Rubin Ridge

The Curiosity rover is exploring Vera Rubin Ridge (VRR), a ~6.5 km long and ~200 m wide topographic feature trending northeast-southwest across Aeolis Mons (informally known as Mt. Sharp) (Fig 1). In orbital data, VRR is distinct from the underlying Murray formation due to its relative erosional resistance and greater exposure of bedrock. Compact Reconnaissance Imaging Spectrometer for Mars (CRISM) orbital data show a hematite spectral signature over much of the ridge (Fig. 2). On the ground, Curiosity also observed hematite associated with the sedimentary rocks of the underlying Murray formation, although these detections are difficult to see with CRISM due to mixing with sand and dust.

Fraeman, A. A.↗
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 NTRS2019

Rock Hard Science: Multispectral and Mineralogical Investigations to Understand Bedrock Spectral Properties and Strength at Vera Rubin Ridge, Gale Crater, Mars

Since the beginning of the Mars Science Laboratory (MSL) mission, Vera Rubin Ridge (VRR) has been a location of interest to the MSL science team because of its apparent erosional resistance and strong near-IR (~860 nm) absorption feature seen from orbit in the Mars Reconnaissance Orbiter mission's Compact Reconnaissance Imaging Spectrometer for Mars (CRISM) data. The strong CRISM absorption feature along VRR was hypothesized to be primarily associated with an increased abundance of crystal-line hematite compared to lower Mt. Sharp units. How-ever, surface multispectral and mineralogic data, from the Mastcam and CheMin instruments onboard the Curiosity rover, suggest hematite is not the only mineral contributing to the near-IR absorption feature measured in VRR or the reason for its relative hardness.

Jacob, S. R.↗
NASA NTRS2019

Compositional Characteristics and Trends Within the Vera Rubin Ridge, Gale Crater, Mars as Determined by APXS: Sedimentary, Diagenetic and Alteration History

The Mars Science Laboratory (MSL) Curiosity rover has spent the last two years investigating a prominent resistant ridge, informally named the Vera Rubin Ridge (VRR), at the base of Mount Sharp (Aeolis Mons). The ridge has been a high priority science target for the MSL mission since landing in Gale crater more than 6 years ago because of the detection of a strong hematite spectral signature, and its distinct topography. Examining the chemistry of the ridge can aid in determining the relationship to other rocks analyzed during the rover traverse, specifically the Murray formation (fm) encountered below the ridge. We can also determine compositional trends with elevation and/or laterally within the ridge, and whether spectral properties observed on the ridge, both from orbit and in situ, correspond with changes in chemistry. The composition of the ridge, combined with mineralogy of drilled samples, can help to elucidate bigger picture questions regarding depositional environment, possible changing lake water chemistry and diagenetic/alteration history.

Thompson, L. M.↗
NASA NTRS2019

Thermochemical Modelling of Fluid-Rock Reactions in Vera Rubin Ridge, Galecrater, Mars

Vera Rubin Ridge (VRR) in Gale Crater, Mars, is a ~200 m wide ~6.5 km long northeast- southwest resistant geomorphological feature on the northern slopes of Aeolis Mons (Mt. Sharp). Analysis of Compact Reconnaissance Imaging Spectrometer for Mars (CRISM) orbital data showed that VRR has strong hematite spectral signatures. Hematite was confirmed in-situ at VRR with the Curiosity rover and has been shown to be present throughout the Mur- ray formation. VRR is stratigraphically continu-ous with the underlying Murray formation. Previous thermochemical modelling showed how hematite at VRR could have formed as the result of open-system weathering at high water/rock ratios. Here we use thermochemical modelling to investigate possible reaction pathways for the hematite-clay- bearing assemblage observed at VRR, starting from an identified least-altered (minimum clay content) Murray composition, and a Mars basal brine.

Turner, S. M. R.↗
NASA NTRS2020

Enhanced Groundwater Flow on and Below Vera Rubin Ridge, the Murray Formation, Gale Crater: Evidence from Thermochemical Modeling.

NASA’s Mars Science Laboratory Curiosity rover has been exploring Vera Rubin ridge (VRR), part of the Murray formation in Gale crater, Mars, between sol 1809 and 2302. Evidence for Fe-oxides and phyllosilicates in mineralogical and geochemical data for this region was returned by Curiosity [1-5]. We applied thermochemical modeling to con-strain the formation conditions of the phyllosilicate-hematite assemblage identified on and below VRR. Average alteration compositions for the Murray formation on and below VRR were derived using CheMin and APXS data. These compositions were reacted with Gale Portage Water (GPW) between 25–100 °C and for 10% and 50% Fe3+/Fetot of the host rock [6]. Here we summarize models run at 50 °C and 10% Fe3+/Fetot for alteration compositions derived from Murray host rock compositions.

Turner, S. M. R.↗
NASA NTRS2020

Mineralogy of Vera Rubin Ridge in Gale Crater from the Mars Science Laboratory CheMin instrument

Gale crater was selected as the landing site for the Mars Science Laboratory Curiosity rover because of orbital evidence for a variety of secondary minerals in the lower slopes of Aeolis Mons (aka Mount Sharp) that indicate changes in aqueous conditions over time. Distinct units demonstrate orbital spectral signatures of hematite, phyllosilicate (smectite), and sulfate minerals, which suggest that ancient aqueous environments in Gale crater varied in oxidation potential, pH, and water activity. Vera Rubin ridge (VRR) is the first of these units identified from orbit to have been studied by Curiosity. Orbital near-infrared data from VRR show a strong band at 860 nm indicative of hematite. Before Curiosity arrived at VRR, the hypotheses to explain the formation of hematite included (1) precipitation at a redox interface where aqueous Fe2+ was oxidized to Fe3+, and (2) acidic alteration of olivine in oxic fluids. Studying the composition and sedimentology of the rocks on VRR allow us to test and refine these hypotheses and flesh out the depositional and diagenetic history of the ridge. Here, we focus on the mineralogical results of four rock powders drilled from and immediately below VRR as determined by CheMin.

Rampe, E. B.↗
NASA NTRS2020

The Role of Diagenesis at Vera Rubin Ridge in Gale Crater, Mars, and the Chemostratigraphy of the Murray Formation as Observed by the Chemcam Instrument

The Mars Science Laboratory (MSL) Curiosity rover explored Vera Rubin ridge (VRR) in Gale crater, Mars, for almost 500 sols (Mars days) between arriving at the ridge on sol 1809 of the mission in September 2017 and leaving it on sol 2302 upon entering the Glen Torridon area south of the ridge. VRR is a topographic ridge on the central mound, Aeolis Mons (Mt. Sharp), in Gale crater that displays a strong hematite spectral signature from orbit. In-situ observations on the ridge led to the recognition that the ridge-forming rocks belong to the Murray formation, the lowermost exposed stratigraphic unit of the Mt. Sharp group, that was first encountered at the Pahrump Hills location. Including VRR rocks, the Murray formation, interpreted to be primarily deposited in an ancient lacustrine environment in Gale crater, is more than 300 m thick. VRR itself is composed of two stratigraphic members within the Murray formation, the Pettegrove Point member overlain by the Jura member. The Pettegrove Point member overlies the Blunts Point member of the Murray formation. Areas of gray coloration are observed in the Jura member predominantly, but also in the Pettegrove Point member. Generally, gray areas are found in local topographic depressions, but contacts between red and gray rocks crosscut stratigraphy. Additionally, cm-scale dark concretions with very high iron-content are commonly observed in gray rocks, typically surrounded by a lighttoned zone that is conversely depleted in iron. A key goal for the VRR campaign was to characterize geochemical variations in the ridge-forming rocks to investigate the role of primary and diagenetic controls on the geochemistry and morphology of VRR. Here, we present observations by the ChemCam instrument on VRR and compare these to the full Murray formation chemostratigraphy. This work was recently submitted to a special issue of JGRPlanets that detail the full VRR campaign.

Frydenvang, J.↗
NASA NTRS2020

Mineralogy of Vera Rubin Ridge from the Mars Science Laboratory CheMin Instrument

Vera Rubin ridge (VRR) is an erosion-resistant feature on the northwestern slope of Mount Sharp in Gale crater, Mars, and orbital visible/short-wave infrared measurements indicate it contains red-colored hematite. The Mars Science Laboratory Curiosity rover performed an extensive campaign on VRR to study its mineralogy, geochemistry, and sedimentology to determine the depositional and diagenetic history of the ridge and constrain the processes by which the hematite could have formed. X-ray diffraction (XRD) data from the CheMin instrument of four samples drilled on and below VRR demonstrate differences in iron, phyllosilicate, and sulfate mineralogy and hematite grain size. Hematite is common across the ridge, and its detection in a gray-colored outcrop suggested localized regions with coarse-grained hematite, which commonly forms from warm fluids. Broad XRD peaks for hematite in one sample below VRR and the abundance of FeOT in the amorphous component suggest the presence of nano-crystalline hematite and amorphous Fe oxides/oxyhydroxides. Well-crystalline akaganeite and jarosite are present in two samples drilled from VRR, indicating at least limited alteration by acid-saline fluids. Collapsed nontronite is present below VRR, but samples from VRR contain phyllosilicate with d(001) = 9.6 Å, possibly from ferripyrophyllite or an acid-altered smectite. The most likely cementing agents creating the ridge are hematite and opaline silica. We hypothesize late diagenesis can explain much of the mineralogical variation on the ridge, where multiple fluid episodes with variable pH, salinity, and temperature altered the rocks, causing the precipitation and crystallization of phases that are not otherwise in equilibrium.

E. B. Rampe↗
NASA NTRSDate not supplied

Formation of Fe(III) (hydr)oxides from Fe(II) sulfides: Implications for akaganeite detection on Mars

Akaganeite (β-FeO(OH,Cl)) is a Fe(III) (hydr)oxide with a tunnel structure typically occupied by chloride. This mineral was first proposed to be present in Meridiani Planum and Gusev crater on Mars and akaganeite was subsequently detected by X-ray diffraction in Yellowknife Bay and Vera Rubin Ridge locations in Gale crater. Akaganeite in Gale crater has been proposed to form from Fe(II) sulfides but formation conditions remain unconstrained. We investigated akageneite formation by oxidative alteration of natural Fe(II) sulfide pyrrhotite exposed to HCl and oxidation-hydrolysis of Fe(II) HCl-leached from pyrrhotite at initial pH0 1.5, 2, 3, and 4. X-ray diffraction and Mössbauer analyses revealed formation of poorly-crystallized akageneite in oxidative alteration experiments. Air-exposure of the HCl-reacted dry pyrrhotite led to an increase in akageneite formation and precipitation of Fe(II) hydrated sulfates, goethite, and hydronium jarosite. Iron(II) oxidation-hydrolysis was sensitive to Si dissolved from phyllosilicates in one pyrrhotite sample. Akaganeite and goethite formed at pH0 1.5 and 2 with akageneite more abundant at dissolved Si/Fe ratio of 0.08 and goethite more abundant at Si/Fe of 0.01. Akaganeite formed together with hematite, ferrihydrite, and goethite at pH0 3, and formation was suppressed at pH0 4. Well-crystallized akageneite precipitated at pH0 1.5 while akaganeite of poorer crystallinity formed at pH0 2 and 3. Akageneite in Gale crater could form from sulfides by both mechanisms: oxidative alteration of sulfide minerals and oxidation-hydrolysis of leached Fe(II). The processes likely occurred during late diagenetic events triggered by interactions of acidic Cl-bearing groundwater with Fe(II) sulfides. Akaganeite in Yellowknife Bay, Gale crater could have formed by Fe(II) oxidation-hydrolysis either as a sole Fe(III) (hydr)oxide at pH<2 or along with ferrihydrite and hematite at 2<pH<4 in Si-enriched conditions. Akaganeite formation at Vera Rubin Ridge, Gale crater could have occurred through oxidative alteration of sulfides in Cl-bearing pH 1.2-1.5 solutions. The presence of well-crystalline akageneite in Vera Rubin Ridge indicates that Fe(II) oxidation-hydrolysis contributed to akageneite formation.

Mars gale crater akaganeite↗
NASA NTRS1993

Can cluster environment modify the dynamical evolution of spiral galaxies?

Over the past decade many effects of the cluster environment on member galaxies have been established. These effects are manifest in the amount and distribution of gas in cluster spirals, the luminosity and light distributions within galaxies, and the segregation of morphological types. All these effects could indicate a specific dynamical evolution for galaxies in clusters. Nevertheless, a more direct evidence, such as a different mass distribution for spiral galaxies in clusters and in the field, is not yet clearly established. Indeed, Rubin, Whitmore, and Ford (1988) and Whitmore, Forbes, and Rubin (1988) (referred to as RWF) presented evidence that inner cluster spirals have falling rotation curves, unlike those of outer cluster spirals or the great majority of field spirals. If falling rotation curves exist in centers of clusters, as argued by RWF, it would suggest that dark matter halos were absent from cluster spirals, either because the halos had become stripped by interactions with other galaxies or with an intracluster medium, or because the halos had never formed in the first place. Even if they didn't disagree with RWF, other researchers pointed out that the behaviour of the slope of the rotation curves of spiral galaxies (in Virgo) is not so clear. Amram, using a different sample of spiral galaxies in clusters, found only 10% of declining rotation curves (2 declining vs 17 flat or rising) in opposition to RWF who find about 40% of declining rotation curves in their sample (6 declining vs 10 flat or rising), we will hereafter briefly discuss the Amram data paper and compare it to the results of RWF. We have measured the rotation curves for a sample of 21 spiral galaxies in 5 nearby clusters. These rotation curves have been constructed from detailed two-dimensional maps of each galaxy's velocity field as traced by emission from the Ha line. This complete mapping, combined with the sensitivity of our CFHT 3.60 m. + Perot-Fabry + CCD observations, allows the construction of high-quality rotation curves. Details concerning the acquisition and reduction procedures of the data are given in Amram. We present and discuss our preliminary analysis and compare them with RWF's results.

Amram, P.↗
NASA NTRSDate not supplied

Mineralogy of the Greenheugh Pediment and Underlying Murray Formation from the Mars Science Laboratory CheMin Instrument

The Mars Science Laboratory Curiosity rover has been investigating a sequence of ancient fluvio-lacustrine and eolian units in Gale crater. For much of the mission, Curiosity has studied the fluvio-lacustrine deposits of the Murray formation. Curiosity has also studied the ancient eolian Stimson formation in a few locations, which unconformably overlies the Murray fm. The Stimson formation was previously studied at the Naukluft and Emerson Plateaus and recently studied at the Greenheugh pediment capping unit. The Curiosity science team also investigated the Murray formation directly underlying the pediment. Curiosity drilled the “Edinburgh” target within the pediment capping unit and the “Hutton” target in the Murray formation near the contact with the pediment and delivered these materials to the CheMin X-ray diffractometer to characterize bulk mineralogy. Edinburgh contains abundant plagioclase, pyroxene, magnetite, olivine, and X-ray amorphous materials, with 10 wt.% smectite and minor sanidine. The mineralogy of the Stimson at Greenheugh is distinct from the mineralogy of the Stimson at Naukluft and Emerson because previous Stimson targets did not contain olivine or clay minerals. This suggests sediments in the pediment may have a different source and/or different aqueous alteration history than those from Naukluft and Emerson. Hutton contains abundant plagioclase, pyroxene, magnetite, and X-ray amorphous materials, 6 wt.% smectite, and minor cristobalite, opal-CT, sanidine, hematite, fluorapatite, and anhydrite. Other Murray targets in the surrounding Glen Torridon region that are farther from the pediment contact contain ~30 wt.% smectite and lack cristobalite and opal-CT. Cristobalite and/or opal-CT are present in a few other targets elsewhere along the traverse, including the top of the nearby Vera Rubin ridge and the top of the Pahrump Hills outcrop. Stimson overlies the Pahrump Hills, and, based on projections of the pediment slope, the Stimson may have overlain Vera Rubin ridge. The proximity of the low-smectite and cristobalite- and/or opal-CT-bearing outcrops to the contact between the Murray and Stimson suggests the contact provided a conduit for diagenetic fluids that altered clay minerals and formed crystalline and paracrystalline silica.

E. B. Rampe↗
NASA NTRSDate not supplied

Recent Mineralogical Discoveries in Gale Crater, Mars from the CheMin XRD Instrument

Curiosity landed in Gale crater in August 2012 and has traversed ~27 km through sedimentary rocks that comprise the lower slopes of a ~5 km-high mound, informally known as Mount Sharp, to investigate depositional/diagenetic environments and potential habitability. Orbital visible/short-wave infrared spectra revealed some strata on lower Mount Sharp contain mineral assemblages that are indicative of water-rock interactions (1-3), with sulfate-bearing units overlying phyllosilicate-bearing units. This mineralogical succession may mark the beginning of the transition from a relatively wet/warm to a very dry/cold Mars (e.g., 1, 4). Curiosity began studying the strata that show mineralogical signatures from orbit in 2018, with the investigation of Vera Rubin ridge. Here, we describe the mineralogical diversity in these strata using X-ray diffraction data collected by the CheMin instrument. We report on the mineral assemblages from the hematite-rich Vera Rubin ridge, the smectite-rich Glen Torridon region, and the transition from the smectite-bearing rocks to the sulfate-bearing unit. We will present hypotheses explaining the changes in mineralogy throughout the strata, including changes in depositional environment, diagenetic reactions with saline groundwater, and groundwater-lake water interactions (e.g., 5-7).

V. M. Tu↗