Engineering topics

Rampe, Elizabeth

Publications and source records attributed to Rampe, Elizabeth.

5 records

NASA NTRS2019

Evolved Gas Analyses of Sedimentary Rocks and Eolian Sediment in Gale Crater, Mars: Results of the Curiosity Rover's Sample Analysis at Mars Instrument.

The Sample Analysis at Mars instrument evolved gas analyzer (SAM-EGA) has detected evolved water, SO2, NO, CO2, CO, O2, and HCl from two eolian sediments and nine sedimentary rocks from Gale Crater, Mars. The SAM-EGA heats samples to 870°C and measures evolved gas releases as function of temperature. These evolved gas detections indicate nitrates, organics, oxychlorine phase, and sulfates are widespread with phyllosilicates and carbonates occurring in select Gale Crater materials. CO2 and CO evolved at similar temperatures suggesting that as much as 2373 ± 820 μgC/g may occur as organic carbon in the Gale Crater rock record while relatively higher temperature CO2 detections are consistent with carbonate (<0.70 ± 0.1 wt % CO3). Evolved NO amounts up to 0.06 ± 0.03 wt % NO3 have been detected while O2 detections suggests chlorates and/or perchlorates (0.05 to 1.05 wt % ClO4) are present. Evolution of SO2 indicated the presence of crystalline and/or poorly crystalline Fe and Mg sulfate and possibly sulfide. Evolved H2O (0.9 - 2.5 wt% H2O) was consistent with the presence of adsorbed water, hydrated salts, interlayer/structural water from phyllosilicates, and possible inclusion water in mineral/amorphous phases. Evolved H2S detections 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, Brad↗

NASA NTRS2017

Investigating Weathering of Basaltic Materials in Gale Crater, Mars: A Combined Laboratory, Modeling and Terrestrial Field Approach

Recent observations from Gale Crater, Mars document past aqueous alteration both in the formation of the Stimson sandstone unit, as well as in the formation of altered fractures within that unit. Geochemical and mineralogical data from Curiosity also suggest Fe-rich amorphous weathering products are present in most samples measured to date. Here we interpret conditions of possible past weathering in Gale Crater using a combination of field, laboratory, and modeling work. In order to better understand secondary Fe-rich phases on Mars, we are examining formation of weathering products in high Fe and Mg and low Al serpentine soils in the Klamath Mountains, CA. We have isolated potential weathering products from these soils, and are analyzing them using synchrotron μXRF and μXRD as well as FullPat for a direct comparison to analyses from Gale Crater. In order to interpret the implications of the persistence of potential secondary Fe-containing phases on Mars, we are also measuring the dissolution rates of the secondary weathering products allophane, Fe-rich allophane, and hisingerite. Ongoing dissolution experiments of these materials suggest that they dissolve significantly more rapidly than more crystalline secondary minerals with similar chemical compositions. Finally, to quantify the specific conditions of past aqueous alteration in Gale Crater we are performing reactive transport modeling of a range of possible past environmental conditions. Specifically, we are testing the conditions under which a Stimson unit-like material forms from a parent material similar to Rocknest or Bagnold eolian deposits, and the conditions under which observed altered fracture zones form from a Stimson unit-like parent material. Our modeling results indicate that the formation of the Stimson unit is consistent with leaching of an eolian deposit with a solution of pH = 6-8, and that formation of the altered fracture zones is consistent with leaching with a very acidic (pH = 2-3) high sulfate solution containing Ca. These results suggest circumneutral pH conditions during authigenesis or early diagenesis in the Stimson formation sediments followed by diagenetic alteration by very acidic solutions along fracture zones.

Hausrath, Elisabeth↗

NASA NTRS2017

Characterizing Nanophase Materials on Mars: Spectroscopic Studies of Allophane and Imogolite

Allophane is an amorphous or poorly crystalline hydrous aluminosilicate material. Allophane's chemical structure represents a hollow nanosphere, 5-6 nm in diameter with 4-7 large pores in the structure. Identification of allophane and other amorphous and nanophase minerals on Mars has provided clues about the aqueous geochemical environment there. These materials likely represent partially altered or leached basaltic ash and therefore, could represent a geologic marker for where water was present on the Martian surface; as well as indicate regions of climate change, where surface water was not present long enough or sufficiently warm to form clays. Characterization of these materials is important for increasing spectral recognition capabilities using visible/near-infrared (VNIR) and thermal infrared (TIR) spectra of Mars. A suite of synthetic allophane samples was created using a method that has been modified to produce allophane with Fe isomorphically substituted for Al in octahedral coordination. Compositions of the materials range from high-Si allophane (molar Al:Si = 1:2) to protoimogolite (Al:Si = 2:1), with Fe(3+) and Fe(2+) isomorphically substituted for Al from 0-10 mol% of total Al. These compositions span the range observed in natural terrestrial allophanes. Fe K-edge X-ray absorption spectroscopy provided information on the speciation and electrochemical and structural position of Fe in the framework. Fourier transform infrared spectroscopy confirmed syntheses and demonstrated changes in infrared spectroscopic signature with Fe substitution. VNIR reflectance spectra and TIR Thermal infrared emissivity spectra were also collected for direct comparison to Martian data. By increasing spectral recognition capacities of nanophase materials, more accurate estimates can be made on the aqueous geochemical environment of Mars.

Jeute, Thomas↗

NASA NTRS2016

Soil Crystallinity As a Climate Indicator: Field Experiments on Earth and Mars

Soil crystallinity is largely determined by leaching rates, as high leaching rates favor the rapid precipitation of short order or poorly-crystalline phases like the aluminosilicate allophane. High leaching rates can occur due to high precipitation rates, seasonal monsoons, or weathering of glass, but are also caused by the rapid onset of seasonal melting of snow and ice in cold environments. Thus, cold climate soils are commonly dominated by poorly crystalline phases, which mature into kaolin minerals over time. Thus, we hypothesize that, in some contexts, soils with high abundances of poorly crystalline phases could indicate formation under cold climatic conditions. This model could be helpful in interpreting the poorly-constrained paleoclimate of ancient Mars, as the crystallinity of ancient soils and soil-derived sediments appears to be highly variable in time and space. While strong signatures of crystalline phyllosilicates have been identified in possible ancient paleosols on Mars, Mars Science Laboratory rover investigations of diverse ancient sediments at Gale Crater has shown that they can contain very high abundances (40-50 wt%) of poorly crystalline phases. We hypothesize that these poorly crystalline phases could be the result of weathering by ice/snow melt, perhaps providing support for sustained cold climates on early Mars punctuated by more limited warm climates. Furthermore, such poorly crystalline soils could be highly fertile growth media for future human exploration and colonization on Mars. To test this hypothesis, we are currently using rover-like instrumentation to investigate the mineralogy and chemistry of weathering products generated by snow and ice melt in a Mars analog alpine environment: the glaciated Three Sisters volcanic complex in central Oregon. Alteration in this glacial environment generates high abundances of poorly crystalline phases, many of which have compositions distinct from those identified in previous terrestrial investigations, and perhaps more similar to poorly crystalline phases identified on Mars.

Horgan, Briony↗

NASA NTRS2013

Data from the Mars Science Laboratory CheMin XRD/XRF Instrument

The CheMin instrument on the Mars Science Laboratory (MSL) rover Curiosity uses a Co tube source and a CCD detector to acquire mineralogy from diffracted primary X-rays and chemical information from fluoresced X-rays. CheMin has been operating at the MSL Gale Crater field site since August 5, 2012 and has provided the first X-ray diffraction (XRD) analyses in situ on a body beyond Earth. Data from the first sample collected, the Rocknest eolian soil, identify a basaltic mineral suite, predominantly plagioclase (approx.An50), forsteritic olivine (approx.Fo58), augite and pigeonite, consistent with expectation that detrital grains on Mars would reflect widespread basaltic sources. Minor phases (each <2 wt% of the crystalline component) include sanidine, magnetite, quartz, anhydrite, hematite and ilmenite. Significantly, about a third of the sample is amorphous or poorly ordered in XRD. This amorphous component is attested to by a broad rise in background centered at approx.27deg 2(theta) (Co K(alpha)) and may include volcanic glass, impact glass, and poorly crystalline phases including iron oxyhydroxides; a rise at lower 2(theta) may indicate allophane or hisingerite. Constraints from phase chemistry of the crystalline components, compared with a Rocknest bulk composition from the APXS instrument on Curiosity, indicate that in sum the amorphous or poorly crystalline components are relatively Si, Al, Mg-poor and enriched in Ti, Cr, Fe, K, P, S, and Cl. All of the identified crystalline phases are volatile-free; H2O, SO2 and CO2 volatile releases from a split of this sample analyzed by the SAM instrument on Curiosity are associated with the amorphous or poorly ordered materials. The Rocknest eolian soil may be a mixture of local detritus, mostly crystalline, with a regional or global set of dominantly amorphous or poorly ordered components. The Rocknest sample was targeted by MSL for "first time analysis" to demonstrate that a loose deposit could be scooped, sieved to <150 microns, and delivered to instruments in the body of the rover. A drilled sample of sediment in outcrop is anticipated. At the time of writing this abstract, promising outcrops are in range and this talk will provide an update on data collected with the CheMin instrument.

Vaniman, David↗