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All sourcesNASA NTRSDOE OSTI
NASA NTRS2003

Issues and Concerns in Robotic Drilling

Exploration of the Martian subsurface will be essential in the search for life and water, given the desiccated and highly oxidized conditions on the surface. Discovery of these, at least in non-fossil form, is unlikely without drilling or other physical access to the subsurface. Hence subsurface access will be critical for both future in-situ science and Mars sample return. Drilling applications present many new challenges for diagnosis and control technology. Traditionally, diagnosis has concentrated on determining the internal state of a system, and detecting failures of system components. In the case of drilling applications, an additional challenge is to diagnose the interactions between the drill and its environment. This is necessary because particular observations of the drilling operation may be consistent with a number of possible problems, including faults in the equipment, but also changes in the material being drilled (for example, from rock to ice). The diagnosis of a particular observation may also depend on knowledge of geological formations previously encountered during drilling, and different remedial actions may be required for each diagnosis. Current 2009 Mars mission scenarios call for no more than 33 sols to be spent drilling. Yet they also call for a baseline of two 2m-deep holes in each of three target areas, for a total of six drilling operations. Using current levels of automation, it is estimated that 15-16 sols would be required to drill each hole. As a result of this, either the drilling part of the mission plan will need to be severely downscoped to no more than two holes total, or on-board automation and robotics must be increased in order to reduce the number of sols required per hole by removing ground control from the drilling control loop. This lecture will discuss salient issues and concerns of robotic drilling automation compares with other applications, and implementation constraints.

Glass, Brian↗
NASA NTRS2001

Organic-Inorganic Hybrids Using Novel Phenylethynyl Imide Silanes

In this presentation, polyimide-silica hybrids using novel phenylethynyl imide silanes are reported. The phenylethynyl group is present in the organic precursor as either a pendent or an end group to bond chemically with the polyimide adhesive containing phenylethynyl groups during processing, while the silane group of the organic precursor would chemically react with the inorganic precursor through oxane bond formation. The chemical compositions of these novel hybrids were examined using X-ray mapping modes of scanning electron microscopy (SEM), which revealed a silicon gradient interphase between the high surface energy substrate and the polyimide adhesive. Novel aromatic phenylethynyl imide silanes (APEISs) and pendent phenylethynyl imide oligomeric disilanes (PPEIDSs) have been synthesized, and sol-gel solutions containing the new silanes, a phenylethynyl terminated imide oligomer (PETI-5), and an inorganic precursor were formulated to develop a gradient hybrid interphase between a titanium alloy and the adhesive. Two different sol-gel systems were investigated to develop organic-inorganic hybrids. Hybrid I was composed of an organic precursor containing both phenylethynyl and silane groups (PPEIDS) and an inorganic precursor. Functional group concentrations were controlled by the variation of the molecular weight of the imide backbone of PPEIDS. Hybrid II was composed of organic and inorganic precursors and a coupling agent containing both phenylethynyl and silane groups. Morphology and chemical composition of the hybrid interphase between the inorganic substrate and the adhesive were investigated, and the bond strength and durability were evaluated using lap shear tests at various conditions. The assessment of how the bonding at an interface is affected by various sol-gel solution compositions and environments is reported.

Park, C.↗
NASA NTRS2001

Sensorimotor adaptations to microgravity in humans

Motor function is altered by microgravity, but little detail is available as to what these changes are and how changes in the individual components of the sensorimotor system affect the control of movement. Further, there is little information on whether the changes in motor performance reflect immediate or chronic adaptations to changing gravitational environments. To determine the effects of microgravity on the neural control properties of selected motor pools, four male astronauts from the NASA STS-78 mission performed motor tasks requiring the maintenance of either ankle dorsiflexor or plantarflexor torque. Torques of 10 or 50% of a maximal voluntary contraction (MVC) were requested of the subjects during 10 degrees peak-to-peak sinusoidal movements at 0.5 Hz. When 10% MVC of the plantarflexors was requested, the actual torques generated in-flight were similar to pre-flight values. Post-flight torques were higher than pre- and in-flight torques. The actual torques when 50% MVC was requested were higher in- and post-flight than pre-flight. Soleus (Sol) electromyographic (EMG) amplitudes during plantarflexion were higher in-flight than pre- or post-flight for both the 10 and 50% MVC tasks. No differences in medial gastrocnemius (MG) EMG amplitudes were observed for either the 10 or 50% MVC tasks. The EMG amplitudes of the tibialis anterior (TA), an antagonist to plantarflexion, were higher in- and post-flight than pre-flight for the 50% MVC task. During the dorsiflexion tasks, the torques generated in both the 10 and 50% MVC tasks did not differ pre-, in- and post-flight. TA EMG amplitudes were significantly higher in- than pre-flight for both the 10 or 50% MVC tasks, and remained elevated post-flight for the 50% MVC test. Both the Sol and MG EMG amplitudes were significantly higher in-flight than either pre- or post-flight for both the 10 and 50% MVC tests. These data suggest that the most consistent response to space flight was an elevation in the level of contractions of agonists and antagonists when attempting to maintain constant torques at a given level of MVC. Also, the chronic levels of EMG activity in selected ankle flexor and extensor muscles during space flight and during routine activities on Earth were recorded. Compared with pre- and post-flight values, there was a marked increase in the total EMG activity of the TA and the Sol and no change in the MG EMG activity in-flight. These data indicate that space flight, as occurs on shuttle missions, is a model of elevated activation of both flexor and extensor muscles, probably reflecting the effects of programmed work schedules in flight rather than a direct effect of microgravity.

NASA Experiment Number 284036↗
NASA NTRS1998

Results From Mars Show Electrostatic Charging of the Mars Pathfinder Sojourner Rover

Indirect evidence (dust accumulation) has been obtained indicating that the Mars Pathfinder rover, Sojourner, experienced electrostatic charging on Mars. Lander camera images of the Sojourner rover provide distinctive evidence of dust accumulation on rover wheels during traverses, turns, and crabbing maneuvers. The sol 22 (22nd Martian "day" after Pathfinder landed) end-of-day image clearly shows fine red dust concentrated around the wheel edges with additional accumulation in the wheel hubs. A sol 41 image of the rover near the rock "Wedge" (see the next image) shows a more uniform coating of dust on the wheel drive surfaces with accumulation in the hubs similar to that in the previous image. In the sol 41 image, note particularly the loss of black-white contrast on the Wheel Abrasion Experiment strips (center wheel). This loss of contrast was also seen when dust accumulated on test wheels in the laboratory. We believe that this accumulation occurred because the Martian surface dust consists of clay-sized particles, similar to those detected by Viking, which have become electrically charged. By adhering to the wheels, the charged dust carries a net nonzero charge to the rover, raising its electrical potential relative to its surroundings. Similar charging behavior was routinely observed in an experimental facility at the NASA Lewis Research Center, where a Sojourner wheel was driven in a simulated Martian surface environment. There, as the wheel moved and accumulated dust (see the following image), electrical potentials in excess of 100 V (relative to the chamber ground) were detected by a capacitively coupled electrostatic probe located 4 mm from the wheel surface. The measured wheel capacitance was approximately 80 picofarads (pF), and the calculated charge, 8 x 10(exp -9) coulombs (C). Voltage differences of 100 V and greater are believed sufficient to produce Paschen electrical discharge in the Martian atmosphere. With an accumulated net charge of 8 x 10(exp -9) C, and average arc time of 1 msec, arcs can also occur with estimated arc currents approaching 10 milliamperes (mA). Discharges of this magnitude could interfere with the operation of sensitive electrical or electronic elements and logic circuits. Sojourner rover wheel tested in laboratory before launch to Mars. Before launch, we believed that the dust would become triboelectrically charged as it was moved about and compacted by the rover wheels. In all cases observed in the laboratory, the test wheel charged positively, and the wheel tracks charged negatively. Dust samples removed from the laboratory wheel averaged a few ones to tens of micrometers in size (clay size). Coarser grains were left behind in the wheel track. On Mars, grain size estimates of 2 to 10 mm were derived for the Martian surface materials from the Viking Gas Exchange Experiment. These size estimates approximately match the laboratory samples. Our tentative conclusion for the Sojourner observations is that fine clay-sized particles acquired an electrostatic charge during rover traverses and adhered to the rover wheels, carrying electrical charge to the rover. Since the Sojourner rover carried no instruments to measure this mission's onboard electrical charge, confirmatory measurements from future rover missions on Mars are desirable so that the physical and electrical properties of the Martian surface dust can be characterized. Sojourner was protected by discharge points, and Faraday cages were placed around sensitive electronics. But larger systems than Sojourner are being contemplated for missions to the Martian surface in the foreseeable future. The design of such systems will require a detailed knowledge of how they will interact with their environment. Validated environmental interaction models and guidelines for the Martian surface must be developed so that design engineers can test new ideas prior to cutting hardware. These models and guidelines cannot be validated without actual flighata. Electrical charging of vehicles and, one day, astronauts moving across the Martian surface may have moderate to severe consequences if large potential differences develop. The observations from Sojourner point to just such a possibility. It is desirable to quantify these results. The various lander/rover missions being planned for the upcoming decade provide the means for doing so. They should, therefore, carry instruments that will not only measure vehicle charging but characterize all the natural and induced electrical phenomena occurring in the environment and assess their impact on future missions.

Kolecki, Joseph C.↗
NASA NTRS2006

An Update of the Ground Testing of the Li-ion Batteries in Support of JPL's 2003 Mars Exploration Rover Mission

In early 2004, JPL successfully landed two Rovers, named Spirit and Opportunity, on the surface of Mars after traveling > 300 million miles over a 6-7 month period. In order to operate for extended duration (>9 months), both Rovers are equipped with rechargeable Lithium-ion batteries, which have enabled operation for over 854 and 834 Sols of operation, respectively, to date. Given that the batteries were required to support the mission for 90 Sols of operation by design, it is significant that the batteries have demonstrated over a nine fold increase in life over mission objectives. In addition to supporting the surface operations in conjunction with a triple-junction deployable solar arrays, the batteries were designed to aid in the launch and the EDL pyros, and allow for anomalies during cruise. In summary, the requirements of the Lithium-ion battery include the ability to provide power at least 90 sols on the surface of Mars, operate over a wide temperature range (-20 C to +30 C), withstand long storage periods (e.g., cruise period), operate in an inverted orientation, and support high current pulses (e.g., firing pyro events). In order to determine the viability of meeting these requirements, ground testing was performed on a Rover Battery Assembly Unit (RBAU), consisting of two 8-cell 10 Ah lithium-ion batteries connected in parallel. The RBAU upon which the performance testing was performed is nearly identical to the batteries incorporated into the two Rovers currently on Mars. The testing includes, (a) performing initial characterization tests (discharge capacity at different temperatures), (b) simulating the launch conditions, (c) simulating the cruise phase conditions (including trajectory correction maneuvers), (d) simulating the entry, decent, and landing (EDL) pulse load profile (required to support the pyros) (e) simulating the Mars surface operation mission simulation conditions, as well as, (f) assessing capacity loss and impedance characteristics as a function of temperature and life. This paper provides further detail to previously reported results1 of the RBAU testing program, especially with regard to the life characteristics. To date, the lithium-ion batteries (fabricated by Lithion/Yardney, Inc.) have been demonstrated to far exceed the requirements defined by the mission, both on Mars and on the ground, and are projected to support an extended mission (> 4 years).

Mars Exploration Rovers (MER) Mission↗
NASA NTRS2006

An Overview of Moessbauer Mineralogy at Gusev Crater, Mars

The Mars Exploration Rover (MER) Spirit landed on the plains of Gusev Crater on 4 January 2004 [1]. The scientific objective of the Moessbauer (MB) spectrometer on Spirit is to provide quantitative information about the distribution of Fe among its oxidation and coordination states, identification of Fe-bearing phases, and relative distribution of Fe among those phases. The speciation and distribution of Fe in Martian rock and soil constrains the primary rock types, redox conditions under which primary minerals crystallized, the extent of alteration and weathering, the type of alteration and weathering products, and the processes and environmental conditions for alteration and weathering.We discuss the Fe-bearing phases detected by Spirit s MB instrument during its first 540 sols of exploration [2,3]. Spirit roved eastward across the plains from its landing site to the Columbia Hills during the first approx.150 sols. Rocks are unweathered to weakly weathered olivine basalt, with olivine, pyroxene (Ol > Px), magnetite (Mt), and minor hematite (Hm) and nanophase ferric oxide (npOx) as their primary Fe-bearing minerals. Soils are generally similar basaltic materials, except that the proportion of npOx is much higher (up to approx.40%). NpOx is an oct-Fe3+ alteration product whose concentration is highest in fine-grained soils and lowest in rock interiors exposed by grinding with the Rock Abrasion Tool (RAT). Spirit explored the lower slopes of the Columbia Hills (West Spur) during sols approx.150-320. West Spur rocks are highly altered, even for interior surfaces exposed by grinding (Fe3+/FeT approx.0.56-0.84). High concentrations of npOx, Hm, and Mt are present. One rock (Clovis) contains significant quantities of goethite (alpha-FeOOH; approx.40% of total Fe). The detection of goethite is very significant because it is a mineralogical marker for aqueous alteration.

Klingelhoefer, G.↗
NASA NTRS2009

Santorini, Another Meteorite on Mars and Third of a Kind

The Mars Exploration Rover (MER) Opportunity has been studying Meridiani Planum for five years. On sol 1634 of its mission, Opportunity left Victoria crater after investigating it for approximately 682 sols [1] and is now on a journey towards Endeavour, a 24 km diameter crater about 12 km southeast of Victoria. A priority along the way is the investigation of cobbles, which in the jargon of the MER science team denotes any loose rock fragment larger than a couple of centimeters. Cobbles investigated thus far are of diverse origin [2] and provide the only means to investigate material other than the ubiquitous sulfate-rich outcrop, basaltic sand or hematiterich spherules dubbed blueberries. Some of these cobbles are meteorites [3]. Meteorites on Mars are not just a curiosity that make Mars a more Earth-like planet. Metallic iron in meteorites, for example, may be used as a more sensitive tracer for volatile surface interactions compared to igneous minerals [4]. Between sols 1713 and 1749, including the period of Mars solar conjunction, Opportunity investigated a cobble informally named Santorini. Its chemical and mineralogical composition is very similar to Barberton and Santa Catarina, two cobbles that were identified as meteorites and which are probably related to each other [3]. Santorini was investigated with the rover s Panoramic Camera (Pancam), Microscopic Imager (MI), Alpha-Particle X-ray Spectrometer (APXS) and Moessbauer (MB) spectrometer. The miniature Thermal Emission Spectrometer (mini-TES) was not operational at the time. The Rock Abrasion Tool (RAT) could not be used to brush off potential dust coatings because of unfavorable geometry.

Schroeder, C.↗
NASA NTRS2004

New Material for Surface-Enhanced Raman Spectroscopy

A chemical method of synthesis and application of coating materials that are especially suitable for surface-enhanced Raman spectroscopy (SERS) has been developed. The purpose of this development is to facilitate the utilization of the inherently high sensitivity of SERS to detect chemicals of interest (analytes) in trace amounts, without need for lengthy sample preparation. Up to now, the use of SERS has not become routine because the methods available have not been able to reproduce sampling conditions and provide quantitative measurements. In contrast, the coating materials of the present method enable analysis with minimum preparation of samples, and SERS measurements made using these materials are reproducible and reversible. Moreover, unlike in methods investigated in prior efforts to implement SERS, sampling is not restricted to such specific environments as electrolytes or specific solvents. The coating materials of this method are porous glasses, formed in sol-gel processes, that contain small particles of gold or silver metal. Materials of this type can be applied to the sample-contact surfaces of a variety of sampling and sensing devices, including glass slides, glass vials, fiber-optic probes, and glass tubes. Glass vials with their insides coated according to this method are particularly convenient for SERS to detect trace chemicals in solutions: One simply puts a sample solution containing the analyte(s) into a vial, then puts the vial into a Raman spectrometer for analysis. The chemical ingredients and the physical conditions of the sol-gel process have been selected so that the porous glass formed incorporates particles of the desired metal with size(s) to match the wavelength(s) of the SERS excitation laser in order to optimize the generation of surface plasmons. The ingredients and processing conditions have further been chosen to tailor the porosity and polarity of the glass to optimize the sample flow and the interaction between the analyte(s) and the plasmon field that generates Raman photons. The porous silica network of a sol-gel glass creates a unique environment for stabilizing SERS-active metal particles. Relative to other material structures that could be considered for SERS, the porous silica network offers higher specific surface area and thus greater interaction between analyte molecules and metal particles. Efforts to perform SERS measurements with the help of sampling devices coated by this method have been successful. In tests, numerous organic and inorganic chemicals were analyzed in several solvents, including water. The results of the tests indicate that the SERS measurements were reproducible within 10 percent and linear over five orders of magnitude. One measure of the limits of detectability of chemicals in these tests was found to be a concentration of 300 parts per billion. Further development may eventually make it possible to realize the full potential sensitivity of SERS for detecting some analytes in quantities as small as a single molecule.

Farquharson, Stuart↗
NASA NTRS2014

Comparison of Martian Surface Radiation Predictions to the Measurements of Mars Science Laboratory Radiation Assessment Detector (MSL/RAD)

For the analysis of radiation risks to astronauts and planning exploratory space missions, detailed knowledge of particle spectra is an important factor. Detailed measurements of the energetic particle radiation environment on the surface of Mars have been made by the Mars Science Laboratory Radiation Assessment Detector (MSL-RAD) on the Curiosity rover since August 2012, and particle fluxes for a wide range of ion species (up to several hundred MeV/u) and high energy neutrons (8 - 1000 MeV) have been available for the first 200 sols. Although the data obtained on the surface of Mars for 200 sols are limited in the narrow energy spectra, the simulation results using the Badhwar-O'Neill galactic cosmic ray (GCR) environment model and the high-charge and energy transport (HZETRN) code are compared to the data. For the nuclear interactions of primary GCR through Mars atmosphere and Curiosity rover, the quantum multiple scattering theory of nuclear fragmentation (QMSFRG) is used, which includes direct knockout, evaporation and nuclear coalescence. Daily atmospheric pressure measurements at Gale Crater by the MSL Rover Environmental Monitoring Station are implemented into transport calculations for describing the daily column depth of atmosphere. Particles impinging on top of the Martian atmosphere reach the RAD after traversing varying depths of atmosphere that depend on the slant angles, and the model accounts for shielding of the RAD by the rest of the instrument. Calculations of stopping particle spectra are in good agreement with the RAD measurements for the first 200 sols by accounting changing heliospheric conditions and atmospheric pressure. Detailed comparisons between model predictions and spectral data of various particle types provide the validation of radiation transport models, and thus increase the accuracy of the predictions of future radiation environments on Mars. These contributions lend support to the understanding of radiation health risks to astronauts for the planning of various mission scenarios.

Kim, Myung-Hee Y.↗
NASA NTRS2014

Noachian Impact Breccias on the Rim of Endeavour Crater, Mars: Opportunity APXS Results

Mars Exploration Rover Opportunity has been investigating the geology of Meridiani Planum since January 2004, and is currently approx. 3830% into its primary mission. Opportunity reached the rim of 22 km diameter Endeavor crater at Spirit Point on the south end of Cape York on sol 2681 and began exploring the geology of Endeavour rim. She left Cape York on sol 3316 and arrived at the next rim remnant to the south, Solander Point, on sol 3387 to begin geological investigations at the contact and up onto Murray Ridge. The Burns fm. of Meridiani Planum lies near the top of the plains-forming unit of western Sinus Meridiani and onlaps onto the Endeavour rim rocks (hereafter rim rocks). Endeavour crater would have excavated approx. 4 km into the existing stratigraphy. Thus, the ejecta that form the rim rocks offer windows into the deeper lithologies of Sinus Meridiani. Here we discuss the polymict breccias of the Shoemaker fm. on Cape York and the breccias from Murray Ridge, with a focus on compositions determined by the Alpha Particle X-Ray Spectrometer (APXS).

Mittlefehldt, D. W.↗
NASA NTRS2008

Performance Testing of Yardney Li-Ion Cells and Batteries in Support of JPL's 2009 Mars Science Laboratory Mission

In 2009, JPL is planning to launch an unmanned rover mission to the planet Mars. This mission, referred to as the Mars Science Laboratory (MSL), will involve the use of a rover that is much larger than the previously developed Spirit and Opportunity Rovers for the 2003 Mars Exploration Rover (MER) mission, that are currently still in operation on the surface of the planet after more than three years. Part of the reason that the MER rovers have operated so successfully, far exceeding the required mission duration of 90 sols, is that they possess robust Li-ion batteries, manufactured by Yardney Technical Products, which have demonstrated excellent life characteristics. Given the excellent performance characteristics displayed, similar lithium-ion batteries have been projected to successfully meet the mission requirements of the up-coming MSL mission. Although comparable in many facets, such as being required to operate over a wide temperature range (-20 to 40 C), the MSL mission has more demanding performance requirements compared to the MER mission, including much longer mission duration (approx. 687 sols vs. 90 sols), higher power capability, and the need to withstand higher temperature excursions. In addition, due to the larger rover size, the MSL mission necessitates the use of a much larger battery to meet the energy, life, and power requirements. In order to determine the viability of meeting these requirements, a number of performance verification tests were performed on 10 Ah Yardney lithium-ion cells (MER design) under MSL-relevant conditions, including mission surface operation simulation testing. In addition, the performance of on-going ground life testing of 10 Ah MER cells and 8-cell batteries will be discussed in the context of capacity loss and impedance growth predictions.

MSL Rover↗
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

Detection of Northern Hemisphere Transient Baroclinic Eddies at Gale Crater Mars

The Rover Environmental Monitoring Station (REMS) on the Mars Science Laboratory’s (MSL) Curiosity rover has been operating in Gale Crater Mars (4.5°S, 137.4°E) for over 2 Mars years. Analysis of its pressure data, which have a precision of approximately 0.2 Pa (see Haberle et al., 2014; Harri et al., 2014), reveal temporal oscillations in its seasonally de-trended daily averaged pressures at some seasons with 2-5 Pa amplitudes that have periods similar to those observed at the Viking Lander 2 (VL-2) site (48.3°N, 134.0°E) several decades ago. As illustrated in Fig 1 there are clear peaks in the variance at a frequency f approximately 0.45 and 0.06 per sol for the fall season of Mars Year (MY) 31, and at f approximately 0.15 and 0.06 per sol for MY 32. These frequencies correspond to periods of 2.2, 6.7, and 16.7 sols, and are very similar to those observed at VL-2 (Fig 2, and see Barnes, 1980). Since orbital imaging data show dust frontal systems associated with eastward traveling baroclinic eddies that occasionally cross the equator (Wang et al., 2003), these findings suggest that MSL may be seeing their signature in its pressure data. To make this case we show that (a) the spectral peaks in the MSL are not only similar to those at VL-2, they have the same seasonal variation, (b) at least for some seasons the peaks are statistically significant and not likely due to random noise in the data, and (c) Global Circulation Model (GCM) results from the Ames GCM support this interpretation.

The Rover Environmental Monitoring Station (REMS)↗
NASA NTRS2016

Winds Measured by the Rover Environmental Monitoring Station (REMS) During the Mars Science Laboratory (MSL) Rover's Bagnold Dunes Campaign and Comparison with Numerical Modeling Using MarsWRF

A high density of REMS wind measurements were collected in three science investigations during MSL's Bagnold Dunes Campaign, which took place over approx. 80 sols around southern winter solstice (Ls approx. 90deg) and constituted the first in situ analysis of the environmental conditions, morphology, structure, and composition of an active dune field on Mars. The Wind Characterization Investigation was designed to fully characterize the near-surface wind field just outside the dunes and confirmed the primarily upslope/downslope flow expected from theory and modeling of the circulation on the slopes of Aeolis Mons in this season. The basic pattern of winds is 'upslope' (from the northwest, heading up Aeolis Mons) during the daytime (approx. 09:00-17:00 or 18:00) and 'downslope' (from the southeast, heading down Aeolis Mons) at night (approx. 20:00 to some time before 08:00). Between these times the wind rotates largely clockwise, giving generally westerly winds mid-morning and easterly winds in the early evening. The timings of these direction changes are relatively consistent from sol to sol; however, the wind direction and speed at any given time shows considerable intersol variability. This pattern and timing is similar to predictions from the MarsWRF numerical model, run at a resolution of approx. 490 m in this region, although the model predicts the upslope winds to have a stronger component from the E than the W, misses a wind speed peak at approx. 09:00, and under-predicts the strength of daytime wind speeds by approx. 2-4 m/s. The Namib Dune Lee Investigation reveals 'blocking' of northerly winds by the dune, leaving primarily a westerly component to the daytime winds, and also shows a broadening of the 1 Hz wind speed distribution likely associated with lee turbulence. The Namib Dune Side Investigation measured primarily daytime winds at the side of the same dune, in support of aeolian change detection experiments designed to put limits on the saltation threshold, and also appears to show the influence of the dune body on the local flow, though less clearly than in the lee. Using a vertical grid with lower resolution near the surface reduces the relative strength of nighttime winds predicted by MarsWRF and produces a peak in wind speed at approx. 09:00, improving the match to the observed diurnal variation of wind speed, albeit with an offset in magnitude. The annual wind field predicted using this grid also provides a far better match to observations of aeolian dune morphology and motion in the Bagnold Dunes. However, the lower overall wind speeds than observed and disagreement with the observed wind direction at approx. 09:00 suggest that the problem has not been solved and that alternative boundary layer mixing schemes should be explored which may result in more mixing of momentum down to the near-surface from higher layers. These results demonstrate a strong need for in situ wind data to constrain the setup and assumptions used in numerical models, so that they may be used with more confidence to predict the circulation at other times and locations on Mars.

Newman, Claire E.↗
NASA NTRS2018

Age of Martian Air: Time Scales for Martian Atmospheric Transport

The mean time since air in the Martian atmosphere was in the low-latitude boundary layer is examined using simulations of an idealized “mean age” tracer with the MarsWRF general circulation model. The spatial distribution and seasonality of the mean age in low- and mid-latitudes broadly follow contours of the mean meridional circulation, with the mean age increasing from 0 at the surface to a maximum of 60–100 sols in the upper atmosphere. Substantially older mean ages (exceeding 300 sols) are found in polar regions, with oldest ages in the lower atmosphere (10–100 Pa), above a near-surface layer with very young ages (around 20 sols). The annual maximum ages occur around the equinoxes, and the age in the polar lower atmosphere decreases during the autumn to winter transition. This autumn-winter decrease in age occurs because of mixing of polar and mid-latitude air when the polar vortex exhibits an annulus of high potential vorticity (PV) with a local minimum near the pole. There is no autumn-winter decrease and old ages persist throughout autumn and winter in simulations with CO2 phase changes disabled, and thus no latent heating, where there is a monopolar vortex (i.e., a monotonic increase in PV from equator to pole) forms. The altitudinal and seasonal variations in the mean age indicates similar variations in the transport of dust into polar regions and the mixing of polar air (with, e.g., low water vapor and high ozone concentrations during winter) into mid-latitudes.

Waugh, D. W.↗
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 NTRSDate not supplied

An Overview of SHERLOC Raman and Fluorescence Spectroscopy Results Obtained During Perseverance’s Green Zone Campaign at Jezero Crater, Mars

The Perseverance rover landed in Jezero crater, Mars, in February 2021. The field site was chosen because orbiter data provided evidence that the crater hosted an ancient (>2.7 Ga) fluvio-lacustrine environment. The Octavia E. Butler landing site is located ~1.9 km east of the erosional remnant of the Jezero river delta. Scanning Habitable Environments with Raman and Luminescence for Organics and Chemicals (SHERLOC) is an arm-mounted instrument that combines fluorescence and Raman spectroscopy with microscopic imaging to analyze geological materials in order to better understand the history of the environments recorded in the rocks within Jezero crater and to search for potential biosignatures. SHERLOC has two microscopic cameras, the Autofocus and Context Imager (ACI) and the Wide-Angle Topographic Sensor for Operations and eNgineering, (WATSON). These subsystems obtain high spatial resolution (10.1–100 µm/pixel) images to identify grain-scale structure and texture. SHERLOC spectroscopy enables high-sensitivity detection, characterization, and spatially-resolved correlation of trace organic materials. SHERLOC’s 248.6 nm deep UV laser generates a 100 µm-diameter spot. Photons generated by Raman scattering and fluorescence emission are collected and the spectra are downlinked to Earth for analysis. Knowledge of where the laser is pointed allows for mineral and compositional maps to be generated and overlain in ACI and WATSON images. Early spectroscopy observations focused on natural rock surfaces at targets named Nataani (sol 83), Bi_la_sana (sol 98) and Foux (sol 141). These surfaces included patches of aeolian dust that had settled upon the rocks. Perseverance’s abrasion tool is expected to become available in August 2021; it will grind to depths of 14 mm to remove dust and penetrate coatings and weathering rinds. This presentation will summarize major results from analysis of the rocks examined by SHERLOC during Perseverance’s first science and sample coring campaign (Green Zone Campaign).

Luther W Beegle↗
NASA NTRSDate not supplied

Calibration and Validation of the SHERLOC Instrument Operating in Jezero Crater, Mars

The Scanning Habitable Environments with Raman and Luminescence for Organics and Chemistry (SHERLOC) is an instrument onboard the Mars 2020 Perseverance rover. It consists of a spectrometer that measures deep ultraviolet (DUV) resonance Raman and native fluorescence photons generated through surface interactions with a 248.6 nm pulsed laser. Two microscopic imagers, the Autofocus Context Imager (ACI) and the Wide-Angle Topographic Sensor for Operations and eNgineering (WATSON), provide high-resolution context images of SHERLOC targets. The ACI is co-boresighted with the spectrometer. To ensure proper calibration, the SHERLOC calibration target (SCT) is mounted on the front of the rover and consists of ten different materials. The SCT was designed, fabricated, assembled, and tested by Jacobs Technology, Inc., and NASA Johnson Space Center. The dimensions of the calibration target housing are 150 x 89 x 33 mm and it weighs ~437 g. The ten targets are arranged in two rows; the first six are hard targets (AlGaN for Raman and fluorescence, diffuse transmission target, a slice of the SaU008 Mars meteorite, an intensity maze, and polycarbonate over geocache coin) and the remaining four are soft-goods targets (Vectran, Ortho-Fabric, Teflon, and nGimat-coated Teflon). The hard targets calibrate the spectrometer’s Raman and fluorescence spectral accuracy, ambient light reflection, and Raman response curve, while the soft-goods targets are spacesuit materials that function as human exploration targets, some of which are also used for spectral calibration. SHERLOC also has an internal calibration target consisting of AlGaN on sapphire (275 nm) located inside the ACI opaque dust cover to ensure proper instrument functioning between calibration target analyses. Initial SHERLOC, ACI, and WATSON calibration and validation on Mars was performed using the internal calibration target on sols 59, 83, 98, and 141; WATSON imaging of the SCT on sols 26 and 62, and SHERLOC spectroscopy and ACI imaging of the SCT on sol 59. These early data provide initial insights into instrument performance and the stability and degradation of the calibration target materials relative to the Martian surface and dust environment. Early observations also have implications for future astronaut spacesuit materials.

Trevor G Graff↗