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All sourcesNASA NTRSDOE OSTI
NASA NTRS1986

Evidence for a complex archean deformational history; southwestern Michipicoten Greenstone Belt, Ontario

The Michipicoten Greenstone Belt extends for about 150 km ENE from the northeastern angle of Lake Superior. In common with many other Archean greenstone belts, it is characterized by generally steep bedding dips and a distribution of major lithologic types suggesting a crudely synclinal structure for the belt as a whole. Detailed mapping and determination of structural sequence demonstrates that the structure is much more complex. The Archean history of the belt includes formation of at least three regionally significant cleavages, kilometer-scale overturning, extensive shearing, and diabase intrusion. Most well defined, mappable 'packages' of sedimentary rocks appear to be bounded by faults. These faults were active relatively early in the structural history of the belt, when extensive overturning also occurred. Steepening of dips, NW-SE shortening, development of steep NE cleavage, and pervasive shearing all postdate the early faulting and the regional overturning, obscuring much of the detail needed to define the geometry of the earlier structures. The results obtained so far suggest, however, that the Michipicoten Greenstone Belt underwent an early stage of thrusting and associated isoclinal folding, probably in a convergent tectonic environment.

Mcgill, George E.↗
NASA NTRS2014

ALMA Observations of α Centauri First Detection of Main-Sequence Stars at 3 mm Wavelength

The precise mechanisms that provide the non-radiative energy for heating the chromosphere and the corona of the Sun and those of other stars constitute an active field of research. By studying stellar chromospheres one aims at identifying the relevant physical processes. Defining the permittable extent of the parameter space can also serve as a template for the Sun-as-a-star. This feedback will probably also help identify stars that potentially host planetary systems that are reminiscent of our own. Earlier observations with Herschel and APEX have revealed the temperature minimum of Alpha Cen, but these were unable to spatially resolve the binary into individual components. With the data reported in this Letter, we aim at remedying this shortcoming. Furthermore, these earlier data were limited to the wavelength region between 100 and 870 um. In the present context, we intend to extend the spectral mapping (SED) to longer wavelengths, where the contrast between stellar photospheric and chromospheric emission becomes increasingly evident. The Atacama Large Millimeter submillimeter Array (ALMA) is particularly suited to point sources, such as unresolved stars. ALMA provides the means to achieve our objectives with both its high sensitivity of the collecting area for the detection of weak signals and the high spatial resolving power of its adaptable interferometer for imaging close multiple stars. This is the first detection of main-sequence stars at a wavelength of 3 mm. Furthermore, the individual components of the binary Alpha CenAB are clearly detected and spatially well resolved at all ALMA wavelengths. The high signal-to-noise ratios of these data permit accurate determination of their relative flux ratios, i.e., S(sub y(sup B)) / S(sub y(sup A))> = 0.54 +/- 0.04 at 440 μm, = 0.46 +/- 0.01 at 870 μm, and = 0.47 +/- 0.006 at 3.1 mm, respectively.. The previously obtained flux ratio of 0.44+/-0.18, which was based on measurements in the optical and at 70 μm, is consistent with the present ALMA results, albeit with a large error bar. The observed 3.1 mm emission greatly exceeds what is predicted from the stellar photospheres, and undoubtedly arises predominantly as free-free emission in the ionized chromospheric plasmas of both stars. Given the distinct difference in their cyclic activity, the similarity of their submm SEDs appears surprising.

Herschel↗
NASA NTRSDate not supplied

Mars 2020 – Landing a 1-ton rover and helicopter in an ancient Martian Lake

The Mars 2020 spacecraft launched in July 2020 and landed the Perseverance rover and Ingenuity helicopter successfully in Jezero crater on Feb. 18, 2021. Mars 2020 is the first stage of the Mars Sample Return campaign that will bring back the first samples from another planet to Earth. The entry, descent, and landing (EDL) sequence of the Mars 2020 spacecraft largely leveraged the previous Mars Science Laboratory (MSL) mission from 2012. Mars 2020 retained most of the EDL sequences of MSL, including active maneuvering during hypersonic flight to accurately target the landing site and use of the Skycrane descent stage that slowly lowered the rover while hovering above the ground. But Mars 2020 also added Terrain Relative Navigation, a machine vision-based system that allowed the spacecraft to navigate using an on-board camera that mapped ground landmarks to an on-board map, allowing the spacecraft to safely land in locations that were too hazardous for any previous Martian mission. Come hear about the “Seven Minutes of Terror” and the eight years of effort that went into the engineering behind the spacecraft.

Soumyo Dutta↗
NASA NTRS2003

Snow and Ice Products from the Moderate Resolution Imaging Spectroradiometer

Snow and sea ice products, derived from the Moderate Resolution Imaging Spectroradiometer (MODIS) instrument, flown on the Terra and Aqua satellites, are or will be available through the National Snow and Ice Data Center Distributed Active Archive Center (DAAC). The algorithms that produce the products are automated, thus providing a consistent global data set that is suitable for climate studies. The suite of MODIS snow products begins with a 500-m resolution, 2330-km swath snow-cover map that is then projected onto a sinusoidal grid to produce daily and 8-day composite tile products. The sequence proceeds to daily and 8-day composite climate-modeling grid (CMG) products at 0.05 resolution. A daily snow albedo product will be available in early 2003 as a beta test product. The sequence of sea ice products begins with a swath product at 1-km resolution that provides sea ice extent and ice-surface temperature (IST). The sea ice swath products are then mapped onto the Lambert azimuthal equal area or EASE-Grid projection to create a daily and 8-day composite sea ice tile product, also at 1 -km resolution. Climate-Modeling Grid (CMG) sea ice products in the EASE-Grid projection at 4-km resolution are planned for early 2003.

Hall, Dorothy K.↗
NASA NTRS1988

Doppler imaging of AR Lacertae at three epochs

Observations from IUE were used to study the structure of the lower chromosphere of AR Lacertae in the light of Mg II k. Sequences of LWR/P-HI images distributed around the binary period at three epochs were obtained. Discrete plage-like regions of enhanced Mg II surface flux in this system are identified. There are temporal variations in the Mg II flux on timescales of hours as well as substantial changes in chromospheric morphology on timescales of years. Even with the limited S/N attainable with the IUE, one can map the gross structures of active stellar atmospheres. With such information, one can begin to study the true 3-D structure of the atmospheres of late-type stars.

Walter, Frederick M.↗
NASA NTRS1989

Space Shuttle to deploy Magellan planetary science mission

The objectives of Space Shuttle Mission STS-30 are described along with major flight activities, prelaunch and launch operations, trajectory sequence of events, and landing and post-landing operations. The primary objective of STS-30 is to successfully deploy the Magellan spacecraft into low earth orbit. Following deployment, Magellan will be propelled to its Venus trajectory by an Inertial Upper Stage booster. The objectives of the Magellan mission are to obtain radar images of more than 70 percent of Venus' surface, a near-global topographic map, and near-global gravity field data. Secondary STS-30 payloads include the Fluids Experiment Apparatus (FEA) and the Mesoscale Lightning Experiment (MLE).

Source record↗
NASA NTRS2012

Decorrelation Times of Photospheric Fields and Flows

We use autocorrelation to investigate evolution in flow fields inferred by applying Fourier Local Correlation Tracking (FLCT) to a sequence of high-resolution (0.3 "), high-cadence (approx = 2 min) line-of-sight magnetograms of NOAA active region (AR) 10930 recorded by the Narrowband Filter Imager (NFI) of the Solar Optical Telescope (SOT) aboard the Hinode satellite over 12 - 13 December 2006. To baseline the timescales of flow evolution, we also autocorrelated the magnetograms, at several spatial binnings, to characterize the lifetimes of active region magnetic structures versus spatial scale. Autocorrelation of flow maps can be used to optimize tracking parameters, to understand tracking algorithms f susceptibility to noise, and to estimate flow lifetimes. Tracking parameters varied include: time interval Delta t between magnetogram pairs tracked, spatial binning applied to the magnetograms, and windowing parameter sigma used in FLCT. Flow structures vary over a range of spatial and temporal scales (including unresolved scales), so tracked flows represent a local average of the flow over a particular range of space and time. We define flow lifetime to be the flow decorrelation time, tau . For Delta t > tau, tracking results represent the average velocity over one or more flow lifetimes. We analyze lifetimes of flow components, divergences, and curls as functions of magnetic field strength and spatial scale. We find a significant trend of increasing lifetimes of flow components, divergences, and curls with field strength, consistent with Lorentz forces partially governing flows in the active photosphere, as well as strong trends of increasing flow lifetime and decreasing magnitudes with increases in both spatial scale and Delta t.

Welsch, B. T.↗
NASA NTRS2000

Autonomy Architectures for a Constellation of Spacecraft

Until the past few years, missions typically involved fairly large expensive spacecraft. Such missions have primarily favored using older proven technologies over more recently developed ones, and humans controlled spacecraft by manually generating detailed command sequences with low-level tools and then transmitting the sequences for subsequent execution on a spacecraft controller. This approach toward controlling a spacecraft has worked spectacularly on previous missions, but it has limitations deriving from communications restrictions - scheduling time to communicate with a particular spacecraft involves competing with other projects due to the limited number of deep space network antennae. This implies that a spacecraft can spend a long time just waiting whenever a command sequence fails. This is one reason why the New Millennium program has an objective to migrate parts of mission control tasks onboard a spacecraft to reduce wait time by making spacecraft more robust. The migrated software is called a "remote agent" and has 4 components: a mission manager to generate the high level goals, a planner/scheduler to turn goals into activities while reasoning about future expected situations, an executive/diagnostics engine to initiate and maintain activities while interpreting sensed events by reasoning about past and present situations, and a conventional real-time subsystem to interface with the spacecraft to implement an activity's primitive actions. In addition to needing remote planning and execution for isolated spacecraft, a trend toward multiple-spacecraft missions points to the need for remote distributed planning and execution. The past few years have seen missions with growing numbers of probes. Pathfinder has its rover (Sojourner), Cassini has its lander (Huygens), and the New Millenium Deep Space 3 (DS3) proposal involves a constellation of 3 spacecraft for interferometric mapping. This trend is expected to continue to progressively larger fleets. For example, one mission proposed to succeed DS3 would have 18 spacecraft flying in formation in order to detect earth-sized planets orbiting other stars. A proposed magnetospheric constellation would involve 5 to 500 spacecraft in Earth orbit to measure global phenomena within the magnetosphere. This work describes and compares three autonomy architectures for a system that continuously plans to control a fleet of spacecraft using collective mission goals instead of goals or command sequences for each spacecraft. A fleet of self-commanding spacecraft would autonomously coordinate itself to satisfy high level science and engineering goals in a changing partially-understood environment making feasible the operation of tens or even a hundred spacecraft (such as for interferometry or plasma physics missions). The easiest way to adapt autonomous spacecraft research to controlling constellations involves treating the constellation as a single spacecraft. Here one spacecraft directly controls the others as if they were connected. The controlling "master" spacecraft performs all autonomy reasoning, and the slaves only have real-time subsystems to execute the master's commands and transmit local telemetry/observations. The executive/diagnostics module starts actions and the master's real-time subsystem controls the action either locally or remotely through a slave. While the master/slave approach benefits from conceptual simplicity, it relies on an assumption that the master spacecraft's executive can continuously monitor the slaves' real-time subsystems, and this relies on high-bandwidth highly-reliable communications. Since unintended results occur fairly rarely, one way to relax the bandwidth requirements involves only monitoring unexpected events in spacecraft. Unfortunately, this disables the ability to monitor for unexpected events between spacecraft and leads to a host of coordination problems among the slaves. Also, failures in the communications system can result in losing slaves. The other two architectures improve robustness while reducing communications by progressively distributing more of the other three remote agent components across the constellation. In a teamwork architecture, all spacecraft have executives and real-time subsystems - only the leader has the planner/scheduler and mission manager. Finally, distributing all remote agent components leads to a peer-to-peer approach toward constellation control.

Barrett, Anthony↗
NASA NTRS2008

Geology of Holden Crater and the Holden and Ladon Multi-Ring Impact Basins, Margaritifer Terra, Mars

Geologic mapping at 1:500K scale of Mars quads 15s027, 20s027, 25s027, and 25s032 (Fig. 1) is in progress to constrain the geologic and geomorphic history of southwestern Margaritifer Terra. This work builds on earlier maps at 1:5M [1] and 1:15M scales [2], recent to concurrent 1:500Kscale mapping of adjacent areas to the east [3-5], and studies of drainage basin evolution along the Uzboi-Ladon-M (ULM; the third valley in the sequence has no formal name) Valles basin overflow system and nearby watersheds [6-9]. Two of the six landing sites under consideration for the Mars Science Laboratory rover are in this map area, targeting finely layered, phyllosilicate-rich strata and alluvial fans in Holden crater [10-12] (26degS, 34degW, 150 km diameter) or deposits southeast of a likely delta in Eberswalde crater [13-16] (24degS, 33degW, 50 km in diameter). Diverse processes including larger and smaller impacts, a wide range in fluvial activity, and local to regional structural influences have all affected the surface morphology.

Irwin, R. P., III↗
NASA NTRS1986

Barberton greenstone belt volcanism: Succession, style and petrogenesis

The Barberton Mountain Land is an early Archean greenstone belt along the eastern margin of the Kaapvaal Craton of southern Africa. Detailed mapping in the southern portion of the belt leads to the conclusion that a substantial thickness is due to original deposition of volcanics and sediments. In the area mapped, a minimum thickness of 12km of predominantly mafic and ultramafic volcanics comprise the Komati, Hooggenoeg, and Kromberg Formations of the Onverwacht Group, and at least one km of predominantly pyroclastic and epiclastic sediments derived from dacitic volcanics comprise the Fig Tree Group. The Barberton greenstone belt formed primarily by ultramafic to mafic volcanism on a shallow marine platform which underwent little or no concurrent extension. Vents for this igneous activity were probably of the non-constructional fissure type. Dacitic volcanism occurred throughout the sequence in minor amounts. Large, constructional vent complexes were formed, and explosive eruptions widely dispersed pyroclastic debris. Only in the final stages of evolution of the belt did significant thrust-faulting occur, generally after, though perhaps overlapping with, the final stage of dacitic igneous activity. A discussion follows.

Byerly, G. R.↗
NASA NTRSDate not supplied

Does Collection Time Bias the Ecology of Cleanroom Air Samples?

Microbial monitoring of astromaterials collections has taken on increased importance with the return of biologically sensitive samples from the asteroids Ryugu and Bennu and the initiation of the Mars Sample Return Program. Terrestrial bacteria and fungi can alter the mineralogy and organic composition of our collections causing irreversible contamination of pristine samples and increasing the risk of false positives for life detection measurements. NASA has conducted routine microbial monitoring of its existing collections since 20181. Initial monitoring focused on surface samples collected with foam swabs. Although, airborne microbiology is often decoupled from surface microbiology in the built environment2 culture-based air sampling techniques like impactors were not compliant with existing contamination control requirements. Bringing organic rich media, gelatin or liquids into curation cleanrooms presents an unacceptable risk to pristine samples. In 2022 NASA purchased a materials complaint air sampler and began collecting air samples from the cleanrooms in addition to surface samples3. The new instrument uses an electret filter to collect samples that are suitable for cultivating organisms or for direct DNA sequencing. Preliminary DNA sequencing results appeared to indicate that longer sampling times biased the microbial community in favor of hearty, spore-forming bacteria3. We present the results of a study comparing overnight sampling (17 hours) to short (1 hour) sampling of unoccupied curation cleanrooms. The results will help us optimize our monitoring protocols and develop a more detailed inventory of the ecology of astromaterials curation cleanrooms. Methods: We analyzed 72 paired air samples from six different cleanrooms including the meteorite processing lab (ISO 7 equivalent, 16 samples), the lunar lab (ISO 6 equivalent, 10 samples), the stardust lab (ISO 5 equivalent 14 samples), the OSIRIS-REx lab (ISO 5 equivalent, 12 samples), the Hayabusa2 lab (ISO 5 equivalent, 14 samples), and the Genesis lab (ISO 4 equivalent, 6 samples). All the samples were collected with an InnovaPrep Bobcat air sampler operating at a sampling rate of 200 L/min. The sampler operates for 5 minutes out of every 20 minute period. Half of the samples were collected by filtering 3,000L (15 min. of active sampling) of air across an electret filter for one hour. The rest of the samples were collected by filtering approximately 51,000 L air across the filter overnight (~17 hours, 255 min. of active sampling). Cells were eluted from the filter using 6-7 ml of pressurized 0.15% tween 20 in PBS (phosphate buffered saline). This liquid was used to cultivate bacteria according to previously published methods1,4,5 and for DNA extraction and next generation sequencing. DNA was extracted with a Qiagen MagAttract PowerMicrobiome kit6. To identify bacteria and archaea, the 16S rRNA gene was amplified using Earth Microbiome primers for the V4 region 7. The amplified DNA was sequenced on an Illumina MiSeq using a V3 reagent kit. The resulting sequences were processed using DADA2 and QIIME2 as implemented on the EDGE bioinformatics platform8–10. Results: Only two of the 72 samples had no amplifiable DNA. Amplified DNA concentrations ranged from 2.67 – 0.272 ng/µl. The median concentration of amplified DNA for the 1 hour samples was 0.770 ± 0.368 ng/µl. The median concentration of amplified DNA for the overnight samples was 0.877 ± 0.434 ng/µl. On average the overnight samples had slightly more sequences (58,960 vs. 59,456) and ASV’s (amplicon sequence variants) (60 vs 64.5) than the one hour samples, but these differences are not statistically significant. The most abundant ASV in every sample mapped to the genus Cupravidus. ASV’s mapping to the genuses Bacillus, Schlegelella, Thermus, and Staphylococcus were also common. Discussion and Future Work: Alpha diversity statistics like Shannon Entropy and Faith Phylogenetic Diversity are used to describe the diversity of organisms in a single sample. If a longer sampling time was biasing the data, we would expect to see a change in these diversity statistics vs. sample time. However, we did not observe this in our data. The median Shannon entropy was slightly higher for the overnight samples (3.773 vs 3.611) as was the Faith Phylogenetic Diversity (4.042 vs 3.596), but both values were within a standard deviation of each other for the two sampling times (Fig. 1). It is unlikely, that the longer sampling time is introducing bias into our data. We do observe a significant decrease in diversity when comparing the air samples by lab. The Genesis lab (ISO 4 equivalent) has a lower median number of ASV’s (45.5) than the other labs (62). Median values for Shannon Entropy (3.717 vs. 3.430) and Faith Phylogenetic Diversity (3.796 vs. 3.548) are also lower for Genesis, but those values are with one standard deviation of each other for the different sampling times. This is consistent with previous culture-based results suggesting that the environment in cleanrooms tends to select for a core group of organisms capable of surviving under dry, low nutrient, conditions. The presence of the ASV’s mapping to Cupravidus and Thermus in our sequencing blanks and controls suggests that several of the most common organisms in our samples represent contaminants from the reagents used to perform the DNA extractions and sequencing. Further work is needed to identify these contaminants, remove them from our data and recalculate the diversity statistics. This is a systematic error. Therefore, we do not expect removing the sequencing contaminants to change our conclusions. Longer air sample collection times appear to result in slightly higher diversity and do not bias the results towards “hardy” bacteria like spore-formers. Based on these preliminary results we conclude that sampling at least 3,000 liters of air is sufficient to capture the microbial diversity of cleanrooms, and that air samples can also be collected overnight without negatively impacting diversity. These results allow us to be flexible when designing microbial monitoring plans so that they do not interfere with routine lab activity. References: 1. Regberg, A. B. et al. 49th Lunar and Planetary Science Conference (2018). 2. The United States Pharmacopeial Convention. USP General Chapter <1116> (2013). 3. Regberg, A. B., et al. 54th Lunar and Planetary Science Conference (2023). 4. Regberg, A. B. et al. 53rd Lunar and Planetary Science Conference ( 2022). 5. Davis, R. E.,et al. 50th Lunar and Planetary Science Conference (2019). 6. Qiagen. MagAttract® PowerMicrobiome® DNA/RNA EP Kit Handbook. (2018). 7. Walters, W. et al. mSystems 1, (2015). 8. Callahan, B. J. et al. Nat. Methods 13, 581–583 (2016). 9. Hall, M. & Beiko, R. G. Microbiome Analysis: Methods and Protocols113–129 (Springer, 2018). 10. Philipson, C. et al. Bio-Protoc. 7, e2622 (2017).

A. B. Regberg↗
NASA NTRS2004

Phylogenetic and physiological diversity of microorganisms isolated from a deep greenland glacier ice core

We studied a sample from the GISP 2 (Greenland Ice Sheet Project) ice core to determine the diversity and survival of microorganisms trapped in the ice at least 120,000 years ago. Previously, we examined the phylogenetic relationships among 16S ribosomal DNA (rDNA) sequences in a clone library obtained by PCR amplification from genomic DNA extracted from anaerobic enrichments. Here we report the isolation of nearly 800 aerobic organisms that were grouped by morphology and amplified rDNA restriction analysis patterns to select isolates for further study. The phylogenetic analyses of 56 representative rDNA sequences showed that the isolates belonged to four major phylogenetic groups: the high-G+C gram-positives, low-G+C gram-positives, Proteobacteria, and the Cytophaga-Flavobacterium-Bacteroides group. The most abundant and diverse isolates were within the high-G+C gram-positive cluster that had not been represented in the clone library. The Jukes-Cantor evolutionary distance matrix results suggested that at least 7 isolates represent new species within characterized genera and that 49 are different strains of known species. The isolates were further categorized based on the isolation conditions, temperature range for growth, enzyme activity, antibiotic resistance, presence of plasmids, and strain-specific genomic variations. A significant observation with implications for the development of novel and more effective cultivation methods was that preliminary incubation in anaerobic and aerobic liquid prior to plating on agar media greatly increased the recovery of CFU from the ice core sample.

Bacteria/classification/genetics/isolation & purif↗
NASA NTRSDate not supplied

Evidence for Early Extension and Pressure Drop Related to Magma Plumbing in Noctis Labyrinthus (Mars)

Noctis Labyrinthus is a complex district located between the western side of Valles Marineris’ large outflow channel and the Tharsis volcanic plateau. This region is characterized by a system of steep-walled canyons and an inter-connected network of scalloped pits that manifest in various orientations and size. The formation history of this area has been a topic of substantial discussion in the past. Previous studies have proposed a karst landscape with associated caves and water-related processes [1,2,3] a network of lava tubes [4,5], or a volcano-tectonic activity as a driving process for the formation of Noctis Labyrinthus [6,7,8,9]. However, none of these models have been confirmed or entirely accepted; although, the erosional nature of Noctis Labyrinthus is supported by the presence of channelized lava flows still visible on its floor [5]. In this work, we use MOLA and HRSC data to produce a new structural map of the region, we analyse fault systems (chronology and orientation), the relationships between faults and pit chains, and we finally propose a deformational model that can explain the sequences of events responsible about the formation of Noctis Labyrinthus.

M. El Yazidi↗
NASA NTRS1973

Mapping of the major structures of the African rift system

The author has identified the following significant results. ERTS-1 imagery of the African rift system has already proved of great value in structural geological studies. One of the interesting megastructures expressed on the imagery occurs some 40 km east of the eastern margin of the main Ethiopian rift, in Arussi province, and extending between latitude 71/2 and 81/4 deg N. The Badda-Encuolo ridge proves to have been a line of major Tertiary volcanism and probably supplied the thick Trap Series flood basalt sequence exposed farther east in the canyons of the Webi Shebeli drainage system. The ridge itself was built up by the waning activity of the Sagatu line of volcanism. Serendipitious has been the discovery on Mt. Badda of several deeply glaciated valleys, many of which show clearly on the ERTS-1 imagery. It seems that Mt. Badda was one of the most important glacial centers in eastern Africa during the Pleistocene. Three major late-Tertiary trachytic centers lie between the Badda-Encuolo ridge and the rift valley. The relationships of these three volcanoes to each other and to the rift faulting is revealed for the first time by the ERTS-1 imagery, as is the form of the cladera of Baltata and the crater of Chilalo.

Mohr, P. A.↗
NASA NTRS1993

Degradation of selected terrestrial and Martian impact craters

The history of degradation of 50,000-yr-old 1.2-km-diam Meteor Crater in Arizona is defined using field mapping, and the degradation states of the progressively more degraded 68,000-yr-old 1.8-km-diam Lonar Crater in Indiana and 0.5-3.0 Myr old 1.75-km-diam Talemzane Crater in Algeria are assessed using air photos. The results on these terrestrial craters are then compared with the gradational morphology associated with craters in southern Ismenius Lacus on Mars, in order to develop first-order constraints on gradational activity. Common degradation signatures associated with craters on both planets are described. These signatures are used to assemble a first-order degradational sequence for the terrestrial craters that is then compared with the Martian degradational signatures to infer past processes and climate.

Grant, John A.↗
NASA NTRS2010

Role of the Russell-McPherron Effect in the Acceleration of Relativistic Electrons

While it is well known that high fluxes of relativistic electrons in the Earth's radiation belts are associated with high-speed solar wind and its heightened geoeffectiveness,less known is the fact that the Russell McPherron(R M) effect strongly controls whether or not a given high-speed stream is geoffective. To test whether it then follows that the R M effect also strongly controls fluxes of relativistic electrons, we perform a superposed epoch analysis across corotating interaction regions (CIR) keyed on the interfaces between slow and fast wind. A total of 394 stream interfaces were identified in the years 1994-2006. Equinoctial interfaces were separated into four classes based on the R-M effect,that is, whether the solar wind on either side of the interface was either(geo)effective (E) or ineffective (I) depending on season and the polarity of the interplanetary magnetic field (IMF). Four classes of interface identified as II, IE, EI,and EE are possible. The classes IE and EI correspond to CIRs with polarity changes indicating passage through the heliospheric current sheet. To characterize the behavior of solar wind and magnetospheric variables, we produced maps of dynamic cumulative probability distribution functions (cdfs) as a function of time over 10-day intervals centered on the interfaces. These reveal that effective high-speed streams have geomagnetic activity nearly twice as strong as ineffective streams and electron fluxes a factor of 12 higher. In addition they show that an effective low-speed stream increases the flux of relativistic electrons before the interface so that an effective to ineffective transition results in lower fluxes after the interface.We conclude that the R-M effect plays a major role in organizing and sustaining a sequence of physical processes responsible for the acceleration of relativistic electrons.

McPherron, R. L.↗
NASA NTRS1993

Chocolate tablet aspects of cytherean Meshkenet Tessera

Meshkenet Tessera structures were mapped from Magellan data and several resemblances to chocolate tablet boudinage were found. The complex fault sets display polyphase tectonic sequences of a few main deformation phases. Shear and tension have contributed to the areal deformation. Main faults cut the 1600-km long Meshkenet Tessera highland into bar-like blocks which have ridge and groove pattern oriented along or at high angles to the faults. The first approach to the surface block deformation is an assumption of initial parallel shear faulting followed by a chocolate tablet boudinage. Major faults which cut Meshkenet Tessera into rectangular blocks have been active repetitively while two progressive or superposed boudinage set formations have taken place at high angles during the relaxational or flattening type deformation of the area. Chocolate tablet boudinage is caused by a layer-parallel two-dimensional extension resulting in fracturing of the competent layer. Such structures, defined by two sets of boudin neck lines at right angles to each other, have been described by a number of authors. They develop in a flattening type of bulk deformation or during superposed deformation where the rock is elongated in two dimensions parallel to the surface. This is an attempt to describe and understand the formation and development of structures of Meshkenet Tessera which has complicated fault structures.

Raitala, J.↗
NASA NTRS2022

Simulating Mars: Enabling Testing of the Perseverance Rover Sampling and Caching Subsystem on Earth

The development of the Sampling and Caching Subsystem (SCS) on the JPL Perseverance Rover lies at the intersection of testing, robotics, and geology. The SCS team established three primary system test campaigns and venues to aid in the development of SCS through verification and validation testing – Qualification Model Dirty Testing (QMDT) to provide a venue for testing in a Martian environment, Vehicle System Testbed (VSTB) for testing while integrated with the mobility subsystem on Martian-like terrain, and the Flight Software Testbed (FSWTB) for conducting tests using the flight motor controllers and software system on a hexapod which had the ability to simulate rover tilt. Each venue contributed a vital piece to the SCS building blocks. However, the QMDT venue operating within a 10-ft diameter Thermal Vacuum chamber to simulate Martian environment provided a sui generis opportunity to fine tune the entire sampling and caching process while building the team’s knowledge base about rock drillability, system life, and target selection. On Earth, because Martian rocks are not readily available, the development team must utilize geoanalogs to the rocks and regolith on Mars. Geologists on the team helped establish a set of standard rock types to use for Mars missions, like Basalt, Sandstone, Mudstone, Gypsum, and other related geoanalogs. These geoanalogs are characterized with a standard suite of tests for density, compressibility, and other characteristics to categorize potential drillability. This concept of drillability is what links the geoanalogs on Earth to the samples we collect on Mars. With the simulant characteristics defined, these geoanalog rocks are ready to be drilled into as we do on the Martian surface. A key aspect of interacting with the surface on Mars is rock target identification and selection. The Perseverance robotic system uses the on-board cameras, instrumentation, and software to collect enough information to identify potential scientific targets. With the targets identified, SCS can place the Corer and abrade the surface or collect a sample. For a ground test activity like QMDT, the test team did not have all of the camera and instrumentation systems that the rover does, so the team developed ground test equivalents to process a rock, build a target map, and define the target. The team constructed a Rock Scanning Station to build a 3D point cloud of the rock. This point cloud was then processed and evaluated with predefined and programmed criteria in a Target Downselect Tool. A primary output of the Target Downselect Tool is a defined target that can be uploaded directly to the robotic software system to simulate and build the robotic sequences used in tests. With these insights and programmatic definition of targets, the QMDT test team was able to make the same decisions that the Perseverance surface operations team does. In addition, valuable lessons learned from developing the target selection ground tools and using them were implemented into the tools used for surface operations.

Kim, Junggon↗