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NASA NTRSDate not supplied

Is LaTeX Use Correlated with the Number of Equations in a Manuscript?

Astronomers often use LaTeX to compose and submit paper manuscripts (1), but its adoption is not universal. Some journals prefer Word submissions, and large organizations with standardized software loads may also pressure their scientists to use Word. Furthermore, text and table transcription has been shown to be more efficient with Word than with LaTeX (2). LaTeX is most favored by fields that are mathematically intensive (1). While Knauff and Nejasmic (2) found Word to be similarly efficient in transcribing equations, users reported greater enjoyment of LaTeX. We suspect that Word may therefore influence its users to include fewer equations, but this underlying hypothesis is not easily tested. We test the hypothesis that manuscripts submitted to the arXiV in LaTeX format have more equations on average than those submitted in PDF format only.

Althea V Moorhead↗
NASA NTRS2021

Challenges in predicting Greenland supraglacial lake drainages at the regional scale

A leading hypothesis for the mechanism of fast supraglacial lake drainages is that transient extensional stresses briefly allow crevassing in otherwise compressional ice flow regimes. Lake water can then hydrofracture a crevasse to the base of the ice sheet, and river inputs can maintain this connection as a moulin. If future ice sheet models are to accurately represent moulins, we must understand their formation processes, timescales, and locations. Here, we use remote-sensing velocity products to constrain the relationship between strain rates and lake drainages across ∼ 1600 ksq.m in Pâkitsoq, western Greenland, between 2002–2019. We find significantly more extensional background strain rates at moulins associated with fast-draining lakes than at slow-draining or non-draining lake moulins. We test whether moulins in more extensional background settings drain their lakes earlier, but we find insignificant correlation. To investigate the frequency at which strain-rate transients are associated with fast lake drainage, we examined Landsat-derived strain rates over 16 and 32 d periods at moulins associated with 240 fast-lake-drainage events over 18 years. A low signal-to-noise ratio, the presence of water, and the multi-week repeat cycle obscured any resolution of the hypothesized transient strain rates. Our results support the hypothesis that transient strain rates drive fast lake drainages. However, the current generation of ice sheet velocity products, even when stacked across hundreds of fast lake drainages, cannot resolve these transients. Thus, observational progress in understanding lake drainage initiation will rely on field-based tools such as GPS networks and photogrammetry.

Kristin Poinar↗
NASA NTRSDate not supplied

Jarosite Formation in Deep Antarctic Ice, an Earth Analogue to Unveil the Origin of Jarosite on Mars?

On Earth, jarosite is a weathering product forming in acidic-oxidative environments from the alteration of iron-bearing minerals in presence of liquid water. Typical settings where this iron-potassium hydrated sulphate is found, are weathering zones of pyrite-rich deposits, evaporative basins and fumaroles. Jarosite is not only known on Earth, it also occurs on Mars, where it has been identified by the Opportunity rover. The mineral was in fact recognized in the finely layered formations outcropping at Meridiani Planum and that were accurately investigated by the rover (Klingelhöfer et al. 2004). Since jarosite requires liquid water to form, its occurrence on Mars has been regarded as an evidence for the occurrence of liquid water in the geologic past of Mars (Elwood-Madden et al., 2004). Since then, many models have been proposed to describe the environments where the precipitation of Martian jarosite took place. The most accepted ones deal with evaporative basins similar to Earth’s playas, others concern volcanic activity and hydrothermal processes. An alternative proposal predicted that jarosite may have formed as a consequence of weathering of mineral dust trapped in massive ice deposits, i.e. the ice-weathering model (Niles & Michalsky, 2009). The hypothesis that jarosite formed on Mars because of low-temperature, acidic and water limited weathering, is not new (Burns, 1987), but until now no direct evidences were available to support it.A potential Earth analogue to investigate such processes is deep Antarctic ice. We present a first investigation of deep ice samples from the Talos Dome ice core (East Antarctica) aimed at the identification of englacial jarosite, so as to support the ice-weathering model. Evidences gathered through independent techniques showed that jarosite is actually present in deep Antarctic ice and results from the weathering of dust trapped into ice. The process is controlled by the re-crystallization of ice grains and the concurrent re-location of impurities at grain-junctions, which both depend on ice depth. This study demonstrates that the deep englacial environment is suitable for jarosite precipitation. Our findings support the hypothesis that, as originally predicted by the ice-weathering model, paleo ice-related processes have been important in thegeologic and geochemical history of Mars.

Lindsay P Keller↗
NASA NTRSDate not supplied

Large Eddy Simulations of Upper-Ocean Turbulence Across the Equatorial Pacific Cold Tongue

Turbulence in the equatorial Pacific cold tongue plays multiple roles in the sea-surface temperature budget. However, observations of turbulence are limited to a handful of field experiments lasting from a few days to one month at 0 N , 140 W, and the key turbulent fluxes can only be inferred. Although explicit simulations of turbulence resolve these fluxes, the required large eddy simulations (LES) are costly and thus also limited to a few weeks. A two-fold hypothesis motivates this contribution to the PUMP pre-field modelling experiments in support of TPOS: 1) that there exist useful relationships between the surface wind, wave, and buoyancy forcing, oceanic shear and stratification, and turbulent mixing, but 2) these relationships differ between regions of equatorial dynamics (f~0) and higher latitudes, such that the state space is insufficiently sampled to understand these relationships and represent them in ocean general circulation models (OGCM). To address the lack of observations, we simulated 35 continuous days of upper ocean turbulence using LES during October-November 1985 at sites in two regions (70 days in total) of the cold tongue: 0 N, 140 W and 3 N, 140 W. The model reproduces many features of the observed turbulence at 0,140W, including the “deep-cycle” observed by Gregg et al. (1985) Nature and the turbulent pulses every few hours during the night and in the early morning. Furthermore, the results at 3 N support the hypothesis advanced by Cherian et al. (2021) JPO that strong, but intermittent deep-cycle turbulence is observed to the north of the equator in the presence of strong shear associated with Tropical Instability Waves. Comparisons with the K-profile parameterization (KPP) scheme show that additional tuning of the KPP parameters can reduce differences between the turbulent fluxes produced by KPP and LES at both sites. The results will suggest modifications to OGCMs and already emphasize the need for a more extensive measurements of vertical profiles of shear, stratification and turbulent mixing to reveal the spatio-temporal structure of turbulence and how it relates to forcing, shear and stratification across the equatorial Pacific Cold tongue.

Large Eddy Simulations↗
NASA NTRSDate not supplied

AstroAmpSeq: Microbial Bioinformatics Education with NASA GeneLab’s Amplicon Pipeline

The prevalence and importance of large sequencing datasets in microbiology has led to a movement to share microbial ecology experimental data through open-access databases. This is particularly true of experiments that are difficult to replicate, such as those conducted in the spaceflight environment and shared via NASA GeneLab. It is now possible and indeed valuable for students to access and re-analyze these shared datasets for educational and research purposes. To provide students with experience utilizing microbial bioinformatics tools, GeneLab for Colleges and Universities (GL4U) has designed AstroAmpSeq, a week-long, virtually implemented project-based learning (PBL) minicourse to instruct undergraduate students on 16S amplicon sequencing. AstroAmpSeq was created to be accessible to students without prior bioinformatics or microbial ecology experience. During the minicourse students work in teams to process, analyze, and visualize a subsample of GeneLab dataset GLDS-280 using GeneLab’s standard amplicon processing pipeline, which is based in R. Students develop a hypothesis related to the dataset then generate and analyze figures to evaluate their hypothesis. Formative assessment of student learning is determined via pre- and post-evaluations, peer feedback, and self-reflection. Project and presentation rubrics serve as a summative assessment of student learning. GL4U AstroAmpSeq not only meets American Society for Microbiology Curriculum Guidelines, but also incites student interest in research by an inquiry-based approach and can be made part of a larger semester-long curriculum. GL4U AstroAmpSeq raises awareness of space microbiology and bioinformatics as a field and career path among undergraduates. Further, by using a GeneLab dataset and nesting microbiology techniques into the real-world application of space biology, AstroAmpSeq enforces deeper and longer-lasting student learning.

microbiology↗
NASA NTRSDate not supplied

One-Carbon Metabolism and SANS 2022 Update

Spaceflight Associated Neuro-ocular Syndrome, or SANS, affects a subset of astronauts (1, 2), and biochemical evidence has documented differences in those astronauts (3). Specifically, they had higher circulating concentrations of metabolites of the one-carbon metabolic pathway (1C), including homocysteine, and these concentrations were higher before flight (3). After ruling out many potential confounding factors in these otherwise healthy individuals (e.g., sex, kidney function, vitamin status, coffee consumption), a study of genetics was warranted. In an initial pilot effort, we documented a genetic predisposition to develop ophthalmic changes after long-duration space flight (4). That is, from a limited study of 5 single-nucleotide polymorphisms (SNPs), we found that the G allele for the MTRR A66G SNP was associated with a greater risk of choroidal folds and cotton-wool spots after flight, and the C allele for SHMT1 C1420T was protective against optic disc edema (4). These data provide a potential pathway for understanding why some individuals develop SANS, while others do not. The initial pilot study of 5 SNPs yielded striking findings, but the 1C pathway is far more complex. An effort was undertaken to examine more than 500 1C SNPs to see if a broader examination could help illuminate this association. That work is ongoing. The astronaut findings led us to advocate for the inclusion of 1C pathway genetic and biochemistry testing on other SANS-related projects, noting that genetics might help identify responders, non-responders, or outliers. The first such effort yielded evidence of an association of specific forms of the MTRR and SHMT-1 SNPs and vitamin B12 status with end-tidal CO2 after acute carbon dioxide exposure (5). The second such effort led to the identification that individuals exposed to strict head-down tilt and CO2 for 30-d who developed optic disc edema also had risk alleles for the two SNPs described above (6). Additionally, we identified a clinical population with many characteristics either attributed or purported to be involved in the ocular changes seen in affected astronauts: women with polycystic ovary syndrome (PCOS). PCOS is a condition of androgen excess and anovulatory menstrual cycles. The shared characteristics and clinical findings between SANS and PCOS generally include higher circulating homocysteine concentrations, increased retinal nerve fiber layer thickness, increased androgen concentrations (or responses), and altered carbohydrate metabolism. To our knowledge, no study has examined whether women with PCOS have asymptomatic ophthalmic anomalies observed in astronauts with SANS. While researchers have evaluated the one-carbon metabolism pathway polymorphisms of PCOS patients, and initial studies show an association with certain one-carbon polymorphisms, none have looked at the set of SNPs identified in our studies that are associated with ophthalmic changes in astronauts. Accordingly, we designed a study to evaluate the association of one-carbon pathway SNPs and ophthalmic findings in patients with PCOS and/or IIH compared to controls. Subjects provided blood samples for vitamin and one carbon biochemistry analyses, an extensive analysis of >500 SNPs associated with one carbon metabolism and had eye examinations and ocular imaging. Data analysis are underway. The data collected to date have shown associations between one carbon pathway biochemistry and genetics and incidence of SANS. The mechanisms for SANS has yet to be identified, although many hypotheses exist. Based on our data, we have developed (8, 9) and expanded (6) a multi-hit hypothesis for how these seemingly disparate findings could be linked. While intriguing, the hypothesis represents the starting point for further research. We aim to clarify the relationship between B-vitamin status and genetics with regard to the risk of SANS. Ultimately, understanding the mechanism(s) behind this will provide a means to predict, prevent, or treat these ophthalmologic pathologies in astronauts, and terrestrial populations.

S M Smith↗
NASA NTRSDate not supplied

B Complex 5-Methyltetrahydrofolate, Riboflavin, Pyridoxine, and Methylcobalamin Supplementation as a Non-Mechanical Countermeasure to Mitigate Optic Disc Edema Changes During Strict 6º Head-Down Tilt Bed Rest

A subset of astronauts on International Space Station missions have experienced optic disc edema, part of what is characterized as Spaceflight Associated Neuro-ocular Syndrome (SANS). While the precise cause of SANS is unknown, it is likely that there are multiple contributing factors, including genetic and environmental factors. Our recent work has shown that crewmembers with SANS have higher concentrations of metabolic biomarkers of impairments in the one-carbon metabolic pathway compared to unaffected astronauts - before, during, and after f light (1). B-vitamin status and the presence of one-carbon pathway single nucleotide polymorphism (SNP) variants predicted the incidence of SANS pathologies, including optic disc edema (2). Specifically, the G allele of methionine synthase reductase (MTRR) A66G and the C allele of serine hydroxymethyltransferase-1 (SHMT1) C1420T were associated with increased incidence of SANS pathologies (2). In a recent 30-d bed rest head-down tilt study with 0.5% CO2 exposure, 5 of 11 subjects developed optic disc edema (4) and the same SHMT1 C1420T and MTRR A66G genetic variants were associated with a larger increase in total retina thickness, a quantitative measure of optic disc edema (5). We published a multi-hit hypothesis of how genetics represents an indispensable element of SANS, which is a multifactorial problem (6). In brief: endothelial dysfunction secondary to genetic, biochemical/nutritional, and physiological (e.g., cardiovascular/fluid shift) f actors could lead to optic disc edema and the other ocular changes that occur in SANS. We expanded this hypothesis to include the possibility that genetic effects on B-vitamin status can alter nitric oxide synthesis and oxidative stress in the endothelium. This in turn could alter the turnover of structural components of the sclera, making it more susceptible to pathologic changes when faced with stressors related to the unrelenting headward fluid shift that occurs in weightlessness and strict head-down tilt bed rest (5). If the relationships that we have observed in flight and ground-based research hold true for the SANS Countermeasure Study, these genetic factors could predict who will be more susceptible to the development of SANS, and more importantly could also provide countermeasure options. As has been shown extensively in the literature, vitamin supplementation can serve to overcome genetic hindrances to one-carbon biochemistry and vascular physiology. Thus, based on our findings, publications, and hypotheses, supported by extensive supporting literature, we had hoped to test in the SANS Countermeasure Study the efficacy of a bioactive B-vitamin complex as a countermeasure to optimize function of the one-carbon pathway and prevent or mitigate optic disc edema during strict 6-degree head down tilt bed rest, and ultimately in space f light. While the supplement is no longer planned to be tested in the SANS Countermeasure Study because of laws regulating supplementation studies like this costing much more than initially planned, we will assess the contribution of one-carbon pathway genetics and B-vitamin status to SANS risk.

S R Zwart↗
NASA NTRS2022

The Joint Assimilation of Remotely Sensed Leaf Area Index and Surface Soil Moisture into a Land Surface Model

This work tests the hypothesis that jointly assimilating satellite observations of leaf area index and surface soil moisture into a land surface model improves the estimation of land vegetation and water variables. An Ensemble Kalman Filter is used to test such hypothesis across the Contiguous United States during April 2015 – December 2018. The performance of the proposed methodology is assessed for several modeled vegetation and water variables (evapotranspiration, net ecosystem exchange, and soil moisture) in terms of random errors and anomaly correlation coefficients against a set of independent validation datasets (i.e., Global Land Evaporation Amsterdam Model, FLUXCOM, and International Soil Moisture Network). Results show that the assimilation of leaf area index mostly improves the estimation of evapotranspiration and net ecosystem exchange, whereas the assimilation of surface soil moisture alone improves surface soil moisture content, especially in the western US, in terms of both root mean squared error and anomaly correlation coefficient. The joint assimilation of vegetation and soil moisture information combines the results of individual vegetation and soil moisture assimilations and reduces errors (and increases correlations with the reference datasets) in evapotranspiration, net ecosystem exchange, and surface soil moisture simulated by the land surface model. However, because soil moisture satellite observations only provide information on the water content in the top 5 cm of the soil column, the impact of the proposed data assimilation technique on root zone soil moisture is limited. This work moves one step forward in the direction of improving our estimation and understanding of land surface interactions using a multi-variate data assimilation approach, which can be particularly useful in regions of the world where ground observations are sparse or missing altogether.

Data assimilation↗
NASA NTRS2019

Satellite Conjunction Assessment Risk Analysis for "Dilution Region" Events: Issues and Operational Approaches

An important activity within Space Traffic Management is the detection and prevention of possible on-orbit collisions between space objects. The principal parameter for assessing collision likelihood is the probability of collision, which is widely accepted among conjunction assessment practitioners; but it possesses a known deficiency in that it can produce a false sense of safety when the orbital position uncertainties for the conjuncting objects are high. The probability of collision is said to be “diluted” in such a situation and to understate the possible risk; certain approaches have been recommended by researchers to provide (largely conservative) risk estimates and remediation methodologies in these cases. The present analysis explores two of the main proposals for quantifying and remediating possible risk in the dilution region and quantifies their operational implications. These implications with regard to imputed additional workload are considerable, especially in anticipating the conjunction event levels expected with the deployment of the USAF Space Fence radar. This effort has been undertaken as part of a larger enterprise that seeks to clarify the philosophical and statistical underpinnings of the conjunction risk assessment process. The analysis presented herein argues that a form of hypothesis testing is implicitly used in conjunction assessment risk analysis, and that there are a number of conceptual and practical reasons for constructing the associated null hypothesis to counsel against a satellite conjunction remediation action. In short, it is concluded that, for the purposes of determining whether a conjunction remediation action should be pursued, dilution-region probabilities of collision should be treated no differently from those produced under other circumstances.

Probability of collision↗
NASA NTRSDate not supplied

Interfacial thermodynamics of cryogenic fluids: The effect on non-condensable gas on fluid storage

Propellant tanks that contain cryogenic fluids (CFs) in low gravity conditions are usually pressurized with non-condensable (NC) gases for fast extraction. Unfortunately, the presence of NC gases causes CFs to exhibit higher boil-offs compared to pure CF systems. For optimal utilization of the cryogenic fuels, these higher boil-off rates must be minimized. Our goal is to quantify the effects NC gases have on the evaporation and condensation dynamics of CFs to develop strategies that mitigate the higher boil-offs. The hypothesis is that the NC gas accumulates around the CF’s liquid vapor interface in the Knudsen layer, creating a kinetic barrier for both evaporation and condensation. Testing this hypothesis with experimental methods is difficult due to the transient nature of the Knudsen layer, which is only a few nanometers thick. Furthermore, experimental capabilities are limited in low gravity conditions and extremely expensive. Accordingly, we approach this problem from a theoretical perspective. In this study, we employ molecular dynamics (MD) simulations to probe the interfacial mechanisms that affect CF’s evaporation and condensation at varying concentrations of NC gases. Specifically, we use nitrogen (N2) and oxygen (O2) as our CFs and neon (Ne) as our NC gas. Using MD simulations, we show that Ne accumulates at N2 liquid vapor interface across a wide range of Ne concentrations, thereby impeding mass transport of N2. Our simulations allow for direct computation of the molar flux as well as the mass accommodation coefficient (MAC) which can then be used as input parameters to continuum fluid dynamics (CFD) models for optimal storage tank design.

Michael Robert DeLyser↗
NASA NTRSDate not supplied

RNASeq and Fluorescence Analysis of the Response of ERF2 and ERF104 in Arabidopsis thaliana under Simulated Altered Gravity

As NASA moves closer to long-term human space exploration, the need to understand how to sustain life in space is increasingly pressing. Plants are essential to human sustenance, making it important to understand how spaceflight affects plant health. We used differential gene expression analysis to examine GLDS-251 (RNAseq analysis of the response of Arabidopsis thaliana to fractional gravity under blue-light stimulation during spaceflight) from NASA’s GeneLab data repository and found downregulation of ERF2 and ERF104, transcription factors of the ethylene response factor families, that integrate hormonal pathways involved in abiotic stress responses. Downregulation of ERF2 and ERF104 during spaceflight may indicate a dysregulation of the ethylene signaling pathway. Our hypothesis is that altered gravity downregulates the expression of ERF2 and ERF104 in Arabidopsis thaliana, altering the ethylene signaling pathway and affecting the electron transport chain and light-dependent reactions in chloroplast thylakoids. To test this hypothesis, we propose to grow A. thaliana seedlings (wild-type and mutant/knockout of ERF2 and ERF104) in altered gravity conditions to determine the effects on the expression of ERF2, ERF104, and photosynthesis. We anticipate that ERF2 and ERF104 will be underexpressed in altered gravity conditions and result in decreased regulation of the ethylene signaling pathway.

Arabidopsis↗
NASA NTRSDate not supplied

The Interplay of Humor and Team Cohesion Over Time

Team bonding and interpersonal relationships are increasingly important as we continue understanding the effects of the pandemic on team dynamics. Specifically, team cohesion, defined as having a sense of belonging and commitment towards the group, has been found to be important for key team outcomes such as performance, relationships, and productivity (Beal, Cohen, Burke, & McLendon, 2003; Bell & Marentette, 2011). Research has stressed the benefits of positive humor on cohesion, with humor creating positive emotions and decreasing social distance (e.g., Robert & Wilbanks, 2012; Robinson & Smith-Lovin, 2001; Romero & Pescosolido, 2008). However, research around the impact of negative humor on cohesion is scarce. This study aims to examine the impact of both positive and negative humor on cohesion for teams over time. The longitudinal design allows us to examine the interplay of humor and cohesion throughout a team’s lifecycle to guide relationship development and management (Romero & Pescosolido, 2008). Humor is defined as remarks recognized as amusing or funny (Martin, 2007). Positive humor can be categorized as good-natured aimed to create mutual agreement, while negative humor is defined as aggressive, hostile, and unreciprocated (Coan & Gottman, 2007). Research has concluded the many benefits of positive humor, showing it can increase open communication, social support, and create a pleasant environment (Martineau, 1972; Robinson & Smith-Lovin, 2001; Romero & Pescosolido, 2008). The Humor Wheel model suggests that positive humor is contagious due to the positive affect produced and mimicked (Lehmann-Willenbrock & Allen 2014). Research has suggested positive humor would increase over time based on the norm of reciprocity; those treated positively are likely to respond similarly (Gouldner, 1960). Multiple parties’ involvement in humor exchanges highlights the interpersonal nature of humor. Thus, long-term consequences on relationships should be considered, such as cohesion (Robert & Wilbanks, 2012). It would be instrumental to understand how humor interactions could weaken or strengthen group cohesion through relational and emotional bonds over time (Martineau, 1972; Romero & Pescosolido, 2008). Positive humor should fundamentally increase team cohesion (Mesmer-Magnus, Glew, & Viswesvaran, 2012; Walter & Baruch, 2008) by promoting group harmony, team member attractiveness, and ingroup identity (Holmes, 2006). Thus, it is expected there is a positive relationship between positive humor and team cohesion over time (hypothesis 1). Humor is not always beneficial, especially when it elicits negative emotions (Dikkers, Doosje, & de Lange, 2011). Negative humor can be used to humiliate, tease, or insult (Coan & Gottman, 2007; Collinson, 1988; Romero & Cruthirds, 2006). It tends to cause distress and damage relationships, and in turn, decrease organizational performance and production (Avolio, Howell, & Sosik, 1999; Janes & Olson, 2000; Yerkes, 2001). Research concludes negative humor may create subgroups and decrease cooperation (Romero & Arendt, 2011). Research has also indicated positive implications for negative humor under specific circumstances. Negative humor could help to solidify ingroup identity and strengthen bonds when directed outside the team (Terrion & Ashforth, 2002; Thomae & Pina, 2015). For example, sport teams may use negative humor towards their opponent before a game, which emphasizes their differences and lowers the status and power of their opponent, ultimately promoting solidarity and cohesion inside the group. For this study, it is anticipated that negative humor toward other teammates will decrease team cohesion over time due to the damage to relationships and negative affect produced (Duncan, Smeltzer, & Leap, 1990; Maples, Dupey, Torres‐Rivera, Phan, Vereen, & Garrett, 2001). We also predicted that negative humor focused on something or someone outside the team will increase cohesion by enhancing ingroup ties and creating a common identity (Thomae & Pina, 2015). Thus, the relationship between negative humor and cohesion will be moderated by the target of the humor. The relationship will be negative when the target is within the team and positive when the target is outside (hypothesis 2).

Melissa M. Vazquez↗
NASA NTRSDate not supplied

Microbial Communities in Microgravity: Simulation in Lab and on the Computer

Microorganisms grow differently in spaceflight than they do on Earth. While much remains unexplained about how microgravity affects microbial growth, one dominant hypothesis is that the lack of density-driven convection in the liquid growth environment makes mixing diffusion-limited, and therefore slower. This is supported by evidence that individual microbial strains experience starvation and acid stress in microgravity. However, if it is true, then microgravity would also have measurable effects on microbes in mixed communities, because many interspecies interactions involve the exchange of soluble metabolites through the medium (cross-feeding). Specifically, cooperative cross-feeding communities would grow more slowly in microgravity, and cooperation would be less stable on evolutionary timescales. Here we describe our efforts to test this hypothesis by simulating microgravity in silico and in the lab, using a model system of Eschericia coli and Salmonella enterica that grow only when they can exchange methionine and acetate. We created CAMDLES (CFD-DEM Artificial Microgravity Developments for Living Ecosystem Simulation) as an extension of CFDEM®coupling software, to carry out computational modeling of biological flows, growth, and mass transfer in microgravity and also in laboratory artificial microgravity devices (rotating wall vessels, RWV). Using CAMDLES, we found distinct differences in growth rates between RWV and true microgravity, and we were able to identify several features, such as spatial distribution, biofilm formation, and product yield parameters, that influence the degree to which RWV growth recapitulates microgravity growth. In addition, we report on the development of a laboratory system for monitoring growth rates and species ratios of the community in RWVs, using fluorescent strains. Pairing CAMDLES with the laboratory model system allows us to generate quantitative predictions about the effects of spaceflight on organisms that will be essential to sustaining human space exploration in the long term.

microbiology↗
NASA NTRSDate not supplied

A Chlorine Isotope Transect Across the Sudbury Impact Deposits Reveals Enigmatic Isotopic Fractionation

Volatile elements play an important role in a variety of cosmochemical and geochemical processes. As such, there has been significant interest in their abundance and isotopic composition. Chlorine is an important element for tracing these processes because it is incompatible in nearly all minerals, extremely volatile, and strongly hydrophilic [1]. The Cl isotope composition ( 37 Cl/ 35 Cl) of meteoritic components, therefore, can provide useful information regarding the isotopic reservoirs that were present in the early Solar System and any secondary processes that may have occurred on different parent bodies (e.g., [2-4]). There is a relatively narrow range in the Cl isotope compositions of terrestrial, Martian, and chondritic meteorites (δ 37 Cl ~ −6 to +4‰) (e.g., [2,3,5,6]), with exceptions to this being the Moon and Vesta (up to ~ +81‰ and ~ +40‰, respectively) [4, 5, 7-10]. One hypothesis for the extreme Cl isotope fractionation observed on the Moon is degassing following large-scale (possibly even crust-breaching) impact events [7-9]. The role of hypervelocity impacts and impact-generated magmatism in the isotopic evolution of planetary materials, however, has been until recently an area of limited published research with the majority of works focusing on the effects of impact shock (e.g., [10-13]). The ~ 1.85 Ga Sudbury impact crater [14] located in Ontario, Canada, is one of the three largest impact craters on Earth with good exposures of its impact melt sheet and overlying breccias [15,16]. The impact melt sheet, called the Sudbury Igneous Complex (SIC), is up to 5 km thick [17], with an estimated original volume of >10 4 km 3 [18], and differentiated. Recent work demonstrated evaporative loss and isotope fractionation of the moderately volatile element zinc and suggest melt sheets produced by impacts could have a significant effect on the Earth’s volatile inventory [19]. In this study we investigate the abundance and isotopic composition of Cl as well the water abundance of apatite from the SIC and the overlying crater-fill to test the hypothesis that large-scale impacts may have generated the extensive Cl isotopic fractionation observed on the Moon.

Sudbury↗
NASA NTRS2017

The Detection of 6.9 µm Emission Features in the Infrared Spectra of IRAS 04296+3429, IRAS 05341+0852, IRAS 22272+5435: Evidence for the Presence of Hn-PAHs in Post AGB Stars

Polycyclic aromatic hydrocarbons (PAHs) are generally believed to be ubiquitous in space and responsible for numerous telltale interstellar infrared emission bands. In Sandford et al., (2013), we suggested that polycyclic aromatic hydrocarbons with excess hydrogenation at their periphery (Hn-PAHs) may be an important subclass of these molecules in some astrophysical environments. These molecules are candidates to explain objects with anomalously large 3.4 μm features, which are presumed to be associated with the aliphatic C—H stretching vibrations of the excess hydrogen. In that work, we suggest that for Hn-PAHs to be a viable candidate as the source for this 3.4 μm feature, we must also expect to observe methylene scissoring modes at 6.9 μm. In this work, we continue to develop the Hn-PAH hypothesis with a focus on the 6.9 μm feature. We also present some new observations of three post-asymptotic giant branch (post- AGB) objects with abnormally large 3.4 μm features, IRAS 04296+3429, IRAS 05341+0852, IRAS 22272+5435, in addition to one post-AGB object with normal PAH emissions, IRAS 20000+3239. These observations were made using the FORCAST instrument in grism mode on the Stratospheric Observatory for Infrared Astronomy (SOFIA) aircraft (Adams et al. 2010) and demonstrate the presence of a 6.9 μm feature for the three objects with abnormally large 3.4 μm features and no detectable 6.9 μm feature for the normal PAH emitter. These results are consistent with the hypothesis that Hn-PAHs are a possible source of these infrared emission bands.

ISM↗
NASA NTRS2023

Wetting and Drying Trends Under Climate Change

The geography and timing of changes in water availability under climate change are of considerable societal interest. Characterizing these changes in a robust and meaningful manner, however, has not been easy. In the past decade, studies have engaged two provocative hypotheses to explain and predict large-scale trends in water availability. One hypothesis holds that there will be increased contrasts in available water, as wet places become wetter and dry places become drier. Another hypothesis states that there will be global aridification, as widespread increases in evapotranspiration overwhelm changes in precipitation in most terrestrial regions. There is an extensive and sometimes contentious literature on the evidence for each. In some cases, these debates reflect direct disagreement, but the appearance of disagreement is exaggerated by the diversity of methods and terminologies employed in different studies. Herein we examine the applicability and limits of both hypotheses across different frameworks, scales and contexts, yielding insights on hydrologic change and the future of water availability.

Benjamin F. Zaitchik↗
NASA NTRSDate not supplied

Nutrient Controls on Net Primary Production Decline in the Subtropical North Atlantic

The subtropical North Atlantic Ocean (STNA) has been experiencing a steady decline in both Chlorophyll a (the primary photosynthetic pigment in phytoplankton used to identify abundance in the ocean) and net primary production (the net amount carbon fixed in the surface ocean by phytoplankton after losses to respiration). This decline is spread across the entire STNA and has been ongoing since the beginning of the satellite ocean color record in 1997. Previous work has attributed these changes to decreased nutrient exchange between nutrient-poor surface waters and nutrient-rich deep waters resulting from increased stratification driven by surface warming due to climate change. Our results from an analysis of satellite data, Argo float data, and historical cruise data show significant inconsistencies with this hypothesis. We observe a trend of increased stratification for half the STNA basin but decreased stratification in the other half. Where we see increased stratification, we also see changes in nitrate that would result in an increased delivery of nitrate to surface waters if vertical transport across the stratified layers was the dominant source of nutrients. Our working hypothesis is that changes in circulation in the subtropical gyre have resulted in an altered mix of source waters with distinct nutrient characteristics. The mechanism behind the decline in primary production in the STNA remains unclear. We will use the ECCO-Darwin data-assimilative global ocean biogeochemistry model to further investigate the mechanisms behind the observed changes in production and nutrients in the STNA.

Nutrient↗
NASA NTRS2023

QBO Deepens MJO Convection

The underlying mechanism that couples the Quasi-Biennial Oscillation (QBO) and the Madden-Julian oscillation (MJO) has remained elusive, challenging our understanding of both phenomena. A popular hypothesis about the QBO-MJO connection is that the vertical extent of MJO convection is strongly modulated by the QBO. However, this hypothesis has not been verified observationally. Here we show that the cloud-top pressure and brightness temperature of deep convection and anvil clouds are systematically lower in the easterly QBO (EQBO) winters than in the westerly QBO (WQBO) winters, indicating that the vertical growth of deep convective systems within MJO envelopes is facilitated by the EQBO mean state. Moreover, the deeper clouds during EQBO winters are more effective at reducing longwave radiation escaping to space and thereby enhancing longwave cloud-radiative feedback within MJO envelopes. Our results provide robust observational evidence of the enhanced MJO activity during EQBO winters by mean state changes induced by the QBO.

quasi-biennial oscillation↗