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At least 109 records · Page 6
All sourcesNASA NTRSDOE OSTI
NASA NTRS2015

Martian Superoxide and Peroxide O2 Release (OR) Assay: A New Technology for Terrestrial and Planetary Applications

This study presents an assay for the detection and quantification of soil metal superoxides and peroxides in regolith and soil. The O2 release (OR) assay is based on the enzymatic conversion of the hydrolysis products of metal oxides to O2, and their quantification by an O2 electrode based on the stoichiometry of the involved reactions: The intermediate product O2 from the hydrolysis of metal superoxides is converted by cytochrome c to O2, and also by superoxide dismutase (SOD) to 1/2 mol O2 and 1/2 mol H2O2, which is then converted by catalase (CAT) to 1/2 mol O2. The product H2O2 from the hydrolysis of metal peroxides and hydroperoxides is converted to 1/2 mol O2 by CAT. The assay-method was validated in a sealed sample chamber using a liquid-phase Clark-type O2 electrode with known concentrations of O2 and H2O2, and with commercial metal superoxide and peroxide mixed with Mars analogue Mojave and Atacama Desert soils. Carbonates and perchlorates, both present on Mars, do not interfere with the assay. The assay lower limit of detection, using luminescence quenching/optical sensing O2-electrodes, is 1 nmol O2 cm(exp. -3) or better. The activity of the assay enzymes SOD and cytochrome c was unaffected up to 6 Gy exposure by gamma-radiation, while CAT retained 100% and 40% of its activity at 3 and 6 Gy, respectively, demonstrating the suitability of these enzymes for planetary missions, e.g., in Mars or Europa.

soil metal superoxides and peroxides↗
NASA NTRSDate not supplied

Quantifying Leak Rates and Vacuum Impact on Granular Soil Column Pneumatic Seal

Introduction: All In-Situ Resource Utilization (ISRU) regolith reactor systems that aim to extract gases or vapors must maintain a seal along the flow path of the regolith from the inlet hopper to where extracted gases or vapors are generated. Using a column of regolith at the inlet has been proposed as an alternative to systems using series of mechanical valves to reduce mass and complexity. Preliminary investigations into the use of regolith itself as a barrier to escaping fluids have been conducted, which this research seeks to expand upon. Different vertical regolith simulant plug diameters and heights were tested under vacuum with dry nitrogen to observe leak rates and approximate steady state pressure gradient equilibria. The effect of absolute ambient pressure was also studied by repeating tests at incremental pressures ranging from 10e-5 Torr up to 1 atm to corroborate ambient bench tests from previous work. The impact of regolith dynamics was addressed to emulate continuous-feed regolith reaction processes by measuring leak rates through continuously draining simulant columns. OB-1 lunar highlands regolith simulant was used. Experimental Setup: Regolith simulant columns were constructed using a motorized butterfly valve separating upper acrylic tubes of various diameters from a larger, lower aluminum pipe plenum (See Figure 1). The butterfly valve was cracked open such that gas could freely pass through whereas regolith would bridge and stay suspended as a cohesive plug above in the acrylic portion. These assemblies were loaded into a vacuum chamber, and a compressed dry nitrogen line was routed into the lower plenum. Pressure transducers measured the absolute pressure of the lower plenum, which was compared to absolute chamber pressure to monitor the pressure gradient across the regolith simulant. A precision mass flow controller enabled fine control of plenum pressure. The plenum pressure was quasi-statically increased to set points informed by previous work [1] before shutting off the gas supply to allow the now pressurized gas volume to dissipate through the simulant into the chamber in what was referred to as a ‘leak test.’ In a separate set of tests, the pressure was allowed to quasi-statically build until visual disturbances in the soil were observed via remote camera feeds. Initial leak rate tests were repeated on the disturbed soil to observe changes in leak rates between initial as-poured and post-bubbling soil conditions. This test schedule was applied to simulant columns of three different diameters (approximately 2, 4, and 6 inches) as well as two different heights (around 8 and 16 inches) and was repeated at least three times for each configuration. Plenums were also pressurized while the butterfly valves were opened slightly further to facilitate slow, controlled, constant flowrate draining of the simulant to observe the impact that continuous-feed systems might have on leak rate through the regolith column. Finally, the regolith columns were reset and refilled and static leak rate tests were repeated approximately every decade in ambient pressure from 10e-5 Torr up to ambient conditions to observe the impact of transitioning out of the molecular flow regime on regolith column seal performance. Analysis: Trends with respect to each factor examined were constructed and reported alongside commentary on the most likely responsible physical phenomena. Confidence intervals were applied to the predictive findings of the data by quantifying instrumentation error and accounting for probabilistic impacts of curve fitting the generic exponential function onto pressure decay data. The leak rate is assumed directly proportional to the exponential term coefficient, while the steady-state static pressure gradient is assumed to be the asymptotic limit of each curve fit. Finally, a generic model developed by Ogino et al. [2] and later tuned for ambient testing was re-tuned using vacuum data to estimate leak rates on the lunar surface. Results: Pressure decay rates decreased up to 27-fold under vacuum when compared to ambient pressure, as shown in Figure 2. Simulant column diameter was found to exponentially correlate to both regolith column leak rate and steady-state equilibrium pressure delta. Height was found to be linearly related to leak rate –doubling the regolith column height consistently yielded around a 40% reduction in leak rate. Dynamic regolith draining was found to slightly increase leak rate, although to a lower degree than expected. Conclusion: Because of the transition into molecular gas flow through regolith, vacuum testing is required to properly estimate performance. Regolith columns should be designed as narrow as possible to avoid bridging and minimize leak rate, and as tall as is feasible to both further reduce leak rate and to help prevent bubbling, which has been shown to degrade the quality of the regolith seal. Disrupted soil was found to exhibit higher leak rates than pristine, as-poured soil, indicating the need to consider the impact of recovery from depressurization events. Regolith columns appear equally feasible for both dosed and continuous-feed reactors.

ISRU↗
NASA NTRS1986

Houseplants, Indoor Air Pollutants, and Allergic Reactions

The technology of using houseplant leaves for reducing volatile organics inside closed facilities has been demonstrated with formaldehyde and benzene. Philodendrons are among the most effective plants tested to date. Philodendron domesticum had demonstrated the ability to remove formaldehyde from small experimental chambers at a rate of 4.31 micro-g/sq cm leaf surface area with initial starting concentrations of 22 ppm. At initial starting concentrations of 2.3 ppm a formaldehyde removal rate of 0.57 micro-g/sq cm was achieved during a 24 hour test. Aleo vera demonstrated a much higher formaldehyde efficiency removal rate than Philodendron domesticum at low formaldehyde concentrations. During a 24 hour exposure period 5 ppm of formaldehyde were reduced to 0.5 ppm demonstrating a removal efficiency rate of 3.27 micro-g/sq cm. Removal efficiency rates can be expected to decrease with concentration levels because fewer molecules of chemicals come in contact with the leaf surface area. Several centimeters of small washed gravel should be used to cover the surface of pot plants when large numbers of plants are kept in the home. The reason for this is to reduce the exposed area of damp potting soil which encourages the growth of molds (fungi). The leaves of Philodendron domesticum and golden pothos (Scindapsus aureus) have also demonstrated their ability to remove benzene and carbon monoxide from closed chambers. A combination of activated carbon and plant roots have demonstrated the greatest potential for removing large volumes of volatile organics along with smoke and possible radon from closed systems. Although fewer plants are required for this concept a mechanical blower motor must be used to pull or push the air through the carbon-root filter. NASA studies on motor sizes and bioregeneration rates should be completed by 1988.

Wolverton, B. C.↗
NASA NTRS2014

Connecting Returned Apollo Soils and Remote Sensing: Application to the Diviner Lunar Radiometer

The Diviner Lunar Radiometer, onboard NASA's Lunar Reconnaissance Orbiter, has produced the first global, high resolution, thermal infrared observations of an airless body. The Moon, which is the most accessible member of this most abundant class of solar system objects, is also the only body for which we have extraterrestrial samples with known spatial context, returned Apollo samples. Here we present the results of a comprehensive study to reproduce an accurate simulated lunar environment, evaluate the most appropriate sample and measurement conditions, collect thermal infrared spectra of a representative suite of Apollo soils, and correlate them with Diviner observations of the lunar surface. It has been established previously that thermal infrared spectra measured in simulated lunar environment (SLE) are significantly altered from spectra measured under terrestrial or martian conditions. The data presented here were collected at the University of Oxford Simulated Lunar Environment Chamber (SLEC). In SLEC, we simulate the lunar environment by: (1) pumping the chamber to vacuum pressures (less than 10‐4 mbar) sufficient to simulate lunar heat transport processes within the sample, (2) cooling the chamber with liquid nitrogen to simulate radiation to the cold space environment, and (3) heating the samples with heaters and lamp to set‐up thermal gradients similar to those experienced in the upper hundreds of microns of the lunar surface. We then conducted a comprehensive suite of experiments using different sample preparation and heating conditions on Apollo soils 15071 (maria) and 67701 (highland) and compared the results to Diviner noontime data to select the optimal experimental conditions. This study includes thermal infrared SLE measurements of 10084 (A11 - LM), 12001 (A12 - LM), 14259 (A14 - LM), 15071 (A15 - S1), 15601 (A15 - S9a), 61141 (A16 - S1), 66031 (A16 - S6), 67701 (A16 - S11), and 70181 (A17 - LM). The Diviner dataset includes all six Apollo sites at approximately 200 m spatial resolution We find that analyses of Diviner observations of individual sampling stations and SLE measurements returned Apollo soils show good agreement, while comparisons to thermal infrared reflectance under ambient conditions do not agree well, which underscores the need for SLE measurements and validates the Diviner compositional measurement technique.

Greenhagen, B. T.↗
NASA NTRS1991

Johnson Space Center's regenerative life support systems test bed

The Regenerative Life Support System (RLSS) Test Bed at NASA's Johnson Space Center is an atmospherically closed, controlled environment facility for the evaluation of regenerative life support systems using higher plants in conjunction with physicochemical life support systems. When completed, the facility will be comprised of two large scale plant growth chambers, each with approximately 10 m(exp 2) growing area. One of the two chambers, the Variable Pressure Growth Chamber (VPGC), will be capable of operating at lower atmospheric pressures to evaluate a range of environments that may be used in Lunar or Martian habitats; the other chamber, the Ambient Pressure Growth Chamber (APGC) will operate at ambient atmospheric pressure. The root zone in each chamber will be configurable for hydroponic or solid state media systems. Research will focus on: (1) in situ resource utilization for CELSS systems, in which simulated lunar soils will be used in selected crop growth studies; (2) integration of biological and physicochemical air and water revitalization systems; (3) effect of atmospheric pressure on system performance; and (4) monitoring and control strategies.

Henninger, Donald L.↗
NASA NTRS2000

BOREAS TGB-5 CO2, CH4 and CO Chamber Flux Data Over the NSA

The BOReal Ecosystem-Atmosphere Study Trace Gas Biogeochemistry (BOREAS TGB-5) team collected a variety of trace gas concentration and flux measurements at several NSA sites. This data set contains carbon dioxide (CO2), methane (CH4), and carbon monoxide (CO) chamber flux measurements conducted in 1994 at upland forest sites that experienced stand-replacement fires. These measurements were acquired to understand the impact of fires on soil biogeochemistry and related changes in trace gas exchange in boreal forest soils. Relevant ancillary data, including data concerning the soil temperature, solar irradiance, and information from nearby un-burned control sites, are included to provide a basis for modeling the regional impacts of fire and climate changes on trace gas biogeochemistry. The data are provided in tabular ASCII files.

Burke, Roger↗
NASA NTRS2011

Concept for Sustained Plant Production on ISS Using VEGGIE Capillary Mat Rooting System

Plant growth in microgravity presents unique challenges associated with maintaining appropriate conditions for seed germination, seedling establishment, maturation and harvest. They include maintaining appropriate soil moisture content, nutrient balance, atmospheric mixing and containment. Sustained production imposes additional challenges of harvesting, replanting, and safety. The VEGGIE is a deployable (collapsible) plant growth chamber developed as part of a NASA SBIR Phase II by Orbitec, Madison, WI. The intent of VEGGIE is to provide a low-resource system to produce fresh vegetables for the crew on long duration missions. The VEGGIE uses and LED array for lighting, an expandable bellows for containment, and a capillary matting system for nutrient and water delivery. The project evaluated a number of approaches to achieve sustained production, and repeated plantings, using the capillary rooting system. A number of different root media, seed containment, and nutrient delivery systems were evaluated and effects on seed germination and growth were evaluated. A number of issues limiting sustained production, such as accumulation of nutrients, uniform water, elevated vapor pressure deficit, and media containment were identified. A concept using pre-planted rooting packs shown to effectively address a number of those issues and is a promising approach for future development as a planting system for microgravity conditions.

Stutte, Gary W.↗
NASA NTRS1989

The C-13/C-12 kinetic isotope effect for soil oxidation of methane at ambient atmospheric concentrations

During a survey of the Alaskan North Slope to estimate the isotopic composition and fluxes of methane (CH4) from the tundra, two sites were encountered that showed net methane consumption within flux chambers. Methane concentrations decreased from ambient (1.78 ppmv) by up to 50 percent, and the delta C-13 increased by up to 10 percent in the two chamber deployments showing CH4 consumption. CH4 consumption rates were measured to be 1.2 and 0.6 mg CH4/sq m per day; the corresponding carbon kinetic isotope effects (k13/k12) were 0.974 and 0.984, respectively.

King, Stagg L.↗
DOE OSTI2024

Warming but not elevated CO 2 depletes soil organic carbon in a temperate rice paddy

In this article, global climate change has the potential to alter soil organic carbon (SOC) stocks in rice paddies, because increases in temperature and atmospheric carbon dioxide concentration ([CO 2 ]) both influence the primary input (i.e., net primary production, NPP) and output (i.e. heterotrophic respiration) of carbon (C). We used two types of open-top chambers representing present conditions (+0°C, +0 ppm CO 2 ) and projected climate change conditions (+2°C, +200 ppm CO 2 ) to investigate the net effect of climate change on SOC stock in rice paddy. Additional chambers with elevated temperature only (+2°C, +0 ppm CO 2 ) allowed us to quantify the individual effects of temperature and [CO 2 ]. We calculated changes in SOC stock using net ecosystem C balance (NECB) analysis (i.e., the balance between C inputs and outputs). Compared to present conditions, projected climate change did not change grain yield due to a trade-off between the effects of warming and [CO 2 ] on grain yield components. NPP during the fallow season significantly decreased under combined warming and CO 2 , as the impact of warming outweighed that of elevated [CO 2 ]. However, rice NPP remained unchanged during the cropping season. Warming plus elevated CO 2 increased SOC mineralization by 157–429 %, particularly through warming-induced soil CO 2 emission during the fallow season. Consequently, climate change conditions decreased (119–271 %) NECB values compared to present conditions, primarily through the response to warming. Our findings demonstrate that rice paddies represent positive feedback on climate change, because accelerated C release from warmed soils will override C gains from NPP under elevated CO 2 . Reducing SOC depletion in rice paddy agriculture under a changing climate therefore requires conservative soil management practices during the fallow season.

54 ENVIRONMENTAL SCIENCES↗
NASA NTRS2016

Near-Infrared Monitoring of Volatiles in Frozen Lunar Simulants While Drilling

In Situ Resource Utilization (ISRU) focuses on using local resources for mission consumables. The approach can reduce mission cost and risk. Lunar polar volatiles, e.g. water ice, have been detected via remote sensing measurements and represent a potential resource for both humans and propellant. The exact nature of the horizontal and depth distribution of the ice remains to be documented in situ. NASA's Resource Prospector mission (RP) is intended to investigate the polar volatiles using a rover, drill, and the RESOLVE science package. RP component level hardware is undergoing testing in relevant lunar conditions (cryovacuum). In March 2015 a series of drilling tests were undertaken using the Honeybee Robotics RP Drill, Near-Infrared Volatile Spectrometer System (NIRVSS), and sample capture mechanisms (SCM) inside a 'dirty' thermal vacuum chamber at the NASA Glenn Research Center. The goal of these tests was to investigate the ability of NIRVSS to monitor volatiles during drilling activities and assess delivery of soil sample transfer to the SCMs in order to elucidate the concept of operations associated with this regolith sampling method.

Neutron Spectrometer System↗
DOE OSTI2026

Data from: Coupled machine learning-ecosystem ensemble models substantially improve predictions of nitrous oxide (N 2 O) fluxes from US croplands

Nitrous oxide (N₂O) is a potent and persistent greenhouse gas, with rising atmospheric concentrations driven in part by inefficient use of synthetic nitrogen (N) fertilizers in agriculture. Predicting soil N₂O emissions is challenging due to high spatial and temporal variability arising from complex soil biogeochemical processes. Process-based ecosystem models and standalone machine learning (ML) approaches without extensive site-specific calibration often miss high emission episodes. Here, we show how an Ensemble Modeling System (EMS) based on outputs from an ensemble of ecosystem models coupled to an ensemble of ML models can improve predictions and understanding of N2O fluxes from US cropland. Trained and validated on approximately 12,000 N2O chamber measurements at 17 U.S. Midwest sites (six crops, 35 management practices), the EMS accurately predicted daily fluxes of N2O at both training (R² = 0.84, RMSE = 16.4 g N ha⁻¹ d⁻¹) and held-out testing sites (R² = 0.84, RMSE = 6.2 g N ha⁻¹ d⁻¹). Analyses identified six dominant N₂O drivers: soil organic carbon (SOC), NH₄⁺, NO₃⁻, water-filled pore space (WFPS), soil temperature, and biomass production. Wet, warm soils produced large N₂O peaks only with sufficient SOC and mineral N; in low-SOC soils, fluxes remained low. Incorporating these drivers into process-based models might significantly improve their predictive capacity. The EMS demonstrates a strong potential to predict N₂O fluxes at unseen sites, enabling more reliable regional inventories, improved gap-filling where measurements are sparse, and enhanced understanding of mechanisms to advance targeted mitigation strategies in food, feed, and bioenergy crops.

agricultural sciences↗
NASA NTRS2011

Measurement of Apparent Thermal Conductivity of JSC-1A Under Ambient Pressure

The apparent thermal conductivity of JSC-1A lunar regolith simulant was measured experimentally using a cylindrical apparatus. Eleven thermocouples were embedded in the simulant bed to obtain the steady state temperature distribution at various radial, axial, and azimuthal locations. The high aspect ratio of a cylindrical geometry was proven to provide a one-dimensional, axisymmetric temperature field. A test series was performed at atmospheric pressure with varying heat fluxes. The radial temperature distribution in each test fit a logarithmic function, indicating a constant thermal conductivity throughout the soil bed. However, thermal conductivity was not constant between tests at different heat fluxes. This variation is attributed to stresses created by thermal expansion of the simulant particles against the rigid chamber wall. Under stress-free conditions (20 deg C), the data suggest a temperature independent apparent conductivity of 0.1961 +/- 0.0070 W/m/ deg C

Yuan, Zeng-Guang↗
NASA NTRS2001

A Study of the Electrostatic Interaction Between Insulators and Martian/Lunar Soil Simulants

Using our previous experience with the Mars Environmental Compatibility Assessment (MECA) electrometer, we have designed a new type of aerodynamic electrometer. The goal of the research was to measure the buildup of electrostatic surface charge on a stationary cylindrical insulator after windborne granular particles have collided with the insulator surface in a simulated dust storm. The experiments are performed inside a vacuum chamber. This allows the atmospheric composition and pressure to be controlled in order to simulate the atmospheric conditions near the equator on the Martian surface. An impeller fan was used to propel the dust particles at a cylindrically shaped insulator under low vacuum conditions. We tested the new electrometer in a 10 mbar CO2 atmosphere by exposing two types of cylindrical insulators, Teflon (1.9 cm diameter) and Fiberglass (2.5 cm diameter), to a variety of windborne granular particulate materials. The granular materials tested were JSC Mars-1 simulant, which is a mixture of coarse and fine (<5microns diameter) particle sizes, and some of the major mineral constituents of the Martian soil. The minerals included Ottawa sand (SiO2), iron oxide (Fe2O3), aluminum oxide (Al2O3) and magnesium oxide (MgO). We also constructed a MECA-like electrometer that contained an insulator capped planar electrode for measuring the amount of electrostatic charge produced by rubbing an insulator surface over Martian and lunar soil simulants. The results of this study indicate that it is possible to detect triboelectric charging of insulator surfaces by windborne Martian soil simulant, and by individual mineral constituents of the soil simulant. We have also found that Teflon and Fiberglass insulator surfaces respond in different ways by developing opposite polarity surface charge, which decays at different rates after the particle impacts cease.

Mantovani, James G.↗
DOE OSTI2025

A minor respiratory process with major global implications: is atmospheric methane oxidation in tree stems driven by stem respiration rather than microbial methanotrophy?

Tree stem surfaces are widely recognized as sites of carbon dioxide (CO₂) efflux and oxygen (O₂) influx, reflecting the dynamics of aerobic respiration of photosynthate substrates, such as sugars, delivered via the phloem. Stems are also largely considered passive conduits for methane (CH₄) produced in anoxic soils via microbial methanogenesis, where CH₄ is thought to be transported upward through the transpiration stream and/or diffusion and emitted through stem surfaces and the canopy. However, recent observations from dynamic stem chambers suggest that stems may also act as active sinks for atmospheric CH₄. Despite these findings, the extent and drivers of stem CH₄ consumption remain poorly characterized across biomes, species, and environmental gradients, and its quantitative relationship to stem respiration has not been established. Moreover, previous studies captured only snapshot fluxes, leaving diurnal patterns of CH₄ exchange uncharacterized. Here, we address these limitations by combining real-time measurements of stem CH₄ and O₂ uptake under ambient conditions in a California cherry tree, using a dynamic stem gas exchange system with three chambers receiving a continuous flow of ambient air and automated chamber and reference air sampling every 10 min. Our results confirm that stems of upland trees can actively consume both atmospheric CH₄ and O₂, but with decreasing temperature sensitivity as daily temperatures increase. Early mornings were marked by rapid influxes of both gases, followed by declining uptake as temperatures rose further. Methane uptake was tightly coupled with O₂ influx and represented a minor (0.012% ± 0.002%) fraction of stem respiratory activity, as determined by concurrent O₂ uptake. These findings suggest that while atmospheric CH₄ oxidation is a minor respiratory process in stems, it is strongly linked with stem physiological activity. This challenges the current assumption that terrestrial CH₄ uptake is driven solely by microbial methanotrophy and raises the possibility that living stem tissues may contribute to CH₄ oxidation through an as-yet-unidentified plant-based mechanism.

Atmospheric greenhouse gases↗
NASA NTRS1992

Emissions of biogenic sulfur gases from Alaskan tundra

Fluxes of the biogenic sulfur gases carbonyl sulfide (COS), dimethyl sulfide (DMS), methyl mercaptan (MeSH), and carbon disulfide (CS2) were determined for several freshwater and coastal marine tundra habitats using a dynamic enclosure method and gas chromatography. In the freshwater tundra sites, highest emissions, with a mean of 6.0 nmol/m(sup -2)H(sup -1) (1.5-10) occurred in the water-saturated wet meadow areas inhabited by grasses, sedges, and Sphagnum mosses. In the drier upland tundra sites, highest fluxes occurred in areas inhabited by mixed vegetation and labrador tea at 3.0 nmol/m(sup -2)h(sup -1) (0-8.3) and lowest fluxes were from lichen-dominated areas at 0.9 nmol/m(sup -2)h(sup -1). Sulfur emissions from a lake surface were also low at 0.8 nmol/m(sup -2)h(sup -1). Of the compounds measured, DMS was the dominant gas emitted from all of these sites. Sulfure emissions from the marine sites were up to 20-fold greater than fluxes in the freshwater habitats and were also dominated by DMS. Emissions of DMS were highest from intertidal soils inhabited by Carex subspathacea (150-250 nmol/m(sup -2)h(sup -1)). This Carex sp. was grazed thoroughly by geese and DMS fluxes doubled when goose feces were left within the flux chamber. Emissions were much lower from other types of vegetation which were more spatially dominant. Sulfure emissions from tundra were among the lowest reported in the literature. When emission data were extrapolated to include all tundra globally, the global flux of biogenic sulfur from this biome is 2-3 x 10(exp 8) g/yr. This represents less than 0.001 percent of the estimated annual global flux (approximately 50 Tg) of biogenic sulfur and less than 0.01 percent of the estimated terrestrial flux. The low emissions are attributed to the low availability of sulfate, certain hydrological characteristics of tundra, and the tendency for tundra to accumulate organic matter.

Hines, Mark E.↗
DOE OSTI2026

Coupled machine learning–ecosystem ensemble models substantially improve predictions of nitrous oxide (N 2 O) fluxes from US croplands

Nitrous oxide (N 2 O) is a potent and persistent greenhouse gas, with rising atmospheric concentrations driven in part by inefficient use of synthetic nitrogen (N) fertilizers in agriculture. Predicting soil N 2 O emissions is challenging due to high spatial and temporal variability arising from complex soil biogeochemical processes. Process-based ecosystem models and standalone machine learning (ML) approaches without extensive site-specific calibration often miss high-emission episodes. Here, we show how an Ensemble Modeling System (EMS) based on outputs from an ensemble of ecosystem models coupled to an ensemble of ML models can improve predictions and understanding of N 2 O fluxes from US cropland. Trained and validated on ~12,000 N 2 O chamber measurements at 17 US Midwest sites (six crops, 35 management practices), the EMS accurately predicted daily fluxes of N 2 O at both training (R 2 = 0.84, RMSE = 16.4 g N ha −1 d −1 ) and held-out testing sites (R 2 = 0.84, RMSE = 6.2 g N ha −1 d −1 ). Analyses identified six dominant N 2 O drivers: soil organic carbon (SOC), NH 4 + , NO 3 - , water-filled pore space, temperature, and aboveground biomass production. Wet, warm soils produced large N 2 O peaks only with sufficient SOC and mineral N; in low-SOC soils, fluxes remained low. Incorporating these drivers into process-based models might significantly improve their predictive capacity. The EMS demonstrates a strong potential to predict N 2 O fluxes at unseen sites, enabling more reliable regional inventories, improved gap-filling where measurements are sparse, and enhanced understanding of mechanisms to advance targeted mitigation strategies in food, feed, and bioenergy crops.

AI↗
NASA NTRS1994

Lunar mineral feedstocks from rocks and soils: X-ray digital imaging in resource evaluation

The rocks and soils of the Moon provide raw materials essential to the successful establishment of a lunar base. Efficient exploitation of these resources requires accurate characterization of mineral abundances, sizes/shapes, and association of 'ore' and 'gangue' phases, as well as the technology to generate high-yield/high-grade feedstocks. Only recently have x-ray mapping and digital imaging techniques been applied to lunar resource evaluation. The topics covered include inherent differences between lunar basalts and soils and quantitative comparison of rock-derived and soil-derived ilmenite concentrates. It is concluded that x-ray digital-imaging characterization of lunar raw materials provides a quantitative comparison that is unattainable by traditional petrographic techniques. These data are necessary for accurately determining mineral distributions of soil and crushed rock material. Application of these techniques will provide an important link to choosing the best raw material for mineral beneficiation.

Chambers, John G.↗
NASA NTRS1979

Mars ultraviolet simulation facility

A facility was established for long-duration ultraviolet (UV) radiation exposure of natural and synthetic materials in order to test hypotheses concerning Martian soil chemistry observed by the Viking Mars landers. The system utilized a 2500 watt xenon lamp as the radiation source, with the beam passing through a heat-dissipating water filter before impinging upon an exposure chamber containing the samples to be irradiated. The chamber was designed to allow for continuous tumbling of the samples, maintenance of temperatures below 0 C during exposure, and monitoring of beam intensity. The facility also provided for sample preparation under a variety of atmospheric conditions, in addition to the Mars nominal. As many as 33 sealed sample ampules have been irradiated in a single exposure. Over 100 samples have been irradiated for approximately 100 to 700 h. The facility has performed well in providing continuous UV irradiation of multiple samples for long periods of time under simulated Mars atmospheric and thermal conditions.

Zill, L. P.↗