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At least 145 records · Page 8
All sourcesNASA NTRSDOE OSTI
NASA NTRS2018

The Contrast in Outgassing of Germanium Between Shergottites and Nakhlites

Final Paper and not the abstract is attached. Introduction: Germanium is generally thought to follow Si in its geochemical behavior, but little data has existed to rigorously understand the behavior of Ge in the Martian mantle. Germanium is known to be more siderophile than Si, and its partitioning into the martian core has been studied by. Typical abundances in igneous martian meteorites range from 0.5-3 ppm, a larger range than what is observed in terrestrial basalts (1.5 +/- 0.1 ppm). In situ measurements by the MER and MSL rovers have revealed a surprisingly large range in Ge abundances in surface rocks (30-650 ppm), but many igneous rocks and soils are shown to have greater than 30 ppm Ge (the detection limit of the APXS). Recently, reported that shergottite minerals showed a depletion of Ge with increasing fractionation, while nakhlites and chassignites exhibited Ge behavior compatible with closed system igneous differentiation. They interpreted their observations as tentatively indicating volcanic outgassing of Ge from shergottites (but not from nakhlite-chassignites) with recondensation of the Ge vapor into soils and breccias. Recent experimental studies show that Ge is significantly volatile from magmas. In this study, we followed up on those results by analyzing minerals in five nakhlites and five shergottites by laser ablation ICP-MS (LA-ICP-MS). See Attached

Yang, S.↗
NASA NTRS2019

A Two Gigayear History of Germanium Outgassing from Shergottites

Germanium (Ge) and Zn enrichment in martian sedimentary rocks has been reported from rocks at Gale Crater, showing concentrations of Ge from tens to hundreds ppm [1]. The Ge concentrations in martian meteorites are significantly lower (0.5-2.5 ppm) [2]. Our recent studies [3-4] have revealed that Ge is lost from shergottites due to volatility. Recent experimental studies confirm that Ge and Zn are both significantly volatile under magmatic conditions [5-7]. Further, Ge is moderately incompatible during magmatic differentiation [8] so Ge contents in olivines or pyroxenes increase during igneous fractionation in nakhlites and chassignites [4]. Shergottites for which Ge abundances had been determined included rocks with ages of 150-600 Ma, while the enrichments reported from Gale Crater rocks likely occurred over 3 Ga ago. The recent discovery of two unpaired ancient (2.4 Ga) depleted shergottites, NWA 7635 [9] and NWA 8159 [10], afforded the prospect of obtaining an extended history of martian volcanic outgassing. Both of the ancient shergottites are depleted in incompatible elements and share a similar GCR exposure age to younger depleted shergottites implying derivation from a single, long-lived (>2 Ga) volcanic center [9].

Yang, S.↗
NASA NTRS2020

Volatile Composition and Outgassing in C/2018 Y1 (IWAMOTO): Extending Detection Limits for High-Resolution IR Cometary Spectroscopy at the NASA-IRTF

We used iSHELL, the powerful high-resolution ( λ/Δλ~ 40,000) cross-dispersed IR spectrograph at the NASA-IRTF to measure the native ice composition and outgassing of moderately bright, long-period comet C/2018 Y1 (Iwamoto) (hereafter Y1) within weeks of its discovery. We measured production rates for H2O, and production rates and abundance ratios relative to H2O for eight trace molecules, including the most complete measure of cometary CH4 achieved to date. Compared with mean abundances measured among comets, our study revealed enriched CH3OH and C2H6 yet depleted CO and C2H2, perhaps indicating highly efficient H- atom addition on interstellar grains prior to their incorporation into the nucleus. The combined high spectral resolving power and broad spectral coverage of iSHELL allowed characterizing cometary composition using only three instrument settings, and its long-slit coverage allowed comparing the spatial distributions of molecular emissions and dust continuum.

DiSanti, M. A.↗
NASA NTRSDate not supplied

Molecular flow venting of a volume with an outgassing or desorbing source

A venting equation commonly used to describe the transient evolution of pressure within a volume containing an outgassing or offgassing source and a restrictive vent conductance under conditions of molecular flow has been solved analytically. Solutions are found for sources of finite thickness characterized by classical diffusion-limited behavior (proportional to inverse square root of time), as well as responses for thick material sources often observed in testing that are characterized by a more general form of power-law decay, up to inverse time behavior associated with surface desorption. Solutions involve evaluating integrals where both numerators and denominators of the integrands diverge with time, making wide-ranging transient solutions difficult to directly compute numerically. Usually, one can avoid evaluating these integrals by assuming quasistatic conditions at long time scales. A novel approach is used in this work to analytically produce solutions by generating bespoke mathematical functions, some of which solve integrals that have apparently had no previous analytical solution.

Michael Woronowicz↗
NASA NTRSDate not supplied

Molecular flow venting of a volume with an outgassing or desorbing source

"A venting equation commonly used to describe the transient evolution of pressure within a volume containing an outgassing or offgassing source and a restrictive vent conductance under conditions of molecular flow has been solved analytically. Solutions are found for sources of finite thickness characterized by classical diffusion-limited behavior (proportional to inverse square root of time), as well as responses for thick material sources often observed in testing that are characterized by a more general form of power-law decay, up to inverse time behavior associated with surface desorption. Solutions involve evaluating integrals where both numerators and denominators of the integrands diverge with time, making wide-ranging transient solutions difficult to directly compute numerically. Usually, one can avoid evaluating these integrals by assuming quasistatic conditions at long time scales. A novel approach is used in this work to analytically produce solutions by generating bespoke mathematical functions, some of which solve integrals that have apparently had no previous analytical solution."

Michael Woronowicz↗
NASA NTRS2026

CH3OH and HCN in Interstellar Comet 3I/ATLAS Mapped with the ALMA Atacama Compact Array: Distinct Outgassing Behaviors and a Remarkably High CH3OH/HCN Production Rate Ratio

We report the detection of methanol (CH3OH) toward interstellar comet 3I/ATLAS using the At-acama Compact Array of the Atacama Large Millimeter/Submillimeter Array (ALMA) on UT 2025 August 28, September 18 and 22, and October 1, and of hydrogen cyanide (HCN) on September 12 and 15. These observations spanned pre-perihelion heliocentric distances (r H ) of 2.6 – 1.7 au. The molecules showed outgassing patterns distinct from one another, with HCN production being depleted in the sunward hemisphere of the coma, whereas CH3OH was enhanced in that direction. Statistical analysis of molecular scale lengths in 3I/ATLAS indicated that CH3OH included production from coma sources at Lp > 258 km at 99% confidence. However low signal-to-noise on long baselines, which sample emission on small spatial scales closest to the nucleus, prevented definitively ruling out CH3OH as purely a parent species. In contrast, HCN production was indistinguishable from direct nucleus sublimation. The CH3OH production rate increased sharply from August through October, including an uptick near the inner edge of the H2O sublimation zone at rH = 2 au. Compared to comets measured to date at radio wavelengths, the derived CH3OH/HCN ratios in 3I/ATLAS of 124+30−34 and 79+11−14on September 12 and 15, respectively, are among the most enriched values measured in any comet, surpassed only by anomalous solar system comet C/2016 R2 (PanSTARRS)

Comae↗
NASA NTRS1996

Effects of Nucleus Ice Annealing History on Cometary Outgassing (abstract)

An important consideration for comet modeling is the dependence of the thermal conductivity on the comet structure. The microporosity of the comet ices changes with time as the phase of the ice and its annealing history progresses. Effects of these [modeled] changes on the overall gas production, as a function of time, are presented.

comet outgassing annealing ice dust thermal conduc↗
NASA NTRS1971

A study of boundary layer transition on outgassing cones in hypersonic flow

Surface heat-transfer rates and pressures were measured at hypersonic speeds on sharp cones at zero angle of attack with and without gas injection. Using the non-injection results for reference data the effects on heating and transition location of surface roughness and injectant rate, distribution and composition were determined. The transition location was sensitive to the injectant distribution. The transition Reynolds numbers were significantly greater when the injectant distribution was constant than with a variable distribution. The measured heat-transfer distribution were also strongly dependent upon the injectant distribution. Transition Reynolds number results obtained during this program with a variable injectant distribution were correlated with a limited amount of data available for a degrading model tested in a different facility. Transitional data with constant injectant distribution were correlated with earlier results. An empirical correlation of heat-transfer reduction due to gas injection in turbulent flow was developed for both distributions tested. Several effects of mass addition on heating and transition, which have been earlier reported, were observed.

Stalmach, C. J., Jr.↗
NASA NTRS1972

Radiation effects on contaminants from the outgassing of silastic 140 RTV

Exposure of the volatile condensable material (VCM) from Silastic 140 RTV adhesive sealant to 147. 0-nm radiation, simulating the space radiation environment in synchronous earth orbits, induces absorption of visible light by the VCM. This results in an increase in the absorptance of coated optical elements, such as solar cell cover glasses and second-surface mirrors for thermal control. A contaminant thickness of 0.1 micron or more could result in a change in solar absorptance of the second-surface mirrors from 0.06 to approximately 0.16 in a period of about 1.5 years in space. Calculations indicated that the VCM thickness would have to be less than approximately 0.005 micron to keep the change in solar absorptance 0.01 for a 3-year mission.

Jones, P. F.↗
NASA NTRS1973

Volatile elements in Apollo 16 samples - Possible evidence for outgassing of the moon.

Several Apollo 16 breccias, including one containing goethite, are strikingly enriched in volatile elements such as bromine, cadmium, germanium, antimony, thallium, and zinc. Similar but smaller enrichments are found in all highland soils. It appears that volcanic processes took place in the lunar highlands, involving the release of volatiles including water. The lunar thallium/uranium ratio is .0002 of the cosmic ratio, which suggests that the moon's original water content could not have exceeded the equivalent of a layer 22 meters deep. The cataclastic anorthosites at the Apollo 16 site may represent deep ejecta from the Nectaris basin.

Krahenbuhl, U.↗
NASA NTRS1976

Reduction of acoustic losses by outgassing

Heat treatment procedure at low pressure increases internal-friction quality factor of treated samples. Method can reduce propagation losses in porous ferroelectric ceramics by as much as a factor of 100.

Cirlin, E. H.↗