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At least 451 records · Page 25
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NASA NTRS2020

TOI-1235 b: A Keystone Super-Earth for Testing Radius Valley Emergence Models around Early M Dwarfs

Small planets on close-in orbits tend to exhibit envelope mass fractions of either effectively zero or up to a few percent depending on their size and orbital period. Models of thermally driven atmospheric mass loss and of terrestrial planet formation in a gas-poor environment make distinct predictions regarding the location of this rocky/nonrocky transition in period–radius space. Here we present the confirmation of TOI-1235 b (P = 3.44 days, r(p)=1.738(+0.087,-0.076)R(ꚛ)), a planet whose size and period are intermediate between the competing model predictions, thus making the system an important test case for emergence models of the rocky/nonrocky transition around early M dwarfs (R(s) = 0.630 ± 0.015 R(ꙩ), M(s) = 0.640 ± 0.016 M(ꙩ)). We confirm the TESS planet discovery using reconnaissance spectroscopy, ground-based photometry, high-resolution imaging, and a set of 38 precise radial velocities (RVs) from HARPS-N and HIRES. We measure a planet mass of 6.91(+0.75,-0.85) M(ꚛ), which implies an iron core mass fraction of 20(+15,-12)% in the absence of a gaseous envelope. The bulk composition of TOI-1235 b is therefore consistent with being Earth-like, and we constrain an H/He envelope mass fraction to be <0.5% at 90% confidence. Our results are consistent with model predictions from thermally driven atmospheric mass loss but not with gas-poor formation, suggesting that the former class of processes remains efficient at sculpting close-in planets around early M dwarfs. Our RV analysis also reveals a strong periodicity close to the first harmonic of the photometrically determined stellar rotation period that we treat as stellar activity, despite other lines of evidence favoring a planetary origin (P=21.8(+0.9,-0.8) days, m(p) sin i= 13.0(+3.8,-5.3)M(ꚛ)) that cannot be firmly ruled out by our data.

Ryan Cloutier↗
NASA NTRS1984

Observations of Highly-ionized Interstellar Iron

The spectra of 24 stars, including 5 at distances d 200 pc, have been observed in the regions of the coronal Fe X lambda 6375 and Fe X lambda 5303 lines at detection limits near an equivalent width of 1 mA in the best cases. In general agreement with predictions based on a multi-phase model of the interstellar medium, no absorption which can be attributed to Fe X or Fe X4 ions in hot interstellar gas emitting the soft X-ray background is seen in any of these spectra, except for two. Toward lambda Cephei an absorption line near lambda 6375 is measured with an equivalent width of 8.1 + or - 2 mA, a width corresponding to 20 + or - 5 km/sec or a temperature T or = (0.5 + or - 0.25) x 10 to the 6th power K, and, if it is caused by Fe X ions, a radial velocity of -355 km/sec. On that hypothesis, the interstellar gas constitutes at least 63% of the column density of gas along this light path.

Hobbs, L. M.↗
NASA NTRS1987

An evaluation of metallized propellants based on vehicle performance

An analytical study was conducted to determine the improvements in vehicle performance possible by burning metals with conventional liquid bipropellants. These metallized propellants theoretically offer higher specific impulse, increased propellant density and improved vehicle performance compared with conventional liquid bipropellants. Metals considered were beryllium, lithium, aluminum and iron. Liquid bipropellants were H2/O2, N2H4/N2O4, RP-1/O2 and H2/F2. A mission with a delta V = 4267.2 m/sec (14,000 ft/sec) and vehicle with propellant volume fixed at 56.63 cu m (2000 cu ft) and dry mass fixed at 2761.6 kg (6000 lb) was used, roughly representing the transfer of a chemically propelled upper-stage vehicle from a low-Earth orbit to a geosynchronous orbit. The results of thermochemical calculations and mission analysis calculations for bipropellants metallized with beryllium, lithium, aluminum and iron are presented. Technology issues pertinent to metallized propellants are discussed.

Zurawski, Robert L.↗
NASA NTRS1987

An evaluation of metallized propellants based on vehicle performance

An analytical study was conducted to determine the improvements in vehicle performance possible by burning metals with conventional liquid bipropellants. These metallized propellants theoretically offer higher specific impulse, increased propellant density and improved vehicle performance compared with conventional liquid bipropellants. Metals considered were beryllium, lithium, aluminum and iron. Liquid bipropellants were H2/O2, N2H4/N2O4, RP-1/O2 and H2/F2. A mission with a delta V = 4267.2 m/sec (14,000 ft/sec) and vehicle with propellant volume fixed at 56.63 cu m (2000 cu ft) and dry mass fixed at 2761.6 kg (6000 lb) was used, roughly representing the transfer of a chemically propelled upper-stage vehicle from a low-Earth orbit to a geosynchronous orbit. The results of thermochemical calculations and mission analysis calculations for bipropellants metallized with beryllium, lithium, aluminum and iron are presented. Technology issues pertinent to metallized propellants are discussed.

Zurawski, Robert L.↗
NASA NTRS2004

Web-Based Toxic Gas Dispersion Model for Shuttle Launch Operations

During the launch of the Space Shuttle vehicle, the burning of liquid hydrogen fuel with liquid oxygen at extreme high temperatures inside the three space shuttle main engines, and the burning of the solid propellant mixture of ammonium perchlorate oxidizer, aluminum fuel, iron oxide catalyst, polymer binder, and epoxy curing agent in the two solid rocket boosters result in the formation of a large cloud of hot, buoyant toxic exhaust gases near the ground level which subsequently rises and entrains into ambient air until the temperature and density of the cloud reaches an approximate equilibrium with ambient conditions. In this paper, toxic gas dispersion for various gases are simulated over the web for varying environmental conditions which is provided by rawinsonde data. The model simulates chemical concentration at ground level up to 10 miles (1 KM grids) in downrange up to an hour after launch. The ambient concentration of the gas dispersion and the deposition of toxic particles are used as inputs for a human health risk assessment model. The advantage of the present model is the accessibility and dissemination of model results to other NASA centers over the web. The model can be remotely operated and various scenarios can be analyzed.

Bardina, Jorge↗
NASA NTRS1969

High voltage electron microscopy and electron diffraction of pyroxenes in type B lunar samples from Apollo 11

Lunar pyroxene 10044 specimens cleaved and sectioned by diamond knife ultramicrotomy were examined by standard (75 to 100 kV) and high voltage (200 kV) electron microscopy and diffraction. Salient findings based on evaluation of 2000 plates show uniform 300 to 600 A-wide bands, probably corresponding to single crystal domains, with lattice spacings of 2. A High resolution bright and dark field images of iron-rich and magnesium-rich crystals were compared with corresponding electron diffraction patterns. Possible relations of observed structures to magnetic domains were considered.

Fernandez-Moran, H.↗
NASA NTRS1986

A continental rift model for the La Grande greenstone belt

Stratigraphic relationships and the geochemistry of volcanic rocks contrain the nature and timing of the tectonic and magmatic processes in the pre-deformational history of the La Grande greenstone belt in the Superior Province of north-central Quebec. The lowermost supracrustals in this belt are obscured by syntectonic granitoid intrusives. The supracrustal succession in the western part of the belt consists of a lower sequence of immature clastic sediments and mafic volcanoclastics, overlain by pillowed and massive basalts. Further east, along tectonic strike, a lower sequence of mafic volcanoclastics and immature clastic sediments is overlain by a thick sequence of pillowed and massive basalts, and resedimented coarse clastic sediments and banded iron formation. These are overlain by assive basaltic andesites, andesites and intermediate volcanoclastics intercalated with immature clastic sediments. In contrast, in the eastern part of the belt lenses of felsic volcanics and volcanoclastics occur at the base of the succession and pillowed and massive basalts are overlain by komatiites at the top. The La Grande greenstone belt can be explained as the product of continental rifting. The restricted occurence of komatiites, and eastwardly directed paleocurrents in clastic sediments in the central part of the belt are consistent with rifting commencing in the east and propagating westward with time. The increase in depth of emplacement and deposition with time of the lower three units in the central part of the belt reflects deposition in a subsiding basin. These supracrustal rocks are believed to represent the initial rift succession.

Skulski, T.↗
NASA NTRS1990

On the dependence of solar flare X-ray spectral line intensity ratios of highly ionized sulfur, calcium, and iron on electron temperature, differential emission measure, and atomic physics

This paper focuses on what can be learned about the emission measure distribution and certain atomic physics parameters from spectral lines of highly ionized ions of sulfur, calcium, and iron that appear in solar flare spectra. The particular lines chosen for analysis allow the electron temperature to be determined independently of the assumption of ionization equilibrium. An attempt is made to find emission measure models based on selected functional dependences of emission measure on temperature that reproduce the observed temperatures deduced from spectral line ratios as well as the relative intensities of resonance lines of different elements.

Doschek, G. A.↗
NASA NTRS1996

Lunar Meteorite Queen Alexandra Range 93069 and the Iron Concentration of the Lunar Highlands Surface

Lunar meteorite Queen Alexandra Range 93069 is a clast-rich, glassy-matrix regolith breccia of ferroan, highly aluminous bulk composition. It is similar in composition to other feldspathic lunar meteorites but differs in having higher concentrations of siderophile elements and incompatible trace elements. Based on electron microprobe analyses of the fusion crust, glassy matrix, and clasts, and instrumental neutron activation analysis of breccia fragments, QUE 93069 is dominated by nonmare components of ferroan, noritic- anorthosite bulk composition. Thin section QUE 93069,31 also contains a large, impact-melted, partially devitrified clast of magnesian, anorthositic-norite composition. The enrichment in Fe, Sc, and Cr and lower Mg/Fe ratio of lunar meteorites Yamato 791197 and Yamato 82192/3 compared to other feldspathic lunar meteorites can be attributed to a small proportion (5-10%) of low-Ti mare basalt. It is likely that the non- mare components of Yamato 82192/3 are similar to and occur in similar abundance to those of Yamato 86032, with which it is paired. There is a significant difference between the average FeO concentration of the lunar highlands surface as inferred from the feldspathic lunar meteorites (mean: approx. 5.0%; range: 4.3-6.1 %) and a recent estimate based on data from the Clementine mission (3.6%).

Korotev, Randy L.↗
NASA NTRS1992

An ionized accretion disk in Cygnus X-1

Results of an analysis of archival Exosat and HEAO 1-A2 observations of Cyg X-1 are presented. It is found, in agreement with Ebisawa (1991), that the X-ray spectrum of Cyg X-1 exhibits a 'high-energy excess' above 8 keV, similar to that seen in Ginga spectra of AGN. It is shown, on the basis of a likelihood ratio test, that the data are significantly better fit by a Compton reflection model than by a partial covering model. Even with the energy resolution of the Exosat GSPC, it is found that the derived iron line energy and shape are very dependent on the continuum model used. The best-fit temperature for a Suniaev-Titarchuk Comptonization model is found to be significantly larger than that found in previous analyses based primarily on data in the 30-140 keV band. This suggests that the 5-50 keV continuum is not well fit by the same spectrum form applicable at high energies and that a multiple temperature thermal Compton model is necessary to fit the broadband data.

Done, C.↗
NASA NTRS1997

Mars Dynamics from Earth-Based Tracking of the Mars Pathfinder Lander

Measurements of Mars' rotational variations can be conducted via Earth-based radio tracking observations of the Mars Pathfinder lander during an extended mission. Two-way range measurements between an Earth tracking station and the lander will enable precise monitoring of the planet's orientation, allowing details of Mars' internal structure and global surface/atmosphere interactions to be determined. An analysis has been performed to investigate the accuracy with which key physical parameters of Mars can be determined using the Earth-based radio tracking measurements. Acquisition of such measurements over one Martian year should enable determination of Mars' polar moment of inertia to 1% or better, providing a strong constraint on radial density profiles (and hence on the iron content of the core and mantle) and on long-term variations of the obliquity, which influences the climate. Variations in Mars length of day and polar motion should also be detectable, and will yield information on the seasonal cycling of carbon dioxide between the atmosphere and the surface.

Folkner, W. M.↗
NASA NTRS2005

Using IKONOS Imagery to Estimate Surface Soil Property Variability in Two Alabama Physiographies

Knowledge of surface soil properties is used to assess past erosion and predict erodibility, determine nutrient requirements, and assess surface texture for soil survey applications. This study was designed to evaluate high resolution IKONOS multispectral data as a soil- mapping tool. Imagery was acquired over conventionally tilled fields in the Coastal Plain and Tennessee Valley physiographic regions of Alabama. Acquisitions were designed to assess the impact of surface crusting, roughness and tillage on our ability to depict soil property variability. Soils consisted mostly of fine-loamy, kaolinitic, thermic Plinthic Kandiudults at the Coastal Plain site and fine, kaolinitic, thermic Rhodic Paleudults at the Tennessee Valley site. Soils were sampled in 0.20 ha grids to a depth of 15 cm and analyzed for % sand (0.05 - 2 mm), silt (0.002 -0.05 mm), clay (less than 0.002 mm), citrate dithionite extractable iron (Fe(sub d)) and soil organic carbon (SOC). Four methods of evaluating variability in soil attributes were evaluated: 1) kriging of soil attributes, 2) co-kriging with soil attributes and reflectance data, 3) multivariate regression based on the relationship between reflectance and soil properties, and 4) fuzzy c-means clustering of reflectance data. Results indicate that co-kriging with remotely sensed data improved field scale estimates of surface SOC and clay content compared to kriging and regression methods. Fuzzy c-means worked best using RS data acquired over freshly tilled fields, reducing soil property variability within soil zones compared to field scale soil property variability.

Sullivan, Dana↗
NASA NTRS2010

RESOLVE's Field Demonstration on Mauna Kea, Hawaii 2010

In cooperation with the Canadian Space Agency, and the Northern Centre for Advanced Technology, Inc., NASA has undertaken the In-Situ Resource Utilization (ISRU) project called RESOLVE (Regolith and Environment Science & Oxygen and Lunar Volatile Extraction). This project is an Earth-based lunar precursor demonstration of a system that could be sent to explore permanently shadowed polar lunar craters, where it would drill into regolith, quantify the volatiles that are present, and extract oxygen by hydrogen reduction of iron oxides. The resulting water could be electrolyzed into oxygen to support exploration and hydrogen, which would be recycled through the process. The RESOLVE chemical processing system was mounted on a Canadian Space Agency mobility chasis and successfully demonstrated on Hawaii's Mauna Kea volcano in February 2010. The RESOLVE unit is the initial prototype of a robotic prospecting mission to the Moon. RESOLVE is designed to go to the poles of the Moon to "ground truth" the form and concentration of the hydrogen/water/hydroxyl that has been seen from orbit (M3, Lunar Prospector and LRO) and to test technologies to extract oxygen from the lunar regolith. RESOLVE has the ability to capture a one-meter core sample of lunar regolith and heat it to determine the volatiles that may be released and then demonstrate the production of oxygen from minerals found in the regolith. The RESOLVE project, which is led by KSC, is a multi-center and multi-organizational effort that includes representatives from KSC, JSC, GRC, the Canadian Space Agency, and the Northern Center for Advanced Technology (NORCAT). This paper details the results obtained from four days of lunar analog testing that included gas chromatograph analysis for volatile components, remote control of chemistry and drilling operations via satalite communications, and real-time water quantification using a novel capacitance measurement technique.

Captain, Janine↗
NASA NTRS2009

Lunar Water Resource Demonstration (LWRD) Test Results

NASA has undertaken the In-Situ Resource Utilization (lSRU) project called RESOLVE (Regolith and Environment Science & Oxygen and Lunar Volatile Extraction). This project is an Earth-based lunar precursor demonstration of a system that could be sent to explore permanently shadowed polar lunar craters, where it would drill into regolith, quantify the volatiles that are present, and extract oxygen by hydrogen reduction of iron oxides. The RESOLVE chemical processing system was mounted within the CMU rover "Scarab" and successfully demonstrated on Hawaii's Mauna Kea volcano in November 2008. This technology could be used on Mars as well. As described at the 2008 Mars Society Convention, the Lunar Water Resource Demonstration (LWRD) supports the objectives of the RESOLVE project by capturing and quantifying water and hydrogen released by regolith upon heating. Field test results for the quantification of water using LWRD showed that the volcanic ash (tephra) samples contained 0.15-0.41% water, in agreement with GC water measurements. Reduction of the RH in the surge tank to near zero during recirculation show that the water is captured by the water beds as desired. The water can be recovered by heating the Water Beds to 230 C or higher. Test results for the capture and quantification of pure hydrogen have shown that over 90% of the hydrogen can be captured and 98% of the absorbed hydrogen can be recovered upon heating the hydride to 400 C and desorbing the hydrogen several times into the evacuated surge tank. Thus, the essential requirement of capturing hydrogen and recovering it has been demonstrated. ,

Muscatello, Anthony C.↗
NASA NTRS1978

The redox state of planetary basalts

Redox variations of terrestrial and lunar basalts and the redox variations in single cooling units (e.g., lava flows and lava lakes) are reviewed. Estimates for the redox states of inner solar system planetary basalts are presented; these estimates are based on consideration of a number of cosmogenic properties, models for planetary interiors, and the sequence of condensation with heliocentric distance from the protosun. It is suggested that basalts on Mercury and the Moon crystallized below the iron-wustite buffer curve; Venusian basalts are more oxidized than those on Mercury, less oxidized than those on earth, and crystallization within the field of wustite stability is thought likely; basalts on earth are dominantly in the field of magnetite stability; Martian basalts are estimated to crystallize in the upper regions of magnetite stability and well into the hematite field of stability expressed in terms of temperature and oxygen fugacity.

Haggerty, S. E.↗
NASA NTRS1980

Electromagnetic inductive heating of the asteroids and moon as evidence bearing on the primordial solar wind

Thermal evolutionary models of the asteroids and the moon based on the hypothesis of electrical inductive heating by a dense primordial solar wind are compared with observation. Inferences (derived from spectroscopy) of asteroidal mineralogy when compared with electrical heating models, the variation of cooling rates recorded in iron meteorites, and the occurrence of the lunar magma ocean event lend support to the hypothesis of inductive heating. A high primordial solar rotation rate and magnetic field together with the loss due to plasma outflow of a substantial fraction of the initial solar mass would follow.

Herbert, F.↗
NASA NTRS1981

Multi-ring basin formation - Possible clues from impact cratering calculations

Finite difference continuum mechanics code calculations make it possible to vary the controlling variables in an impact event and to determine basic trends at scales unavailable to experimental analysis. Orphal et al. (1980) have summarized the results of a pair of such calculations for identical projectile/target characteristics but different impact velocities. One calculation considered a relatively low velocity iron impactor (5 km/s); the other, a high velocity iron impactor (15.8 km/s). The primary purpose was to investigate the generation and transport of impact melt for the two impact energies. Attention is given to crater growth, crater ejecta, and possible implications for basin-size events. Based on extrapolations, a new scenario is proposed. The scenario incorporates elements of several existing basin models.

Schultz, P. H.↗