Engineering Papers⌕ Search

SEARCH · Engineering Papers

Results for “mercury”

Search indexed NASA NTRS and DOE OSTI research on propulsion, heat transfer, battery materials and energy systems. Follow report and document links to the original sources.

Quote a phrase for an exact phrase match. Source license links do not imply unrestricted reuse.

At least 379 records · Page 21
All sourcesNASA NTRSDOE OSTI
NASA NTRS1972

On mercury clouds in the atmosphere of Venus.

Calculation of the reflectivity of Lewis' (1969) mercury cloud systems to determine the limits placed upon such models by the requirement that they reproduce the observed high albedo of Venus. In this way an upper limit is placed on the mercury droplet cloud mass. This limit is a function of the droplet size. If the droplets are less than 10 microns in radius, models with mercury clouds of mass greater than 0.005 g/sq cm are excluded the values for the masses of the Hg2Cl2 and HCl-H2O clouds given by Lewis are adopted. Relations are given which make it possible to determine whether a particular model satisfies the constraints imposed by the requirement that it produce the high albedo of Venus.

Potter, J. F.↗
NASA NTRS1974

Magnetic field observations near Mercury: Preliminary results from Mariner 10

Results are presented from a preliminary analysis of data obtained near Mercury by the NASA/GSFC Magnetic Field Experiment on Mariner 10. A very well developed, detached bow shock wave, which developed as the super-Alfvenic solar wind interacted with the planet Mercury was observed. A magnetosphere-like region, with maximum field strength of 98 gamma at closest approach (704 km altitude) was also observed, and was contained within boundaries similar to the terrestrial magnetopause. The obstacle deflecting the solar wind flow was global in size, but the origin of the enhanced magnetic field was not established. The most plausible explanation, considering the complete body of data, favored the conclusion that Mercury has an intrinsic magnetic field.

Ness, N. F.↗
NASA NTRS1973

Neutral and ion-exospheres in the solar wind with applications to Mercury

Construction of a model neutral and ion exosphere for a planet weakly interacting with the solar wind. The model is constructed in general terms and is then specialized to possible neutral and ion exospheres for the planet Mercury. The neutral exosphere model allows for density and temperature variations and for rotation at the exobase. The ion exosphere is produced by ionization of the neutral exosphere in the solar wind, and its density distribution is obtained by solving the continuity equation in the drift approximation. Applying to Mercury a surface temperature distribution inferred from infrared data and a vanishing bound neutral flux at the base, He and He(+) density distributions are found. When the He atmosphere of Mercury is due entirely to the surface bombardment by solar wind He(2+), the resulting He(+) density is found to vary from 0.15 to 0.001 per cu cm over the range from 1.5 to 5 planetocentric radii on the dayside. These densities are found to be detectable by typical solar-wind plasma instruments.

Hartle, R. E.↗
NASA NTRS1974

A new upper limit for an atmosphere of CO2, CO on Mercury

High-resolution infrared spectra of Mercury (1.9-2.7 microns, resolution limit 0.134 wavelength/cm) obtained with the original 'Connes' interferometer at the Steward Observatory 90-inch telescope have provided a very sensitive test for the possible presence of a CO2, CO atmosphere. An improved upper limit of 0.12 cm-atm has been set for CO2, and a new upper limit of 0.05 cm-atm has been set for CO. Upper limits of similar magnitude can be established for CH4 and NH3. From the separation of the Mercury signal into reflected sunlight and thermal emission, we determine that the reflectivity decreases toward longer wavelengths and has a value of about 0.06 at 2.25 microns. Implications for the possible evolution of an atmosphere on Mercury are discussed.

Fink, U.↗
NASA NTRS1974

Mercury's atmosphere from Mariner 10 - Preliminary results

Analysis of data obtained by the ultraviolet experiment on Mariner 10 indicates that Mercury is surrounded by a thin atmosphere consisting in part of helium. The partial pressure of helium at the terminator is about 5 trillionths of a millibar. The total surface pressure of the atmosphere is less than about 2 billionths of a millibar. Upper limits are set for the abundance of various gases, including hydrogen, oxygen, carbon, argon, neon, and xenon. The wavelength dependence of Mercury's surface albedo is similar to that of the moon over a broad range of wavelengths from 500 to 1600 A. Strong signals were recorded by the airglow instrument as Mariner 10 passed through the cavity behind Mercury. They are as yet unexplained but may provide information on the properties of the local plasma.

Broadfoot, A. L.↗
NASA NTRS1974

Mercury's surface - Preliminary description and interpretation from Mariner 10 pictures

The surface morphology and optical properties of Mercury resemble those of the moon in remarkable detail and record a very similar sequence of events. Chemical and mineralogical similarity of the outer layers of Mercury and the moon is implied; Mercury is probably a differentiated planet with a large iron-rich core. Differentiation is inferred to have occurred very early. No evidence of atmospheric modification of landforms has been found. Large-scale scarps and ridges unlike lunar or Martian features may reflect a unique period of planetary compression near the end of heavy bombardment by small planetesimals.

Murray, B. C.↗
NASA NTRS1974

Mercury - Results on mass, radius, ionosphere, and atmosphere from Mariner 10 dual-frequency radio signals

Analysis of the radio-tracking data from Mariner 10 yields 6,023,600 plus or minus 600 for the ratio of the mass of the sun to that of Mercury, in very good agreement with values determined earlier from radar data alone. Occultation measurements yielded values for the radius of Mercury of 2440 plus or minus 2 and 2438 plus or minus 2 kilometers at latitudes of 2 N and 68 N, respectively, again in close agreement with the average equatorial radius of 2439 plus or minus 1 kilometers determined from radar data. The mean density of 5.44 grams per cubic centimeter deduced for Mercury from Mariner 10 data thus virtually coincides with the prior determination. No evidence of either an ionosphere or an atmosphere was found.

Esposito, P. B.↗
NASA NTRS1974

Model atmospheres for Mercury based on a lunar analogy

Similarities in daytime spectral reflectivities and nighttime infrared emission from Mercury and the moon are shown to imply that the atmosphere of Mercury must be tenuous, like that of the moon. The theory of formation, transport, and loss in the lunar atmosphere is applied to Mercury. Models of the Hermian atmosphere at perihelion and aphelion are presented, based on the solar wind as the dominant source of gases. Only the noncondensable species - hydrogen, helium and neon - are considered. Of these, helium is the most abundant atmospheric gas, with maximum concentration of about 40,000,000 per cu cm at the nighttime surface. The maximum concentration of H2 is 6,000,000 per cu cm, and that of neon is 700,000 per cu cm.

Hodges, R. R., Jr.↗
NASA NTRS1974

The magnetic field of Mercury, part 1

An updated analysis and interpretation is presented of the magnetic field observations obtained during the Mariner 10 encounter with the planet Mercury. The combination of data relating to position of the detached bow shock wave and magnetopause, and the geometry and magnitude of the magnetic field within the magnetosphere-like region surrounding Mercury, lead to the conclusion that an internal planetary field exists with dipole moment approximately 5.1 x 10 the 22nd power Gauss sq cm. The dipole axis has a polarity sense similar to earth's and is tilted 7 deg from the normal to Mercury's orbital plane. The magnetic field observations reveal a significant distortion of the modest Hermean field (350 Gamma at the equator) by the solar wind flow and the formation of a magnetic tail and neutral sheet which begins close to the planet on the night side. The composite data is not consistent with a complex induction process driven by the solar wind flow.

Ness, N. F.↗
NASA NTRS1974

Substorms on Mercury?

Qualitative similarities between some of the variations in the Mercury encounter data and variations in the corresponding regions of the earth's magnetosphere during substorms are pointed out. The Mariner 10 data on Mercury show a strong interaction between the solar wind and the plant similar to a scaled down version of that for the earth's magnetosphere. Some of the features observed in the night side Mercury magnetosphere suggest time dependent processes occurring there.

Siscoe, G. L.↗
NASA NTRS1974

Mercury's infrared phase effect

Predictions based on a smooth spherical blackbody do not agree with the observed brightness temperatures of the planet Mercury. The curves of measured effective brightness temperature as a function of phase angle are more steep than and reach lower values near absolute values of i of about 180 deg and higher values near absolute values of i of about 0 deg than those of a smooth sphere. Phase curves of the moon have also been obtained which confirm earlier measurements. The distribution of Mercury's emitted energy in wavelength is dependent upon phase angle, changing from clearly identifiable thermal spectra for absolute values of i less than 150 deg to a superposition of thermal emission at several color temperatures for greater phase angles. No significant variation of infrared brightness temperature with subearth longitude intensity was found. These results provide further evidence that the surfaces of Mercury and the moon are similar and that the top layer of the planetary terrain is rough on a millimeter scale.-

Murdock, T. L.↗
NASA NTRS1975

The magnetic field of Mercury. I

An updated analysis and interpretation are presented of the magnetic field observations obtained during the Mariner 10 encounter with the planet Mercury on March 29, 1974. The combination of data relating to position of the detached bow shock wave and magnetopause and the geometry and magnitude of the magnetic field within the magnetosphere-like region surrounding Mercury lead to the conclusion that an internal planetary field exists with dipole moment approximately 5.1 times 10 to the 22nd G per cu cm. The dipole axis has a polarity sense similar to that of earth and is tilted 7 deg from the normal to Mercury's orbital plane. The magnetic field observations reveal a significant distortion of the modest Hermean field by the solar wind flow and the formation of a magnetic tail and neutral sheet which begins close to the planet on the night side. Presently, an active dynamo mechanism in the planetary interior appears to be favored in the interpretation of the field origin.

Ness, N. F.↗
NASA NTRS1975

Our present view of Mercury and Venus

The discipline of planetology received a quantum jump in new information on the planets Mercury and Venus from the Mariner 10 spacecraft. A detailed look at the ultraviolet markings in the upper atmosphere of Venus and their attendant motion has stimulated a considerable reevaluation of theories concerning the circulation, composition, and nature of this planet's upper atmosphere. The geologic history of Mercury as revealed by Mariner 10's television science data, from two close flybys, has challenged the prevalent theories of planetary evolution. The Mercury surface morphology and optical properties resemble those of the moon and seem to record a similar sequence of events despite their differences in density and proximity to both the sun and the asteroid belt.

Danielson, G. E., Jr.↗
NASA NTRS1976

Secular resonance, solar spin down, and the orbit of Mercury

A mechanism is investigated which may provide an evolutionary explanation for the large mean eccentricity and inclination of Mercury. It is proposed that if the gravitational field of the rapidly rotating early sun had a larger second-degree harmonic, the decreasing value of this harmonic during the subsequent solar spindown would drive Mercury through two secular resonances with Venus, one involving a commensurability in the apsidal motion of the two planets and the other involving their nodal rates. An analysis is performed, showing that these resonances could increase both the inclination and eccentricity of Mercury at nearly the same time, that an initial solar rotational period of 5.5 hr or less would guarantee passage through the resonances, and that a spindown time of about 1 million years could have produced the observed inclination and eccentricity.

Ward, W. R.↗
NASA NTRS1976

Solar wind induction in Mercury - Constraints on the formation of a magnetosphere

A model is outlined in which the origin of Mercury's magnetic field is attributed to electromagnetic induction from the interplanetary magnetic field. Both transverse magnetic (TM) and transverse electric (TE) induction are considered. It is found that neither mode can produce a totally detached magnetopause, so the highly nonlinear dynamics of magnetopausal flux deflection is investigated as a potential inhibitor of the decaying tendency of linear induction. No mechanism is discovered which can account for the large distance of the magnetopause, its temporal stability, and the orientation of the magnetic field. It is shown that the stochastic trapped-field TE model comes close to fulfilling these requirements, but cannot explain the Mariner 10 observations of Mercury's field. Noting the potential difficulties of the convective magnetic dynamo model, it is concluded that the source of Mercury's field is still poorly understood.

Herbert, F.↗
NASA NTRS1976

Implications of an internal dynamo for the thermal history of Mercury

Constraints placed on the thermal evolution of Mercury by the dynamo model of the planet's magnetic field are investigated. It is assumed that Mercury is a differentiated planet possessing an iron-nickel core with a radius approximately three-fourths of the planetary radius, that the mantle is made of silicates with thermal and rheological properties similar to those of earth's upper mantle, and that differentiation was a global process which resulted in the removal of radioactive heat sources from the core and the upward segregation of heat sources in the mantle. These assumptions are found to lead to the conclusion that the existence of a molten core requires the retention of a minimum concentration of heat sources throughout the mantle, the value being comparable to the mantle-wide average concentration for earth. Thus, it is suggested that the differentiation of Mercury could not have resulted in the complete removal of heat sources from the mantle into a crust near the planet's surface.

Cassen, P.↗
NASA NTRS1976

Mercury - Spectral reflectance measurements /0.33-1.06 microns/ 1974/75

The spectral reflectance (0.32-1.06 microns) of Mercury was measured during two elongations, September-October 1974 and March 1975. The spectra are much improved over the previously available measurements. The reflectance increases almost linearly with wavelength, and no electronic transition absorption bands are evident to the precision of the data. The new spectra agree very well with the reflectance of mature lunar mare and upland soils and are not similar to those of any other observed solar system object. This suggests that the surface materials and the weathering processes controlling their optical properties are similar for both the moon and Mercury. Differences between the spectra for the two-observation periods may indicate differences in the average composition for the different regions of Mercury observed.

Vilas, F.↗
NASA NTRS1976

Mercury and Mars - The role of ionospheric conductivity in the acceleration of magnetospheric particles

Although Mercury and Mars appear to have magnetospheres of comparable size, Mercury's magnetosphere accelerates charged particles, whereas Mars' magnetosphere apparently does not. We propose that this difference results from the fact that rapid steady-state convection, and the associated particle acceleration, cannot occur in a Martian magnetosphere because of its connection to a highly conducting ionosphere. Mercury, which has no conducting ionosphere and probably an insufficiently conducting surface, can exhibit rapid solar-wind-induced convection and hence particle acceleration in its magnetospheric tail.

Hill, T. W.↗