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Heymann, D.

Publications and source records attributed to Heymann, D..

At least 37 records · Page 2
All sourcesNASA NTRSDOE OSTI
NASA NTRS1979

Sodium-22, Al-26, and Be-10 in He-3-rich flares

The theory of He-3-rich flares by Colgate et al. (1977) implies that the composition of the solar cosmic ray-event associated with a He-3-rich flare is grossly nonsolar. The relative abundances (relative to hydrogen) of carbon, nitrogen, and oxygen, as well as those of heavier elements are significantly reduced, and the isotopic compositions of virtually all elements are bound to be strongly anomalous. In addition, the abundances of Na-22, Al-26, and Be-10 (of which there are approximately 10 to the 25th power atoms each in a He-3-rich flare) are at least comparable to the abundances of stable isotopes of these elements. Conditions for the detectability of the three radioactive species are discussed.

Heymann, D.↗
NASA NTRS1979

Xenon from intermediate zones of supernovae

The paper examines the photodisintegration and neutron capture in massive stars which show that the bulk of the p-isotopes of Xe is formed during the gamma-process of Woosley and Howard (1978) by stripping of the Xe + Be seeds. The environments in which the chondrites can be formed were determined by the neutron-capture calculations; they show that the Xe-124-rich gas must be associated at the sources with anomalously large overabundances of Nd-142, Sm-144, and possibly Ba-130, and with anomalously small overabundances of the p-isotopes of Se, Kr, Sr, and Mo.

Heymann, D.↗
NASA NTRS1978

Effects of proton irradiation on a gas phase in which condensation takes place. I Negative Mg-26 anomalies and Al-26

In the present paper, isotopic effects in magnesium generated in a proton-irradiated gas phase are examined, taking only (p,n), (p,d), and (p, alpha) reactions in magnesium, aluminum, and silicon into consideration. In the presence of proton radiation, the three elements are 'removed' from the gas phase by condensation. It is required that a value of Al-26/Al-27 greater than 6 times 10 to the -5th must be reached, consistent with the value deduced by Lee Papanastassiou, and Wasserburg (1976) from their studies of the Allende meteorite. The calculations show that fast aluminum condensation reduces the required proton fluence substantially, that a significant fraction of aluminum remains uncondensed when the above value of the Al-26/Al-27 ratio is reached, that a detectable MG-24 excess is very likely to occur, that detectable negative MG-28 anomalies can be generated, and that proton fluxes and irradiation times can be varied simultaneously, and over a wide range of values, without significant changes in the required proton fluence.

Heymann, D.↗
NASA NTRS1978

Solar gases in meteorites - The origin of chondrites and C1 carbonaceous chondrites

Evidence suggesting that chondritic meteorites broke off from parent bodies in earth-crossing orbits is considered. It is suggested that ordinary chondrites have an asteroidal origin, and the possibility that C1 chondrites have a cometary origin is examined. Indications of heavy shock and reheating among L and H chondrites provides support for an asteroidal origin, while the Apollo and Amor objects are too small to be unfragmented asteroids, as proposed in the Anders theory of the origin of gas-rich meteorites. Events associated with the megaregolith are discussed in the framework of the proposed cometary origin of C1 chondrites.

Heymann, D.↗
NASA NTRS1977

Ar-40 intercept values and young apparent /K-40/-/Ar-40/ ages of five Apollo 15 fines

Correlations between Ar-40 and Ar-36 from size fractions of three Apollo 15 fines (15071, 15421, 15501) have been obtained. The Ar-40 intercept values of these fines and of 15091 and 15601 are generally lower than what one would expect for fines resulting from the comminution of rocks having ages of about 3.3 billion yr, typical for basalts of the landing site. This is interpreted to be the result of contamination by ray material from the Copernican age (equal or less than about 1 billion yr) craters, Autolycus and Aristillus, north of the landing site.

Jordan, J. L.↗
NASA NTRS1976

Cross sections for He and Ne isotopes in natural Mg, Al, and Si, He isotopes in CaF2, Ar isotopes in natural Ca, and radionuclides in natural Al, Si, Ti, Cr, and stainless steel induced by 12- to 45-MeV protons

Stacks of thin Mg, Al, Si, Ca, CaF2, Ti, and stainless steel foils were bombarded in twelve irradiations by a variable energy cyclotron. Cross sections are reported for He and Ne in natural Mg, Al, and Si, and for He in CaF2, and for Ar in natural Ca, as determined from mass spectrometer analysis of the inert gases. In addition, cross sections of Na-22 in natural Al and Si, of V-48 in natural Ti, and of Cr-51, Mn-52, and Co-57 in stainless steel are reported. From these were deduced Cr-51 and Mn-52 cross sections in natural Cr.

Walton, J. R.↗
NASA NTRS1976

Early irradiation of matter in the solar system - Magnesium /proton, neutron/ scheme

The occurrence of positive and negative Mg-26 anomalies in inclusions of the Allende meteorite is explained in terms of proton bombardment of a gas of solar composition. A significant fraction of Mg-26 in the irradiated gas is stored temporarily in the form of radioactive Al-26 by the reaction Mg-26(p, n)Al-26. Proton fluxes of 10 to the 17th power to 10 to the 19th power protons per square centimeter per year at 1 million electron volts are inferred. Aluminum-rich materials condensing from the gas phase have positive Mg-26 anomalies, whereas magnesium-rich materials have negative Mg-26 anomalies. The proton flux required to account for the observed magnesium anomalies is used to investigate possible isotopic anomalies in the elements from oxygen to argon. Detectable isotopic anomalies are predicted only for neon. The anomalous neon is virtually pure Ne-22 from Na-22 decay. The predicted amount of anomalous Ne-22 is about 10 to the -8th power cubic centimeter (at standard temperature and pressure) per milligram of sodium.

Heymann, D.↗
NASA NTRS1976

Limits for the accretion time of the earth from cosmogenic Ne-21 produced in planetesimals

Arguments are presented which show that no more than 23% of all neon-21 in the atmosphere consists of spallation Ne-21 formed by the bombardment of the earth's accreting objects by galactic cosmic rays. The amount of spallation Ne-21 depends strongly on the interpretation of the primitive, 'unirradiated' neon in the atmosphere. On the assumptions that (1) the planetesimals were irradiated by galactic cosmic rays of present-day intensity, (2) their mean lifetimes against accretion were 0.1 billion years, and (3) spallation Ne-21 was quantitatively retained by the accreting earth, and on the basis of Anders' (1965) reconstructed size distribution No. 2 of asteroids, the number of spallation Ne-21 atoms yielded amounts to 8.7% of the total number of Ne-21 atoms now on earth.

Heymann, D.↗
NASA NTRS1975

Light and dark soils at the Apollo 16 landing site

Lunar soils are discussed within the framework of a three-group classification scheme. Group I comprises North Ray Crater soils, group II contains light soils, and group III is made up of dark soils. It is suggested that group I soils originated from the light friable unit, one of the three units inside North Ray Crater. Group II soils were probably derived from the light matrix breccia unit; group II soils are mixtures of materials from all three units. It is concluded that soils with group III properties have been at the surface continuously for long periods. Group II soils show a record of solar wind exposure in the distant past (i.e., they have large (Ar-40/Ar-36)T ratios). Thus the regolith at the Apollo 16 site, which was observed to have marked layers of dark against light soils, contains sizeable 'pockets' or horizons at depth which are the sources of the group II soils.

Heymann, D.↗
NASA NTRS1975

Inert gases in fines at three levels of the trench at Van Serg Crater

Inert-gas measurements were conducted with three soil samples collected from a trench of about 17 cm depth which had been dug at Station 9, approximately 60-m southeast of the rim of Van Serg Crater on the moon. The particular trench is interesting because it is located in the continuous ejecta blanket of a relatively young crater. The results of the inert-gas measurements are presented in a table. They confirm an earlier conclusion reported by Heymann et al. (1974) that fines from Station 9 are among the most gas rich in the whole landing site. The three fines are agglutinate rich and most of the trapped gas is contained in the constructional particles. Agglutinate contents of fines tend to decrease rapidly for particles greater than about 250 micrometers.

Jordan, J. L.↗
NASA NTRS1974

Origin of inert gases in 'rusty rock' 66095

The amount of trapped inert gases present in rock 66095, as well as the elemental and isotopic composition of these gases can be explained by 'contamination' of this rock - on the lunar surface - with as little as 0.2% of fines. There is no compelling evidence that these gases come from the impact of a comet or a carbonaceous meteorite on the moon, or that they represent genuine primordial lunar gas. The Ne-21 radiation age of 66095 is 1.1 plus or minus 0.5 m.y., which strongly suggests that this rock was excavated by the South Ray Crater event.

Heymann, D.↗
NASA NTRS1974

Inert gases in twelve particles and one 'dust' specimen from the Lunar-16 sample

Mass spectrography was used to measure inert gases in lunar breccia and basalt particles. The He-4/Ne-20 ratio (mean value of 49) in the breccia was systematically lower than in basalt (mean value of 78). Possibly, this may be due to fractionation of He and Ne during and after breccia formation. Pronounced differences observed in the He-4/Ne-3 ratio are attributed to the presence of variable quantities of cosmogenic He-3. This means that either the solar wind intensity varied in time, or that small-ratio particles were exposed to solar radiation rich in He-3 and/or H-3. The exposure ages of four particles are several hundred million years. The Ar-40/Ar-36 ratio is 0.65 for breccia and basalts.

Heymann, D.↗
NASA NTRS1973

Green spherules from Apollo 15 - Inferences about their origin from inert gas measurements.

Green spherules from the 'clod' 15426 and from fines 15421 contain about 100 times less trapped inert gases than normal bulk fines from Apollo 15. These spherules have apparently never been directly exposed to the solar wind. Spherules from other fines contain about 10 times more trapped gas than those from the 'clod.' The gas in the former is surface correlated. However, spherules from fines 15401 are exceptionally gas-poor. The trapped gases can be of solar-wind origin, but this origin requires a two-stage model for the spherules from the clods. Another possibility is that the gases were absorbed from an ambient gas phase. The trapped gases may also be assumed to represent primordial lunar gas. The composition of this gas is then similar to the 'solar' or 'unfractionated' component of gas-rich meteorites, but unlike that in most of the carbonaceous chondrites.

Lakatos, S.↗