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At least 163 records · Page 9
All sourcesNASA NTRSDOE OSTI
NASA NTRS1971

The role of ionizing radiation in primordial organic synthesis.

Attempt to reveal how ionizing radiation may have been effective in producing the molecules necessary for life. In examining the sequence of events leading to the appearance of the first organisms the problem is considered in two parts: the formation of the small molecules such as amino acids, purines, pyrimidines, and carbohydrates; and the condensation of these molecules to give rise to polypeptides and polynucleotides. It is concluded that in the accumulation of organic compounds on the early earth ionizing radiation was not only a substantial part of the available energy, but was also an effective form of energy.

Ponnamperuma, C.↗
NASA NTRS1971

Primordial organic chemistry and the origin of life.

Aspects of Darwinian revolution are discussed together with spontaneous generation, the inorganic chemical evolution, the primitive atmosphere, and interstellar matter. The significance of the change of the earth's reducing atmosphere to an atmosphere with oxidizing characteristics is considered. Experiments regarding the abiogenic synthesis of nucleic acids and proteins are reported. It was found that micromolecules can be formed in simulation experiments. The condensation reaction taking place in the presence of water was studied together with the condensation reaction taking place in the relative absence of water or under hypohydrous conditions. Jupiter simulation studies were conducted, and lunar and meteorite material was analyzed.

Ponnamperuma, C.↗
NASA NTRS1973

On the primordial condensation and accretion environment and the remanent magnetization of meteorites

In the context of various models for the early evolution of a solar nebula, the possible roles assigned to ambient magnetic fields and the paleointensities required to establish the stable natural remanent magnetization observed in meteorites, are discussed. It is suggested that the record of paleofields present during condensation, growth, and accumulation of grains is likely to have been preserved as chemical or thermochemical remanence in unaltered meteoritic material. Fine particle theories appear adequate for treating meteoritic remanence, if models based on corresponding types of permanent magnet materials, e.g., powder ferrites for chondrites and diffusion hardened alloys for iron meteorites, are adopted.

Brecher, A.↗
NASA NTRS1974

Primordial noble gases in separated meteoritic minerals. II

A stepwise heating technique was used to analyze eight silicate samples from the Orgueil carbonaceous chondrite for He, Ne, Ar, and Xe. Six samples, of which two were etched with NaOH, were density fractions. The other two samples were grain-size fractions separated according to their ability to form a colloid at pH 11.5. Results showed the LiCl separation procedure to be gentler than the NaOH procedure. All fractions were found to be deficient in cosmogenic neon. Above 950 C the fractions gave low 20Ne/22Ne ratios particularly in the low-density and noncolloidal fraction. Compared to the other fractions the fraction from 2.35 to 2.45 g/cu cm contained less Xe and released it more rapidly at low temperatures.

Herzog, G. F.↗
NASA NTRS1978

Primordial metamorphism of asteroids via electrical induction in a T Tauri-like solar wind

Possible heating mechanisms for an intense thermal cycle in the early solar system are considered, and inductive asteroid heating in a T Tauri environment is examined. Calculations of thermal models based on recent measurements of the electrical conductivity of carbonaceous meteorites are reported which are presumably more representative of actual conditions in the early solar nebula. Asteroidal thermal evolution is computed using a highly simplified code that restricts induction to the dc limit of the TM mode, approximates the complete unipolar-generation differential equation by a simple series-resistance model, and restricts the modeling of thermal conduction to a calculation of heat transfer across a thin planar shell of given thickness increasing with time, which blankets a body assumed to have an isothermal core. A grid of results is obtained for 20 combinations of asteroid radius and solar distance representing the populaton of asteroids. It is found that there is a relative heating maximum with respect to body radius, that this effect is due to the operation of two distinct heating-rate restrictions which have opposite radius dependences, and that the maximum current density is roughly proportional to the inverse of interior radius.

Herbert, F.↗