Engineering Papers⌕ Search

Engineering topics

Gilmore, J. S.

Publications and source records attributed to Gilmore, J. S..

6 records
All sourcesNASA NTRSDOE OSTI
NASA NTRS1986

Conodont survival and low iridium abundances across the Permian-Triassic boundary in south China

The Permian-Triassic sedimentary sequence of China includes one of the most complete and fossiliferous Paleozoic-Mesozoic boundaries known. Closely spaced sampling across the boundary, which is an important extinction event for most organisms, has produced good conodont faunas that show little diversity change. A drop in conodont abundance is the only apparent response to the extinction event. A low concentration of iridium in the boundary clay (0.002 part per billion + or - 20 percent), as well as in samples immediately below and above, that range from 0.004 to 0.034 part per billion do not support the proposal of an extraterrestrial impact event at this boundary in China.

Clark, D. L.↗
NASA NTRS1985

A search for evidence of large body Earth impacts associated with biological crisis zones in the fossil record

The natural history of the Earth, how the present plant and animal species developed, how others completely died out, etc., was studied. The rock strata sampled and studied were at the time of deposition at sea bottom. It was found that, exactly at the stratigraphic level corresponding to the extinction, a thin clay layer was greatly enriched in the the rare element iridium. It was hypothesized that the excess irridium at the boundary came from a large steroid like object that hit the earth, and that the impact of this object threw up a dust cloud dense enough and long lasting enough to bring about the extinction of a wide variety of plants and animals, producing the unique break in in the fossil record, the cretaceous-tertiary boundary. The same iridium and platinum metals enrichement are found in a thin clay layer that corresponds with the boundary as difined by sudden radical changes in plant populations. The irridium enrichement is confirmed at other fresh water origin rites in the Raton Basin.

Orth, C. J.↗
NASA NTRS1976

Crystal activation experiment MA-151

The crystal activation experiment consisted of two sample packages that were flown in the command module and returned to earth for analysis of the radioactivity induced in them during the flight. The objective of the experiment was to define the background caused by detector activation that interferes when gamma radiation is measured in the 0.02- to 10-megaelectronvolt range from earth orbit. Preliminary results show that the activation of the NaI(Tl) crystal was a factor of 3 below that from a similar measurement on Apollo 17. The identification of certain species and the level of activation observed show an important contribution from the interactions of thermal and energetic neutrons produced as secondaries in the spacecraft. That the activation was reduced by only a factor of 3 compared with the Apollo 17 experiment, despite the geomagnetically shielded orbit, possibly indicates more efficient secondary neutron production by the more energetic cosmic rays.

Trombka, J. I.↗
NASA NTRS1975

Hydrogen, socio-environmental impact

The concept and logic flow of a hydrogen technology assessment are described along with a specific procedure for such an assessment. The development of hydrogen technology is discussed. Factors considered in the development and use of hydrogen include: stimulus of societal needs and technological innovations; economic factors; and social and environmental effects.

Gilmore, J. S.↗