The wavelength dependence of atmospheric extinction
Atmospheric extinction coefficients dependence on wavelength, comparing theoretical prediction to observational data
Blitzstein, W.↗
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Supernovae and the extinction of the dinosaurs
Supernova explosion or solar outburst theory of climatic effects on mass extinction of organisms at Cretaceous-Tertiary boundary
Russell, D.↗
Structure in the interstellar-extinction curve
Fine structure of reddening interstellar extinction curves of stellar radiation, using photographic spectrophotometry
York, D. G.↗
Stellar ultraviolet colors and interstellar extinction
A sample of celescope results is studied. Most of the sample stars belong to the Orion and Vela regions. Stars with visual excess E(B-V) less than 0.05 are selected in order to derive relationships of intrinsic color index versus spectral type. The resulting intrinsic color-color relations are compared with existing blanketed and unblanketed model calculations. Finally, the preceding intrinsic relations are utilized to derive some results on interstellar extinction. Owing to the rather large scatter in the celescope data, the Vela stars give the more significant results because their visible excess E(B-V) is, in general, larger than that for the Orion stars.
Peytremann, E.↗
Fission xenon from extinct Pu-244 in 14,301.
Xenon extracted in step-wise heating of lunar breccia 14,301 contains a fission-like component in excess of that attributable to uranium decay during the age of the solar system. There seems to be no adequate source for this component other than Pu-244. Verification that this component is in fact due to the spontaneous fission of extinct Pu-244 comes from the derived spectrum which is similar to that observed from artificially produced Pu-244. It thus appears that Pu-244 was extant at the time lunar crustal material cooled sufficiently to arrest the thermal diffusion of xenon. Subsequent history has apparently maintained the isotopic integrity of plutonium fission xenon. Of major importance are details of the storage itself. Either the fission component is the result of in situ fission of Pu-244 and subsequent storage in 14,301 material, or the fission xenon was stored in an intermediate reservoir before incorporation into 14,301.
Drozd, R.↗
Investigation of ultraviolet interstellar extinction
The progress made during the past six months in utilizing Celescope OAO-2 data in a study of extinction is reported along with conclusions drawn from each inquiry. Areas recommended for further investigation are indicated.
Payne-Gaposchkin, C.↗
Temperature and pressure dependence of CO2 extinction coefficients.
Results are presented of CO2 extinction coefficient measurements that were performed under conditions of temperature and pressure different from those used by previous investigators. The results show that, whereas pressure effects are generally negligible, temperature dependence is strong enough to invalidate the use of room temperature data for the Mars atmosphere.
Demore, W. B.↗
Extinct lunar radio activities - Xenon from Pu-244 and I-129 in Apollo 14 breccias.
Two Apollo 14 breccias have been found to contain xenon from the spontaneous fission of 82 my Pu-244. A third contains 60 times as much fission xenon as local uranium can account for and is probably of similar character. One of the breccias shows a Xe-129 excess most likely due to the decay of 17 my I-129. That these components can be separated and identified at all implies that complete isotopic homogenization has not occurred over a period which encompasses both extinction of these radionuclides and compaction of the breccias into their final form. In this sense isotope pre-history has been preserved in some lunar breccias providing information that pre-dates the formation of the rock itself (as determined by conventional techniques).
Behrmann, C. J.↗
Studies of K-Ar dating and xenon from extinct radioactivities in breccia 14318; implications for early lunar history
The lunar breccia 14318 is one of three Apollo-14 breccias containing substantial amounts of parentless xenon from the spontaneous fission of extinct Pu-244. The argon and xenon contained in this breccia were studied by stepwise heating of pristine and neutron-irradiated samples. The isotopic composition of xenon from fission, determined by an improved method, is shown to be from Pu-244. Concentrations of this fissiogenic xenon are in substantial excess (15-fold) of what could be produced by spontaneous fission of U-238. The breccia is found to contain abundant trapped argon with an Ar-40/Ar-36 ratio of roughly 14. Otherwise, the argon is radiogenic and gives a convincing K-Ar age of 3.69 plus or minus 0.09 b.y. by the stepwise Ar-40/Ar-39 method, nearly in agreement with ages for other Apollo-14 breccias.
Reynolds, J. H.↗
Interstellar extinction in the ultraviolet from celescope observations
Celescope observations of 550 stars made in four broad ultraviolet passbands (1500 to 2600 A) were used to derive intrinsic ultraviolet colors for main sequence stars (Haramundanis and Payne-Gaposchkin, 1973). Color excesses, E(Ui-V) = (Ui-V) - (Ui-V) sub 0, are qualitatively in agreement with those obtained by the Wisconsin Experiment (Bliss and Savage, 1972) for stars common to the two experiments. Excluding emission stars, binaries, and supergiants whose ultraviolet fluxes cannot be compared with the intrinsic colors, it has been verified that extinction in the ultraviolet is wavelength dependent. The results further indicate that the slope of the reddening line differs with galactic latitude in the U2 and U3 passbands.
Haramundanis, K.↗
Pulsar extinction
Radio emission from pulsars, attributed to an instability associated with the creation of electron-positron pairs from gamma rays was investigated. The condition for pair creation therefore lead to an extinction condition. The relevant physical processes were analyzed in the context of a mathematical model, according to which radiation originated at the polar caps and magnetic field lines changed from a closed configuration to an open configuration at the force balance or corotation radius.
Sturrock, P. A.↗
Ultraviolet television data from the orbiting astronomical observatory. II - Stellar ultraviolet colors and interstellar extinction
The results from the Celescope Catalog of Ultraviolet Stellar Observations (Davis, Deutschman, and Haramundanis 1973) are studied, emphasizing statistical groups and subgroups of stars. In spite of the rather large observational errors, the great number of Celescope observations make it possible to do that kind of study with reasonable accuracy. Some stars have ultraviolet colors that differ significantly from those of the group to which they have been assigned on the basis of ground-based observations. An attempt is made to describe the general properties of the ultraviolet colors of the stars as observed by the Celescope experiment on board NASA's Orbiting Astronomical Observatory (OAO-2). Besides the direct applicability of these results to the general study of stellar atmospheres and of interstellar extinction, they are also considered as a frame of reference for further studies of individual stars and groups of stars.
Peytremann, E.↗
Extinct superheavy element in the Allende meteorite
Radiochemical neutron activation analysis of seven Allende samples for 26 trace elements were conducted. In addition, Cr and Fe were studied with the aid of instrumental neutron activation analysis. The investigation had the objective to identify the extinct superheavy element which was present in meteorites and decayed to Xe isotopes by spontaneous fission. The superheavy element was found to reside mainly in a rare mineral (probably a Fe, Ni, Cr, Al-sulfide), comprising only 0.04% of the meteorite. It is pointed out that of the nine volatile superheavy elements 111 to 119, only 115, 114, and 113 are expected to condense as sulfides in the temperature interval between 400 and 500 K corresponding to mineral formation conditions in the solar nebula.
Anders, E.↗
Condensation time of the solar nebula from extinct I-129 in primitive meteorites
Mineral separates from five carbonaceous chondrites were dated by extinct 16 million year I-129, in an attempt to establish the condensation time of the solar nebula. Two Fe3O4 or Fe3O4-FeS samples from the Murchison and Orgueil meteorites are older than any other material dated thus far, and apparently formed within 200,000 years of each other. The great age, close isochronism, and primitive nature of the samples suggest that the event recorded was the condensation stage of the solar nebula. It provides a suitable zero point for the chronology of the early solar system. The I-129/I-127 ratio during condensation of the nebula was (1.46 plus or minus 0.04) times 0.0001. The recrystallized C4 chondrite Karoonda began to retain Xe-129 1.8 plus or minus 0.5 million years after the above event. This short cooling time implies rapid accretion (not exceeding 1 million years) and a shallow origin (not exceeding 10 km) below the surface of its parent body.-
Lewis, R. S.↗
Results of a comprehensive atmospheric aerosol-radiation experiment in the southwestern United States. I - Size distribution, extinction optical depth and vertical profiles of aerosols suspended in the atmosphere. II - Radiation flux measurements and
Results are reported for a field test that was aimed at acquiring a sufficient set of measurements of aerosol properties required as input for radiative-transfer calculations relevant to the earth's radiation balance. These measurements include aerosol extinction and size distributions, vertical profiles of aerosols, and radiation fluxes. Physically consistent, vertically inhomogeneous models of the aerosol characteristics of a turbid atmosphere over a desert and an agricultural region are constructed by using direct and indirect sampling techniques. These results are applied for a theoretical interpretation of airborne radiation-flux measurements. The absorption term of the complex refractive index of aerosols is estimated, a regional variation in the refractive index is noted, and the magnitude of solar-radiation absorption by aerosols and atmospheric molecules is determined.
Deluisi, J. J.↗
Comments on 'Extinct radioactivities: Trapped residuals of presolar grains'
It has recently been suggested that extinct I-129 and Pu-244 were trapped in primitive-solar-nebula ('presolar') grains and decayed into radiogenic Xe-129 and fission Xe before the grains were incorporated into meteorite bodies. This idea is reconsidered in light of the thermal and metamorphic history of meteorites. The criteria that parent and daughter species should never separate and that minerals or grains containing the anomalous xenon should not be subjected to temperatures exceeding 500 C are applied to iron meteorites, achondrites, and chondrites to determine whether presolar grains could be the carriers of rare-gas anomalies to meteorites. The results strongly indicate that the xenon anomaly could not have originated in presolar grains. Other difficulties with the presolar-grain model are discussed, including insufficiently small grain sizes, large variations in Xe-129/I-127 ratios in various meteorites, and apparently unrealistic meteorite formation times and locations.
Trivedi, B. M. P.↗
Inversion of solar extinction data from the Apollo-Soyuz Test Project Stratospheric Aerosol Measurement (ASTP/SAM) experiment
The inversion methods are reported that have been used to determine the vertical profile of the extinction coefficient due to the stratospheric aerosols from data measured during the ASTP/SAM solar occultation experiment. Inversion methods include the onion skin peel technique and methods of solving the Fredholm equation for the problem subject to smoothing constraints. The latter of these approaches involves a double inversion scheme. Comparisons are made between the inverted results from the SAM experiment and near simultaneous measurements made by lidar and balloon born dustsonde. The results are used to demonstrate the assumptions required to perform the inversions for aerosols.
Pepin, T. J.↗
Occultation of Epsilon Geminorum by Mars. II - The structure and extinction of the Martian upper atmosphere
The occultation of Epsilon Geminorum by Mars on April 8, 1976, was observed at three wavelengths and 4-ms time resolution with the 91-cm telescope aboard NASA's G. P. Kuiper Airborne Observatory. Temperature, pressure, and number-density profiles of the Martian atmosphere were obtained for both the immersion and emersion events. Within the altitude range 50-80 km above the mean surface, the mean temperature is about 145 K, and the profiles exhibit wavelike structures with a peak-to-peak amplitude of 35 K and a vertical scale of about 20 km. The ratio of the refractivity of the atmosphere at 4500 A and 7500 A is consistent with the atmospheric composition measured by Viking 1. From the 'central flash' - a bright feature in the light curve midway between immersion and emersion - an optical depth at 4500 A of 3.3 + or - 1.7 per km atm (about 0.23 per equivalent Martian air mass) is found for the atmosphere about 25 km above the mean surface near the south polar region. This large value and its weak wavelength dependence rule out Rayleigh scattering as the principal cause of the observed extinction.
Elliot, J. L.↗