γ-spektroskopische Untersuchungen an Steinmeteoriten

1962 ◽  
Vol 17 (10) ◽  
pp. 921-924
Author(s):  
C. Mayer-Böricke ◽  
M.M. Biswas ◽  
W. Gentner
Keyword(s):  
Single Crystal ◽  
Specific Activity ◽  
Cosmic Ray ◽  
Mean Value ◽  
Exposure Age ◽  
Specific Activities ◽  
Exposure Ages ◽  
Cosmic Ray Exposure Age ◽  
Coincidence Spectroscopy

Cosmic ray produced Al26 and Na22 activities in chondrites have been studied by nondestructive γ (511 keV) — γ coincidence spectroscopy. The values of the Αl26 specific activities of the four measured hypersthene chondrite samples are nearly equal, and have a mean value of 0.061 Αl26 e+-decays/min. g.The Na22 specific activity of the Bruderheim chondrite was found to be 0.094 Na22 disint./min. g in agreement with the results obtained by other authors using different methods. From the Na22 activity and the Ne22 content of our sample we have calculated a cosmic ray exposure age of 26 × 106 y for Bruderheim. Exposure ages of other chondrites are discussed.Single crystal γ-spectroscopy of Bruderheim shows in addition to Al26 and Na22 the presence of Mn54 and K40.

scholarly journals Cosmic Ray Exposure Age Determinations of Cosmic Spherules from Marine Sediments

1985 ◽  
Vol 85 ◽  
pp. 179-181
Author(s):  
Kazuo Yamakoshi
Keyword(s):  
Mass Spectrometry ◽  
Cosmic Ray ◽  
High Energy ◽  
High Energy Accelerator ◽  
Exposure Age ◽  
Cosmic Spherules ◽  
Inner Region ◽  
Exposure Ages ◽  
Cosmic Ray Exposure Age ◽  
Cosmic Ray Exposure Ages

AbstractThe cosmic ray exposure ages of deep sea metalic lie spherules were determined by various methods; low level countings (Ni-59), neutron activation analysis (Mn-53), high energy accelerator mass spectrometry (Be-10, Al-26) and mass spectrometry (K isotopes). The exposure ages of 0.3 - 50 Ma were obtained. According to Poynting-Robertson effect, the starting points (supplying sources) are located at inner region of the orbit of Saturn.

scholarly journals 6. Mixing Process of the Lunar Surface Materials and their Cosmic-Ray Exposure Age

1977 ◽  
Vol 39 ◽  
pp. 301-306
Author(s):  
J. Iriyama ◽  
M. Honda
Keyword(s):  
Lunar Surface ◽  
Formation Rate ◽  
Cosmic Ray ◽  
Population Data ◽  
Mixing Process ◽  
Exposure Age ◽  
Surface Materials ◽  
Meteoroid Impact ◽  
Exposure Ages ◽  
Cosmic Ray Exposure Age

From the cosmic ray exposure age data, (time scale 107 - 108 years), of the lunar surface materials, we discuss the mixing process of the lunar surface layer caused by the meteoroid impact cratering. The gardening effect calculated using a crater formation rate slightly modified from the current population data is consistent with observed exposure ages of the lunar samples.

scholarly journals Specific Activities of Natural Radionuclides and Annual Effective Dose Due to the Intake of Some Types of Children Powdered Milk Available in Baghdad Markets

2017 ◽  
Vol 14 (3) ◽  
pp. 619-624
Author(s):  
Baghdad Science Journal
Keyword(s):  
Effective Dose ◽  
Sodium Iodide ◽  
Specific Activity ◽  
Annual Effective Dose ◽  
Natural Radionuclides ◽  
Mean Value ◽  
Powdered Milk ◽  
Effective Doses ◽  
The Mean ◽  
Specific Activities

In this research the specific activity of natural radionuclides 226Ra, 232Th and 40K were determined by sodium iodide enhanced by thallium NaI(TI) detector and assessed the annual effective dose in Dielac 1 and 2 and Nactalia 1 and 2 for children of less than 1 year which are available in Baghdad markets. The specific activity of 40K has the greater value in all the types which is in the range of allowed levels globally that suggested by UNSCEAR. The mean value of annual effective doses were 2.92, 4.005 and 1.6325 mSv/y for 226Ra, 232Th and 40K respectively.

scholarly journals Petrology, geochemistry, and cosmic-ray exposure age of Iherzolitic shergottite Northwest Africa 1950

2005 ◽  
Vol 40 (8) ◽  
pp. 1175-1184 ◽  
Author(s):  
P. GILLET ◽  
J. A. BARRAT ◽  
P. BECK ◽  
B. MARTY ◽  
R. C. GREENWOOD ◽  
...  
Keyword(s):  
Cosmic Ray ◽  
Northwest Africa ◽  
Exposure Age ◽  
Cosmic Ray Exposure Age

scholarly journals 3. Fragmentation of Asteroids and Delivery of Fragments to Earth

1977 ◽  
Vol 39 ◽  
pp. 283-291 ◽  
Author(s):  
G. W. Wetherill
Keyword(s):  
Cosmic Ray ◽  
Asteroid Belt ◽  
Combined Effects ◽  
Iron Meteorites ◽  
Exposure Age ◽  
Impact Rate ◽  
Dynamical Time ◽  
Spectrophotometric Data ◽  
Exposure Ages ◽  
Cosmic Ray Exposure Ages

Earth-impacting meteoroids are derived from both comets and asteroids, and some uncertainty still exists regarding with which of these bodies some stone meteorites should be identified. In contrast, the long cosmic ray exposure ages of iron meteorites strongly suggest a long-lived asteroidal source capable of providing ~108 g/yr of this material to the earth’s surface over at least much of solar system history. Spectrophotometric data show that differentiated asteroids are concentrated in the inner portion of the asteroid belt. The orbital histories of fragments of inner belt asteroids are investigated, considering the combined effects of close planetary encounters, secular perturbations, and secular resonances. Particular attention is given to the low inclination (<15°) objects with small semimajcr axis (2.1 to 2.6 A.U.), which can make fairly close approaches to Mars (<0.1 A.U.). It is found that the annual yield and dynamical lifetime of collision fragments of these asteroids is in agreement with the observed impact rate and exposure age of iron meteorites. A smaller yield of stone meteorites (-107 g/yr) is expected, because elimination of these objects by collision is probable on the long dynamical time scaTe. Achondrites could be produced in this way; the yield is probably too low to account for chondrites. Chondrites could possibly be derived indirectly from these bodies insofar as these asteroids are also sources of Apollo and Amor objects.

scholarly journals Cosmic-ray exposure age and preatmospheric size of the Bunburra Rockhole achondrite

2011 ◽  
Vol 47 (2) ◽  
pp. 186-196 ◽  
Author(s):  
Kees C. WELTEN ◽  
Matthias M. M. MEIER ◽  
Marc W. CAFFEE ◽  
Matthias LAUBENSTEIN ◽  
Kunihiko NISHIZUMI ◽  
...  
Keyword(s):  
Cosmic Ray ◽  
Exposure Age ◽  
Cosmic Ray Exposure Age

Cosmic-ray exposure age of Martian meteorite GRV 99027

2007 ◽  
Vol 50 (10) ◽  
pp. 1521-1524 ◽  
Author(s):  
Ping Kong ◽  
D. Fabel ◽  
R. Brown ◽  
S. Freeman
Keyword(s):  
Cosmic Ray ◽  
Martian Meteorite ◽  
Exposure Age ◽  
Cosmic Ray Exposure Age

Review of asteroid-family and meteorite-type links

2018 ◽  
Vol 14 (A30) ◽  
pp. 9-12 ◽  
Author(s):  
Peter Jenniskens
Keyword(s):  
Source Region ◽  
Cosmic Ray ◽  
Major Axis ◽  
Main Belt ◽  
Semi Major Axis ◽  
Collision Event ◽  
Exposure Age ◽  
Statistical Sense ◽  
Cosmic Ray Exposure Age ◽  
Asteroid Families

AbstractThe materials of large asteroids and asteroid families are sampled by meteorites that fall to Earth. The cosmic ray exposure age of the meteorite identifies the collision event from which that meteorite originated. The inclination of the orbit on which the meteoroid impacted Earth measures the inclination of the source region, while the semi-major axis of the orbit points to the delivery resonance, but only in a statistical sense. To isolate the sources of our meteorites requires multiple documented falls for each cosmic ray exposure peak. So far, only 36 meteorites have been recovered from observed falls. Despite these low numbers, some patterns are emerging that suggest CM chondrites originated from near the 3:1 resonance from a low-inclined source (perhaps the Sulamitis family), LL chondrites came to us from the ν6 resonance (perhaps the Flora family), there is an H chondrite source at high inclination (Phocaea?), and one group of low shock-stage L chondrites originates from the inner main belt. Other possible links are discussed.

Sign in / Sign up

Export Citation Format

Share Document