Upper atmospheric dimensions of meteorite

Lavrukhina, A. K.

English

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National Aeronautics and Space Administration 
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S T  - ACH - CR -10 513 I 
DETERMINATION OF ABOVE-ATMOSPHERE DIMENS IONS OF METEORITES 
bY 
A. K .  Lavrukhina 
(USSR) 
52) 
Microfiche (MF) 
ff 653 July 85 
26 SEPTEMaER 1966 
https://ntrs.nasa.gov/search.jsp?R=19670002876 2020-03-16T16:58:21+00:00Z
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ST- ACH -CR- 10 513 
DETERMINATION OF ABOVE-ATMOSPHERE DIMENS IONS OF METEORITES 
Doklady A. N. SSSR 
As tronomiya 
Tom 168, No. 6, 1275-8, 
I~datel~stvo "NAUKA", 1966 
by A. K . Lavrukhina 
S U M M A R Y  
The absence of data on above-atmosphere dimensions of meteoritic bodies 
and the position of those specimens having fallen on Earth constitutes one of 
the most essential gaps in our knowledge of meteorites. The only method allow- 
ing to evaluate the above-atmosphere dimensions of meteorites is the study of 
the depth dsitribution of the formation rate of cosmogenow isotopes arising in 
nuclear interactions of cosmic rays with the meteoritic matter. The accuracy of 
the assumed method resides mainly in the precision of radiometric methods and the 
correctness of the adopted hypothesis on the constancy of spatial distribution of 
cosmic rays in the solar systems. The method is practically applied in the case 
of the Yardymlin iron shower. 
* 
* * 
The basic source of cosmic matter is in metesrites. Ths i istter of ;=~te=r!- 
tes and of their parent bodies, i.e. the asteroids, varied in the course of the 
time of their existence 
degree than the substance of the Earth. This is why meteorites constitute the 
most important source of information about the early stages of formation of solar 
system's bodies. Moreover, they are the only source of knowledge on temporal and 
spatial variations of cosmic rays, for the meteoritic matter stores the product8 
of nuclear interactions. 
of data on above-atmosphere (or pre-atmosphere) dimensions of meteoritic bodies, 
and the position of the specimens of these bodies having fallen on Earth. It is 
known only that a substantial part of meteoritic body invading-the terrestrial 
atmosphere is lost at the expense of the ablation Drocess. 
The only method to determine the above-atmosphere dimensions of meteorites 
(nearly 4.5 billion years) to a substantially lesser 
One of the most essential gaps in our knowledge of meteorites is the lack 
is the study of the distribution in depth of the formation rate of cosmogenous 
isotopes emerging in nuclear interactions of cosmic rays with the ,meteoritic 
matter. The foundation of this method lies in the existence of differences in 
the excitation functions, i.e,, the dependence of formation cross sections on 
the particle e n e r g y 6 ~ ~ -  f (EDart) for the various grouos of products of nuclear 
reactions. 
* OPREDELENIYE DOATMOSFERNYKH RAZMEROV METEORITOV 
r 2. 
As follows from experiments on irradiation of iron targets by protons of 
various energies from 0.1 to 2.5 giga ev b-51, all products of nuclear reactions 
may be divided into two groups : 
indicated proton energy range (see curve 1 in Fig. 1); 
6 A i  in the region Ep < 1 giga ev 
larly to the curve 2, Fig.1). 
tity q (distance from the surface) of tie meteorite body of radius , iS afunc- 
tion of the intensity of primary cosmic radiation and secondary nucleo-active nar- 
ticles, which depend on ri and Ri and on the quantities 
1) isotopes with ‘Atatget - Aprod410; for them dAi is constant in the 
2) isotopes with A A  >lo; for them there is observed a sharp increase of 
and a small variation for Ep>l giga ev, simi- 
The rate of formation of isotopes HA at the i-th point, defined by the quan- 
- E ,  E ,  
uAi = $ D.q (E)  F (E)  dE/ 1 F (E)  dE; (1) 
E. - 
( J A ~  depend on the form of the spectrum of nucleoactive particles and on the excite- 
tion functions of isotopes. 
f P - 
Fig.1. Excitation functions of 
V49 (curve 1) 
in the reactions of protons with 
iron nuclei. 
and Xa2* (curve 2) 
ntL \, ’.\ 
zoo 
\ I \ \ \ 
Fig.2. Distributlon in denth of 
the formation rate of HNa22 and 
H v ~ ~  in iron meteorites with dif- 
f erent R 
In the model proposed by us i n  bv 73 , the values of HAi (ri, R i )  in iron 
meteorites are 
N -nepa -nABH HA, (rtv f i t )  = A I U A ,  Ineps + ( J A ~  Inn,, + 
+ (rLi1, -I- G i i L  + 2 i I I l ‘  + G?*1Il,lv ( 2 )  
3.  
/ 
( J A ~  is the mean non-weighted formation cross section of the isotope A ;  the 
indices I'nePB 'I, "JIEIBH, 'I, p, a, n and n2 are respectively related to the pri- 
mary cosmic radiation, to shower particles (Ep>l gigaev, to fast protons, mesons 
and neutrons (0.1 giga ev < ISp < 1 giga ev) and slow neutrons (0.001 giga ev < E p  & 
< 0.1 giga ev). 
The role of particles of each form in the formation of the Ai-isotope is deter- 
mined by the form of the spectrum of particles and the function Ai - f (E). This 
is why the character of the depth distribution HA1 in meteorites with different Ri 
for the isotopes of the two above indicated groups is different. This is clearly 
seen from the curves of Fig.2 obtained by us for the following parameters: 
IO - 0.23 particle/cm2 secester - 0.386 nucleons/ cm2 sec0ster according to . 
the spectrum of primary radiation for the solar activity minimum by the 1953-1956 
dataC81 ; the spectrum form variation was taken into account €or various ti at the 
expense of ionization losses. The multiplicities of secondary mesons and protons 
were determined by their spectra obtained during photoplate exposure in the atmo- 
sphere [SI. In correspondence with these data it was admitted that the spectra of 
secondary particles are not deuendent on either ri or Ri . When determining 
Ip  (ri, Ri ) and I, (ri, Ri ), the ionization losses were taken into account. The 
multiplicity of neutrons was determined from the neutron spectrum in the atmosphere 
c101 at normalization to the value for R * 26 cm and r = 13 cm 11 . The multipli- 
cities are S,, = 0,27,'Sp = 0,70, S ,  = 0,46, S,, ='3,46, Snz = 37,53. It was assumed that 
the excitation functions are identical for protons, mesons and neutrons, and that 
the meteorite body had a spherical shape before entering the Earth's atmosphere. 
From the course of the curves in Fig.:! substantial differences result in the 
absolute formation rates of Na22and V49and in their distribution in denth. 
most essential that the ratio H v ' ~ / H N ~ =  generally varies little on the surface of 
meteorites with various Ri (for example, for R-5cm it is equal to 28, for 
R -40 cm - to 25 and for R -  200 cm -to 191,  whereas for the centers these varia- 
L L W P  ere SubStantiai  (for R = j c m  tney are 36.7; for R-40cm they are 80 and 
f i r  R =  200cm they are 44). As Ri increases, there is observed a rise in the 
values of the ratio (gAq2SUrf/ (HA1 )cent ; for example, if at R -  5 cm it is 0.85 
for V49 and 1.07 for Na , we shall obtain at R-100 cm respectively 11.4 for 
V49 and 5 2  for Na22. 
excitation functions are still more clearly revealed in the graphs of Fig. 3 in the 
coordinates HA and HAL/  HA2 , which represents a nomogram from mutually intersec- 
ting parallel lines corresponding to Ri const and ri ,4Ri = const. 
itic body and the distance of the samole investigated from its surface or center 
according to the activity of the respective isotopes in the given samole of iron 
meteorite. In order to exclude the p o s s i b l e  temporal intensity variation of cosmic 
rays, isotope pairs with close decay aeriods should be chosen. 
(T -2.58 years) and fig (T - 330 days) Gr id4 (T 1.291 days) for freshly fallen 
meteorites and Belo (T -2.5*1!l6yeers or A 1 2 % T  -7.4 -197 years) *for meteor- 
ites having fallen five or more years back.  According to the maximum value of 
Na22 activity and the average activity of V49 in the Arus Yardymlin iron shower 
1123 (point in Fig. 3), we deterrnlried the above-atmosqhere radius and the weight 
of the meteoritic body having started that shower (see Table 1). fiad the fallen 
body had the shape of a sphere  of radius Rafteatme *15.5cm, its weight would 
* also ~ n 3 3  (T 2 .  106 years) 
It is 
L 1  ^ -I 
These peculiarities of HAi distribution in depth for isotopes with various 
Such a nomogram allows to determine the above-atmasphere radius of the meteor- 
Such are Na2* 
4. > 
M a  
IS0 
t20 
90 
60 
30 
have been equal to 550kg, value close to that of open specimens (150 kg). The 
difference between these weights is explained by the irregularity of melted layer's 
blowing off the surface of the body moving at cosmic velocity. The value of - r
for the specimen investigated was found to be 10.4cm. 
- 
- 
- 
- 
- 
- 
QI 
U 
=L 
General 
weight, kg 
Degree or 
ablation, % 
aJ w 60 70 90 
I@ 3@ 
u
tu rr: 
Ratio of formation rates V49 & Na22 
R, cm r /  R 
Fig.3. Dependence of Hv49 on H ~ 4 9 / H ~ ~ 2 2  for 
various ri and ri / Ri 
r, cm R - r, cm 
Above-atmosphere dimensions of a meteoritic body fallen 
in the form of Yardymlin ironshower 
26 
39 
0.4 10.4 15.6 
0.6 -. 0.4. 23.4 - 15.6 15.6- 23.4 550 I I 1850 
75 
92 
Source 
present 
work --I 13 
I I I I I I 1 I 
Our estimates of dimensions and weight of the meteortic body having fallen in 
the form of the Yardymlin iron shower differ from the data of a3 , obtained on the 
basis of analysis of the dependences of ratios of He3 / Ne21 and !le3 / He4 contents 
on H ~ ~ 3 8 .  in the Arus specimen. The nomograms were constructed according to data 
on depth distribution o f  these otopes in the Grant meteorite, whose cosmic age 
was, according to the 
susbtantial discrepancies were revealed in 841 in the dependence of C13'0~~~er9 
Ar36 
meteorite, apparently on account of snatial erosion which may distort t o  pattern 
of distribution in depth of stable isotopes. Nor can be excluded the oossibility 
of temporal variation of cosmic rays which will lead to various effects on stable 
and radioactive isotopes. 
/ C j '  rbethod, equal to 600 million years. 
on depth and in the values of cosmic ages for various areas of the Grant. 
5. > 
The method proposed by US is devoid of these uncertainties. Its orecision 
is determined mainly by the precision of radiometric determinations of low acti- 
vities and the correctness of the adopted opinion on the constance of spatial 
distribution of cosmic rays in the solar system, 
I wish to express my gratitude to L.D. Revina, T. A.  Ibrayev and T. I. 
Kholodkovskaya for their assistance in the completion of the work. 
Institute of Geochemistry and Analytical 
Chemistry in t'le n a m  of 
V.I.Vernadskiy, of 
the USSR Academy of Sciences 
Contract No. N A S  - 5 - 12487 
VOLT TECHNICAL COKPORATIO?! 
1145 19th st. NW 
WASHINGTON D.C. 20036 
Telephone: 223- 6700 
Manuscript received 
on 25 August 1065 
Translated by ANDRE L. BRICHANT 
on 2 1 -  22 September 1966 
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CIARK, TOWNSEND 
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McDONALD (6) 
KUPPERIAN (3) 
McCRAQCEN 
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BEHRING 
KASTNER 
BAUER 
GOLDBERG 
HERMAN 
MAIER 
STONE 
HESS (3 1 
O'KEEFE 
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HARRIS 
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LIBRARY 
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D I S T R I B U T I O N  
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NEWELL, NAUGLE 
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OTHER CENTERS 
A M E S R.C. 
SONETT (3)  
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LANGLEY R.C. 
160 ADAISON 
116 KATZOFF 
213 DAVIS 
242 GARRICK 
185 WEATHERWAX 
J P L  -
LOOMIS 183-501 
CONEL 183-501 
SP,SC. 186-133 (3)  
WYCKOFF Vis-Lab. 
T-122 LPS 
LIBRARY 111-113 
U.CAL BERKELEY 
WILCOX 
plus the perm.rddressees 


Determination of above-atmosphere dimensions of meteorites

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