A
SOME SURFACE CHARACTERISTICS AND G S INTERACTIONS OF
APOLLO 1 4 FINES AND ROCK FRAGMENTS, by D . A . Cadenhead ( p r i n -
c i p a l ~ n v e s t i g a t o r ) , N . J . Wagner, B . R . J o n e s and J . R . S t e t t e r ,
Department o f Chemistry, S t a t e U n i v e r s i t y N . Y . a t B u f f a l o , Buf-
f a l o , N.Y. 14214.
Over t h e p a s t s i x months a s u r f a c e s t u d y o f Apollo 14 f i n e s
and r o c k fragments have been c a r r i e d o u t w i t h t h e f o l l o w i n g ob-
jectives: (1) A c o r e l l a t i o n o f g e o l o c i a l f e a t u r e s and l u n a r
e v e n t s w i t h s u r f a c e a r e a ( 2 ) The o b s e r v a t i o n o f i n t e r n a l p o r e
s t r u c t u r e ( 3 ) An e v a l u a t i o n o f t h e a d s o r p t i o n c h a r a c t e r i s t i c s o f
t h e s e m a t e r i a l s t o g a s e s such a s n i t r o g e n , hydrogen and w a t e r
v a p o r . O b j e c t i v e s 1 and 2 were r e a l i z e d by t h e o b s e r v a t i o n ,
t h r o u g h b o t h o p t i c a l a n d e l e c t r o n (scanning and t r a n s m i s s i o n )
microscopy, o f t h e s u r f a c e f e a t u r e s o f t h e samples, w h i l e ob-
t a i n i n g t h e s u r f a c e a r e a (and c o - i n d i d e n t a l l y t h e he1 ium d e n s i t y ) .
Helium d e n s i t i e s were o b t a i n e d u s i n g a c l a s s i c a l B.E.T. v o l u -
m e t r i c s y s t e m . l T y p i c a l d e n s i t y v a l u e s ranged from 2 . 7 t o 3 . 1
g/cc, and were used t o p r o v i d e a c c u r a t e t a r i n g o f samples f o r
gravimetric adsorption. S u r f a c e a r e a were d e t e r m i n e d by g r a v i -
m e t r i c a l l y measuring n i t r o g e n a d s o r p t i o n a t l i q u i d n i t r o g e n
tempera u r e s , l u s i n g an a r e a / a d s o r b e d n i t r o g e n m o l e c u l e o f
16.2 L ' S u r f a c e a r e a s o f 0.2 t o 1 . 0 m2/g were found f o r f i n e s
(<< 1 mrn) and f o r b r e c c i a s u r f a c e fragments, w i t h c o n s i d e r a b l y
lower v a l u e s f o r s u r f a c e c r y s t a l l i n e f r a g m e n t s . P r e l i m i n a r y ob-
s e r v a t i o n s i n d i c a t e t h a t geode and p r e s s u r e f u s i o n b r e c c i a
f o r m a t i o n enhance s u r f a c e a r e a , w h i l e t h e f o r m a t i o n o f g l a s s
l i n e d p i t s t h r o u g h m i c r o m e t e o r i t e impact r e d u c e s s u r f a c e a r e a .
The e l e c t r o n microscopy i n p a r t i c u l a r r e v e a l s t h a t t h e
measured s u r f a c e a r e a s a r i s e i n l a r g e p a r t from s m a l l p a r t i c l e
s i z e ( f i n e s ) , from p r e s s u r e f u s i o n o f s m a l l p a r t i c l e s t o form
l a r g e r o n e s ( f i n e s and b r e c c i a ) and from s u r f a c e r o u g h n e s s . So
f a r we have n o t observed i n t e r n a l p o r e s t r u c t u r e which a r i s e s
t h r o u g h rock c r y s t a l l i z a t i o n accompanied by g a s e v o l u t i o n .
P h y s i c a l a d s o r p t i o n o f m o l e c u l a r hydrogen on l u n a r f i n e s
was observed a t low t e m p e r a t u r e s ( - 1 9 7 ' ~ ) b u t n o t a t h i g h e r
t e m p e r a t u r e s . P o s s i b l e c h e m i s o r p t i o n o f m o l e c u l a r hydrogen a t
h i g h e r t e m p e r a t u r e s (up t o 1 3 0 ' ~ ) and a t o m i c hydrogen a t b o t h
low and h i g h t e m p e r a t u r e s w i l l b e s t u d i e d . Adsorption o f w a t e r
vapor on l u n a r f i n e s a t room t e m p e r a t u r e s t a k e s p l a c e w i t h
t y p i c a l c a p i l l a r y condensation h y s t e r e s i s a t high r e l a t i v e pres-
s u r e s b u t w i t h complete r e v e r s a b i l i t y a t low p r e s s u r e s . T h i s
b e h a v i o r a s w e l l a s good r e p r o d u c i b i l i t y is c o n s i d e r a b l y d i f -
0Lunar and Planetary Institute Provided by the NASA Astrophysics Data System
S u r f a c e C h a r a c t e r i s t ias and Gas I n t e r a c t i o n s
D . A. Cadenhead
f e r e n t from p r e v i o u s l y r e p o r t e d b e h a v i o r on l u n a r f i n e s.* These
d i f f e r e n c e s could a r i s e through t h e d i f f e r e n t n a t u r e of t h e
samples, t h e i r d i f f e r e n t p r e t r e a t m e n t p r i o r t o a d s o r p t i o n s t u d i e g
r
d i f f i c u l t i e s i n t h e c a l i b r a t i o n o f t h e g r a v i m e t r i c ~ y s t e m ,o~ a
combination o f a l l t h r e e .
Our o b s e r v a t i o n s , s o f a r , a r e t h a t t h o s e f a c t o r s which most
i n c r e a s e s u r f a c e a r e a o r roughness a r e t h e f r a c t u r i n g o f rocks
t o f i n e p a r t i c l e s a s w e l l a s t h e accompanying l i g h t p r e s s u r e f u -
sion processes. The f o r m a t i o n o f g e o d e s and g l a s s l i n e d m i c r o -
m e t e o r i t e p i t s i n c r y s t a l l i n e r o c k m a t e r i a l s a p p e a r t o produce
o n l y small i n c r e a s e s o r d e c r e a s e s i n s u r f a c e a r e a . Molecular
hydrogen w i l l have no e f f e c t on t h e c h e m i c a l c o m p o s i t i o n o f ex-
posed m a t e r i a l s a t low t e m p e r a t u r e s (-130 t o O O C ) b u t may do s o
a t h i g h e r t e m p e r a t u r e s ( 0 " t o 1 3 0 ' ~ ) . A more l i k e l y c a n d i d a t e
i s a t o m i c hydrogen. Exposure o f l u n a r m a t e r i a l s t o w a t e r v a p o r
has n o t shown any r a p i d w e a t h e r i n g e f f e c t s , hence b r i e f a c c i d e n -
t a l exporues t o a n e a r t h - l i k e atmosphere i s n o t l i k e l y t o b e
h a r m f u l . Under l u n a r c o n d i t i o n s , any w a t e r v a p o r , t o which t h e s e
~
m a t e r i a l s m i g h t b e e ~ p o s e d ,would r a p i d l y b e l o s t .
References
1. Mellon I n s t i t u t e B u l l e t i n , "The Assembly, C a l i b r a t i o n and
O p e r a t i o n o f a Gas A d s o r p t i o n Apparatus f o r t h e Measurement
o f S u r f a c e Area, Pore Volume D i s t r i b u t i o n and D e n s i t y o f
F i n e l y Divided S o l i d s " , P. A . F a e t h and C . B. Willingham
(1955).
2. D. A. Cadenhead and N . J . Wagner, Vac. M i c r o b a l a n c e Tech.,
-
8, 97 ( 1 9 7 1 ) .
3. A . T . McClellan and H . F. Harnsberger, J . C o l l . I n t e r f a c e
u.,577
23, (1967).
4. E . L. F u l l e r , H . F . Holmes, R . B . Gamrnage and K . Becker,
T i t l e s o f t a l k s p r e s e n t e d a t 2nd Lunar S c i e n c e Conference,
Houston J a n u a r y 1971. Talk e n t i t l e d , " C o l l o i d and S u r f a c e
Chemistry: The I n t e r a c t i o n o f Gases w i t h Lunar M a t e r i a l s ",
Wed. J a n u a r y 1 3 t h 2 P.M. 1 9 7 1 . K . Becker and R . B. Gammage,
R e p r i n t s 2nd Lunar S c i . Conf., Houston J a n u a r y 1971. P a p e r :
" E x o e l e c t r o n m i s s i o n and S u r f a c e C h a r a c t e r i s t i c s o f Lunar
Materials " .
5. B . Evans and T . E . White, Vac. M i c r o b a l a n c e Tech. & 157
(1967) .
6. Chemical and E h g i n e e r i n g News, November 1st I s s u e 1971.
0Lunar and Planetary Institute Provided by the NASA Astrophysics Data System
Woter Adsorption
0 Adsorption
A Desorption
0 4 8 12 16 20 24 28 32 36 40 44 48
P in torr
0Lunar and Planetary Institute Provided by the NASA Astrophysics Data System