Lunar Material
51
terial during impact, already mentioned by WALTER and CLAYTON (1967)
or by mixing of a Si02-rich igneous component and a low-Si02 component formed at a much lower temperature. TILLES (1961 a, 1964) showed
that tektites have a quite constant 30Sij28Si ratio, which is not different
from the terrestrial range. FRIEDMAN (1955) determined the water and
deuterium content of tektites. The DjH ratios of the water in the tektites
are in the same range as that in terrestrial water.
3. Lunar Material
Stable isotope determinations on lunar material may be important
for several reasons, two of which are: 1) to search for any evidence for a
possible origin of the moon by fission from the earth and 2) to obtain
better understanding of cosmic isotope abundances. The study of the
carbon isotope composition is important to determine whether organic
matter resembling that found in carbonaceous chondrites is present and
to identify primordial carbon compounds that may lead to an understanding of early biochemical evolution on earth. The determination of
the deuterium contents is important because a knowledge of the DjH
ratios may lead to a better understanding of the development and history of the earth's hydrosphere.
EpSTEIN and TAYLOR (1970), FRIEDMAN et al. (1970), and ONUMA et
al. (1970), and CLAYTON et al. (1971) analyzed the 180rO ratio of the
silicates and oxides in the lunar material. The (j180-values for the plagioclases, pyroxenes, and ilmenites are generally uniform, indicating isotopic equilibrium in the mineral assemblages. The (j180-values of these
minerals are comparable to terrestrial mafic and ultramafic rocks. Lunar
glass, breccia, and dust are slightly enriched in 18 0.
The temperatures of crystallization, based on plagioclase-ilmenite
temperature estimates, range from around 1070 to 1340
0
C.
EpSTEIN and TAYLOR (1970, 1971) also determined the 30Sij28Si ratio
in lunar rocks and minerals. Plagioclase is enriched in 30Si relative to
coexisting pyroxene. The glass-rich dust and breccia are also richer in
30Si than the whole-rock gabbros. EpSTEIN and TAYLOR suggested that
this enrichment results from vapor fractionation (impact melting) of the
glass during its formation.
EpSTEIN and TAYLOR (1970) and FRIEDMAN et al. (1970) determined
the (jD of lunar hydrogen gas, which was extremely depleted in deuterium, with (jD's between - 830 and 970%0. (jD was hypothesized to have
originated from solar wind (i.e., protons originating from the sun). The
small amount of water ranged from - 580 to - 870%0. (FRIEDMAN et al.,
1970) and -150 to -482%0 (EpSTEIN and TAYLOR, 1970). The differences
between these determinations may result from different amounts of absorbed contaminating terrestrial water vapor.
51
terial during impact, already mentioned by WALTER and CLAYTON (1967)
or by mixing of a Si02-rich igneous component and a low-Si02 component formed at a much lower temperature. TILLES (1961 a, 1964) showed
that tektites have a quite constant 30Sij28Si ratio, which is not different
from the terrestrial range. FRIEDMAN (1955) determined the water and
deuterium content of tektites. The DjH ratios of the water in the tektites
are in the same range as that in terrestrial water.
3. Lunar Material
Stable isotope determinations on lunar material may be important
for several reasons, two of which are: 1) to search for any evidence for a
possible origin of the moon by fission from the earth and 2) to obtain
better understanding of cosmic isotope abundances. The study of the
carbon isotope composition is important to determine whether organic
matter resembling that found in carbonaceous chondrites is present and
to identify primordial carbon compounds that may lead to an understanding of early biochemical evolution on earth. The determination of
the deuterium contents is important because a knowledge of the DjH
ratios may lead to a better understanding of the development and history of the earth's hydrosphere.
EpSTEIN and TAYLOR (1970), FRIEDMAN et al. (1970), and ONUMA et
al. (1970), and CLAYTON et al. (1971) analyzed the 180rO ratio of the
silicates and oxides in the lunar material. The (j180-values for the plagioclases, pyroxenes, and ilmenites are generally uniform, indicating isotopic equilibrium in the mineral assemblages. The (j180-values of these
minerals are comparable to terrestrial mafic and ultramafic rocks. Lunar
glass, breccia, and dust are slightly enriched in 18 0.
The temperatures of crystallization, based on plagioclase-ilmenite
temperature estimates, range from around 1070 to 1340
0
C.
EpSTEIN and TAYLOR (1970, 1971) also determined the 30Sij28Si ratio
in lunar rocks and minerals. Plagioclase is enriched in 30Si relative to
coexisting pyroxene. The glass-rich dust and breccia are also richer in
30Si than the whole-rock gabbros. EpSTEIN and TAYLOR suggested that
this enrichment results from vapor fractionation (impact melting) of the
glass during its formation.
EpSTEIN and TAYLOR (1970) and FRIEDMAN et al. (1970) determined
the (jD of lunar hydrogen gas, which was extremely depleted in deuterium, with (jD's between - 830 and 970%0. (jD was hypothesized to have
originated from solar wind (i.e., protons originating from the sun). The
small amount of water ranged from - 580 to - 870%0. (FRIEDMAN et al.,
1970) and -150 to -482%0 (EpSTEIN and TAYLOR, 1970). The differences
between these determinations may result from different amounts of absorbed contaminating terrestrial water vapor.