Chapter 2: Energy at the Lunar Surface - Lunar and Planetary Institute

Apol lo 12 : 12028(3x)
PHYSICAL PROPERTIES
I
-
"~eteoric" Elements In Mare Soil I
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- Apol lo l I: 10084 (6x1
Apollo 15: 15081 and 15501 -
I
Luna 16
Ir Re
-Volatiles-
Fig.' 2.10. All mare soils studied to date are enriched in 'meteoritic' elements, relative to crystalline
rocks. Net meteoritic component is obtained by subtracting an indigenous lunar contribution,
estimated from crystalline rocks. Numbers above histogram indicate signal-to-noise ratio (i.e. ratio of
net component to correction). Abundance pattern is flat, with siderophiles and volatiles almost
equally abundant. Apparently the meteoritic component has a primitive composition (cf. Fig. 2.11)
(from Anders et al., 1973).
in alkalis, uranium and thorium. After correcting for this enrichment Anders
et al. (1973) found that the soil at the four sites examined all show
essentially the same picture, with siderophiles enriched to 1.5-2 per cent C1
chondrite equivalent and volatiles enriched to a similar if more variable
extent. In figure 2.10 the data are normalized to C1 chondrites to permit
characterization of the meteoritic component. The abundance patt- ~rn is flat
with siderophile and volatile elements almost equally abundant. This pattern
rules out all fractionated meteoroid classes when compared to the right side
of Figure 2.1 1. Ordinary chondrites, E5-6 chondrites, irons, and stony irons
are too deficient in volatiles (especially Bi) relative to siderophiles, whereas
achondrites are too low in siderophiles. The attention is then focused on
primitive meteorites on the left side of the figure in which all siderophiles
and volatiles occur in comparable abundances. A weak trend in the Apollo
data suggests a slight depletion of volatiles that may be due to a small