Geology Reference
In-Depth Information
Figure 4.23. A map of lunar basins; rings and ring-arcs are shown solid where exposed, dotted where buried or inferred. Names of basins
having mapped deposits are in capital letters. Names of other de
nite basins are written out in lower case. Initials refer to inde
nite basins:
AG, Amundsen
-
Ganswindt; AK, Al Khwarizmi
-
King; FB, Flamsteed
-
Billy; In, Insularum; LF, Lomonosov
-
Fleming; Ma, Marginis; MV, Mutus
-
Vlacq; PH, Pingré
-
Hausen; SR, Sikorsky
-
Rittenhouse; TS, Tsiolkovsky
-
Stark; and WA, Werner
-
Airy (from Wilhelms,
1980
).
Orientale (
Fig. 4.25
) is the youngest impact basin on
the Moon. So-named from the older system of lunar
geography in which telescopic images invert positions,
the
“
eastern
”
(i.e.,
“
orient
”
) basin is actually on the west-
ern limb of the Moon. Although it has not been dated
directly, superposition of the ejecta deposits from
Orientale, the Hevelius Formation, shows that it is
younger than the Imbrium basin. Unlike most of the
impact basins on the near side, the Orientale basin is
only partly
flooded by younger mare lavas, enabling its
structure to be studied. Mapping by Jack McCauley and
others identi
ed the key formations and basin rings
(
Fig. 4.26
), including the Inner Rook, Outer Rook, and
Cordillera Mountains. The Maunder Formation lies
between the Inner and Outer Rook Mountains. Its
s-
sured, high-albedo appearance suggests that it is melted
rock generated from the Orientale impact. The Montes
Rook Formation (
Fig. 4.27
) is found between the Outer
Rook Mountains and the Cordilleras and is also thought
to be impact melt, but includes non-melted materials,
probably representing material formed late in the ejec-
tion process. Topographic mapping of Orientale, as well
Figure 4.24. The Apollo 16 astronauts took this photograph of the
“
northwest of the crater Ptolemaeus; the
texture resulted from the gouging by ejecta from the Imbrium basin,
which is visible on the horizon (NASA AS 16
Imbrium sculpture
”
-
1412).
