Featured Image - 03/10/2009
Letronne Crater: Plunging Into the Ocean of Storms
Letronne Crater is nestled on the southwestern edge of Oceanus
Procellarum (Figure 1). The southern half of the crater rim is
exaggerated by a sharp highlands-mare contact, while the northern half of the rim
seems to plunge beneath the Procellarum mare. This abrupt northern boundary
suggests faulting may have lowered the northern portion of the crater
before the mare lavas were erupted (Masursky et al., 1978).
Figure 1. Letronne Crater in southwest
Oceanus Procellarum (Apollo Image AS16-M-2995 [NASA/JSC/Arizona State
Spectroscopic studies of Letronne's remaining ejecta show that
the ejecta from Letronne is a mix of highlands and mare
materials (Hawke et al., 1993; Mustard and Head, 1996). The
implication is that both highlands and mare materials were already
present in the target area when the crater was formed. Dark-haloed craters
to the southwest of Letronne (not shown) suggest that the highland
materials on the southern edge of the crater and in the region between
the southern tip of Oceanus Procellarum and Mare Humorum are relatively
thin and overlie a cryptomare layer. Cryptomare, or hidden mare, are
formed when a thin blanket of highland material is thrown on top of
mare material. As impacts later form, they punch through the thin
blanket of highland ejecta and expose darker mare to the surface.
In the future, data returned by ongoing and future lunar missions, such as the Lunar Reconnaissance Orbiter, will
be used to study the Letronne region in order to help lunar scientists
increase our understanding of both lunar tectonism and lunar volcanic
Over the Moon: A View from Orbit (1978) H. Masursky, G. W. Colton,
F. El-baz, eds. NASA SP-362.
B. R. Hawke, et al. (1993) Remote Sensing Studies of the Terrain
Northwest of Humorum Basin, Geophysical Research Letters,
J. F. Mustard and J. W. Head (1996) Buried Stratigraphic Relationships
Along the Southwestern Shores of Oceanus Procellarum: Implications for
Early Lunar Volcanism, 101:18,913-18,925.