February 23, 2013
Railway Tracks
image from Kaguya Archives
This is a classic LPOD from Dec 30, 2008.
Can you imagine being in lunar orbit and seeing scenes like this passing by? A number of new stills from the Kaguya HDTV
are now available including this remarkable view looking north over the Hippalus Rilles. Campanus is the crater with a rille on
its floor at bottom right, and Hippalus is the large crater near the middle whose left side is missing and is embayed by lavas
from Mare Humorum. It is not completely clear why mare-facing crater walls disappear, but this oblique view shows that the
wall becomes progressively lower from its high right side until it disappears. This means that Hippalus formed on sloping terrain and/or it was tilted inward as the basin's center subsided, and then was covered by lavas. The oblique view also suggests
that the floor of Campanus is at a higher level than the mare surface outside it to the right. This isn't certain, but if true means
that the mare and the lava inside the crater were not fed from the same reservoir.
Chuck Wood
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2013 Update Using the LRO QuickMap altimetry data
it is now possible to check the 2nd to last
statement above about the height of lava
inside Campanus compared to nearby Mare
Nubium. The floor is slightly domed but
actually about 1.3 km LOWER than the
mare! Off the bottom right corner is another
mare-floored crater, Mercator, whose floor
is the same elevation as the mare. That suggests that Mercator may have been fed by
the same source as the mare but Campanus'
lavas had a source with a different hydrostatic
pressure.
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Related Links
Rükl plate 53
Yesterday's LPOD: Another Passing of the Apollo Era
Tomorrow's LPOD: Camouflage Moon
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