June 4, 2013

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Still a Little Zupid

images from LRO QuickMap; left and center image WAC mosaic; right image M3. (NASA-ASU)

Four years ago LPOD asked if Zupus really was a crater. I thought that with the availability of LRO imagery and topography data this would be a good time to revisit that question. It turns out that there still isn't adequate information for a definitive answer, but re-examining the area made two things clear. First, Mario Weigand's 2009 LPOD image is still the best available for this feature (including terrestrial and spacecraft efforts). Second, as is always the case, the area is more complicated than I previously thought. The first thing I noticed was a possible ancient crater immediately northwest of Zupus- its size and location are indicated in the central image by the circle of slightly lower brightness. The bright mountain north of Zupus, the curved edge to basin ejecta at top, and brightness along small craters at bottom suggest a rim. The interior has numerous bright little hills - which are rarer outside the putative crater - and a rille passes near its center. This may be an old crater pummelled with Orientale and other ejecta, but it doesn't improve understanding of Zupus. The QuickMap altimetry tool shows that the massive Zupus east peak is 2 km high, but there is effectively no rim for the crater elsewhere. The best arguments for it being an old, largely destroyed crater are that its roughly circular in outline, and that it contains mare lava. But notice on the high Sun M3 image at right that there are similar dark exposures of dark lava to the southeast and north, northeast of Zupus; fractures under an impact crater are not necessary for magma to escape to the surface in this immediate area. Seeing that that is true made me look over a broader area to see if a large scale feature might have controled the lava leaks. But I couldn't identify anything; these dark puddles are outside the main rings of Humorum so they are probably not basin related. If Zupus was/is not a crater what is the explanation of the tall eastern peak? Usually massifs such as this are remnants of an ancient basin rim, but I don't see one here. So, I conclude that there is still insufficient evidence to know what Zupus was/is.

Chuck Wood
P.S.: Make sure you look at Mario' great image to better understand Zupus!

Related Links
Rükl plate 51
21st Century Atlas chart 26.

Yesterday's LPOD: Half a Globe is Better Than a Flat Image

Tomorrow's LPOD: Blue Ice


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