Thanks, Chuck

Chuck

Ho hum, another exquisite image of Sinus Iridum. I want to use it for LPOD so I’ll have to find something new to say… Wait, what is that thin line near top right between the west end of the Straight Range and the isolated peak? A little Photoshop unsharp mask and voila - see the dark inset at bottom right! There is definitely a squiggly interrupted line with short shadows cast on the left and slightly bright edges on the right, indicating a depression. It looks like a very closely spaced crater chain, previously unknown, I think. To check, the brighter insert is from Lunar Orbiter IV (from the seamless mosaic of Map-A-Planet). The upper part of the chain, near shore, is definitely a secondary crater chain cluster. But the bottom part doesn’t show as chain on the Orbiter image, in fact there is hardly anything there at all at that magnification. But blow up the Orbiter image and there is a very narrow sinuous rille! It starts near the eastern side of the Prom. Laplace, wanders pass the isolated peak, crosses the mare ridge, and abruptly turns south and disappears. Comparison to the nearby 11 km wide Laplace D crater shows that this sinuous rille is about 500 m wide. Not bad for a 10″ Mak in Buffalo! More about the rille tomorrow.

Chuck Wood

Technical Details:
October 4, 2007, 10:44 UT. A-P 10″ mak/cass working at f30/ DMK 41BF02 firewire camera. Mosaic of two images, each with 200 frames from a stream of 900.

Related Links:
Rükl chart 11
Alan’s website.
The rille is just there in Mike Wirth’s image.

Note: Without fixing it, the LPOD software seems to work again…

Selene and the other lunar orbiters will do much more than capture images of the Moon’s surface. Measurements to be made include topography, chemical and mineral compositions, temperature, magnetism and gravity. Data from each of the sensors requires more processing and calibration than do the images so it will take a while for finished products to be released. This Clementine image with superposed Selene altimetry tracks is an example of high resolution topographic mapping we will ultimately have for the whole Moon. Seven swaths of altimetry data cross the center of the Orientale Basin. According to the color scale the lowest part of Orientale is 2-3 km below the average lunar radius of 1737.4 km, and the tallest peaks of the Rook Mountains are about 3-4 km above that radius. The highest parts of the Cordillera Mountains - the outer prominent Orientale ring - are 5 km above the average radius. The rim to floor depth of the Orientale Basin from Clementine altimetry is 6 km, but Clementine had poorer vertical resolution and larger footprints. The JAXA website says that their color calibration isn’t complete yet, but the promise of Selene and the other missions is that uncertainties will be removed and the Moon will become known.

Chuck Wood

Related Links:
Rükl Plate VII

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Comparative planetology is a powerful approach to understanding processes on different worlds. It has been used since early observers compared lunar features to landforms on Earth. The first stage of such a comparison is simply noticing similarities in morphology. Here KC points out the curved shores of a small bay on the East coast of Hong Kong with the Bay of Rainbows on the Moon. KC does not imply that Sinus Iridum resulted from water erosion of less resistant rock, but the similarity of a lowland being surrounded on three sides and open on the fourth is striking. In fact, that is probably why Riccioli called it a sinus/bay about 360 years ago. If we look more closely we see that bays on Earth occur along interfaces of land and liquid. That is true on the Moon too, but we also notice that completed lunar bays (craters) occur away from interfaces of mare and highlands, but not on Earth. So we might conclude that different processes caused the three landward sides of the bay on the Earth and the Moon. But there is a similarity in that the sea sides have missing walls. Did erosion remove the sea sides of lunar bays? Maybe. Was it erosion by mare lavas that destroyed the western rim of Le Monnier or the northern rim of Letronne? Or were these simply craters that formed on the edges of basins that dipped (or faulted) down toward their centers? There is little evidence for lava erosion of crater rims, yet the walls of Flamsteed P and other craters in the maria are often missing. Looking at a beautiful bay in Hong Kong caused us to consider how bays form on Earth and Moon, and even though there are few similarities in the processes, the thinking has been informative.

Chuck Wood

Technical Details:
none

Related Links:
Rükl Plate 10

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Deslandres has been featured on LPOD a number of times, and each new image reveals something new. This piece of a larger image by Paolo has a tonal balance that shows different floor characteristics. The southern part of the floor is lighter hued, more cratered and slightly more elevated than the northern half. The north appears to have a smooth surface sheen as if it is a lava. There are a dozen or more craters that have been covered entirely or partially filled by the smooth fill on the northern floor. At the very top of the floor of Deslandres is a patch so dark that it is visible at full Moon. This appears to be mare lava, rather than pyroclastics for there are no eruption vents visible. This broad area of smoothness stretches across about 160 km of northern Deslandres - I wonder if it is an old crater superposed on Deslandres, enlarging it toward the north. One final feature. Notice the string of about 12 closely spaced craters at the top left of the frame. Jump across the rim of Deslandres and a half dozen similar pits continue in the same trend. These could be secondary craters from Tycho, but they seem too old. Perhaps this is another example of a crater chain such as in Davy Y that formed from a series of impacts from a shredded projectile. I wonder.

Chuck Wood

Technical Details:
3 October 2007, 4:58 UT. Gladius CF-315 Lazzarotti telescope (f/25), LVI 1392 PRO experimental camera, Edmund Optics R filter, 150 frames stacked out of 2000.

Related Links:
Rükl plates 64 & 65
Paolo’s website

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A ring of light, with traces of a rainbow’s color, seems a magical sight, but its only bending of Moonlight by ice in cirrus clouds. Mars, below, and Capella, just inside the left ring, are like dots that mark the time on a cosmic clockface. And the remarkable thing is that some one could determine the date and time of the image based on the positions of the these three heavenly orbs. Perhaps enjoying the image is pleasure enough.

Chuck Wood

Technical Details
November, 2007. Canon XTi (400D) on a tripod.

Related Links:
One of Rogelio’s websites

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Mare Humorum and Orientale are such compelling targets that the region between is often overlooked. Oliver has resisted that urge and captured a wonderful image of this complex area. The jumbled texture between the craters is ejecta from the formation of various basins, with that from the Humorum Basin being buried by debris from Imbrium and then Orientale. Some of the isolated mountain masses are probably segments of the basin’s rings. At bottom right is a pond of lava captured between the Humorum mare-edge ring (diameter 425 km according to Paul Spudis) and the next one out. This mare patch is cut by linear rilles whose directions seem unrelated to Humorum basin structure. One rille peters out in the basin debris between Mersenius (top-right) and Cavendish (bottom-center). The nearly twin craters once named for the 19th century Henry brothers are at far left. The main focus of attention though is Mersenius, whose floor is rarely imaged so clearly. The rilles have an odd distribution, being mainly on the western half of the floor - I wonder why?

Chuck Wood

Technical Details
2007-12-21 22:16 UT. 9.25″ Celestron XLT + Televue 2.5X Powermate + Astronomik Red type II filter + DMK21AF04.AS @60fps, 632 frames used, 12 point auto MAP processing.

Related Links:
Rükl plate 51
Oliver’s website

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Very near the terminator the grazing Sun magnifies small differences in lunar topography to reveal subtle features we hardly know. The thing that jumped out immediately to me was the broad very low dome near the middle of Agatharchides at the bottom of the image. Another interesting feature at the top left is a elongated oval swell cut down the middle by a curved depression. This and the large swell to its south, on the other side of the wrinkle ridge, are probably intrusions of magma that did not quite break out onto the surface. The rimless pit near the southeast end of the upper swell is evidence for magma movement within a narrow conduit - a reduction of pressure allowed the roof to collapse in one place. Another type of volcanism that is less obvious is the hilly mass with one soaring peak, at least with the shadow magnification. Informally called the Helmet, this feature has a spectral coloration showing that is is volcanic but not the same composition as mare basalts. We haven’t even talked about the mare ridges and rilles - this little corner is full of interest.

Chuck Wood

Technical Details:
21 Oct 2007. 250mm f/6 Newtonian + new DMK31AF03 camera; processing with CS2. Lat.: 22º 15′ N, Long.:114º 10′ E; elevation is 0 meter. CAW enhanced the image, causing the processing excesses at the bottom.

Related Links:
Rükl Plates 52 & 53
A colorful helmet

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