Hitchhiker's Guide to Rukl Chart 34

Rima Ariadaeus (JRF <freeman _at_ netcom.com>)
The Ariadaeus Rille is one of the easiest on the Moon.
Rima Ariadaeus (Robin Casady)
This feature might be a graben, two parallel faults where the area between them has dropped, or it might be a collapsed lava tube.
Boskovitch (David North <d _at_ timocharis.com>)
Boskovitch is really remarkable as a largish feature near the terminator (at least I'm pretty sure that's what makes the brown smudge in that location). For some reason it really stands out as a complex structure. Well, it is a weird crater anyway...

I enjoy that area closer in, especially the smeary Julius Caesar (messed around good by the "Imbrium Event" -- I kinda like the understatement of these terms).

Rima Hyginus (JRF <freeman _at_ netcom.com>)
This very odd rille seems in places to be composed of closely adjacent craters, laid out in a row.
Rima Hyginus (Bill O'Connell <imbrium449 _at_ sprynet.com>)
[Rima Hyginus] The Hyginus Rille (Rima Hyginus). Match this view to Plates 33 & 34 in Ruckl's _Atlas of the Moon_. The circled feature is the spiral mountain described by Wilkins & Moore, looking here like a small letter "e" fallen over to the left.

CCD image by Bill O'Connell using an 8" SCT.
The Hyginus Rille is a favorite target for amateur telescopes. Nearby are the Ariadaeus Rille and the Triesnecker Rilles, making this part of the lunar surface unusually rich in these somewhat mysterious clefts.

Sinuous rilles may be the remains of long-ago lava tubes, perhaps once roofed, where the thin lunar lava once cut a path. Other rilles, like Ariadaeus, may be grabens, where the surface has dropped between two faults. Still others, especially around the edges of the maria, may be cracks caused by isostatic "settling" of the maria. Rima Hyginus doesn't clearly fit any of these patterns. It often appears like a crater chain in the telescope, but lunar photogeologists say the "craters" are collapse pits, where the wall of the rille has fallen in. The crater midway along the rille is a true crater.

Many portions of the lunar surface show forth hidden treasures for those who look a little longer, and the Hyginus area is no exception. Under low lighting conditions, a very odd spiral feature is visible, as described below in a passage from Wilkins & Moore's classic book, The Moon:

North of Hyginus and connected by a wide but shallow valley is a curious spiral mountain (Schneckenberg). This has broad low walls and the interior is depressed only about 700 feet. Schmidt and Goodacre drew a central craterlet, but Brenner and Fauth many more. Wilkins found two craterlets and a hill on the interior, all difficult objects. Krieger, in his Mond Atlas, Vol. I, Pl. 8, depicts the interior as filled with shadow except for a central strip, on which is a pit. Anther drawing, under a higher angle of illumination, shows two pits, from the more northerly of which a branching cleft runs north-east. Krieger also found other delicate clefts, confirmed in part by Fauth and Klein."
(The Moon, Wilkins & Moore, Macmillan, 1961 (2nd Edition), Page 57)

Fortunately, the name "Mt. Schneckenberg" didn't stick (the feature has no IAU approved name), but the odd spiral mountain is still there.

[Apollo 10 view of Hyginus rille] This Apollo 10 oblique telephoto view of the lunar nearside is centered on the crater Hyginus ...the crater is about 10 kilometers (6.5 statute miles) in diameter. From the crater the prominent Hyginus Rille extends east-southeast toward the camera and northwest toward the Sea of Vapors. The rille is about 3 kilometer (2 statute miles) wide and more than 200 kilometers (130 statute miles) long.
(NASA Photo ID: AS10-31-4650 File Name: 10075150.jpg
Film Type: 70mm Date Taken: 05/18/69)

Look for Hyginus at first quarter, or just before last quarter.

Julius Caesar (David North <d _at_ timocharis.com>)
Julius Caesar is appropriately named, as it has the look of something worn and ancient, yet proud and persistent.

There are quite a few elongated blobs of stuff in that area, most commonly theorized to be huge ejecta deposits from the Mare Imbrium Event (or Big Honking Smash). To me, that zone looks like someone smeared it with a pallette knife, or like wall texturing...

Julius Caesar (Akkana)
[Julius Caesar] My sketch of Julius Caesar at sunrise, including the prominent gash (still in darkness) just to the crater's north. The apparent crater just beginning to peek into the light to the south of Julius Caesar isn't shown clearly at all on Rukl's chart 34; I'm not sure what it is.
Catena near Godin (David North <d _at_ timocharis.com>)
There seemed to be a broken line running directly northeast from the eastern tangent of Godin... hmm. I didn't recall noting this before, but wondered why something would show up at 45 degrees from the terminator when 90 seems so much better than zero..?

Nevertheless, out come the books, riffle riffle. In Rukl (page 34), nothing there. But in the Times Atlas, I hit paydirt. There's a broken catena of craters, mostly of two sizes (small and smaller) running in exactly that position, as yet unnamed. Very striking in this exact light -- another one of those things that make you wonder why you haven't seen it before. Of course, it's a question of a lot of things: exact light angles, steadiness, equipment, etc.

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This page last modified: Dec 06, 2020
