APOD: Alphonsus and Arzachel (2021 Jul 17)

[APOD Robot]

Alphonsus and Arzachel

Explanation: Point your telescope at tonight's first quarter Moon. Along the terminator, the shadow line between night and day, you might find these two large craters staring back at you with an owlish gaze. Alphonsus (left) and Arzachel are ancient impact craters on the north eastern shores of Mare Nubium, the lunar Sea of Clouds. The larger Alphonsus is over 100 kilometers in diameter. A low sun angle highlights the crater's sharp 1.5 kilometer high central peak in bright sunlight and dark shadow. Scouting for potential Apollo moon landing sites, the Ranger 9 spacecraft returned closeup photographs of Alphonsus before it crashed in the crater just northeast (left) of its central mountain in 1965. Alpetragius, between Alphonsus and Arzachel, is the small crater with the deeply shadowed floor and overly large central peak.

<< Previous APOD

This Day in APOD

Next APOD >>

[Steve Randall]

Both of these craters seem to have grooves near the northern rim. Alphonsus has several other lesser grooves too. How do we explain the grooves?

[wolfie138]

i was just comng to ask the same. maybe fractures caused by the impact that have filled w/ dust over time?

[XgeoX]

Both of these craters seem to have grooves near the northern rim. Alphonsus has several other lesser grooves too. How do we explain the grooves?

Those are lunar rilles. The cause of their formation is in dispute. They could be collapsed lava tubes. They could also be tectonic in nature where the crust broke apart under pressure with one side falling or they were pulled apart.

Here are two examples…





There are rilles on mars but they are said to be inhabited…




Eric

[JohnD]

Both of those are "Rille", a German word for 'groove' that seems to be given a Latin name in the plural, "Rimae", for some reason. They may be straight or more usually 'sinuous'.

There are many rimae on the Moon and other bodies of the Solar System, and many explanations for them, all of which may be true. One of the most prominent on the Moon is Hadley Rille, visited by the Apollo 15 crew, so we probably know more about that than any other. This report summarizes all that is known, and suggests that it is a collapsed lava tube. https://www.lpi.usra.edu/resources/USGS ... o-0041.pdf

Of different interest is the oblique line above the craters in the ApoD and tangential to Alphonsus. Obscured by later impacts, including Alphonsus, such straight lines have raised suggestions of intellegent intent, especially when seen on Phobos (https://www.wired.co.uk/article/phobos- ... ry-created) but are the relic of ancient crater chains.

XgoeX jests!

John

[De58te]

Interesting observation because these two craters are so close together. The larger crater seems to be shallower than Arzachel. The walls of Arzachel appear to be at least twice as tall and if an astronaut were to slip and fall into it he probably couldn't climb out without help, whereas there seems to be a valley on the side of Alphonsus at around 3 o'clock where the astronaut could potentially walk out. Could this be because the larger asteroid hit with a much gentler force and speed, or that it hit with the same force but was originally just as deep but it was filled up with much more molten lava?

[orin stepanek]

To me Arzachel seems to have struck when the
moons surface was like a thick gooey paste before
hardening! IMO

[tf1212]

Lovely image, but you have it tilted 90 degrees. Northeast is upper right

[tf1212]

my error, lower left.

[JohnD]

See: http://adsabs.harvard.edu/full/1989LPI....20..185C

[JohnD]

And to prove that great minds think alike, see:
https://epod.usra.edu/blog/2019/07/the- ... moon-.html

[Fred the Cat]

This owl has a nice supercilium!

[neufer]

This owl has a nice supercilium!

<<supercilious (adj.) 1520s, "lofty with pride, haughtily contemptuous," from Latin superciliosus "haughty, arrogant," from supercilium "haughty demeanor, pride," literally "eyebrow" (via notion of raising the eyebrow to express haughtiness), from super "above" (see super-) + second element akin to cilium "eyelid," related to celare "to cover, hide."

Since cilium is more recent than supercilium, the former can be interpreted as a back-formation to the latter .... If indeed derived from the root *kel- 'to hide', we must still assume that a noun *kilium 'eyelid' existed, since the eyelid can 'hide' the eye, whereas the eyebrow does not have such a function. Thus, supercilium may originally have meant 'what is above the cilium'.>>

[Fred the Cat]

Alphonsus and Arzachel

Explanation: Point your telescope at tonight's first quarter Moon.

Well I only used the camera and the skies were a little hazy from our surrounding fires but the moon did reveal some nice detail. Now where was that owl?

[johnnydeep]

Alphonsus and Arzachel

Explanation: Point your telescope at tonight's first quarter Moon.

Well I only used the camera and the skies were a little hazy from our surrounding fires but the moon did reveal some nice detail. Now where was that owl?
IMG_1868 (2).JPG

That was from a camera alone? I see from the image data that it was a Canon EOS 80D. What lens did you have and were you zoomed in at all? Did you use a tripod?

[JohnD]

Several members above have posted images. I see from the FAQ page that image posting is allowed if so enabled for that thread (which clearly has been done) and if that member has the priviledge. May I post images, please?
JOhn

[XgeoX]

Several members above have posted images. I see from the FAQ page that image posting is allowed if so enabled for that thread (which clearly has been done) and if that member has the priviledge. May I post images, please?
JOhn

With the vast amount you have posted I can’t believe you don’t have that privilege. I have only a 100 posts and I have never had to ask.
Question: do you use the advanced editor and the picture tag?

Eric

[JohnD]

XgeoX,
I'm looking at the 'Full Editor' now. It has an "Insert Image" button which generates pairs of square backets, with 'img' and '/img' in them.
But pasting anything into the space in the middle gets nothing.

There's something in the FAQ about posting images that are online, not on one's hard disk, but are all the above, and elsewhere, pics online somewhere? EG Fred's Moon pic, which he took himself.

What am I doing wrong?
John

[johnnydeep]

XgeoX,
I'm looking at the 'Full Editor' now. It has an "Insert Image" button which generates pairs of square backets, with 'img' and '/img' in them.
But pasting anything into the space in the middle gets nothing.

There's something in the FAQ about posting images that are online, not on one's hard disk, but are all the above, and elsewhere, pics online somewhere? EG Fred's Moon pic, which he took himself.

What am I doing wrong?
John

There are several ways to post images that show up as pictures in posts. The "picture" button gives you the [ img ] ... [ /img ] tags between which you put a url link to an online image. There are also the "img2" and "img3" buttons and tags that are variations of that. I find "img3" most useful because you can include caption text with the image. Just hover over a button to get some format help on how to use it.

Then, for uploading pics from your local PC (or iPad, or smart phone), you can use the often overlooked "Attachments" tab below the full editor text entry frame. I don't recall ever being prevented from posting an image except due to exceeding size restrictions. It is recommended to keep your images below 1 MB if possible

[JohnD]

AaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaH! The "Attachments" button!! Thank you, johnny!
Just to check, a quick shot by mobile of the half moon in my sky.

JOhn

And it works! I promise not to abuse!

[johnnydeep]

IMG_20210716_200810.jpg

AaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaH! The "Attachments" button!! Thank you, johnny!
Just to check, a quick shot by mobile of the half moon in my sky.

JOhn

And it works! I promise not to abuse!

Yes, it worked. But note that this is an 8.3 MP image and will likely be flagged and removed by the moderator(s). Not sure why it even allowed it to be uploaded, but ideally, it should prevent it in the first place.

[ EDIT: oops - never mind. Though the image is indeed 8.3 Megapixels, it's still well under 1 MB in actual size. So, it should be fine. ]

[bystander]

...
May I post images, please?

See: How to post images

While these are instructions for posting to the Submissions threads, they apply to the rest of the forum as well.

[Fred the Cat]

Alphonsus and Arzachel

Explanation: Point your telescope at tonight's first quarter Moon.

Well I only used the camera and the skies were a little hazy from our surrounding fires but the moon did reveal some nice detail. Now where was that owl?
IMG_1868 (2).JPG

That was from a camera alone? I see from the image data that it was a Canon EOS 80D. What lens did you have and were you zoomed in at all? Did you use a tripod?

Sorry. I hadn't noticed your question. Had it mounted on a tripod with a shutter release on the Canon. The 55-250mm lens was at its highest magnification.

[johnnydeep]

Well I only used the camera and the skies were a little hazy from our surrounding fires but the moon did reveal some nice detail. Now where was that owl?
IMG_1868 (2).JPG

That was from a camera alone? I see from the image data that it was a Canon EOS 80D. What lens did you have and were you zoomed in at all? Did you use a tripod?

Sorry. I hadn't noticed your question. Had it mounted on a tripod with a shutter release on the Canon. The 55-250mm lens was at its highest magnification.

Impressive!