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cap603

Cracks in Moon?

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On the evening of August 19, I was viewing the moon with my 8" reflector at a magnification of 144x. I happened to notice what appeared to be a straight line segment between two craters. The line segment was situated northwest to southeast.

It appeared to be a thread or hair in the eyepiece. Of course, it wasn't. It really looks like someone drew it with a ruler and pen. I had never seen or heard of anything like this before. Coincidentally that evening, Fox News Online carried a story about lobate scarps caused by the contraction of the moon possibly due to internal cooling. Apparently, 14 lobate scarps have recently been discovered.

I've attached a photo of the scarp with an arrow pointing to the feature in question. I'm attaching two photos; one wide-angle showing the location of the suspected lobate scarp; the other is a cropped enlargement to show detail.

Can anyone confirm this is, in fact, a lobate scarf? :D

(FYI, I tried to post this last night but it hasn't appeared on forum, so I'm trying again.)

Many thanks.

post-19052-133877473232_thumb.jpg

post-19052-133877473241_thumb.jpg

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That is a feature known as Rupes Recta or the straight wall.

Dave

post-14654-133877473242_thumb.jpg

Edited by Dave Smith

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As Dave said thats Rupes Recta and the crater above it is Birt.

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The feature you have highlighted is a rectilinear fault known as Rupes Recta or the Straight Wall. It is best seen just after first quarter when the steeper west side of the slope is in shadow and stands out more.

Peter

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Nicely done. Thank you.

Thanks to everyone who has replied. I knew I'd get the answer from this forum.

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Fascinating. I had never heard of this so I googled it and found a site with excellent photos by Thierry Legault.

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Typical, I spent a good two nights dodging cloud tying to look for the wall last week and you "discover" it by accident!

Congrats though, just because its already documented doesn't mean its not a discovery.

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It was just so unusual to see a "straight line" on the surface of the moon. It was as though someone had drawn it in with pen and ruler. I'd never heard of it before. I knew there had to be an explanation since the moon is them most scrutinized body in the heavens.

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Hi Jim, it's a shadowed fault line.. one area is actually higher than the other, and the lightplay is creating a dark shadow. Look at it again when the sunlight is coming from the other direction and actually hitting the fault, and you'll see a white line instead of the dark shadow. :D

EDIT:

Here's a few images of mine that i pasted together.

One shows the shadow you saw, and the other shows the fault being illuminated by the sunlight.

post-13732-133877473758_thumb.jpg

Edited by Talitha
added image

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Nice pic's Talitha, I sometimes view the moon during the day so I will look out for this next time. I have seen several lines over the moon but I assumed them to be dried up rivers???? I take it this one mentioned above if from tectonic plates crushing against each other?

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The lines you see on the lunar surface are referred to as, "rilles," and are the result of volcanic action. They can be either channels cut by flowing lava, or cracks due to the contraction of cooling lava. They are not the result of fluvial action since the Moon cannot sustain liquid water. The formation of the Rupes Recta was most likely as a result of the cooling of the Lunar Crust shortly after formation. The Moon does not have plate tectonics.

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Thanks, Spaceboy. :( Try using a red filter for daytime viewing, it cancels out the baby blue sky and increases the contrast.

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The lines you see on the lunar surface are referred to as, "rilles," and are the result of volcanic action. They can be either channels cut by flowing lava, or cracks due to the contraction of cooling lava. They are not the result of fluvial action since the Moon cannot sustain liquid water. The formation of the Rupes Recta was most likely as a result of the cooling of the Lunar Crust shortly after formation. The Moon does not have plate tectonics.

I kind of understand whats being said. Are you saying the moon is a solid rock and these rilles were formed when the moon was first formed or there was volcanic sometime after it became the moon?

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The moon's volcanic period was approximately between 600 million and 1000 million years after it's formation 4500 million years ago. The volcanism was caused by heat generated by radioactive decay of some of the heavy elements in the lunar core. After about 2500 million years, the heating ceased and the Moon has since then been effectively a solid body, with the exception of the Regolithic surface overlying the crust.

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The volcanism was caused by heat generated by radioactive decay of some of the heavy elements in the lunar core.

Really? I thought the heating was primarily the result of friction due to gravitational compression during the moon's formation (as with all other planetary bodies).

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Yes, really! If the volcanism had been as a consequence of the heat caused by gravitational contraction, then it would have occurred during and immediately after the moon's formation. The resultant maria would therefore have suffered the same impact cratering as the rest of the lunar surface. The fact that the maria have relatively few craters demonstrates that they were created long after formation, and it follows that another heat source was the cause of the volcanism.

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Yes, really! If the volcanism had been as a consequence of the heat caused by gravitational contraction, then it would have occurred during and immediately after the moon's formation. The resultant maria would therefore have suffered the same impact cratering as the rest of the lunar surface. The fact that the maria have relatively few craters demonstrates that they were created long after formation, and it follows that another heat source was the cause of the volcanism.

Hi Thomas. Think I'm going to have to concede on this one. Guess my lunar geology is a bit rusty!

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