IPB

Welcome Guest ( Log In | Register )

 
Reply to this topicStart new topic
Lunar swirls created by comets?, Whispy bright region on Earth's moon, remants of comet collisions.
TheAnt
post Jun 11 2015, 03:32 PM
Post #1


Member
***

Group: Members
Posts: 495
Joined: 12-February 12
Member No.: 6336



This piece is not about any specific mission, even though the swirls have been imagined by orbiters.
I might be relevant since it could give an insight for some various features we discuss on this forum.
Crashing comets may explain mysterious lunar swirls
Go to the top of the page
 
+Quote Post
ZLD
post Jun 11 2015, 05:40 PM
Post #2


Member
***

Group: Members
Posts: 555
Joined: 27-September 10
Member No.: 5458



I'm out of the loop as far as these types of simulations. What does such data look like when they say it appears consistent?


--------------------
Go to the top of the page
 
+Quote Post
marsbug
post Jun 12 2015, 09:18 PM
Post #3


Member
***

Group: Members
Posts: 401
Joined: 5-January 07
From: Manchester England
Member No.: 1563



QUOTE (TheAnt @ Jun 11 2015, 04:32 PM) *
This piece is not about any specific mission, even though the swirls have been imagined by orbiters.
I might be relevant since it could give an insight for some various features we discuss on this forum.
Crashing comets may explain mysterious lunar swirls


I blogged on this a litte while ago. I can't say my research was PhD level exhaustive (writing the blog is just a hobby) but these patterns seem to be fairly well accepted. Some of the images and the correlaton between the discoloured areas and the local magnetic fields are quite interesting.


--------------------
Go to the top of the page
 
+Quote Post
dvandorn
post Jun 13 2015, 01:10 AM
Post #4


Senior Member
****

Group: Members
Posts: 3419
Joined: 9-February 04
From: Minneapolis, MN, USA
Member No.: 15



Yeah -- I just can't see comets producing the extremely large extent of the swirls as observed. The brightening effects of gas flow over the surface would be darkened over the course of time, such that if the swirls were from such gas transport, we would see them for a relatively short time. Since gas transport just "freshens up" the regolith, the constant rain of small to tiny impactors will darken that kind of thing in timescales far, far shorter than the darkening of rays from impacts.

Also, over a long period of time, you'd expect cometary impacts all over the lunar surface, and in fact they'd have to have happened all over the Moon's globe. We're supposed to believe that they only happened around Reiner Gamma and the few other places we actually see them? I also strongly question that gas transport brightening of the soils would last even a hundred thousand years, much less the 100 million years noted in the article.

Finally, the swirls do seem to be associated with magnetic anomalies. Why would gas transport cause magnetic anomalies? And only in the limited areas where we see the swirls?

I just don't think the comet impact theory works.

-the other Doug


--------------------
“The trouble ain't that there is too many fools, but that the lightning ain't distributed right.” -Mark Twain
Go to the top of the page
 
+Quote Post
TheAnt
post Jun 13 2015, 07:51 AM
Post #5


Member
***

Group: Members
Posts: 495
Joined: 12-February 12
Member No.: 6336



@marsbug: Oh you even wrote a blog about them, Im not the only one who noted this research then. =)

I fully agree with dvandorn that finding these features at the same sites as magnetic anomalies is an odd coincidence so don't think we should embrace this hypothesis fully yet. Unless someone could explain how the impact of a comet create a magnetic field. Nevertheless, with higher resolution images coming up at Ceres, not to mention Pluto, I thought this might be one kind of surface feature we could be on the lookout for in days to come. =)
Go to the top of the page
 
+Quote Post
marsbug
post Jun 13 2015, 11:18 AM
Post #6


Member
***

Group: Members
Posts: 401
Joined: 5-January 07
From: Manchester England
Member No.: 1563



Ah, i thought you were unconvinced that the swirls were a real phenomena, maybe in the same way that many see crepuscular rays as being some kind of optical illusion. Also I was shamelessly taking a chance to mention my blog, but i do also love a chance to point out how much interesting lunar science there still is to do.

Actually i do have a further thought: Many years ago i did my phd on plasma sputterinng, incluxing sputtering of powders. It should be fairly easy to set up powder targets of simulated lunar regolith, and a sputtering atmosphere of solar wind composition and the right energy. Not trivial, but completely do-able. Vararions in magnetic field can also be aarranged, and so we could try to gauge the possible effects of soar wind on regolith and see if it explains the swirls. I expect this has been done, but i don't recall reading any papers on it...


--------------------
Go to the top of the page
 
+Quote Post
TheAnt
post Jun 13 2015, 01:47 PM
Post #7


Member
***

Group: Members
Posts: 495
Joined: 12-February 12
Member No.: 6336



Oh I have no doubt that they're real features, but now that you mention it, it's true that light have to fall in the right angle to make them clearly visible. So the swirls are a bit elusive.

It was however dvandorn who expressed the strongest doubt, and I tend to agree insofar that a second look at the alternative explanations should be looked into. And I think you nailed it there marsbug, since the solar wind is the alternative I had in mind. It would also provide a mechanism to maintain the swirls even in one environment of constant micrometeorite bombardment.
Go to the top of the page
 
+Quote Post
dvandorn
post Jun 13 2015, 06:24 PM
Post #8


Senior Member
****

Group: Members
Posts: 3419
Joined: 9-February 04
From: Minneapolis, MN, USA
Member No.: 15



The explanation I have read is that localized magnetic fields redirect some of the incoming solar wind charged particles, "shadowing" the areas in the swirls from solar wind bombardment. The idea is that the solar wind darkens the regolith over time, and the shadowing effect reduces the solar wind flux along the magnetic field lines. Since the swirls can be thought of as a 2D representation of the 3D field lines above these areas of localized magnetic fields (just as a shadow of a 3D object on the floor is a 2D representation of the object casting the shadow), you get swirling patterns of regolith that has not been darkened by the solar wind flux, and thus appear lighter.

There may be other magnetic effects, including electromagnetic lifting and depositing of dust, with the localized magnetic fields affecting the pattern of deposition. I've seen papers about this "levitation" of lunar dust along the dawn terminator (possibly observed by both ALSEP dust detectors and by one of the Surveyors), and I read one theory (sorry, can't remember where) that the magnetic anomalies disrupt that process and cause suspended dust to fall abruptly, or at least be transported along the field lines. That could also explain how the brighter regolith is "freshened" over time.

Again, I think these theories (especially the first one) are somewhat well-accepted. I'd believe them more than the Brown University study.


--------------------
“The trouble ain't that there is too many fools, but that the lightning ain't distributed right.” -Mark Twain
Go to the top of the page
 
+Quote Post

Reply to this topicStart new topic

 



RSS Lo-Fi Version Time is now: 28th March 2024 - 11:30 PM
RULES AND GUIDELINES
Please read the Forum Rules and Guidelines before posting.

IMAGE COPYRIGHT
Images posted on UnmannedSpaceflight.com may be copyrighted. Do not reproduce without permission. Read here for further information on space images and copyright.

OPINIONS AND MODERATION
Opinions expressed on UnmannedSpaceflight.com are those of the individual posters and do not necessarily reflect the opinions of UnmannedSpaceflight.com or The Planetary Society. The all-volunteer UnmannedSpaceflight.com moderation team is wholly independent of The Planetary Society. The Planetary Society has no influence over decisions made by the UnmannedSpaceflight.com moderators.
SUPPORT THE FORUM
Unmannedspaceflight.com is funded by the Planetary Society. Please consider supporting our work and many other projects by donating to the Society or becoming a member.