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Author Topic: LRO photo's... what's going on?  (Read 3104 times)

Offline Anywho

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LRO photo's... what's going on?
« on: 17/03/2012 00:16:24 »
Hi, I have seen all the Lunar reconaissance Orbitor (LRO) photo's and I have a question about the tracks that are shown emanating from the descent modules.

Why are the tracks darker?

It cannot be shadows because the tracks are shallow and every photo from every angle, including different positions of the sun, the tracks show up as darker.



It is well established that disturbed lunar soil has a significantly higher albedo than older undisturbed soil, therefore the tracks should be brighter, not darker, than the surrounding soil.

What gives?


 

Offline Airthumbs

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Re: LRO photo's... what's going on?
« Reply #1 on: 17/03/2012 23:16:14 »
I love this picture thanks for putting it up.  You know I understand what your saying about the top soil.  But it's not really a question of disturbing the soil that gives it a higher Albedo effect but that of taking the top surface away.  The subsurface layer beneath the topsoil would appear lighter then the surrounding area.  You can see that maybe in some of the more recent craters in the picture and at the landing site itself.  I am an expert on soil and having done a little reading I would hypothesise that this is the reason for the darker areas of soil; The Lunar soil would consist of different layers, the top surface layer has been exposed to radiation for quite some time and has most likely been bleached by the Sun. You can see the same effect on Earth.  When you disturb the top layer you are then exposing fresh subsoil which will be the original colour of the soil pre-bleaching.  To get to that brighter sub strata you are thinking of you would have to remove the surface layer completely. 

The mechanics of both walking and using the Lunar Rover would only serve to mix up the top layer or at least break through it.  You would also expect to see darker area's at the edge of whiter exposed areas because of this freshly exposed top soil layer. I think that is also observable in the picture, especially around the landing site.

Recently I was looking at the Nazcar lines on G-Earth and some berk has been razing around in a 4x4 all over them. All of the tyre marks look darker then the surrounding top soil.  Any impression in the soil will also cast a shadow even if it is a small one, that would definitely add to the darker colours of the impressions made on the Lunar surface.

I don't really see what the big fuss is about.  I think it should be easy to get back to the Moon.  All we need to do is send everything we need there first, including robots operated by ground staff.  And then when a basic base is set up it should not be that hard, with the objective of only needing to get Spacemen there and back. Richard Branson can already get 4 people at a time into Space!

Apparently we did it before all in one go, tons and tons of stuff went along, including a lunar rover, and all the fuel needed. They did it with, by comparison to today, antiquated technology and materials. Talk about suicidal!! 

The fact it is so easy to get to the moon today is what I find to be the most disturbing thing given that we have not yet done so.  Maybe it's better that we just spend all our money on killing each other instead hey, at least then we don't have to expand as we can cull ourselves and make money from it.
 

Offline Anywho

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Re: LRO photo's... what's going on?
« Reply #2 on: 20/03/2012 11:39:56 »
  The Lunar soil would consist of different layers, the top surface layer has been exposed to radiation for quite some time and has most likely been bleached by the Sun. You can see the same effect on Earth.

This is sort of the point I was trying to make, except that everything I have read says that the top layer has been exposed to "space weathering" which darkens the soil.

The surface of the Moon is supposedly darker than the parent rock from which it came due to this phenomenon.

This is very obvious with avalanches in craters and newly formed craters (the higher the albedo, the newer the crater)

This is why I would have thought that, if the top layer is the darkest, then disturbing it should expose a brighter subsurface, even if the two are mixed.

Yet every LRO photo shows all tracks, which is very very recently disturbed soil, as being distinctly darker.
 

Offline CliffordK

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Re: LRO photo's... what's going on?
« Reply #3 on: 20/03/2012 12:46:13 »
The angle of the sun appears to be from the left, perhaps lower left side of the photo.  is it possible that you are getting shadows?
 

Offline Anywho

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Re: LRO photo's... what's going on?
« Reply #4 on: 25/03/2012 00:57:14 »
The angle of the sun appears to be from the left, perhaps lower left side of the photo.  is it possible that you are getting shadows?

I consider that it is not possible for shadows to be the cause because all the photo's show darker tracks from all angles, including differing sun positions.

If it were shadows causing the darkness and the tracks were actually lighter, or even the same colour, then this would be reflected (no pun intended) in a noticable manner on tracks that are aligned with the Sun.

The tracks are very shallow, we know this from all the close up's of astronauts on the Moon, they weren't up to their knees making tracks and nor were the rovers making deep tracks.
 

Offline damocles

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Re: LRO photo's... what's going on?
« Reply #5 on: 25/03/2012 09:54:16 »
There are three reasons why I still believe it to be likely that the darkness is in fact shadows, even if the tracks are very shallow:

(1) The sun angle is low; all of the missions landed at fairly high latitudes, fairly early in the lunar morning. The large shadows cast by the small craters confirm a low solar angle. (whoops -- some of the photos were taken from orbiters long after the mission had departed -- high latitude remains, time of lunar day might not, though I suspect a time early in the lunar morning would have been chosen to highlight surface features {see 3 below}).

(2) The shadows we are used to looking at/for on Earth are much gentler than the harsh black and white of lunar shadows. Even in high bright sun conditions, skylight/cloudlight is at least 10% as bright as sunlight on earth (usually much more), and shadows are soft and grey. Not so on the moon, where there is no skylight.

(3) I quote from the NASA website these images come from:
      Image brightness and contrast have been altered to highlight surface details.

 

The Naked Scientists Forum

Re: LRO photo's... what's going on?
« Reply #5 on: 25/03/2012 09:54:16 »

 

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