Strange areas of cleared ground around/between rocks in MER images. What causes that?

In a lot of MER images from Opportunity and Spirit, there are areas where there are no small stones. These could be between rocks or in small channels in the ground. There are small stones all around the area concerned but for some reason, they are not in these cleared areas. I can understand how these may be places where there are rocks under the surface where the soil has sunk into these groves between rocks. That has been an explanation offered by others to similar queries.

However, there are too many of these areas for them all to be explained away as this. Some look like there has been a fluid flowing which has moved the small stones to the edge - rather like a stream or river does. Some cleared areas do not seem to be linked to anything in particular and appear around a rock. ALL the way around, not just on the windy side. If it was caused by the wind, you would expect the stones to have been moved to the side opposite the windward side.

As an example, take a look at this front hazcam image taken by Opportunity at site C7 On the right in the corner, you will see a rock cleared on 3 sides and in front of the rover you will see a few channels between rocks where there are no small stones. Both these areas are strange because there does not appear to be any way the liquid (if it was caused by that) could reach these places.

I cannot post images to the upload area at the moment, not sure why, otherwise I would show an image in the thread.

In this image of the same bottom right hand corner rock area, there is also a grooved cleared area to the left of the rovers solar panel and to the right of that same area cleared around the rock.

reply to post by qmantoo


Love looking at images of Mars. As to your question; perhaps the slabs of rocks are slightly higher than the surrounding pebbly soil, and the few pieces of soil that are on the rocks are there because of wind etc.?

Just my opinion.

reply to post by qmantoo


I think the conventional wisdom is that the areas are scoured by winds, pushing the lighter debris and stones aside.

Thats where the life forms have been grazing!

reply to post by MysterX

I think the conventional wisdom is that the areas are scoured by winds, pushing the lighter debris and stones aside.

I would love that to be the case, but I and others have a problem with the wind. You see the wind in the thin atmosphere of Mars is not strong enough to push even 5mm 'blueberries' into piles, so it cannot be pushing any small stones about the surface. I argued my face off in a thread I started about the dust being deposited on Mars and so many folks jumped on me that I am going around flat now !

reply to post by qmantoo


Perhaps the small stones were originally under the soil, but not scattered in a homogeneous way -- i.e., maybe they were originally under the soil in groups and clumps. Then the wind comes along and blows the light soil away, exposing these groups and clumps of small stones.

As to why would the small stones be grouped like that in the first place? it may have something to do with the conditions on Mars hundreds of Millions or Billions of years ago when those small stones were first grouped. Maybe a stream put them in there present location to begin with, then they were covered, and then a billion+ years later the wind uncovered them again


And, by the way, even though the wind pressure itself is not that strong on Mars, there is enough wind to create sandstorms. Maybe the wind alone can't push a small stone to move it, but pieces of dust in the air can possibly pack a bit more punch (with more mass behind it), and perhaps this wind-born dust and sand could move these small stones. So maybe that is another possibility.

Yep, She is running Mars also

reply to post by Soylent Green Is People

And, by the way, even though the wind pressure itself is not that strong on Mars, there is enough wind to create sandstorms. Maybe the wind alone can't push a small stone to move it, but pieces of dust in the air can possibly pack a bit more punch (with more mass behind it), and perhaps this wind-born dust and sand could move these small stones. So maybe that is another possibility.

Read the thread linked to about dust being carried by the wind and 'cleaning events'. Yes, I have no doubt that sandstorms occur on Mars and some large enough to be seen from space and covering most of the face of the planet. That is why I do not understand why there is not more blown about by the wind in the MER and Curiosity images. But.. what you suggest about the wind moving small stones, the others say this is not going to happen as these stones are too large to be moved by the thin atmosphere.

Unfortunately, everyone cannot be right, even if they argue both sides of the discussion in different places which they do. Confuse and bewilder is the name of the game played by NASA due to making statements which support both sides.

reply to post by qmantoo


I'm just speculating here, but I am NOT saying that the pressure thin wind ALONE can move small stones. I'm saying that possibly the wind blown sand may pack more punch because of the mass behind it, and THAT may be able to move stones.

For example, I can stand in a 50 mph wind with the wind hitting my face, but I should be fine, and the wind isn't really going to do any damage. However, introduce some pieces of gravel into 50 mph stream of air hitting my face, and I bet I'll really feel it.

reply to post by Soylent Green Is People


Yes, I agree that extra stuff being blown with the wind will add to its ability to move things. I would also expect it to move the 5mm blueberries but from what the others have said, this is not true. I wish it were true as well because it would add evidence to the wind being a proper force to be reckoned with on Mars.

I can only tell you what they have said in that other thread and as much as I dont like it, it seems to be what they are arguing. Of course, they may all be paid by NASA, but until I (and you maybe) can find more reasons why they are wrong, I cannot say much more, other than to point to what they say.

reply to post by qmantoo


Who cares, it's most likely a natural reason why even bother about it

reply to post by wmd_2008

Who cares, it's most likely a natural reason why even bother about it?

And I have to ask myself why would you even bother to reply if you feel this way.

Unless you either need to have the last word or else you are paid to keep putting downer comments on threads for others to read.
Either of these two alternatives are really rather sad.

qmantoo
reply to post by wmd_2008

 

Who cares, it's most likely a natural reason why even bother about it?

And I have to ask myself why would you even bother to reply if you feel this way.

Unless you either need to have the last word or else you are paid to keep putting downer comments on threads for others to read.
Either of these two alternatives are really rather sad.

Your lucky I am here because it seems I was right looking at the response!!!