Hello all,


some of us (in the Free! thread) noticed a round dark stain near Oppy:
visible here on the NASA site (look bottom right, just above Oppy's solar panel).
So I open this thread for this.

What such a stain could be? It looks just like a mere change in color, with the same texture than around it.

The more trivial explanation would be a drop of lubricant fallen from the apparatus at the end of Oppy's solar panels, when she passed here just before she got stuck. With a temperature of 20° oil could spread, and certain oil compositions would not evaporate, at least not fast.

But there would be more enthralling explanations. For instance a colony of bacteria could look like this. Or other really unexpected explanation.

In any case we do not know what it is and it may be potentially very interesting. So I think it is worth a bit of examination with the instruments. Just be cautious not to place the microscope right on it, if it is oil it would irremediably dirty the lens.

Someone noticed similar spots elsewere...
As already written in another thread, could be the dark spot a "tiny crater" completely filled with fresh (darker) sand?
Note that in image you posted, in the other side of the same dune there is a tiny crater with approximately the same size; it is uncovered by sand probably because main wind direction is from right...

[/quote]

mmmmh... I don't think so, its surface is the continuation of the surrounding surface, with the same little ridges, as if the spot was just painted on the ground. It is this which makes it strange.




we are not far from the first discovered tiny crater (10m maybe) so all the discution about the statistical repartition of the tiny craters still applies. (It was considered unlikely that the tiny craters were grouped, but meteorites or fallout from the cruise stage could give a very irregular repartition).

Eventually we are still so close of the first tiny crater that it would be worth to go back a while, and eventually scuff in it to have a cut view or eventually find the object which created it (meteorite or bolt)

Maybe it was a cat?..... no,... they usually leave a little mound with radial claw marks.

I think we've determined that all the cats are on Titan

I really don't think it's an oil leak - even though Opportunity spent a month sitting in the garage waiting for the AA man!

It's interesting, though - there's no obvious change of texture that I can see. Well, maybe there'll be some Mini-TES scans of the area in the next few days (if we're lucky).

I'm not a mechanical guy - but how much/what kind of oil would Oppy have?

I'd assume some kind of lubricant in all the wheels/suspension/drive system, and in the IDD/mast actuators. I'd also assume that it wouldn't be enough to make a stain like that, and if it was a leak, we'd see an impact on the rover's systems.

I think I'm in the tiny crater camp right now...

Its formation only can happens :

1) Extint cat and it was filled with windsand.

2) Evaporation of water from inside to outside

3) Contamination of something different kind of stone inside the sand

4) Oil drip from Oppy's one of its wing.

5) An old black stone which was desintegrated due to the water reaction.

Many more speculations. It is worth that the Oppys approach it and analyze it with instrument and let us know about why are these pretty blacks.

Rodolfo

Surely any stain from a "leak" would mean that we would see tracks adjacent to the stain location?

The only alternative might be that it came from a joint on the arm that moves the RAT and Microcopic Imager.

Doesn't sound plausible to me.

Doug - I wonder why RW and ES haven't jumped on this one (you know who I mean)!!!

I'm sure they will given time

Are there any PC frames of these things - I'll try and draw some graphs of intensity compared to wavelength

Doug

Nah, there are cats on Mars too. They're everywhere.

There are at least three of the "oil stains" in this picture, with a small crater of the same size as well. Two of the stains are together at about five o'clock in the and another about one meter to the right of the tracks.



http://qt.exploratorium.edu/mars/opportuni...V4P1914L0M1.JPG

Is there a song "Who let the cats out"?

[quote=Phillip,Jun 21 2005, 02:47 PM]There are at least three of the "oil stains" in this picture[/quote]
I think that the crater and stain in the right bottom are the same that the one I noted in my first post. But they are more visible in your view.



[quote=maycm]Surely any stain from a "leak" would mean that we would see tracks adjacent to the stain location?[/quote] Yes there are, as you can see on Phillip's image. But remember that the solar panels form "wings" reaching far on the sides. So to have an oil stain so far of the tracks, it could come only from the aparatus at the end of that "wings". These aparatus were, as far as I know, playing a role into unfolding Oppy at landing, so they could be more or less destroyed in this process.


[quote=odave]I'm not a mechanical guy - but how much/what kind of oil would Oppy have?[/quote]
Not the cheapest I think. Such a lubricant would be submitted to fast evaporation, due to vacuum or weak atmosphere, even with the best gasket. So they may use special oils, which do not evaporate, such as silane or synthetic, not just petroleum oil which evaporate quickly, and not organic oil which is chemically unstable.
[quote=odave]we'd see an impact on the rover's systems.[/quote] No as the oil stain, far from the tracks, can leak only from the actuators at the end of the "wings".


[quote][quote]Doug - I wonder why RW and ES haven't jumped on this one (you know who I mean)!!! [/quote]
I'm sure they will given time[/quote]
If so tell them it's a rock (joke for initiates)

Ah - I understand what you mean now. I think the navcam image Philip pointed out was taken during/after the 3-point turn, so the closest stain would be on the same side of Oppy as the one by the deep tracks. That would support the leak hypothesis.

Are there any images of Purgatory before Oppy got stuck that might show the stain?

As far as I know sadly no. The only pics that I found for a before-picture were from sol 439: http://www.unmannedspaceflight.com/index.p...findpost&p=9698

I am not only concerned on the cirle black stains but also of different colors of sand around the purgatory sand.

It might have some relationship with a kind of material that is located by that is desintegrated by some kind of erosion on the past time. It might sound that the material is not of windblown origin but it is from a volcanic origin or fallen material from any nearby crater.

No other places I haven't seen like this situation unless the different colors are caused by dust devils (it is very noticeable since it marks a line of dark land).

Yes this supports the leak hypothesis, but please note that in the vicinity of Purgatory dune, on your image, there are black blocks of matter which could be some yet unanalysed variety of rock, perhaps carbon chondrite from meteorite (too old to be the cause of the tiny craters). Maybe one of this blocks may crumble, leaving a dark stain, not of oil, but of some dark powder.

The Tagish Lake chondrite that landed in the Canadian Yukon territory shows that that's not totally implausible, these were so soft that crumbled to the touch and were reduced to an oily black sludge on contact with water.

Sol 503 navcam released a round panoramic view of the landscape (still unchanged since the beginning of this thread).

Our tiny round stain is still visible here (right bottom) together with the tiny crater (top centre).

Two other dark spots are visible here although more blurred. And they are not aligned with Oppy's traces, which seems to exclude some oil leak. But an oil drop may roll on dry sand before infiltrating in it...

Another tiny crater is visible here top left.


This discution is somewhat mixed with the one on tiny craters although there are no evidences that the two objects are linked.

My guess (admittedly reading tea leaves) is that if the stains were in fact leaked oil, Sqyres would have mentioned it by now. If nothing else than from the perspective of maintenance/health of vehicle. I did not realize that there was oil to be leaked or that the conditions would allow for it. I also see no evidence that NASA is trying to take pictures of the stains, which leads me to conclude that they have a pretty good idea of what the stains are and they have decided the stains do not merit further investigations. So maybe some type of infill of tiny craters is the most likely answer after all. It will be interesting to see if they bring the arm over an "oil patch." Otherwise, I am in the camp that the stains are more curiousities than anything else. On the other hand, I sure would like to understand them better!