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Dark Streaks At Victoria Crater, MGS: MOC image
SigurRosFan
post Oct 12 2005, 01:20 PM
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Release date: Today (12 October 2005)

http://www.msss.com/moc_gallery/r22_s04/im...2/R2200640.html


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Marcel
post Oct 12 2005, 01:45 PM
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QUOTE (SigurRosFan @ Oct 12 2005, 01:20 PM)

Ohboy this looks interesting. Black streaks (on the leeside?). Furthermore: walls seem very steep, except to the southeast. Entry might be possible from there. AND, offcourse: a very tempting outcrop on the east/southeast rim, pointing INTO the crater for some 50 meters or so !!! For the rest a very sharp rim.....looks like a "fresh" one to me (more fresh than Endurance ?). Except that there's no visible ejecta around (from this point of view). It is consistent with orbital imagery of other craters around here however: craters, but no ejecta. Nowhere ! Easily weatherable stuff, this evaporite.......
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RNeuhaus
post Oct 12 2005, 02:21 PM
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Is the big crater ones of Victoria crater? The black streaks might be caused by Dust Devil.

Rodolfo
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Guest_Richard Trigaux_*
post Oct 12 2005, 04:27 PM
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The dark streaks were NOT on the previous photos!!!

Is is just a matter of wavelenth or of weather?

Note that endurance had a whitish streak leading S-E. It is still visible, but less. Now is a qark streak leading N-0 which was not on the previous images.

The direction of streaks may reflect the changes of wind. But why changes in color? Is it a matter of grain orientation relative to the sun light, or of mineralogy?? It is difficult to admit that wind blowing in the same place may eject a different material according to its direction.


And about Victoria crater...

It looks as if it was dug into... sand. As if the impact punched through a relatively thin layer of evaporites, into an underlying sand layer. Difficult to enter into such a place, except for two places on the west side.
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Zigtag
post Oct 12 2005, 04:49 PM
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QUOTE (Richard Trigaux @ Oct 12 2005, 12:27 PM)
It looks as if it was dug into... sand. As if the impact punched through a relatively thin layer of evaporites, into an underlying sand layer. Difficult to enter into such a place, except for two places on the west side.
*


I've been lurking here for quite a while. I'm not a scientist by any stretch of the imagination. So my observations are not as educated as those by others here. Sometimes though a step back and look from not so educated eyes can bring to light some 'unseen' things.

Is it possible that it isn't a crater at all? What about being a sinkhole? I don't have all the fancy tools you all have to process the images to look at height variation on the 'rim' to see if it is raised significantly or not. But is it possible that it is a sinkhole or collapsed caldera?

If it is a crater and with the lack of ejecta maybe it's a matter of the ejecta is there just buried under the loose 'sand'. Obviously there is quite a bit of material moving in this area as seen with the 'Tour de Dunes'.
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algorimancer
post Oct 12 2005, 05:15 PM
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This is a really nice pic... covers everything from Endurance to Victoria, including Erebus. Notice the excess of small craters in the Victoria ejecta? Also the abrupt transition between etched terrain and ejecta? If I didn't see evaporite exposed in Victoria's rim I would have guessed that Victoria was much older that the etched terrain, but under the circumstances I'm forced to assume that the drifting dunes of the etched terrain hide or cover many of the remaining craters (still visible, but you have to hunt for them). Still, it seems clear that the evaporite layer is relatively thin on the scale of the Victoria impact, while the ash/sand the evaporite is embedded in would appear to continue to considerable depth. I would agree with Richard and Zigtag that Victoria is predominantly sand ... certainly that's all I see in the ejecta blanket; as such it ought to offer much better traction than the dusty dunes, but will probably limit the slopes that Opportunity can handle.

Pretty nifty... I look forward to the rim panorama smile.gif
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deglr6328
post Oct 12 2005, 05:37 PM
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It's kind of comforting in a way to still see that little dot in the center of eagle...... smile.gif
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RNeuhaus
post Oct 12 2005, 07:03 PM
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QUOTE (algorimancer @ Oct 12 2005, 12:15 PM)
I would agree with Richard and Zigtag that Victoria is predominantly sand ... certainly that's all I see in the ejecta blanket; as such it ought to offer much better traction than the dusty dunes, but will probably limit the slopes that Opportunity can handle.
*

The MER's rovers are designed to stay stable with slopes of up to 45 degree but in the under exceptional conditions and with 30 degree is for general safety margen. The Endurance maximum slope which MER went down and up was around 20 degree and hope this would be similar to ones of Victoria's crater.

Rodolfo
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dvandorn
post Oct 12 2005, 07:17 PM
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QUOTE (Zigtag @ Oct 12 2005, 11:49 AM)
Is it possible that it isn't a crater at all? What about being a sinkhole?
*

Possible, but unlikely. From above, the terrain around Victoria looks idenitcal to the plains where Oppy landed. And Victoria itself looks a lot like Endurance, just a lot larger.

And Endurance is pretty obviously an impact crater.

I think the difference between something like Erebus (which actually looks old and degraded) and Victoria or Endurance (which don't look nearly as old) is the state of the ground where the impactors struck. I think Victoria and Endurance were made well after the place dried out, and represent what happens when a crater is made in the "finished" evaporite layer (i.e., nothing has come along after those impacts to degrade them with the exception of wind). Whereas Erebus and other very degraded-looking craters were made back when the place was still wet, and further evaporite has been deposited on top of the impact features before the whole thing dried up and no more water was available to lay down more evaporite.

And, in response to Richard earlier, yes, those dark streaks *are* there around Victoria on earlier images. They're just not as pronounced. I'd bet it has something to do with sun angle and angle of incidience at the time each image was taken, as to the dark wind-blown dust streaks being more or less visible. And no, I doubt seriously they're made by dust devils -- there has been absolutely no sign of dust devils at Meridiani, and these streaks obsviously follow a pattern that shows they're formed by the aerodynamic disruption caused by the crater rim itself, so no need to conjure dust devils to explain them...

-the other Doug


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RNeuhaus
post Oct 12 2005, 07:24 PM
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QUOTE (dvandorn @ Oct 12 2005, 02:17 PM)
And, in response to Richard earlier, yes, those dark streaks *are* there around Victoria on earlier images.  They're just not as pronounced.  I'd bet it has something to do with sun angle and angle of incidience at the time each image was taken, as to the dark wind-blown dust streaks being more or less visible.  And no, I doubt seriously they're made by dust devils -- there has been absolutely no sign of dust devils at Meridiani, and these streaks obsviously follow a pattern that shows they're formed by the aerodynamic disruption caused by the crater rim itself, so no need to conjure dust devils to explain them...

-the other Doug
*

I agree that I made a mistake sad.gif with the dust devils because it does not draw a straight lines as the shown ones on the north side of Victoria Crater. It is definitely a wind streak caused by a aerodynamic disruption between two stones on the crater rim. cool.gif
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ljk4-1
post Oct 12 2005, 07:41 PM
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QUOTE (deglr6328 @ Oct 12 2005, 12:37 PM)
It's kind of comforting in a way to still see that little dot in the center of eagle...... smile.gif
*


Are the tracks of a certain rover also visible in this image?


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and feel as if I had done some wrong, and it is hard to forget the ugly circumstance.
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djellison
post Oct 12 2005, 09:36 PM
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I've tried stretching, and even grabbed the pds file to have a look, but I couldnt pull tracks out of it.

Doug
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Bill Harris
post Oct 13 2005, 03:33 AM
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Too bad that the parachute/backshell was just off the edge of R2200640. It would be interesting to see how it looked after 600+ Sols. I note that the retro-rocket smudges are still visible, although muted, and the heatshield scar is still there.

I think that the Victoria dark streaks are wind-related and the changes are also wind-related.

Here are three MOC images of Victoria shown at a similar scale and orientation. Although I feel that wind is a major player here, some of the differences in these streaks are likely due to differences in the images.

R1400021 2/01/2004 LS 342.91
R1500822 3/10/2004 LS 2.35
R2200640 10/11/2004 LS 99.27

--Bill


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jamescanvin
post Oct 13 2005, 04:42 AM
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QUOTE (Bill Harris @ Oct 13 2005, 01:33 PM)
Too bad that the parachute/backshell was just off the edge of R2200640. It would be interesting to see how it looked after 600+ Sols.  I note that the retro-rocket smudges are still visible, although muted, and the heatshield scar is still there.
*


Only 250 Sols of course tongue.gif

I'm sure once MRO arrives we'll have some fantastic images of the parachute after a 1000 or more sols. May we even be able to see it move in the wind?

James


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Pando
post Oct 13 2005, 06:12 AM
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QUOTE (algorimancer @ Oct 12 2005, 10:15 AM)
Pretty nifty... I look forward to the rim panorama smile.gif
*


Umm, yeah. Meanwhile we'll have to do with this.... And wait until you see the animation! smile.gif

Unfortunately with all the software issues Oppy is experiencing it seems less and less likely that oppy will ever peek into the darn thing...
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