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Solander Point, Sol 3387 - 3511 (August 4, 2013 - December 12, 2013)
dilo
post Sep 5 2013, 06:27 AM
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I guess Oppy wasn't in autonomous navigation mode, but I wonder there wasn't any sort of proximity alarm and automatic safe stop for such situations, eventually triggered by hazardcams!


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Tesheiner
post Sep 5 2013, 12:43 PM
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The F/R-Hazcams "per se" can't do that. You need a sort of hazard avoidance SW built on top to do that function. And IIRC autonav includes this feature but it is quite slow.
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ngunn
post Sep 5 2013, 01:16 PM
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I'm struggling to understand how colliding with a rock at a speed of a few centimetres per second could have been "mission catastrophic". (Just as well my car is more robust.)
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djellison
post Sep 5 2013, 01:26 PM
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It would probably damage solar panels quite badly. Moreover, you're then hung up on a rock with the arrays - you need to get 'off' that, which will cause more damage.
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Phil Stooke
post Sep 5 2013, 02:02 PM
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I would have thought that constant monitoring of tilt and engineering data from wheels etc. would stop the drive before anything got hung up too much. But obviously much better to avoid it than to test my assumptions.

Phil



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mhoward
post Sep 5 2013, 02:57 PM
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In stereo, it didn't look to me like Mulla Mulla was tall enough to hit the arrays. Unless she tilted more - which could easily have been in the cards I guess.

Wopmay looked scarier smile.gif

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Tesheiner
post Sep 5 2013, 04:18 PM
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Not tall enough but its size was only known with a given margin when it was seen from the position before that drive was executed. It might not have contacted the wings but damaged the wiring under them.

Regarding tilt and other data monitoring, I think that would not be enough to stop the rover in this kind of scenario.
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serpens
post Sep 6 2013, 10:49 PM
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Referring back to post 51, the PS update confirms that "Coal Island" is the contact between the planar and tilted laminae. But the planar bench ("Grasberg unit") was designated altered material eroded from old Endeavour rim "Shoemaker" material. Is this implying that the tilted laminae represents pre impact sedimentary layering rather than Grasberg unit material tilted due to a local subsidence?
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Phil Stooke
post Sep 6 2013, 11:08 PM
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The Grasberg unit is the lowest layer of the Burns Formation, the stack of sulfate-rich sandstones seen all over Meridiani. They sit on top of the layer of debris eroded off the Endeavour rim hills. The scarp here, the little step up above the bench, is presumably that eroded debris. The exact relationship is not easy to figure out just looking at the images here, but it seemed to be clearer at the north end of Cape York.

More interesting to me is the origin of the basalt boulders like Tick Bush. Are they ejecta thrown in from a distant impact? I don't see any sign of basalt flows in the vicinity.

Phil



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serpens
post Sep 7 2013, 11:06 PM
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Not sure that you are correct there Phil. On CY the Burns Formation sulphate sandstone onlaps the bench (Deadwood - Grasberg unit) which is eroded material from Cape York (Shoemaker), and the same seems true here. The basaltic boulders seem to be eroding out of the upturned rim remnant. Given that Endeavour was formed by an impact into hundreds of meter thick Miyamoto ejecta they could well pre-date the impact. Coal Island is a contact between two units with, in false colour, seemingly different lithology and what I find fascinating is the possibility that the tilted laminae could be a pre-impact deposit.



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walfy
post Sep 7 2013, 11:37 PM
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Nice view of the "shore" in 3D, sol 3419:

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Phil Stooke
post Sep 8 2013, 04:11 AM
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Re: the Grasberg unit:

https://gsa.confex.com/gsa/2013AM/webprogra...aper233091.html

"The bright outcrop margin (the “Grasberg unit”) is the most prominent of several successive onlaps of thinly-laminated sulfate sediments onto the crater rim inselbergs."


And also:

http://www.lpi.usra.edu/meetings/lpsc2013/pdf/2292.pdf

"A stop at the site named “Grasberg” confirmed through MI and APXS analysis that this band is a material distinct from either the materials of Cape York or the Burns Formation.
Grasberg is an unusual composition with elevated Cl, and a grain-size finer than the MI resolution, in contrast to the coarse sandstone typical of Meridiani. This is a relatively thin
(several tens of cm thick) unit that unconformably overlies the slopes of an eroded Cape York."

Phil



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serpens
post Sep 8 2013, 07:16 AM
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I think the following paper goes a little deeper into explanation of the bench Phil: http://www.lpi.usra.edu/meetings/lpsc2013/pdf/2294.pdf
To quote, A rock unit ringing the base of Cape York was investigated at Deadwood and again at Grasberg, at Cape York’s northern tip. This unit is bright-toned with platy, millimeter-scale layering. Its elemental composition is intermediate between the rocks of the Shoemaker formation and the Burns Formation, with elevated Ca and S concentrations, interpreted as a clastic sedimentary rock formed by erosion of the Shoemaker Formation and later modified to create the S enrichment. Squires also tributed the bench to shoemaker detritus in his Nature article Ancient Impact and Aqueous Processes at Endeavour Crater, Mars although he differentiated between inner and outer bench material (outer being Burns formation onlap which is quite pronounced to the west of CY). Identifying the bench as eroded rim breccia material seems an important call in defining Endeavour, confirming that the Burns unit was deposited a long time after the impact, when the rim had eroded away.
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MahFL
post Sep 9 2013, 10:37 AM
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QUOTE (ngunn @ Sep 5 2013, 01:16 PM) *
I'm struggling to understand how colliding with a rock at a speed of a few centimetres per second could have been "mission catastrophic". (Just as well my car is more robust.)


Remember Oppy does not travel very fast but she has tons of torque, so she could crunch herself pretty bad.
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atomoid
post Sep 9 2013, 09:16 PM
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One wonders whether Oppy's accelerometers are used in general drive usage for instance to adjust drive behavior over small rocks, which should nullify hazards such as this, since any sensed impasse should signal to adjust suspension, wheel spin, etc. in adaptation to the terrain feature encountered... or maybe they are only used to measure degree of tilt? i'm sure im oversimplifying it and someone here is probably familiar with those specs..
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