On the Road Again - volume 8 - Page 9

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Barsoomer


Posts: 344

Reply: 161



PostPosted: May 6, 2011 8:26 PM 

Notice the 'X' feature. Is that a ridge, or a trench, or ... what?

Context is from Horton's 152.

LWS


Posts: 3062

Reply: 162



PostPosted: May 6, 2011 11:12 PM 

Hi Barsoomer

What do you think the knobby straight object is in your reply #60?

Winston

Barsoomer


Posts: 344

Reply: 163



PostPosted: May 7, 2011 1:15 AM 

The 'X' feature looks to me like two vine-like objects crossing. I see a third vine-like object draped over the knobby object. The knobby object itself looks to me as something like a lava tube but possibly formed from water flow in the distant past. Maybe billions of years ago, it was an underground water conduit. The water cemented the tube around it. At some point the water froze into ice. Later thermal cycling of the ice distorted the shape somewhat, making it knobby. The ice might still be there, or it might have sublimed away if the seal was broken somewhere, but the cemented tube would remain.

Just speculating.

Barsoomer


Posts: 344

Reply: 164



PostPosted: May 7, 2011 1:16 AM 

The 'X' feature looks to me like two vine-like objects crossing. I see a third vine-like object draped over the knobby object. The knobby object itself looks to me as something like a lava tube but possibly formed from water flow in the distant past.

Maybe billions of years ago, it was an underground water conduit. The water cemented the tube around it. At some point the water froze into ice. Later thermal cycling of the ice distorted the shape somewhat, making it knobby. The ice might still be there, or it might have sublimed away if the seal was broken somewhere, but the cemented tube would remain.

Just speculating.

Kye Goodwin


Posts: 1166

Reply: 165



PostPosted: May 7, 2011 2:53 AM 

Ben, re your 159 and my 157, I've read the latest Planetary Society Report again (linked in Serpens' 124, page Cool and it seems that the rover team considers these craters to be the same age, part of the same strewn field. Interesting. Crater erosion is so mysterious at Meridiani that I can believe they are all the same age despite the diversity. I'm thinking that the smooth little craters have been shaped by some of the same processes that shape the big ripples, that is, material is added as well as eroded and the shapes we see are, or were, partially shapes in soil. It looks like some ripples, and maybe the smallest craters may be made of indurated soil, something seen fairly frequently in orbital images of other places on Mars, but I think this would be the first hardened soil structures that Oppy has encountered. I'm still waiting to see how the north-south oriented ridges, that look like they might have been ripples, respond to the weight of the rover.

hortonheardawho


Posts: 3465

Reply: 166



PostPosted: May 7, 2011 9:01 AM 

sol 2588 ( May 6, 2011 ) next drive direction:

It is now 17:50 LST and the images from today's 110-140 meter drive ( sol 2589 ) should be on their way to Earth.

hortonheardawho


Posts: 3465

Reply: 167



PostPosted: May 7, 2011 12:08 PM 

Here is a WAG of the sol 2589 position, based on this partial image.

Oppy is now over 2 km from Santa Maria crater and on the next drive should be less than 4 km from Cape York.

Kye Goodwin


Posts: 1166

Reply: 168



PostPosted: May 8, 2011 4:11 PM 

The ripples or ripple-like ridges east of Santa Maria don't look like any ripples we've seen before:

I've been wondering what they're made of for a few sols and from this image it seems I'm getting at least a partial answer:

Probably some part of the volume of these ridges is made up of bright rock. Maybe there is only a thin layer of dark soil even at the ridge-tops. We'll probably find out soon.

hortonheardawho


Posts: 3465

Reply: 169



PostPosted: May 9, 2011 12:19 PM 

sol 2589 ( May 7, 2011 ) in next drive direction:

It is now sol 2591 19:45 LST and no new images downloaded - and today was not a driving day.

Wonder if there was a communication problem?

hortonheardawho


Posts: 3465

Reply: 170



PostPosted: May 9, 2011 6:11 PM 

Here is a revised sol 2589 map position, based on this sol 2590 "stamp" 360 degree L1 panorama.

The new position is about 12 meters from the old guestimated position.

Ben


Posts: 5

Reply: 171



PostPosted: May 9, 2011 6:19 PM 

Kye; I have difficulty thinking the cores of these ridges are "bright rock"

What would have caused that ??

Kye Goodwin


Posts: 1166

Reply: 172



PostPosted: May 9, 2011 8:53 PM 

Ben, re your 171 and my 168, I don't know that the cores of these ridges are bright rock, but I'm wondering. In the second image in my 168 it sure looks like at least the base of a ripple is explained by relief in the bedrock, because the bottom of the slope shows typical plains outcrops. There are many examples in the library of bright bedrock sloping upward where it disappears under the big plains ripples, far more than chance would produce if there were no correlation. One example:

It is part of the mainstream model that the bright rock erodes more easily than the armoured ripples. Sometimes impact breccia appears to be eroded to match the surface of ripples:

A thick covering of soil might prevent erosion, whether the erosion be by particle scour, thermal cycling or chemistry. If we could see Meridiani with all the soil removed, some areas might show undulations in the bright rock corresponding to the ripples and inter-ripples.

The area Oppy is now crossing is really novel compared with any landscape earlier in the traverse. The reticulated ground pattern, a few sols back shows a network of ridges, though we never got to see what material makes up most of their depth.

Ben


Posts: 5

Reply: 173



PostPosted: May 9, 2011 11:33 PM 

Kye; Your first image in 172 is a good example and I agree with your description of differential erosion due to ripple cover.
THe current terrain is novel and one other item is that it lacks the "lag gravel" that was abundant a short distance back.

A small ridge could trap sand but why would it occur on both sides? shifting wind ?

THis area is a new environment it being due to deposition or erosion , I don't know.

hortonheardawho


Posts: 3465

Reply: 174



PostPosted: May 10, 2011 7:46 AM 

Oops.

Here is the official sol 2588 position. My guestimate missed the mark by about 60 meters.

Basically I erred by assuming ( without checking ) that the sol 2587 next drive direction ( NDD ) images were on the 108 degree heading used for some sols now. In fact the sol 2587 NDD was 76 degrees. From the map the actual drive heading was 93 degrees. The sol 2588 NDD was again 108 and I think I might have located the position based on the L1 panorama of reply 170 - but I'm not going to post the result ( or any others from now on ) as the official maps should be posted in a few days.

Today's ( sol 2592 ) drive should be about over now.

hortonheardawho


Posts: 3465

Reply: 175



PostPosted: May 10, 2011 4:50 PM 

Sol 2592 ( May 10, 2011 ) L0 3x1 in next drive direction:

with links to the L2 3x1 detail panorama and the official sol 2592 map position.

Ah, looks like Oppy is headed eastwards towards the crater "Young Blocky" now quite distinct in the pancam detail.

Psych Author Profile Page



Posts: no

Reply: 176



PostPosted: May 11, 2011 12:32 AM 

OT but, Horton, what in the universe is your Fliker avatar? I thought it was a crater or a RAT hole but it sorta looks elephantine too.

Kye Goodwin


Posts: 1166

Reply: 177



PostPosted: May 11, 2011 1:00 AM 

Ben, Re your 173, You wrote, "A small ridge could trap sand but why would it occur on both sides? shifting wind ?" I think that the SW-NE trending cross-ripples, far from growing in sheltered spots, have formed preferentially on pre-existing high points in the terrain like crater rims:

the tops of the larger, older N-S trending ripples:

and on the reticulate ridges east of Santa Maria:

I think that this is more or less consistent with the cross-ripples being dormant granule ripples, which I think is the mainstream view. I'm interested in an alternative idea: Dust is preferentially trapped by these rough projecting structures and ends up underneath the armour, something like the aeolian deposits that form under desert pavements on Earth, slowly raising them. Here is a paper that dates the last episode of big ripple movement to 100,000 to 300,000 years ago based on crater counting:

http://www.lpi.usra.edu/meetings/lpsc2010/pdf/2373.pdf

This work assumes that the changes to the big ripples are episodic and caused by winds that do not ever blow under current climatic conditions. I think that the gradual accumulation of change would also be consistent with the evidence presented. Clearly there are some aeolian processes currently active that alter the ripples because even the effects of the most recent impacts on the ripples have been smoothed out.

hortonheardawho


Posts: 3465

Reply: 178



PostPosted: May 11, 2011 3:39 AM 

Psych, sol 214 ( Aug 31, 2004 ) colorized MI panorama:

from this list.

I believe it was Mizar that pointed out it sort'a looked like an elephant.

Psych Author Profile Page



Posts: no

Reply: 179



PostPosted: May 11, 2011 8:06 AM 

Well, I'll be horns-waggled. An elephantine Rat hole. Thats great Very Happy !

Fred


Posts: 73

Reply: 180



PostPosted: May 11, 2011 8:28 AM 


Er....I see a mouse.

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