Burns cliff

Ald,
What would be transporting the spherules to the gullies?

I'm still wondering about the origin of the "pavers" that line much of the crater. It seems evident from the problems Opportinity wa having, that the "pavers" are underlain by sand. Are the fragments of the clliff that have fallen into the crater and then have been planed flat by wind abrasion?

Those "gullies" look like chemical stains or weathering.

You can see horixotnal bedding planes cross the vertical dark features almost undisturbed, so they are not an erosioanl feature like a gully, they are chemical weathering. Some fluid is weeping from the top of burns cliff and altering the rocks underneath it.

PS, where the heck is HORTON!

I made a 3-D GIF animation with R1/L7 (both IR) and it looks cool, but as usualy I can't post it here so if someone else wants to do that you can see that the dark vertical features are not carved gullies. Either some dark sandy material is flowing from higer up and leaving these trails, or it is a flouid causing chemical alteration and staining. If it is sand, it must be sticky or very heavy because otherwise the windo would blow it away quickly. There isn't much on that clif for the sand to stick too. I'm voting for fluid and cehmical alteration.

This might be a similar mechanism to gullies we have seen from orbit, although those only occur at high latitudes. IT might be that only much smaller gullies form at mid latitudes, the mechanism is stronger and forms larger gullies at higher latitudes.

One thing is for sure, burns cliff was worht all the slipping and sliding it took to get here. I hope we can get closer to those dark features and see what they are made of.

Ooh, look at this:

This is from sol 272, I think that is very recent. Look at all that material in the cliff right above us! We really made it right to the base of burns cliff. But, I still want to see those vertical features off to the left a bit.

Rlewis
I refer you to the following link. Hortons last post says he will be away for a week or so.http://www.markcarey.com/cgi-bin/mt/mt-view.cgi/18/entry/19710/discussion_page?start=81&show=20
FM Richard

Wow what a picture lewis,the rock people must be going out of their minds about now.
I must admit with all the slip sliding around I had my doubts we'd make it here. This is outstanding. Kinda of the Martian equilvalent of a road cut. I'm guessing that every geologist worth their salt are looking at this and muttering under their breath I want samples of that and that and that and do a rat of every layer in sight

Mars on Earth, or is it the other way around?:

The little hoodoo formations in the upper right of the image, posted by r lewis in reply #8, resemble certain sandstone formations on Earth.

[link]

shows the Fiery Furnace in Arches National Park in Utah (everyone should visit this park at least once).

In Utah, wind and water erosion have worked on and widened joints in the rock. On Mars, wind is likely the only participant, at least in this case.

Yes, we rock guys are muttering. Forget RATS, I want some of those for a paperweight and bookends.

The gray strips running down the surface of Burns Cliff are just plain weird. They appear as if they were painted on the layers without disturbing them. I would've guessed that they're chemical alteration along hair-line fractures, but the features that are fractures are either filled with similarly colored material or lack any staining at all.

Can't wait until it's time for a close-up.

Mitch, I agree with your comment that the vertical stripes look painted on, which is why I think they ARE chemical alteration. What else could produce a feature that is in effect painted on? It is an alteration of the material in the cliff without removing the material, since it preservers the texture of the surrounding cliff face.

If the cliff material was altered without removing it, it mustr be some kind of chemical alteration. The only alternative is an overlay of some other material, maybe sand, whihc is coming down from above, but in that case, why is it sticking to the clif face? It must be chemical alteration of some kind, and that points to fluid flow.

> The little hoodoo formations in the upper right of the image...

My first impression is that they are little Wopmays. I'm looking at eariler images, pre-entry, along the top of Burns Cliff, in the Sol 123-127 range. I'm sure we'll look at that once we get to the rim, but I can't wait.

Those dark strips are indeed just plain weird. Look like weathering in joints, but we'll see what closeups look like.

Whew.

--Bill

WOW!

The geology here is dazzling.

What if..and I'm just throwing this out there...

The dunes that NASA didn't RAT sample at the bottom of Endurance are a kind of ice (myself and others have suggested this previously).

Not necessarily a water ice, perhaps primarily a sulfurous and/or halogenated ice/evaporite deposit (what is the estimated chemical composition of that stuff?).

At one time this material may have been more abundant in this and other craters but has sublimed and ablated and is now less abundant. millions of years ago it may have filled the crater but has sublimed to such a presently small visible volume. Millions of years ago the crater walls and the adjacent martian soils/rock layers may have been saturated with this icy material, like a perma-frost on Earth. The spherules may have formed within this permafrost by biological and/or chemical reaction where the ice and the martian sediment/rock interacted.

As the icy material sublimated and ablated it shrank in volume. Some spherules moved with the shrinking ice field and others were left behind. Some of the spherules that were left behind on or near the surface would have a tendancy to be effected by gravity after the material supporting them was removed by wind erosion. Gravity would have of course caused unsupported spherules to roll downhill to stopping points (with or without ice at that time), gullies, and other low lying areas. The mechanical action of the spherules rolling downhill would have been sufficient to produce many of the channels that we see in crater walls. Channels may have been carved by rolling spherules instead of running water and the spherules may form in conjunction with a type of evaporite-like permafrost.

Robert Page

Also,
The "stems" may represent a time in the history of the spherules where they were exposed to the martian atmosphere or permafrost free zone on one side but still connected to the permafrost on the other.

And for conspiracy oriented folks that believe NASA is covering something up for not RAT sampling the Endurance "ice":

What if NASA believed sufficient information was present to indicate that the Endurance ice was a potential haven for biological organisms. Perhaps they didn't samle/drive on them so that they would not contaminate them with Earth bacteria. I was very disappointed that the "ice" dunes were not sampled.

What ice?

Jon

Re the gullies, I meant that the spherules roll down any inclines by gravity. Maybe that's inconsistent with recent images? I can see that I'll have some catching up to do this weekend when I'm back home on DSL. (heavy week here)

Jon,

There may or may not be ice at the bottom of Endurance Crater. The "dune field" in Endurance is believed by most people to be a simple sand (or silt) dune deposit. It is possible that it is nothing more than a dune deposit, perhaps it was deposited during one of the global dust storms that envelope Mars from time to time. It may have been deposited relativly recently or more likely sometime long ago (millions of years).

Maybe it was deposited at a time when Mars was going through a warmer period and water vapor or other cohesive vapors mixed with the dust in a storm, these dunes formed, and then become more solidified when the temperatures dropped. For example: If it snows on Earth and the temperature is between say 30 and 20 degrees F and then the winds blows the snow around we typically see snow drifts form. If the temperature drops to say 10 to 0 degrees F the drifts usually become more solid or cemented and remain stable during subsequest snow storms as long as the temperature remains below freezing. Perhaps the dunes at the bottom of Endurance are "fossilized sand or silt dunes that formed in conjunction with a cohesive material or vapor.

The "ice" refers to what myself and some other people believed they were seeing. The Endurance dune field appears similar to ablated ice or ablated ice-like/evaporite material. If the rover had performed a simple RAT sample on the "dune material" we would likely understand much more about this material. If it is an ablated briney ice and not simple sand/silt dunes (fossilized or otherwise), then the implications of this material could be instrumental in explaining the spherule formation.

L2/L5 Burns Cliff:

Warning: 1.9 MB link.

Color by horticolor.

(R,G,B)=(L2,0.70(L5),2G-R) -- plus final tweak of color.

OK, Rock guys, go crazy.

> OK, Rock guys, go crazy

Whew, insane. Thanks!

Orient my thinking: those gray streaks left of center, are they running down dip? Why would they not follow the joints in many instances? The streaks look painted on!

I presume that the bedding dip is caused by the upturned rim created by the impact. The stata ought to be essentially flat-lying.

Waiting for a close up examination!

--Bill

The "painted-on" strips could be along especially narrow cracks. In these, water could remain in place as it slowly passed through and altered the surrounding rock. Wider cracks could have been unable to hold water as effectively. It would simply flow through too quickly to do any alteration.

Perhaps they may be able to figure out some characteristics of the (former) subsurface hydrology if there is any correlation between crack size and alteration.

The dunes are merely the top of sand that is slowly filling all of the craters in the vicinity. Endurance is relatively fresh. The oldest craters, as seen on MGS images, are no more than light, faint rings. They are completely filled in, and the raised bedrock rims are eroded down to nearly the level of the surrounding plain.

The image at:

_tiled/R14/R1400021.jpg

(left half) shows Endurance (bottom) and a larger crater above it that is nearly filled in and stripped down. The presence of dunes in the center indicate that it is still filling in. The other half of the image, featuring Victoria, seems to show a few of these filled-in "ghost" craters in the light mottled terrain.

Ok, I'll try to make it easier.

Just remove the double underline "__" between "jp" and "g" in the middle after copying and pasting.