Another example of holes and possibly caverns can be seen in MGS photo R0701365

http://www.msss.com/moc_gallery/r03_r09/fu...07/R0701365.gif

There are a lot of sinks along some ridges along the northwest flank of Arsia Mons.

The most prominent feature is given as attachment, but there are several more.

Besides this, in the upper part of the original frame there are some black

streaks at another ridge which may indicate water or ice rich sediments

common to the Arsia Mons terrain.

So it could be said that the area is a collaps region loosing its icy layers and the caves may be sinkholes.

The center of the original image is at 238.11°E and 5.40°S.

Interestingly, dark downward running streaks and gullies are slso found in the higher layers of the Tharsis vulcanos and even across the caldera of Ceraunius Tholus.

Due to the lower pressure at high altitude the streaks should be shorter than those in valleys.

Harkeppler

Those are interesting images. I'd like to see a HiRise image of this region. I'm not sure I would describe it as a "complex" cave system, but it did look like a lava tube that has some sinks being buried by sand/dust.

Question from a non-geologist. Why would a lava tube (if that is what it is) follow a ridge?

Maybe the tube makes the ridge, the lava drains from the middle while the outside cools solid making the tube - and then sand etc form over the top of it to make a ridge? Then the ceiling of the tube collapses. Pure guesswork.

Doug

Interestingly, the holes are on the highest level of the landscape at the side of the rigde and there are several bright sediment layers at their walls.

I do not think it is a dune system or a a lava tunnel. It looks more like a collapsed region which has lost ground ice which seems to be presents in all Tharsis Montes. If one browse through the MGS picture collection showing the flanks of these mountains (especially Arsia Mons), there are a lot of ridges showing black streaks and gullies similar to them indicating water or brine flows.

Larges amounts of ice inside the mountains would form a lot of mud in case of eruptions, and I think the aureole around Olympus Mons and that around the Northeast of Arsia Mons are nothing else.

At the Arsia Mons I think that some of the large "lava tunnel" are water drainage and collapse features and not empty lava tubes (they are very large, probably too large to be stable when hollow).

But this is only an idea.

Gullies in the summit caldera (!) of Ceraunius Tholus can be seen here:

http://www.msss.com/moc_gallery/r03_r09/fu...07/R0701361.gif

Gullies at tha flank of Pavonis Mons:

http://www.msss.com/moc_gallery/s05_s10/fu...06/S0601434.gif

Gullies at the flank of Ascraeus Mons:

http://www.msss.com/moc_gallery/s05_s10/fu...07/S0700545.gif

Dark gullies at the Arsia Mons flank were shown in the thread before.

So, water seems to be present an the Tharsis Montes.

Some years ago there was an interesting theory that the Tharsis Planitia was situated billions of years before at the pole due to a slow wandering of the whole planetary crust (one large continent drift) against the core and Olympus Mons and the others penetrated the polar cap.

Harkeppler

The depressions along the top of the ridge are quite fascinating, and they do look different from the ones on the flanks of Arisia Mons. Has anyone tried to estimate their depth?

Um.. I hate to be the dense one yet again but am I looking at gullies or dark streaks here? I may just have missed something but I see dark streaks running down the slopes on a lot of these pictures, rather than gullies with heads incised chanels and debris aprons at the bottom. Sorry but could someone clarify this for me or just point out what we're looking at?

To explain the feature:

The dark gullies (indicated yet for clarity) give a hint that water (or brine) is draining from the walls of the ridges at the flanks several Mars vulcanos. This gives the idea, that the lava tunnels in that area may be collapse structures in ice rich regions when volcanic heat melted the ice and produced a lot of mud. Some of the lava tunnels are mud streams or collapsed and drained areas.

So, the Tharsis landscape seems to be water rich and a cave system in water rich sediments is of more biological interest than a dry magmatic one.
The gullies at the Arsia Mons flank are in the ultimate vicinty of the multiple-hole-cave-complex mentioned above.

In other words: If I have to look for life on Mars I would look in these caves at the Arsia Mons flanks.

Harkeppler

From a few streaks, you're making an entire region 'water rich'.

That's a leap of faith.

Doug

The context image on this page shows what appears to me to be a large, meandering lava channel. I'm not an expert on these things, but it looks like inverted topography. Apparently the material around the channel was softer, so it eroded away leaving the filled channel as a ridge.

Like marsbug, I see lots of dark streaks, but no gullies. Calling for a water explanation seems quite a stretch.

The dark streaks a) start at different levels and b ) leave no long-term flow signatures on the surface. I'm sticking to the dust streak explanation.

The very dark and faily short streaks in this image maybe shadows instead of water streaks...just a trick of the light.

Click to view attachment

I suppose some of the others could be dust streaks of some sort; yet some seem more like water streaks to me. It's hard to be sure.

It may be.

I think it is interesting that at 5.5 km hight these gullies can be seen at the summit of Ceraunius Tholus. I am sure that there must be an ambient temperature and an sufficent pressure to allow the spilling of a fluid. So, I would not wonder that there are no such gullies at higher levels, so at the summits of the Tharsis main vulcanos.

Maybe it is possible to calculate the lenght of such gullies in dependence of the temperature, pressure and inclination of the walls.

Harkeppler

Yes, it looks like a channel. But the holes are at the upper level of the landscape and persisted although the tunnel collapsed and got broader then before. All in all it looks strange.

These are not the features usually called gullies; the conventional view is that they are dry dust avalanches and do not involve a liquid. See, for example, Rob Sullivan's abstract http://www.lpi.usra.edu/meetings/lpsc2000/pdf/1911.pdf

The "Tharsis Montes" are shield volcanoes. Lava flows. Where does this ice come from?

Resublimation of water vapor at high, cold places like a cold trap. In 1985 there was an interesting idea that the Tharsis Planitia was situated for a while at one of the both poles:

1985.P Schultz P.H. Polar wandering of Mars. Scientific American 253, pp. 94-102.

The main calderas of the large vulcanos seems not to have been ever something like the Hawaian "lava sees". They are only sunken depressions. No pots of molten stone, more an uplift of the original crust with layers of vulcanic ash, lava and - ice. The main vulcanic activity was seen more at the flanks.

If You have a look at the "Dena"-site (attachement), You see a widely collapsed landscape at the flanks of Arsia Mons. This does not look like the work of lava tunnel systems. Furthermore, the Dena-Depressions are at the floor of another larger depression - we have a multi-stage and multi-layer collapse telling me that there are several layers of ice gon away more or less effectively.

Harkeppler

This may be of interest:

An Article from 2004 reflects some informations to water and ice at the Tharsis Planitia. It does not look completly dry...


Enhanced Water-Equivalent Hydrogen on the Western Flanks of the Tharsis Montes and Olympus Mons: Remnant Subsurface Ice or Hydrate Minerals?


http://www.lpi.usra.edu/meetings/lpsc2004/pdf/2011.pdf

The best is the last sentence of that paper:

"Modeling is underway to determine if avalanche velocities and dynamics are sufficient to suspend dust during entrainment as the avalanche front moves downslope."

Maybe "if"... maybe not...

The dark streaks and fans looks very sharp and structured. There are at least four possibilities: 1. the dark material is the underground and the light toned one has been removed. 2. The dark material has been added. 3. The dark material is light toned material getting soaked. 4. The dark streak is a mix-up of the light toned maybe by turbulent gas.

Harkeppler

How sure? Have you done the leg work? Found typical atmospheric pressures at that altitude, looks at phase diagrams. Remember - even at lower altitudes we're working in a very thing part of the phase diagram that allows water only over a very small temperature range.

And - if, as you say, there is so much water here - where is the minerological evidence for it?

It's easy to go 'looks like water'. It's very hard to make a water tight case for it. You're a long way from that.

Doug

Doesn't work that way, Hark. You've got a shaky theory supported with suppositions...

That abstract is seven years old, so you may want to follow where the research went after that. It's not like you were the first to notice these features.

I am posting this MRO picture, because it appears to have both the dark streaks and a cave in the same image. The cave appears at the bottom portion of the image, and looks to be pretty large. It appears that the top layer of dust appears to have been removed around the opening of the cave. Very interesting picture!

http://hirise-pds.lpl.arizona.edu/PDS/EXTR..._RED.browse.jpg

That doesn't look like a cave to me, more like very dark dust on a sunward facing cliff?

I guess it could be dark dust, but it looks to me that the top of the cliff is overhanging, no?

Thats very interesting!

Obviously, the dark patch looks much the same in a Mars Global Surveyor Image.

http://www.msss.com/moc_gallery/e01_e06/im...2/E0202590.html

There are a few new streaks in MRO imagery compared with this older picture.

Coordinates are

11.3 ° Longitude 181.0° East /179° West (used for MGS imagery)



See also Mars Odyssey imagery for an overview


http://themis-data.asu.edu/img/I18416013.html
http://themis-data.asu.edu/img/I17193052.html








Harkeppler

As I see yet: there is a second "dark cliff" in this picture:

http://www.msss.com/moc_gallery/r16_r21/im...8/R1800437.html

What do we see here? Is that a natural bridge? Monument valley on Mars?

The formation is situated a little more east with respect to the primary one.

Some similar knobby hills in the vicinity:

http://www.msss.com/moc_gallery/e07_e12/im...1/E1101435.html
http://www.msss.com/moc_gallery/r10_r15/im...2/R1204047.html
http://www.msss.com/moc_gallery/r10_r15/im...3/R1303642.html
http://www.msss.com/moc_gallery/r10_r15/im...1/R1102555.html

Harkeppler

You can find some relevant NIAC (NASA Institute of Advanced Concepts) studies & material in the following links:

Study 1

Study 2

Sorry, newbie question: MGS got lost months ago. So, are these images just been "discovered" after probe's death? I mean, we had them, but we didn't examine them yet?

Small features in tens of thousands of fairly large pixel-dimension images.. did she reach 100,000 images?..1024 x 4000 is not unusual.. they can be LONG ribbons take a lot of cumulative looking to spot. And the researchers: Professors, postdocs, grad students, civil service scientists... have a lot more to do than just oogle images all day.

Mmmh...then i guess some manned mission will actually reach those craters before we'll be able to examine ALL this amount of data!!
...unless some guy will write a simple software to automatically "look for holes" in the images database! It wouldn't be difficult... but I don't think somebody will try to download ALL full-res images to automatically scan them! Nasa people should prepare such a SW, IMO.

http://lc84.altervista.org/marte/buchi-marte-2.html