My suspicion is that the apron is covered with cobbles. My hope is that they will be small (gravel- or blueberry-sized), but my nightmare is that they may be boulder-sized.

--Bill

Hmm.. I don't suspect boulders. My nightmare so far has been loose sands causing multiple P-events and ..oh well, we'll see, I'm actually pretty optimistic about it.

Nico

I wouldn't expect sand-sized particles: if present, they would form ripples, like those on the etched plain or the crater floor. I'm hoping for cobbles.

--Bill

I've never considered the possibilty of cobbles or boulders, until now ... Whenever i've looked at the apron surrounding Victoria, i've always assumed, from the ground, it would look very much like the original landing site - small ripples and pretty flat.

Has there been any word on what the science team members think it will be like?

The thing I'm wondering about is the nature of the edge of the apron. A good deal of it is
rimmed with light, evaporite-looking matierial. This suggests that the apron is somehow
suppressing dune formation near it.

My suspicion is that at least portions of the edge of the apron form a bluff - how high,
I don't know, but no more than a few feet at most, and this sudden relief channels
the winds enough to prevent sand from settling immediately below it. We can see the
direction of the prevailing winds in the 'plumes' headding NW from the edge of Victoria.

Fortunately, in the area just to the east of Corner Crater, the transition seems quite
gradual. I'd been having nightmares of Oppy getting to CC, then finding an impassable
2 foot step up onto the apron.

C.E.

LOL -In my nightmare, it is a 10 foot wide, 6 foot deep trench

My guess, like Sunspot, is that the apron will look very like the plains just outside of Eagle crater, and have the same apparently "sticky" surface consistency and good traction. The big crater floors (Eagle, Victoria) are highly specific dune-forming environments where wind-borne material steadily floats in but never gets out, hence the prominent dunes steadily accumulating in a confined space. Thus the apron is a quite different aeolian environment from the crater interiors.

As for the underlying differences between the apron and the dune-rippled etched terrian, this is a harder one to explain, but my guess is the slope - there is a gentle slope down from the rim to the etched terrain and gravity and wind moves the sand downhill. In the etched terrain it is alternating wind directions which cause the longitudinal ripples, and that only works on the flat.

But these are just intuitive thoughts... Kenny

My other nightmare is a 10-inch wide, 6-inch deep trench.

We'll see what we see when we see it...

--Bill

Well, Spirit made a mountain goat leap onto Home Plate...

Bob Shaw

I think the apron material will look a lot like the material out near the original landing site, with a pretty thick substrate of blueberries mixed with basaltic sand forming the ground.

I also think this is the case because of the splash-pattern ejecta blanket around Victoria. The surface rock mobilized via liquifaction (as you sometimes see during earthquakes here on Terra-Sometimes-Firma) and rippled away from the crater, leaving a less blocky, smoother-topped, shocked apron chock full of semi-jumbled evaporite. Which eroded down to a blueberry pavement, exactly the same as happened with the evaporite out on the plains.

I don't know why there is less ripple formation in this area, but the ripples seem to almost completely vanish as we approach the rim of Victoria. There is some significant rippling going on near the borders of the splash blanket, but it doesn't extend very far in from the outer border.

-the other Doug

oDoug:

Liquifaction? That's an interesting mechanism to invoke. Is there sufficient mechanical energy plus liquid water (or other) to make such an effect become dominant? I'm not challenging the idea, merely intrigued - liquifaction creates some very odd results (as in the Port au Prince earthquake (and Madrid?)) where there was a sorting effect which literally exploded low-density buried items out of the ground. And what might be of lower density than basaltic rock and buried underground on Mars? Ice...

Bob Shaw

Yes, Bob -- so you see my point about thinking that Beagle Crater and the contact between the etched terrain and the basal unit around Victoria deserves 15 or 20 sols of close observation.

And I say liquifaction because that's a mechanism that has been proposed for the classic martian splash-pattern ejecta blankets. If you look at these blankets, the splash pattern is always relatively smooth, with little in the way of ejecta boulders or other materials evident on its surface. However, just outside of the splash pattern, you see the classic forms of an ejecta blanket, including block populations and deposition of melts and fines.

The question was, how do you erase the signs of the falling ejecta from the splash patterns? The answer was that the splash patterns were in a state of liquifaction, into which immediate-striking debris *sinks*. The whole thing shivers through the shock reverberations, erasing the immediate ejecta patterns, leaving a well-shaken plateau. That, yes, has brought to the surface low-density materials from below.

This does fit well with what we see at Victoria -- note that in the high-quality MOC images of Beagle and its surroundings (always available for viewing in the Route Map thread), there are a good dozen small craters in the near vicinity of Beagle -- all of them in the etched terrain portion. Not one of them appears in the apron itself, as far as I can see. So, like other splash-pattern craters, you can see evidence of Victoria's classical ejecta blanket, *just* outside of the basal apron.

I do hope they spend at least a few sols looking over this area...

-the other Doug

oDoug:

The only argument I can see against the process is based on crater sizes - Victoria seems a bit small to be a rampart crater. Otherwise, though, it's a very interesting way of looking at such matters, and may neatly explain a lot of oddities.

Bob Shaw

I don't necessarily see fewer craters on the apron than i do on the general plains, although on the surrounding plains they are somewhat obscured by dune features. Whats so odd is the lack of exposed bedrock on the apron, suggesting its much thicker with sand, yet at the same time apparently dune-free as can be seen in the MOC image, well, except for a few small parts near the edge. Although, it could be that its only apparently thicker because there are no dunes to spirit the sand away and expose the bedrock in palces. It certainly looks like a pretty flat apron all around.

So why no dunes and why so even?
...is it simply because the crater terrain dispells and takes the coherent energy out of any previaling winds, leaving just gentle breezy gusts that simply cant get it together enough to build dunes? The smoothness seems to stick to a certain radii from Victoria, implying the wind patterns havent quite been consistent, but almost too evenly distributed around, however, i'd expect there to be seasonally directional winds consistently over very long times that should make this not nearly so symetrical as it is, guess im back in the doghouse agian.

We've got our first look with pancam at the highest part of Victoria (including the beacon!) in many sols today (sol 855) in this shot.

That shot is pretty dark, so I attached an adjusted image:
Click to view attachment
The angular difference between near/far rim positions for the beacon is about 3 degrees for this latest shot, based on the orbital imagery. Ie, if the beacon were near, it would be 13 degrees to the left of the left rim of Beagle, if far only 10 degrees. I measure 12.8 degrees from the pancam image (for 16 degree fov). There's uncertainty in pinning down the rim of Beagle in the pancam shot. But this is very reliable otherwise since only one pancam frame is needed - no splicing.

This is similar to Tesheiner's technique, so I'm curious to hear his results from this.

This basically nails down the beacon as near rim.

Thankyou, Freddo. Precision work as always!
I'm sure the spongeheads will ascribe it to marsh gas or ball lightning, but I think we should begin planning the gala celebration of the Knights Who Say "Near". Appropriate adult beverages should be stockpiled, decorations hung, music chosen etc. I'm hoping Ustrax will appear in full duck costume, just to add to the festive mood.
Christmas comes early this year!

The ejecta blanket or apron is going to prove to be a, if not _the_, major area for investigation on this traverse. It's going to give us geochemistry through a Bassomatic, but it will be a great working example for the major erosional-depositional processes on Mars: impact and aeolian.

The thing that befuddles me is the rim of exposed evaporite at t he etched plain-apron contact. I've not quite got that worked out in my head, yet.

Three weeks or so and we'll be in geo-geek nirvana...

--Bill

It's not settled by any means. My gut is still hanging in there.

About measurements. Did you measure the angle view of the beacon from Oppy's position using the measure tool from Photoshop? I have done this so.

However, now, how did you measure the angle from the Pancam view?

Rodolfo

About the smooth surface of Victoria crater apron, It is somewhat odd. As the rule, VC must have tall rims due to the impact crater. However, it has no rims but only smooth apron all around 290-330 meters of radius. I think, as atomoid that the smoothness of apron is related to aeolian process which is not prevalent but somewhat disturbed due to the round shape of the Victoria crater which does not permit to build line of sand crest. The wind goes into the crater and also climbs as close as on the surface. Hence, after the wind climbs from the inside crater, there are sand deposition which forms apron.

It is just my toughts as everybody trying to explain why there is that APRON!

Rodolfo

I'm not sure that I fully buy into all of the mechanisms, but that certainly is an interesting and new vision of Blueberry Hill.

Rodolfo, I don't have photoshop - to measure the angles on the orbital map I just drew sight lines from today's location to the near and far rim beacon locations and to the rim of Beagle using "ms paint" and used good old fashioned trigonometry to get the angles.

Measuring the angle from the pancam frame is easy - just count pixels from Beagle rim to beacon, divide by 1024, and then multiply by 16 degrees.

Don't hope...I'm ready...

[quote name='RNeuhaus' date='Jun 21 2006, 06:40 AM' post='59242']
The wind goes into the crater and also climbs as close as on the surface. Hence, after the wind climbs from the inside crater, there are sand deposition which forms apron.
Rodolfo

I buy this one! Do we have other exemples of craters nearby than can prove this theory?

I was eager to get a new shot of the beacon from somewhere around the current position exactly because of that 3 degree angular difference; that would be more then enough (imho) to overcome all the uncertainties on pancam fov, map's distortion, human (mine) errors, etc.

I did a similar exercise as yours, but using the first and second pancam shots in a manually "stitched" mosaic. By including the second image we get the right rim of Beagle on the fov and that adds to better fit the headings. The results are the same as yours i.e. beacon definitely at the near rim... unless the far-rimmers have some "green men" there at the far rim moving the beacon from sol to sol.

The headings to the left/right rim and to the beacon can be seen on the following images. The first has a polar projection overlay and the second don't, so opening both pictures and switching between them creates a sort of "polar projection on/off" effect.

Click to view attachment Click to view attachment

Edited: Polar projection (and headings) slightly rotated, based on pancam pointing data taken from the tracking web.

I don't see any features on the near rim that correspond to what is observed visually. It still appears to me that what we're observing are features on the far rim visible through a gap on the near rim.

The "green men" in my head are still insisting on this...:

http://i16.photobucket.com/albums/b14/ustrax3/beacon8.jpg

Near anyway...

Me too. If I look at the MOC image I can't see any shadow indicating an elevated feature.
But, as I said on a previous post, the near-rim hypothesis is not based on "perception" but just geometry, and the results have been the same since at least sol 820: near-rim.

Sorry my dear friend but it can't be. The features pointed by arrows spawn about 14º, which would be almost the full width of a pancam image.

Bah! Details...

[quote name='ustrax' date='Jun 21 2006, 02:47 PM' post='59288']
Bah! Details...



I realy enjoy near-rimers disputes

'I realy enjoy near-rimers disputes...'

You know...I'm portuguese, so, before our team scores, I'll just keep on dribling the opponents with all this 'artistic' way of playing...

Let's have some chilli!

[quote name='ustrax' date='Jun 21 2006, 03:35 PM' post='59292']
You know...I'm portuguese, so, before our team scores, I'll just keep on dribling the opponents with all this 'artistic' way of playing...
Let's have some chilli!


We've got some good driblers in France too but I must admit that so far (rim ) Portuguese as well as Spanish are doing much better than ourselves in the world cup. Anyway, winning the soccer's World Cup will never compensate loosing the Beacon's competition. Sorry guys

We may win both the World Cup and the Beacon Cup.
(Don't forget where I come from: Spain & Brazil.)

Ooops, we shouldn't be talking about religion.

I agree with your conclusions, clearly what we are seeing tracks with the near rim. But my point is, the aggregate of what we're seeing is consistent with a "window" or "keyhole" on the near rim through which different features are observed over time from the far rim.

Until we are close enough to measure the parallax associated withl recognizable features of the "beacon" as Oppy moves, I'm not sure how we could disambiguate features on the near rim, from a near-rim "keyhole" hypothesis.

Anyway, very nice work.

The "keyhole" theory would imply that both near and far rims must align perfectly as seen not only from the current line of sight but since many, many sols ago. If that alignment don't exist, either nothing would be seen through it (far rim below the hole) or the beacon (at the far rim) would be always visible over the hole. On the latter case, parallax measurements would have to be consistent with a far rim location... but they aren't.



But where is the "keyhole" on sol 855 images? The beacon is above the horizon line.

Great job, Tesheiner! I like the polar overlay. Just one question: your orbital map is a splice of three images, and the alignment is out a bit - you can see it by comparing outcrop along the seam at top. Is this important to your conclusions? Could you use a single orbital image, like the press release map at the bottom of this page?

Good comment Fred.
I was using already that pic as a "backup" but it's too big and the contrast is not so good. About the alignment errors, have a look to this post.

Anyway, I double-checked the headings using that single background image like on the referred post and the results (lines in red) are quite similar. If you move/rotate the lines to fit BC rims, the beacon heading will cross with the original JPL's line almost exactly at the near rim.

Click to view attachment

[quote name='Tesheiner' date='Jun 21 2006, 04:10 PM' post='59298']
We may win both the World Cup and the Beacon Cup.
(Don't forget where I come from: Spain & Brazil.)

That's too easy to have two tries. Your only chance could be that VC is an old volcano PELE

Actually, I'm not suggesting we're seeing the same part of the far rim, but rather different parts of the far rim at different times through a depression in the near rim:

I've annotated a version of your figure to hopefully explain better what I mean:



My point is that the "beacon" is poorly enough resolved that currently we can't tell if we're seeing the same features or different ones with the two views. The background of the crater remains relatively fixed, and it is the parallax of the depression on the near rim that is causing a shift in the field of view through the "keyhole". (So the parallax measurements simply give the location of the keyhole, through which "white light" is shining.)

The only reason I find this "more likely" is that to the extent we can distinguish any features, they appear like classic Mars "white cliffs", and there simply isn't any detail on the near rim consistent with this. The only way we could distinguish the two hypotheses would be to resolve enough features in the "beacon" to track the features of the beacon, and not just it's location.

Why is this a problem for viewing part of a raised far-side rim through a keyhole?

Anyway, I hope I've made myself a bit clearer!

Sorry that it took me a bit to figure out what you meant. Actually if you trace out the horizontal line, Victoria crater appears to rise above it (the dashed line is my rendition of the horizon):

Click to view attachment

Further if you trace out the top edge of the crater, the beacon does not (to me at least) appear to jut about above the top of the crater (the solid blueish line). I've also drawn in a red line showing what I consider a plausible profile for the near rim based on a "keyhole" hypothesis.

I'll admit these reconstructions are very risky given that we are starting from a blow-up of a JPEG. But it seems to me to be as reasonable a hypothesis as a near-rim prominence...

Not necessarily. If the far rim were a continuous light colored "wall" across from the key hole then the beacon would appear no matter what the angle or position it is viewed from. Moreover, if the far wall were not homogenous in appearance then the the beacon would seem to fluctuate over time, possibly even shrinking or disappearing altogether (on the occasion where a dark area of the far wall lined up with the keyhole). I believe, in fact, this has been happening. I don't have the time to research the sols right now, but I do recall that we actually "lost" the beacon at one point.

Can anyone with the imagery knowledge that I don't have yet help me visulize The size of Endurance Crater compared to Victoria?

If one of you imagery guru's can take an overhead shot of Endurance and lay it next to Victoria and also take an image of Endurance from ground level like this one:
http://marsrovers.jpl.nasa.gov/gallery/pre...-B096R1_br2.jpg

and take that image and blow it up to the size of Victoria and have both the true size Endurance and The Victoria sized Endurance laying side by side? I would like to see how big a Victoria sized Endurance would be? If there is a better image of Endurance from ground level then use that one.

Thanks

Thankfully, nothing bad will happen to the people on the losing side in this debate. I had originally come in as a far-sider, and then was pursuaded to join the near-side team just before we closed the polls. The next day someone showed a great blink-image showing Beacon moving with respect to near-rim features. At the time, I thought "Doh!". Looking back, it is amazing how ambiguous this issue is. I haven't talked about it much because I'm locked in as a near-sider, but to me the more natural explanation is that it is a far-side feature, where we are seeing the white material under the blanket that can't be seen on the near side from our vantage point.

For it to be a near-side object, it would have to be a large salt-lick sitting precariously on the lip of the crater, and, for some reason, not crushing the unsupported sand underneath it. I'm sure I'm not alone in being impatient to see for sure which side its on.

I'm not convinced that can't be explained by optical properties given that we are trying to resolve a distant, bright object with magnification and vertical stretching. Especially if you factor in the light bending properties of the alien gravity generator buried under the near rim.

It doesn't matter. The beacon will be found on the far rim. We will simply choose an appropriate definition of "far" when the time is right.

Brian

I understand your point, but we still have a misunderstanding.
When I say "that both near and far rims must align perfectly as seen not only from the current line of sight but since many, many sols ago" I'm trying to speak in terms of elevation/height. If the far rim is higher then the near rim, we would be actually be seeing far rim features; if the far rim is much lower then the near rim if would be impossible to see any feature on it. The keyhole implies that both rims have an elevation which matches exactly with the current line of sight; it could be in theory, but keep such *vertical* alignment for sols and sols is something I can't explain.

Actually, it just requires that the top of the far rim be below the maximum azimuthal angle

I added an additional line (in yellow) to your picture; it tries to represent where the far rim should be to be barely visible through a hollow on the near rim. The hypotetical far rim feature originally seen around sol 800 and identified by JPL would be about 200 pixels to the right (3.5 degrees).
Imho, such a coincidence is too big to be true ... or there are other options?

Ahhhh - this fence is comfy

Doug

I've been quietly watching for a while, but let me throw in a philosophical monkey wrench. If we're seeing the far wall through a gap/keyhole in the near wall, is the beacon at the far wall or the near gap? Could we have a situation where both the nearside and farside people are right?