My position remains unchanged. If we now had an unobstructed view of the far edge of the crater, we should see a panoply of bright white reflections from the edges of the evaporite (not just Beacon), interspersed and underlain by hard, black shadows, not just diffuse dark areas. Everything is sort of smudgy-dark because we are looking at a relatively featureless surface sloping away from us - the near apron of Victoria. If I'm wrong, I will bake a hat-shaped cake and eat it.

I'll join you in a slice of that hat, Shaka. This has to be the outer rim on our side of the crater.

Phil

Bill, I understand your point about altimetry... it seems reasonable, but I see that the majority still in favour of near rim hypothesis (and I'm still uncertain!).
Let's see in the next few weeks...

Then I'll give you a definite maybe to all the above.

But, as you say, we'll know for sure in a few weeks.

--Bill

Sure I know that VC is confusing but never imagined that speculations would run this wild...

While it's always good to propose new ideas, I anyway give my provisional verdict in the Victoria Crater case:

Victoria seems to be a 'rimshot' crater herself, or more precisely, shot just inside into what's possibly 3--5 times larger paleocrater. The VC impactor happened to hit the ~NW sector of this shallow depression, which is why the NW portion of Vicky's rim rises higher than the rest. The 'beacon' must be the highest point there, let's say 10 m above Oppy's level. Oppy is approaching from NNW and thus can't see the interior. But she can see part of the paleocrater (the depression to the left) and distant dunes on its opposite 'slope' (pancam sol 817), and probably marginally over the left edge of VC. The stretched images revealed that the horizon in this ESE direction is bent slightly down from the expected level, so it must be really far away (and the depression large). This makes sense also if the peaks on the horizon belong to the rim of the more distant SE crater (35 km), as others have stated.

Owing most of these deductions to others than myself, I refrain from further speculations on the features of VC until Oppy arrives at the near rim.

Call this image a wild speculation. (Orig. [corrected] R1400021, cropped and reduced to 50 %, south up)

I've figured out why I think it's the near side of the crater.

The features are running down and to the right - which is what I'd expect if we were looking at the western half of the near side rim because of the slope. If they were on the far rim, then I'd expect them to be running down and to the left.

Just my 2p's worth - but hey - we'll only find out in a couple O months

Doug

By the same token, if the entire near edge of Victoria is in view, why no panoply of bright refections from it? If the beacon is on the near side, it would be a unique, small feature -- perhaps a lone boulder rather than part of a continuous outcrop. If it is on the far side, it would only have to be the tip of the highest outcrop. If parallax calculations show that it cannot be a single point on the far side I would have to respect that.

I am still not sure of any of them (north or south) rim.

However, I feel that the indicated arrows are of near rim.

I see the black features corresponds to near rim and not of the far rim. Not sure because the image is still blurr.

The selection of near rim was based on the following deduction:

The prevalent wind comes from SouthEast to NorthWest. Hence, I suspect that the far rim (southEast) would be mostly covered by sand (light color) and the near rim (northWest) has strips or streaks of winds and hence the land is somwhat darker. According to my desert experience, the wind deposits sand or powder on the falling of hole and cleans the hill and its post after the wind leaves the surface of a hole.

The other hypothesis, if the meteorite that hit Victoria Crater comes from NorthWest and the tallest part of rim should be on the SouthEast. That is that the rim would be of far side. This hypothesis contracits to the previous. However, as I see VC as almost circular and not as an elagnoted shape made by a coming impact meteorite direction.

I am still peeling off the leaves of a flower.

Rodolfo

The "edge" (the broken sides of evaporite layers) on the near side face away from us to the south, so they are only visible to observers south of Victoria. We are looking at the crater apron (and its coating of sand, concretions or whatever) up to the break point. The "edge" is out of sight. The white and black panoply is hidden from view.
"The beacon" is something special, and requires a special explanation. You offer two, others have been mentioned: A view of the bright far edge through a gap in the near edge (like the "boat ramp"), or a section of white edge with an adjacent darker turned-down section (also on the far edge) which therefore move together despite parallax changes. I'm eagerly awaiting each day's pancams to see if it disappears.
One thing I'm sure of: thank heaven for the Beacon! Without it what would we have to argue about?

I would like to start an informal poll regarding Beacon Rock or Outcrop ending on May 20 when we might know where it's located at? Is Beacon Rock on the near rim or far rim? I will say far Rim. I will log the votes daily and see what everyone thinks.

Marswiggle, the idea of a paleocrater around VC temepted me too some days ago: the tilted profile and the depression on the left strongly suggest this structure! however, satellite images and Mola data do not show clear hints of it, apart the abrupt end of the etched terrain that could coincide with northern end of this supposed crater.
And Doug, I think your argument in favour of the near rim interpretation (absence of bright outcrops) is the most convincing up to now!
Anyway, this is the Sol818 PanCam stretch (if someone wants to add to the movie!):
Click to view attachment

I'm going to go out on a limb (or should I say going out on a rim? ) and say it's the FAR rim. For lack of a better term it appears like a discontinuity -- it's out of place along the near rim. My guess is that when we finally do see that far rim, the beacon is going to be one of many similar such bumps and lumps, albeit the highest one.

By the way this is a fun game to play for those who like to hike or mountain climb -- especially with two or more companions. Pick out features in the distance and speculate on their nature or placement. As your perspective changes the group can continue to debate the evolving information. It works on a long drive too, especially through desert regions with wide open vistas.

The shadows in this 8x vertical xeyed stretch are suggestive that we may be seeing the inside of the far rim

Click to view attachment

Well folks, my initial gut feel was far rim, but the parallax changes favor the near rim (or less likely, a unique gap in the near rim than frames a view of the far rim).

I think I have to go with near rim. I would guess that it is a large piece of evaporite that overturned onto the apron (or somewhat less likely, just sticks up at a steep angle). There may be other such pieces, but this one would be by far the biggest.

We'll see what we find.

Scott

if we are allowed to use our gut then here is my purely O.O.M.A. guesstimate - green is near rim, red is far rim.
I have no idea what I am doing....

I'm not sure what's going on on the left (I don't think we have the imagery to tell yet) but the lump to the right is the near rim, I'm increasingly sure of it. The features on it are orientated 90 degrees out from what they would be for far rim features.

Doug

This analysis suggests the far rim is significantly elevated above the near rim:

http://gallery.perfext.com/displayimage.php?album=2&pos=69

Click to view attachment

My take is for near rim.
Given that a "restricted sols" period is just starting (unsure), I have my doubts about knowing the answer to the "Beacon's Mystery" by the end of this week.

I think we'd argue that one to death - because it's basically a pixel or three - and I can imagine someone arguing that those pixels had a contribution from near and far rims together as the crater resolves itself.

Doug

If we take into account the beacon alone, I agree with you.
But if you consider the change of angular separation between the beacon and Corner Crater since e.g. sol 800, I think it's quite clear where is it located.

Given that we're stretching a few tiny pixels into a whole swath of detail... I wouldn't say anything is 'clear' yet.

It's still very confusing really - why do we only see an elevated area for half of what should be the near rim. What do we see where there isn't an elevated area. etc etc etc

I swing toward what we see being the near rim, but it's a whole lot of infering from a few stretched pixels.

Doug

My bet would be on the near rim, here:

http://i16.photobucket.com/albums/b14/ustrax3/beacon3.jpg

OK, if there is a pool I would say, it's the FAR rim for 3 reasons.
1- As Doug said, it's the far rim because it's the far rim
2- I want to win at least once over Tesheiner
3- What we see has to be vertical, and, if I refer to Endurance, vertical rocks were inside the crater. Like this : http://www.unmannedspaceflight.com/index.p...=15&#entry54153

Perhaps I've missed it, but has anyone here looked at the orientation of Victoria in terms of sunrise and sunset? I'm thinking of the classic view of Endurance with Burns Cliff illuminated by the sun as seen across the plain. In terms of the projected drive route, how does that line up with the illumination?

Bob Shaw

Well - at sunrise you'd have the east exterior slope and western interior slope illuminated. At sunset, the western exterior slope and eastern interior slope

Unfortunately, we're coming from the north so we won't have that facing-east-at-sunset-with-sun-behind-us illumination we had at Endurance.

HOWEVER - a time lapse of Pancam imagery centered on VC would be interesting.

Doug

Doug:

I'd sorta worked that out in general terms - however, the time of year on Mars will change the illumination to some degree. Perhaps some lines on a map exist, somewhere? (hint!)

Bob Shaw

For the informal poll, I think we are seeing the near side of the crater. I would be expecting to see more evaporite if we were seeing the far side.

Chris

I say far rim.

The beacon is on near rim. I relay to the wind prevalence and image colors to deduct the position of beacon. Clear color is far ream and dark color is of near ream. If the near rim is higher, then the impact meteorite would comes with a southern angle.

The image is still blur at this distance. What distance wouldl the PANCAM image become clear enough to distinguish the near/far rim?

Rodolfo

Well, on other some sites 3 pixels would be evidence of a whole civilization....

No detail from the pixels forming the beacon, but a precise position. Is Tesheiner the only one who has studied the parallax changes as Opportunity angles away from a straight line drive to the beacon? I think that is currently the most powerful argument and not hindered by even a one pixel beacon. I'd like to see others more adept than I do the calculations and support or rebut Tesheiner's position.

As far as a near and far rim contribution to the beacon, I'd say 'no way'. Surely with even a slight deviation from a straight-line path by Opportunity, a separation of the two points (near and far) would be seen, even if they were an one time alined.

Intuatively, I see the beacon as the tip of a prominence on the far rim, but Teishner's parallax argument, if supported, would make me agree that it is a near rim point. In fact, may it not be a chunk of rock laying out on Victoria's apron, tens of meters from the edge?

That's exactly the point. The beacon could be a whole 100x100 pixels feature with a lot of detail but what's really important is not *how* it looks but *where* is it located (the angular separation) in relation to other known features.

As will the time of day obviously. For thissol for example sunrise azimuth is 70.0deg (at 06:02 LTST) and sunset is 290.1deg(at 17:58 LTST) while at 10:00AM LTST it's 51.7deg.
If you don't want to do the calculations yourself Mars24 shows them all quite nicely on the Local Panorama display, you just set the location, date and time.

I think the hummocky terrain on the right side of the now-emerging "Victoria Complex" is a near-rim feature. In specific, I think it is the planview of one of the lobe-shaped overhang features we see in the orbital, overhead views of Victoria. It appears that some of these lobe-shaped features have topography of their own, and are not simply mass-wastage forms resulting from rim collapse and expansion. (That makes them a lot more interesting, in my book...)

As for the beacon, I must rely upon the analysis presented heretofore in this thread. It would seem that the beacon is a near-rim feature. But we're far too far away to have any other information about it.

Since we're able to pinpoint it as a near-rim feature from parallax information, can we use that information to at least constrain its location on the near rim? I have seen a few speculations here, but we're not even presenting images of Victoria in a standardized way -- some use the north-is-up convention, others try to place Oppy's current drive direction as the 'up' vector... I can't get a good handle on where on the near rim the beacon might be located.

-the other Doug

I'm for 'near', fwiw. I think the dark area some way to the left of the Beacon is the wind-deposited 'tail' that emerges from the downramp, and that we're looking at the raised nearside rim.

What makes this fascinating is that AFAIK, no-one can claim to be absolutely 100% positive - we're still within the margins of error for parallax at this range (I think?) How about a follow-up poll about the number of Sols before everyone agrees with one option or the other? I vote for a long period of ambiguity, say... Sol 850.

I made my personal attempt to measure beacon parallax, but results still confusing me...

Starting from PanCam stitches and assuming an angular scale of 0.28mrad/pixel, I found the following angular distances between the beacon and east (left) rim of "corner crater":
Sol pixel deg
796 525 8,42
800 581 9,32
803 597 9,58
813 689 11,05
815 735 11,79
818 744 11,94

Then, using Theseiner route map, I reported azimuth of beacon for each Sol (blue lines):
Click to view attachment
Incredibly, the "least distance" between these headings lie in a point closer than Victoria (orange ellipse) ; this could be due to error in stitched images and route map and, anyway, the "near rim" hypothesis seems to be favorite. However, in the portion of the rim where we should have the beacon, I do not see any clear feature suggesting such a tall structure... (see enlargements of original and "press release" pictures of this region).
On the other hand, headings matches enough with "far rim promontory" suggested by JPL, even if last heading (Sol818) seems to point to another adjacent structure (to the right of it).

At this point, the only matching explaination seems we are seeing the far rim trough a hole in the close rim, as already suggested by someone... however, also this odesn't satisfy me because:
i) we should see some change in the beacon appareance due to parallax
ii) the beacon appear clearly elevated in all images.

See following collection referred to the Sol numbers reported at the beginning of the msg:
Click to view attachment

Good job dilo...

and, get real, guys. A big white triangular promontary? It's the far rim.

On one shot a little while back, when I posted a stereogram, the right eye picture showed the beacon and another spot of white a little further along. I wonder if we have seen the second beacon sometimes?

Great work, Dilo.

I'm also puzzled by the lack of evidence of a clearly visible feature at the near rim on MOC images, but for the time being I should keep with the "near rim" hypothesis because the apparent "drift" of the beacon location on VC's far size, imho rules out the far rim option.

But to be sure, we should better wait for some 200m driving south and do again the same exercise.

The beacon is obviously going to be a roughly pyramidal structure, twice as high as a man, set in the rock like a gigantic, many-faceted jewel. Oh, and I can smell sausages burning!

Bob Shaw

Bob you aren't supposed to use "pyramidal structure", "many faceted" and "beacon" in the same paragraph here. "They" will surely be along any moment now with theories of aircraft hangars and such.

and some sulphide salt oxidation smelling.

Rodolfo

Can I mention s*usages, then?

Bob Shaw

Yes, but not f*ying s*usauges.

That's O.K., Dilo. If we don't act fast to rescue this topic from frying sausages, things could get really ugly! (Emily might even complain. )


How tall do you think Beacon must be? If it's on or near the north rim, as your trigonometry implies, it does not have to be very tall. It seems to have changed very little in your sequence of pancam images. If it were on the far rim it should be getting smaller in height, since we are presumably descending, with more of it being hidden by the near rim. (Unless we are viewing it through a deep notch, which I don't see along that line.)

I hate to say it but I don't think we can take it on faith that JPL has got it right.

I think this is a key point. Beacon appears perched on top of the near rim. If that were an optical illusion, it should have changed over past weeks as our viewpoint has moved laterally and downward. Since it has not changed, beacon must really be on top of the near rim.
So why can't we see it in the MOC plan view? That gets back to the real size question. If beacon were a slab of evaporite say 2 by 2 meters and half a meter thick - with blown sand or dust on the top - Would there really be much to see from orbit? From Oppy's location we would see the bright clean edge, but not from overhead.
Keep on truckin'! Keep on thinkin'!)

Actually one of the reasons I favour the far rim location is that the beacon used to be 5 pancam pixels high, and now it's only 1-2.

Holy Cow. ( I assume you're comparing images with no vertical stretch.) It would be a huge help to me if you could link or thumbnail images that bring this change out. I didn't see it.

My money is on the far rim. I think what we are seeing (based on Dilo's triangulation) is the far rim seen in a gap in the near rim. I do not think its a single tall structure but nothing more than a "lensed" or windowed view of a long exposed face on the far rim viewed through the near rim. Each view we have seen over the last few sols is thus a small section of the far rim, but not the same section, as exposed as we move south.

The problem I see is that any deviation of Opportunity from the ideal line of sight through such a gap should block out the view of the far rim and extinguish the beacon. If the gap is wide enough to prevent this, the beacon should widen or narrow depending on how well Opportunity is lined up with the gap. But ever since the beacon was spotted, it has maintained its presence and size despite opportunity's deviations from a straight-line path to it.

Any chance of getting the rover drivers to take a hard left or right and drive as far as it takes to get an unambiguous answer by parallax?

At my post on 2 May I had this unstretched image of the beacon:

Click to view attachment

and now the poor litte thing has shrivelled away to nothing - pancam, 14-May, no stretch:

Click to view attachment

- maybe it's cold...

Edit: Odd... I can see the previous image in preview but not in the thread

Click to view attachment
I don't know how valid a comparison of these two images is. The May 2 one (on top) is a particularly wormy jpeg and I don't know if the scales are the same. Are they crops of individual pancam images or of mosaics?

If there is real shrinkage, it could as well be the result of a small topographic rise in front of a near rim beacon.