Actually, it just requires that the top of the far rim be below the maximum angle of inclination for the front rim, and above (on average) the minimum angle of inclination for the near rim, after correcting for the curvature of Mars. See the enclosed figure:



From a quick back-of-the-envelope calculation, the far rim will be reduced in apparent height by a distance,

h = (rfar^2-rnear^2)/(2*R)

where rnear = distance to near rim, rfar = distance to far rim, and where R = 3.390e6 meters is the radius of Mars. Given that the diameter of the crater is 750m, this gives

h = 0.5 m when rnear = 2000m
h = 0.3 m when rnear = 1000m
h = 0.2 m when rnear = 500m.

Since the relief of the crater is expected to be pretty small, probably only a few meters at maximum, the curvature effect should be pretty important, and unless there were a significant height difference for the far rim, it would never broach the top of the near rim.

Perceptually, I know, it seems especially from early images that the beacon was above the height of the rim. However, I think this is just a result of bleed-over from the highly saturated pixels containing the beacon. The nearer shots, like the one I included above, seem to suggest that the beacon height is roughly the same as the height of the Victoria Crater profile. The pixel resolution is so poor (esp. for those of us using JPEGs) that I don't think you can say much more than that.

Beyond the fact that we can see the beacon, really it's so poorly resolved that it would be hard to argue that we can really say whether it stays at exactly one height or another. The only condition for viewing the far wall would be the height of the far rim be tall enough (including the curvature correction) to peak above the dip in the near rim.

I don't think it requires much of a coincidence. I'm suggesting that there isn't a real prominence on the back rim, and the "keyhole" is just allowing you to see the otherwise obscured wall of the back rim. So it's not a "feature".. it's just light reflected from the higher albedo of the interior wall of the crater generating a "glow through the keyhole."

The prominence shape (I think) is nothing more than CCD or JPEG bleed, or possibly glare due to dust on the optics fattening the glow through the keyhole.

OK, just so you know...

Some of us gut feeling far rim types are growing just a tad uncomfortable with all the math being used to support our position. Bad science can be easily slapped down, whereas nebulous conjecture is really unchallengeable. I guess I could deal with the loss of faith that would ensue, I'm just concerned you might drive a few people off their comfy perch, and into the embrace of a very strange looking duck.

Brian

Wherever that confounded Beacon lies, how near or how far.

Heres some soon-to-look-very-similar approach views, these from back on the Endurance approach.

SOL 85
SOL 88
SOL 92
SOL 93

I'm still a somewhat dejected Far-rimmer now... but noting that we didnt see anything substantial on the near side at Endurance, the approach was so smooth, nothing but a few floor tiles to pave the wa, virtually all the bright stuff was poking up, way up from that view, from the Far side. its too soon to call it i say.

Yikes, Tesheiner, just when we clinched the near rim location, the far-rimmers go on one more attack!

Well, as I wrote before, the 3 frame composite pancam view of the beacon on sol 848 is very good! See the image in my post here.

This image shows clearly that the beacon features are higher than the rim - we are not looking through a keyhole!! That image is not magnified, it is not vertically stretched, and the pixels aren't anywhere near exposed enough to exhibit bleeding!

Is that another way of saying, "My mind is made up - do not confuse me with the facts"?

The Nearsighted are clearly grasping at straws now. Your picture isn't vertically stretched, but to claim the pancam shot isn't magnified?!!! Look at what you see in the navcam shots. That's more representative of the current view. The higher resolution pancam shots are being blown up to try and reveal more detail at a distance. Unfortunately, at the distance to either rim, those enhancements are simply fraught with deception.

And we really need to move away from the "keyhole" concept. It is a smoothly transitioned low area on the near rim, not a distinct notch. You can definitely see how the natural arc of the rim line does dip down at the beacon point.

The Fence Sitters are technically correct in that both near and far interpretations are far from certain. Each of the camps is clearly taking a leap of faith. But the Nearsighted should not be thinking just yet of engraving their names on the Beacon Cup. We of the Deeper Vision have answered their evidence with a plausible, if not probable, alternate explanation of their angular measurements.

This contest is still too close to call.

Brian

The contest will prolong for a long time since the Oppy rover is heading in a decreasing angle between Near and Far rim until the BC. Then from this, if Oppy will continue toward the Near rim, the angle will remain between 1.5 to 2.0 degree. Still tough. The only way to clear the suspense is to ask to JPL to divert the SouthEast route to East or South in order to see better the beloved Beacon. That will last for a long time, at BC would be between July 12 to 24 and at VC would be after 1st week of September after visiting at BC for 20 sols.

Rodolfo

Err... I meant that the image I posted was not magnified from the original pancam shot.

That depends on who's making the call!

1) Pancam images *are* reported by the MER team to represent a similar picture as the human eye, while navcams are just wide-angle pictures. So speaking in terms of "what-would-I-see-if-I-have-been-there" a pancam mosaic is better then a navcam.

2) Just a simple comparision with a digital camera's zoom capabilities: digital 3x or analog 3x. The former is what would happen if you enlarge a navcam image to the same ifov as a pancam; the features would be bigger but the details would be doubtful. The latter is what would happen if you compare a navcam shot with a similar one taken by the pancam; you actually see the features bigger *and* more detail. In other words, the details shown by the pancam are absolutely valid.

The VC crater doesn't appear to be resolved in your image at all, except for the "beacon". Certainly the beacon stands about the foreground, but that doesn't prove very much. The images I was referring to were much earlier ones, where we were maybe only getting a single pixel.

Here is essentially the same viewpoint, with the rim of the crater visible.

Click to view attachment

Clearly the beacon isn't jutting above anything.

[Edited to fix the attachment.]

This "possible depression in the near rim" would bring a "certain depression in the near rim camp"

Clt, your image from sol 855 is pretty noisy, since there's only one frame. My sol 848 image is the sum of 3 frames, so it's a lot cleaner as you can see, even if it's from a slightly greater distance.

The issue isn't just noise level... it's how much contrast you have between the sky & the crater rim. You don't appear have enough contrast to resolve the crater rim for the conditions in which your image was taken.

Now I'm confused - are we talking about the same image? I'm talking about my 3 frame composite in this post. There's plenty of contrast to differentiate sky and rim!

I took your image & blew it up some, rotated it with my image, then plopped the boundary that I obtained from my newer image onto your averaged image. Here is what I see:

Click to view attachment

What I see is consistency between the two images for the location of the rim, but that is about it.

I don't think we can conclude that the beacon is a tall prominence, as is perceptually suggested by your image. Nor do I think it's plausible, based upon the satellite view of Victoria Crater, simply because a shadow should have been clearly visible from such a feature. Finally, as I noted earlier, there simply is no identifiable feature with the colorations observed on the near rim, at least at the location that Tesheiner has triangulated to.

That's what started me wondering whether it really is a prominence at all, or just background images filtered through a closer-ranged notch in the rim wall.

Certainly you're welcome to disagree with me about all of these conclusions, but that's the best reading I can get from what data we have in front of us. Hopefully, we will soon know the truth!

I would be a bit confused if trying to plot the crater rim on sol 855 pics, but on those from 548? I think too that the rim is quite clear on your composite and definitely *below* the beacon; no gap.

Our eyes play tricks with noisy images (esp. those that have been handled unkindly by JPEG compression). I think it could go either way. Hopefully we will know soon.

Clt, I see we are going to disagree on the position of the rim. But I'll add that if you calculate how tall and wide the entire beacon "complex" is based on my image, and for a near-rim location, you get 10 metres wide and roughly 1 metre tall, as I've said before. This is not a "tall prominence", more of a flat slab, so we shouldn't expect to see a shadow on the orbital view.

Can you remind me how you calculate this for your image?

Count the pixels wide and high. Divide by 1024. Multiply by 16 degrees (for pancam). That gives you the angular width and height in degrees.

Measure the distance from Oppy to near rim from orbital map. Use trigonometry to translate the angles into distances. Eg, width in metres = distance in metres * tan(width in degrees)

Have you ever considered a career in politics? Be cautious of the pickets to the left and right of you. In the last minutes of the game, the underdogs call out their surprise player, hastily recruited from a distant planet where keen vision and math skills have been honed by untold generations of Darwinian evolution, not to mention that they can also sprint on broken glass in their bare feet. Go team, go far, and call in the backfield players.

There's no need to fear! Oppy will end this religeous war!
this map or some thing like it with more data points.. but something tells me we should have had enough parallax to settle this objectively by now. making it to CC will only give us only a bit more paralax than we already have, but maybe it'll be enough...

There should easily be enough off axis movement that the parallax to beacon must be unambiguous now.

We may be reaching the point where increased resolution, rather than parallax, will settle the issue.

While awaiting the parallax to Beacon #1 to be confirmed, I thought it would be fun to scribble some lines on maps again. It's now possible to draw a line from Oppy all the way over VC in a single x-eyed presentation.

The result is examinable below with crossed eyes (and fingers, for far-rimmers). My red laser beam towards Beacon #1 - the same level as Beacon #2 - touches the near rim, all but furrowing it, and then continues over VC, hovering considerably above the far rim. The vertical parallax gives a difference of 3 pixels between the far rim level and the beam. Guesstimating that one pixel represents 1-2 m height, the far rim should rise 3-6 m higher than it does to be visible to Oppy.

In other words, we simply cannot see the far rim of Victoria, however deep notch the laser might have cut into the near rim . Actually, the far rim seems to be rising no much taller than what's Oppy's current level!

(Using full resolution non-map-projected MOC images which I think reveal the relative heights the best way. Those prone to x-eyed headaches, try the image first in small size, e.g. by saving it and zooming out, or using StereoPhotoMaker. Another recommendation, look it also south up for comparison.)

Tres cool, MW. That's one of those X-eyed pics I can see without getting migraine. Definitely no way the beacon can be 10m wide and on the far rim, unleass it's a helium-filled balloon!

Thanks, marswiggle for reminding me of StereoPhoto Maker. I had downloaded it last week on the advice of a recently previous poster (I wish I could remember who it was, so I could thank that person, too.) I tried it tonight, and it is an amazing program. I still have much to learn about its abilities, but it makes certain adjustments quite easy to refine. It could very well replace Photoshop for me.

As I am still in the learning phase with SPM, I am not quite ready to use it to post a resulting stereo-pair, but my previous efforts with MOC stereo imagery had been inconclusive before I had this convenient tool. I would be interested to hear your thoughts regarding the use of non-map projected images, though. I think I am getting somewhat different results using the map projected gifs.

Actually I'm a beginner with SPM myself, and have not yet rendered any of my xeyed images by using it. I owe my advice for using it (for looking) to the same person who first mentioned it here.

Regarding the non map-projected images, I'm in the habit of pairing all kinds of possible and impossible images to check if they might make a tolerable stereo pair, and I simply noticed that the (vertical) resolution seems to be the best in these non-projected MOC images. (Didn't the JPL guys use those for their anaglyph?) Surely there are problems in using them for azimuthal and perhaps for vertical measurements, but my basic idea is to show only the relative vertical variations along a line, and I believe the stereo information of these images to be reliable at least for that purpose.

Anyway they make a nice image, and the results are consistent with other similar works, by myself or others.

Well, my own experience with using overlapping MOC images is not that great, but I have noticed that some of the images have a distortion that creates corrugated artifacts when viewing the pair in 3D. I believe this is caused by the fact that the MOC camera scans its images one line at a time while it is moving in orbit. Since the scanning can't be sychronized to the surface for images taken at different times, there is a distortion in the images that results in the periodic corrugations. It is pretty obvious, and I'm sure you would have noticed it, unless you were only working with small areas.

I'm not absolutely sure, but I thought the map projection should correct for this. I found the attached example of an anaglyph I created a while ago that had this defect. I don't have the original images, so I can't provide a x-eyed pair, but I suppose you could extract them from the red and blue channels in the anaglyph, if you really wanted to.

I'm hoping someone will comment on this 3D corrugation, since I would like to know for certain how to avoid it in the future.

Has anyone mentioned the possibility that the reason there are no dunes on Victoria's ejecta blanket may be that Victoria was created after the dune-making process ceased? The main dune structures we see today are composed of large particles that today's thin atmosphere may not be able to move. Only fine powdery dust can move now (and may fill in some areas -- where we sometimes get stuck). While we may find some small powder dunes on the ejecta blanket, we don't see the larger coarser dunes.

Now I have to explain the dunes within Victoria itself though.....

Scott

There are not dunes on Victoria ejecta blanket and it's a good news, the rover will can move better and cover more distance per sol.
And the reason for me is the présence of Victoria who deflect wind and stop the dunes process.

Exactly - there are large dunes inside Endurance and Victoria - whatever made THOSE, can make the dunes we see elsewhere.

Doug

We've seen how fine dust gets blown out of Oppy's track. I think the dripples* inside the craters are made of the same stuff, which is a lot finer than the grains we see forming the dunes out on the plains. Once it gets blown into the crater, there is enough wind to sculpt it into shapes, but not enough to get it out again in any quantity.

Chris

*This was a typo, but good enough to keep

***Thanks to Ultrix for pointing out my error! I misidentified another feature on the horizon as the Beacon.***

These comments are in error, though the stacked image (whatever it is) should still be ok.

I might be wrong but...Isn't the beacon a little bit more to the west?...

Oops! You're right.

I guess this must be that small crater to the south?

We know we are...

Excelsior!

The 'dripples' inside the Craters being composed the white 'talc-like' stuff as we've seen close up in micrographs at various points along the entier trip starting inside Eagle crater. presumably its evaporite dust.

Then we have the dark stuff like the dark streaks blown out of Victoria visible in the overhead views This stuff must be like talc as well, unless it too is old and coarse and frozen in time, i think its similar to the sands of Eldorado, but i havent heard any examination of the dark stuff close up, at least that ive noticed. is it like all the other dark stuff, perhaps dust eroded from cobbles, or like many other 'spots' including the round appraently filled-in craterlet remnants, or that dark stain near Beagle.. anyone?

I agree that the ripples inside the craters are quite fine material. I suspect it may be similar to the El Dorado material, which was analyzed, and I believe described as basaltic and enriched in the mineral olivine. We have also seen that the fine material in Endurance was relatively dark, and not armored with larger clasts as the dunes on the Meridiani plains are. Recall the appearance of it when Opportunity became bogged down near Wopmay.

I've said it before, but I think the dark streaks on Victoria are places where wind has removed the thin coating of light dust that covers most of the planet. In other areas dark streaks are formed when passing dust devils remove the light dust in their path. Perhaps the notches and promontories of Victoria's rim create occasional dust devils, or at least wind vortices that created those streaks. If so, that area of the north rim might be a worthwhile place to park and do a large panorama during the windy season.

Come to think of it, if the dark streaks are caused by wind removal of dust, they would imply that the currently predominant wind direction on Meridiani is SE to NW.

This is consistent with the fact that the soft powdery dunes (that we get caught in), tend to be roughly perpendicular to that SE to NW line, and thus are roughly perpendicular to the older dunes that are made of coarser stuff.

Scott

It's also consistent with the dune structure we see with the "tiger stripes" on the east side (windward side). The stripes are the revealed remnants of sand layers that were once deposited and built up on the west side (leeward side).

Castor

And, to add more intrigue to the drama, the light-toned wind tails downwind from Eagle and Endurance craters suggests that one wind direction is to the Southeast, and the dust observed to be blown from the Rover tracks at Purgatory was blown towards the Southeast also. This implies a seasonal wind direction of NW to SE.

180* out; hows them cookies...

--Bill

That the wind switches between those two directions seasonally was either published in one of the recent LPSC papers or mentioned by one of the speakers. What I would like to know is, at which points in the Martian year do they reverse? Opportunity should have experienced two or three reversals in the time it has been on Mars. It seems that the dark wind streaks on Victoria and the light streaks on Eagle aren't of much use in determining current wind direction because we really don't know when they formed, but dust blown on the tracks are a relevant observation. I wonder if we could determine wind direction from the motion that was detected on the heat shield? Does anyone remember any other wind observations?

I guess the way to infer wind direction from the heatshield mylar blanket motion would be to get Phil's polar projection and match the locations of the pieces we saw flapping in the breeze.

That polar could also be used to evaluate wind direction from the loosened dust in the heatshield gouge if we have enough close observations of the gouge.

Other wind obserations: look at the entrance tracks around Endurance from the time that Oppy exited the crater. And I recall seeing dust being blown SE-ish from the tracks after Oppy left the "Four Lane" to make the detour around the "North Erebus Dunefield".

--Bill

I tried to identify some of the features which can be seen on the pancam images from sol 869.
Here are the results:

A: Another rim feature, seen since sol 855.
B: Little crater SSE of Beagle Crater.
C: Dunno, but it's not the small dark spot right West of BC.
D: Another little crater S of BC.

The beacon is outside the current fov, 11º to the left of A.

Click to view attachment

Edited: Hey, this is new. Sol 869 "drive-direction" pancams were taken not only in L2R2 but in color! (L257R2).

Too bad Beagle Crater can't be seen on them...
I know....patience....

It looks to me like the dark region 'C' is about the same distance as Eagle crater, perhaps a bit further, and there's a similar area proximal (and extending to the right of) of 'D'. They both look a lot like low eroded ridges. My best guess is that they're the edge of Victoria's ejecta blanket, and perhaps associated with small craters ... maybe due to the interaction of the spreading ejecta blanket with small pre-existing craters (speculating out in la-la land at this point). Anyway, pretty clearly near the edge of the ejecta blanket (which I'm guessing is basalt sand), rather than on top of it.

Color will be nice

Isn't it the dark streak south and a little west of Beagle, at a distance of about two Beagle-diameters?