Oh noes! Those dunes look tricky, so after Beagle, should Oppy go SW to see if the apron gets cleaner on its western edge?

Nice bit of driving across the ripples.

Indeed, I'd be very surprised if we didn't at least drive up to Beagle at this point. It looks like a very clear route.

Very nice... *and* the dark stuff looks like Opportunity can drive on it without difficulty.

Goodbye to those cursed dunes, it is clean-rock-driving to Beagle from here, and if the hillock is similar to the apron in texture I think the surface looks very similar to what we had early in the mission. Very promising, and some really interesting sols coming up!

I'm pretty sure that "lump" isn't West Hillock. Compare the features. It might be East Hillock. It might be just some little hillock somewhere along the way. Frankly I'm lost just at the moment.

I share your bafflement that it looks so different close up, but I don't see what else it could be. Navcam images showing Oppy's tracks have now shown up, and I get that our drive direction was about 127 degrees ground-relative azimuth (somewhat north of southeast), which lines up with the map. Given that we are now on the northeast end of the hillock, perhaps the whole thing appears foreshortened.

I'm not so sure about the "goodbye to the dune sea" meme now - the Apron is looking awfully drifty to me. Perhaps the drifts are small enough that they won't really be an issue - but otherwise, could be some more interesting times ahead.

The dunes don't immediately disappear at the start of "apron" sourrounding Victoria, If you look at the routemap they continue for maybe 50m but probably get smaller and smaller as you move inwards towards Victoria. ( I hope lol )

Mmmm, interesting sights await Oppy's attention... look at the detail in those walls...

Crater anaglyphagram

Here, algorimancer, this should help. North is up.

For the apron, the term that comes to my mind is "choppy" like waves in shallow water. Which is strange. Long dune lines I can understand, but if there's enough sand to form dunes, why the abrupt switch in dune structure?

That does help a little. I'm convinced. Once I found that some of the navcam pics showed East Hillock, I measured the distance to there as about 26-27 meters. I also measured the size of the hillock ahead of us. Checked these on the overhead view and yes indeed, it appears we're sittting around the northeast edge of West Hillock. Even the dunes between here and East Hillock check out. Here's my (unofficial) estimate of the current position:

Click to view attachment

Your pic ought to allow an even finer positioning.

Yay. Made it to the "West Hillock". It looks to be composed of a (basalt?) gravel and not sand or boulders; this bodes well for travel on the rest of the apron. I wouldn't be concerned about the ripples seen on the apron surface to the south-- the MOC image shows ripples at the margin of the ejecta apron, but it smooths out within a few tens of meters. I'd suspect that the change in the ripple structure reflects a change in composition.

After months of travel we finally arrive somewhere...

Off to Exploratorium, giddy with anticipation.

--Bill

I think we're just to the right of your position - we appear to be right on top of the little drift there.

Here is a 90 degree perspective view northeast, including the Pancam drive direction images that have come down:



Here is the view due east:



"Choppy" - that's the word. If I may make a wild speculation about the apron: perhaps it's not an apron at all but rather a very shallow depression that has collected dust.

That doesn't sound like it would bode very well for us, but I'm still optimistic we will make it anyway. The folks driving this thing are good.

Hmm... whatever the Martians buried there, I hope we don't encounter any more of them.

Brian

I apply the Duck Criteria: if if quacks and walks like a duck, it must be a duck. From the MOC images, this ejecta blanket looks like thousands that we've seen from above. The difference is that this is the first one we're seeing up close and personal.

One difference in the ripples: they have developed a sharp, narrow crest on the ripple crest (??), which we've seen only for a couple of Sols. Does this represent a change in composition or in wind or what?

Look at the evaporite bedrock. It is starting to have an appearance like broken sea-ice in which the individual angular plates have shifted slightly.

--Bill

Going out on a limb here...perhaps these are the ancient eroded remains of block ejecta. If they are basalt it bodes well for encountering antediluvian basal units deep within the crater. If so, that means that Victoria's walls could well reveal the entire Meridiani layered sequence.

Here's hoping they stop and sniff, and maybe a toe-trench too.

I agree, based on your pic it does indeed appear that we're dug right into that dune.

As to the apron... consider the view over West Hillock. To the left is a dune field which looks a lot like what we just drove out of (this really confused me earlier), while to the right is more like what I'd expect the apron to look like (like the hillock in front of us, only more so). That duny region to the left also looks a little funny on the map view. It may just be a sort of "bay" in the edge of the apron filled with dunes, and thus not typical of the rest of the apron. We'll see shortly... pancams are coming down.

Sol 884 Pancam drive-direction mosaic (a bit distorted again, due to Autostitch weirdness I haven't quite mastered):



Another "top" view:




Alas, the Pancams are all of Beagle. I mean, wow! The Pancams are all of Beagle.

A prediction about Beagle, though: We may go up next to it, but I doubt we'll go inside it - the sides look too steep. Of course, I could be wrong.

mhoward, are you sure these pancams are Beagle? If so, we're right next to it.

http://qt.exploratorium.edu/mars/opportuni...LVP2350R2M1.JPG

Looks like there might be a place to get in over towards the right in your panorama. Other than that, we might even find it hard to get a look in. We'll see how high the rim is and how dense the ejecta scatter is when we get closer.

Nice panorama! Thanks!

That's Beagle all right - but we're still some distance from it. Pancam has quite a 'zoom' to it

Doug

Very sure, unless we've mislabelled it on the map. Sure as I am of anything, anyway. We're probably at least two drives away from it still - it's a big puppy. Edit: What Doug said.

It's certainly Beagle - and what an extraordinary rock-scape the rim makes. A big jumble of shattered ejecta piles which have the appearance of being re-cemented together like conglomerate, and then been smoothed off (by wind erosion?) afterwards. You see that huge segment slab of pale evaporite facing us in the middle? A phenomenal view.

Kenny

I think that heights have tended to be overestimated from a distance. There may be some breaks or ramps in the crater wall anyway.

This was the view North on Sol 884 before the drive (same position as Sol 883, in other words - before we drove to 'East West Hillock'):

Grain size would be the only answer I could think of... I think the apron, like the hillock, is composed of bigger-sized grains, which would make for less risk of bogging down. Maybe.

Beagle Crater, here we come. Probably.

As much as Beagle and Victoria beckon, we do need to spend some time at this spot. The "Hillock" may be special in that it is an 'outlier' of the ejecta sheet created by Victoria and the rock underneath may be the evaporite as it was at the time of the VC impact; this is a unique window into the past. Another question: _is_ this margin area the paleo-surface of the evaporite, or is it a layer of fluidized evaporite created by the VC impact? Some questions will be answered at Beagle and as we cross the ejecta apron on the way to VC, but this is the basal unit of the sequence and needs to be defined as well as possible.

--Bill

Well actually, I could be totally wrong on this one - maybe we are just doing a small bump to get into position to study the hillock over the weekend. Who knows. We should find out soon enough.

Actually, the "pancam_foregrnd_quarter" makes me kind of suspicious it's the latter. Either way, I'm happy.

...not sure if its already been noted but...

nice faultline here

with closeup

Nice. Really nifty the way it's reflected in the dune. Makes me wonder what's been going on here.

Noted, but I've been so overwhelmed by other sights that it didn't get mentioned. This is an example of an Anatolia feature, IMO. It extends into the next Navcam frame to the west (right), I'm not sure it can traced esatward (left).

--Bill

Probably tracks from the previous rover to visit this crater.

Bill, what do you mean by "Anatolia feature"? (For us non-geologists.)

It's not a geology term, it's a rover term. He means it's like Anatolia

Thanks for the reference. I see the similarity, and also a fairly significant difference. Anatolia looks like a dip that reflects something under the surface, although the question is really why it hasn't filled in over the years.

This image looks like whatever fractured the bedrock also disrupted the dune.... which would mean that the dune hasn't changed in a very long time. And that whatever fractured the bedrock, did it without destroying a much more fragile dune.

It's been speculated before that the possibility exists of a different time and "climate" on Mars that would have a light frozen topping at Meridiani -- "fixing the surface" as it were-- created primarily from frozen CO2 that later sublimed without leaving much in the way of traces of its ever being there.

Subsurface movement, caused by unknown/unexplained factors, would certainly manifest itself almost exactly like what we see there with that dune split IF the top was indeed hardened.

Now, it may be that the makeup of that dune wouldn't need a "top hardened by frozen CO2" to accomplish what we see, but if there were bets on the "frozen CO2 topping" this dune pic would be changing those odds. That said, I wouldn't be "all in" with my chips.

My idle question that relates to this: How expensive is it to rent a cold room so as to duplicate how durable frozen CO2 can make a relatively fragile dune to fracturing?

I'm one of the guys who has maintained that the ripples/drifts move and grow in time frames of decades, not millennia. And yet, some of what we're seeing here is making me wonder about that.

Look closely at the base of West Hillock, guys. It looks very much like West Hillock was deposited on top of the existing ripple structure. The ripple that intersects the hillock appears to have been buried -- it does not appear to have been built up to the side of the hillock.

Now, in the overhead imagery, the hillock appears to be a piece of the Victoria apron that has been separated from the main apron by erosion. In other words, it looks like the apron material was emplaced on top of the evaporite base layer, ripples and all, and that as it erodes off of that base layer, the ripples are being exhumed. Which would speak to a much higher cohesiveness and resistance to erosion in the ripple surfaces than in the evaporite or in the apron material.

And that just doesn't make sense. It makes no sense to me that the etched terrain ripples are so old that they pre-date, in their present form and extent, the Victoria impact event.

Maybe I'm just seeing the contact between the ripple and the hillock wrong... but it sure looks like the hillock buries the ripple to me.

-the other Doug

As far as looking or driving into Beagle, it's easy to estimate the rimheight: We can see the horizon completely over the rim of Beagle. Assuming flat terrain (pretty easy assumption here!) that means that pancam is taller than the rim. I'd say the rim is no taller than a metre or so at most. Many areas are much lower. We'll certainly get a very good look inside.

Driving inside is less certain. The inside may be quite steep, but then again it's high-traction rock, not sand, so who knows. Even if we can make it in, the planners may decide to go for the big prize - Victoria.

New Oppy update here. Seems the plan was for software build sols 879-881. I suppose that explains the lack of movement for a few days?

doug - (the other )

I haven't had time to follow this thread the last few days - can you link to the pic of West Hillock with the features that you speak of?

This is the specific image of the contact between hillock and ripple that caught my interest...

-the other Doug

I am so overwhelmed by the abundance of new observations that I don't know where to start, so I'll try not to go too far. The hillock appears to be a pile of disintegrated fragments of an ejecta chunk as predicted. Is it an outlier of the blanket? Perhaps, but since we have seen similar examples in increasing numbers along this southward traverse, it seems more likely to be a random and weathered chunk of ejecta.

I see no significant faults. The thing that disrupts the ripple on sol 883 is simply a fracture, but possibly an enlarged one in earlier stages of enlargement, ala Anatolia. The simplest explanation for the younger and disrupted ripple overlying it is some version of subsidence of the later aeolian fill.

The really curious thing to me are the inward dipping ramparts visible on the far side of Beagle. Such things would fit nicely with Edgett's model of an older eroded crater that had been filled and covered by a younger layer of rock which was later undercut and which subsided after being exhumed. But I was (and still am) thinking that Beagle is too young to have been buried in antiquity and exhumed more recently. What a trip.

Disclaimer...My previous comments about dip direction should be disregarded. I wasn't seeing what I thought I was.

P.S. Approaching and climbing this rim will not be a problem for Opportunity. It is hard to say if she/he will bother to attempt an entry. Whoops, I promised not to take it too far...

We're entering a new world! That noticeable at the excitment here in UMSF. Now, unless Oppy get in trouble, that promise us a brand new mission.
, and

Edit : and another ( )

We're definitely going to Beagle according to the latest from JPL:

"Next Stop: 'Beagle Crater' - sol 872-878, July 20, 2006:

Opportunity is healthy and continued driving towards "Beagle Crater," which is about 140 meters (459 feet) away as of sol 877 (July 12, 2006). The upload of the flight software files was completed on sol 876, and the flight software build process is currently planned for sols 879-881."

The "flight software build process" gave us that halt of a few sols. And they've up-dated their slow version of the map to Sol 578 at 5.28 miles odometry.

http://marsrovers.nasa.gov/mission/traverse_maps.html

Kenny

Mars is a mystery wrapped in an emigma.

As you've seen, an "Anatolia Feature" is simply a fracture with sand disappearing or sapping into it. It is expressed as a lineation in the sand, or as a series of dimples or possibly as a mysterious mini-crater. That is the physical appearance and examples have been observed here on the Meridiani plains many times. Now, _what_ causes it is anybody's guess. Every explanation runs into difficulties, so the best thing to do is to keep looking for examples.

I'm going through the same discomfort as oDoug. The "West Hillock" appears to be related to the VC ejecta and certainly seems to provide and explanation for the many cobble piles we've seen since before Erebus. The sand is a recent and active feature of this region and this hillock is apparently an old feature, so why could it appear to overlie the supposed newer ripple? OTOH, if I tilt my head the other way and look at this contact, it does appear that the ripple overlaps the hillock. We need a close look and a wheel-scuff at this contact point. We'll know for sure if the hillocks are ejecta once we are on the ejecta apron. Heck, maybe we just need a big drink of Ripple, or maybe less drinks of Ripple...

Here is a paper on aeolian processes at Meridiani:

http://www.lpi.usra.edu/meetings/lpsc2005/pdf/1942.pdf


--Bill

Strange, no?
http://origin.mars5.jpl.nasa.gov/gallery/a...G2P0695R0M1.JPG

With "labels"...
Click to view attachment

Was there move in the ground?

Whilst I don't think I can go with your suggests of a mini fault (given your little arrows) - it's possible that the fracture runs under the dune, and as the dune built on top of it, some part of the rock subsided a little, causing the dune to have that small sag that you outline.

Doug

I think suggesting movement across the fracture is a stretch. There are no convincing offset features that can be correlated across the fracture to support that conclusion. I'll try to find and link to the one convincing fault with offset that Bill spotted at Erebus. (...unless he beats me to it...)

edit... That was easier to find than I expected.
http://www.unmannedspaceflight.com/index.p...ost&p=28294

The correlation of the trend of the fracture and the offset dune ridge seems too close to be just a coincidence IMO. With the evaporite layer as disrupted as it is, it could be very hard to recognize any offset across the fracture even if it did exist. Ant suggested a strike-slip tyoe of motion, but as djellison pointed out, the offest could be the result of a slight subsidence on one side of the fracture (the near side I would think) or it could be the result of a "pull-apart" type fracture.

I'll agree with Tom and thank him for finding that earlier observation at Erebus. I looked at this feature, and didn't see any offset feature to correlate. My initial thoughts were that the offset in the ripple face was an aeolian feature caused by the wind going over the depressed area on the dune face.

Here are two images to play with. One is this feature with a 1/3x "vertical de-exaggeration" and the other with a 3x vertical exaggeration. The former emphsizes horizontal features, the latter emphasizes vertical features. I can't spot differential movement along the fracture in either image.

Let's look also at the Navcan frames to the right and left of this image and see if the feature continues on.

--Bill

Looks like Sol 885 saw a turn to look at the hillock. 1F206751421EFF74N8P1214L0M1.JPG

Correction: a turn and a little drive.