That all makes sense to me. What doesn't make sense is how the evaporite-rich ejecta strata seems to be *more* erosion-resistant than the aeolian deposits. We seem to see this phenomenon all around the crater, a lighter-toned bed of apparently evaporite-rich rock that appears to form a resistant bed, which has stayed in place even while the aeolian deposits below them are undercut.

The evaporite we've seen here, both unshocked (out on the plains) and shocked (within Endurance), seems to be the softest rock around. It's certainly a lot softer than the volcanic rocks over at Gusev. It almost appears, at times, so friable that it would simply crumble if held in the hand and squeezed.

Any idea how such soft rock becomes the most erosion-resistant rock in the walls of such a big crater?

-the other Doug

Maybe it's just because I started following space exploration back in the 60s, but I have always been mystified by the negative reaction to "engineering experiments" on board any type of space probe.

I know, we can now use computer models to predict the operation of engineering systems. However, such models are only as accurate as the data input into them. It seems to me that, if an engineer feels the need to gather empirical data to support a model, it should be allowed if at all possible.

Engineering experiments might not return a ton of data about the planets, but they can make possible the next generations of spacecraft that *will* return such data. As such, I think they ought to be embraced and not sneered at...

-the other Doug

Well, that's your House Rock, right there...

-the other Doug

That would be a 533.28-billion-yard Par 3....

-the other Doug

Um, I refer to the foreground depression, Dilo. I knew the bigger hole was Victoria...

Boy, that foreground depression, I guess it's Duck Crater, really looks like a drainage feature to me...

-the other Doug

I don't know why I didn't notice this before, but in Nico's color partial pan, you can clearly see a rocky depression sitting several meters *back* from the rim. It's not just a little hollow, it seems (from this angle) to be a pretty steep-sided little hole.

Impact crater? Or, perhaps, a drainage feature? I can picture a process in which materials slough off into Victoria, opening up drainage routes for fines and smaller bodies to be removed. Perhaps this depression is a sinkhole-type drainage feature and not an impact structure?

-the other Doug

I tossed around a variety of ideas as to where this thread ought to go, and finally decided it should go here.

I'm sure we've all seen the von Braun concepts that were lionized by Disney et. al. back in the 1950s. The Saturn Shuttle, the doughnut-shaped LEO station, the large expedition craft assembled in LEO and dispatched to the Moon and, later, Mars.

In real life, it has taken one of history's most capable cargo-carriers-to-orbit many, many years and tens of flights to *partially* build an assemblage of tubes and flaps that we call a space station. And many of the elements of this station were dispatched not by this real-life shuttle, but by expendable rockets. The whole thing has cost more than a hundred billion dollars thus far.

How much more expensive would von Braun's Saturn Shuttle and his enormous spinning station have been than ISS? Than Apollo? It seems to me we would have had to transport orders of magnitude more material to LEO than we've ever managed for a single project, and assemble it all without *any* prior experience at working in microgravity.

So, while the Disney and Colliers work produced a lot of pretty pictures, isn't it fair to say that such dreams were just that -- dreams? Projects that would have been prohibitively expensive for *any* nation-state to attempt?

Or am I missing something?

-the other Doug

Here's an attempt to hijack the thread and keep it from devolving in to the argument Doug says *will not* happen here:

If we're talking about "what-if" scenarios, and we can change bigger factors, then I'd say the only thing that would have caused an immediate and rapid program for a manned Mars expedition would have been obvious, large-scale signs of life and/or intelligent occupation of the planet (i.e., large structures, etc.).

The real issue, then, becomes: Did the Mariner 4 optics have the ability to show such things? Had we run an Earth encounter with Mariner 4, would the images and other data sent back have been the least bit helpful in identifying whether or not Earth sustained life, much less intelligent life?

I have a pretty fair idea that they would not... And if not Earth, how Mars?

-the other Doug

--------------------

You (machines) can't stop Smith. I can.
- Neo

Nope -- as I've said before, here at Victoria, the map edge notes read, "Here they drag beacons..."



-the other Doug

When Oppy spent weeks inside Eagle, I was impatient to get out of Eagle and take a look at the plains beyond.

When Oppy spent months inside Endurance, I was fascinated by the tale the layers told -- but I still wanted to see what kinds of vistas awaited us out on the plains.

When Oppy set sail for Victoria, I was dubious -- it was a *long* way to go. But I figured we'd get a good look at the etched terrain, if nothing else. And we'd see what the plains had to offer us.

Now we're at Victoria, it hardly seems that the voyage was even possible.

So, for my latest take on this thread, let me steal a line from Al Shepard:

"It's been a long way, but we're here."

-the other Doug

Man, oh man!!!!

All I can say is...

<clink> <clink> <clink> <clink> <clink> <clink> <clink> <clink> <clink> <clink> <clink> <clink> <clink> <clink> <clink> <clink> <clink> <clink> <clink> <clink> <clink> <clink> <clink> <clink> <clink> <clink> <clink> <clink> <clink> <clink> <clink> <clink> <clink> <clink> <clink> <clink> <clink> <clink> <clink> <clink> <clink>!!!!!!!!!!!!!!!

-the other Doug

Resupply is also done by Shuttle, with each Shuttle flight to ISS leaving behind a few thousand kilos of water, among other things. In fact, the station's water needs were a serious concern when Shuttle supply flights were suspended. They've more or less just eked by with 2-person crews and the fairly limited water supply they can get up in Progress craft.

-the other Doug

And, you know, it wasn't until my roommate mentioned it to me that I connected Anousheh Ansari to the Ansari X-Prize... just goes to show you how horrible it is when your mind starts to deteriorate...

-the other Doug

One rather late note, here... I flipped my TV over to NASA-TV this morning, which was running its Video File. Today's Video File included an edited montage of the various tracking cameras during Atlantis' descent and landing.

Maybe it's just a trick of the angles, but I could swear that the nose gear did not come down until *after* main gear touchdown and drag chute deployment, locking into place literally milliseconds before the nose wheel touched the ground.

I've heard it speculated that a failure of the nose wheel to deploy, with the orbiter moving at a good 300 km/hr at touchdown, would dig the nose in and basically destroy the vehicle, with a good likelihood of killing the crew.

Could we have come really, really close to this nightmare scenario the other day?

-the other Doug

Oh, I understand, Doug -- no blame goes out to you or the Forum. It's just that I found in Bob something of a kindred spirit, here, and it's just not as *fun* getting to Victoria with him not here.

Don't worry, I'll get over it...

-the other Doug

While it's tremendously exciting to see Victoria finally hove into view, baring her tantalizing secrets to our searching eyes one little bit at a time, I have to say that, well, it's just not the same without Bob Shaw here to share it with us.

If anyone out there is in general contact with Bob, tell him that some of us miss him and wish he was here to share this experience with us...



-the other Doug

So, here's a nice little short-term thread, to let people get on the record with their wild speculations as to what we'll see when we get "up close and personal" with Vickie.

Some have mentioned seeing gully-like features in the walls, in the MOC images. I'll take this moment to disagree -- it looks to me like the talus slope (which makes up most of the exposed interior of the crater, that and the dune field) is streaked all along the interior, and that some streaks swirl a bit as they approach the upper rim. I think what we're seeing here is mass-wasting down the slopes of a non-homogenous surface. While the bulk composition of the surface layer that's slowly falling into Vickie is probably all pretty similar, there are obviously pockets of lighter and darker materials. Those pockets are sliding down into the crater, leaving a striated look as light deposits slide down adjacent to darker ones.

At this point, the wind circulation system within the crater kicks in, modifying the light and dark streaks -- especially near the upper rim around the capes and down into the bays.

I think the gully-like feature leading down from Duck Bay is probably nothing more than a mass-wastage slide of dark material down into the crater that has been swirled up a bit near where the winds howl in through Duck Bay.

Let's see, what other potentially embarrasing predictions can I make? I think that while the dark spots on the far rim's cape structures aren't entrances into deep caves, I'd bet that some of them are shallow "alcove" caves. Places where softer rock have been windblown out of the near-vertical rock face, leaving dimple-caves in the rock.

While these would be great places to repel down into and set up a sleeping bag for the night (the cliffs keep the big predators away, after all... ), I doubt a MER would ever be able to make its way into one...

-the other Doug

I dunno -- I'm not necessarily convinced that you have to invoke a dust devil to get these changes. Surely an unusual set of straight-line winds could have caused the same type of track? I mean, wouldn't it all depend on where, when and how straight-line winds blow as to what effect it might have on the ground? And this *is* the leeward, "protected" side of Husband Hill, which has allowed the dust to settle into El Dorado in the first place... you'd think that any straight-line wind events would be fairly rare, and thus a lot more noticeable here than elsewhere around the hills.

It just seems awfully soon past the winter solstice to be seeing actual dust devils. For all of me, I could be wrong, though.

-the other Doug

Yeah -- I bet there are just *tons* of festoons in it! We ought to sit here for sixty or seventy sols and look at it...


Right behind ya, Nico...!



-the other Doug

IIRC, spacecraft from Mariners 6 through 10, and through to Pioneers 10 & 11 and Voyagers 1 & 2, used the same basic octagonal spacecraft bus as the "starting point" for their development. Yes, each iteration went through a great deal of redesign and change based on the given missions, but I seem to recall that each one started out with the same sized-and-shaped bus unit...

Please, someone verify this old man's fading memory...?

-the other Doug

I seriously think that the plan is going to be to get up on top of *both* of the capes to get a good stereo view of about 80% of the crater's walls, and then (if it's navigable) take Duck Bay down to see what the outcrops look like from here.

After getting as much "first look" data as we can from the layers exposed on this portion of the rim, we can go to the now-well-studied pans from the capes and plot out where else on the rim to go next.

This strategy maximizes the chances of getting a good look at the extent of exposed strata at our current location, and gives the boys in the back rooms a chance to develop the smartest possible plan for gettkng the most out of the rest of the crater...

-the other Doug

Wonderful, ustrax!!!! Of course, we're leaving aside the fact that the air is far too thin to support Oppy's mass...

However, I have these seriously cringing moments when I imagine her first attempt at *landing* after such a flight!



-the other Doug

In re the effect of craters on wind patterns -- recall that craters undergo regular cycles of differential heatng and cooling, too. As the sun rises, it heats the eastward-facing slopes of the crater more than the surrounding terrain, and much more than the shadowed west-facing crater slopes.

Air rises over the heated slopes and sinks over the shadowed slopes. The bowl shape of the crater encourages a vortex-like pattern of airflow, making it racetrack within the crater itself.

Now, as the day progresses, the prevailing winds of the area pass over this crater. The racetrack pattern pulls up and involves this wind in its little circulation pattern, causing a local intensification of wind around and inside the crater. In some cases, this causes a much higher column of rotating air than you get from the crater heating effects along, a pattern that can sustain itself for several minutes. As the air mass that contains this vortex moves along, the newly-born dust devil departs the crater and wanders out onto the adjacent terrain.

I would think it possible that morning heating would produce one rotation vector, and afternoon heating would produce another, perhaps opposite, vector. I seem to recall that most of the dust devils observed by Spirit last Martian spring were in the afternoon. Perhaps the racetrack patterns induced by heating effects in craters are counter to Mars' rotation in the mornings, thereby less likely to cause dust devils, but become synced with Mar's coriolis effect to end up with reinforced rotation patterns and free-standing dust devils in the afternoons?

In any event, we *did* see evidence of overhang development, vertical cliff maintenance, and internal wind erosion in Endurance. And, of course, it featured a central floor dune field. So, I think that there is good evidence that the same aeolian erosional patterns were in effect in Endurance as we will see have sculpted the interior of Victoria.

-the other Doug

Last winter on Mars, Oppy was inside Endurance. And, IIRC, she saw a fair number of clouds during that period, too.

It would seem that clouds preferentially form over Meridiani during the winter.

-the other Doug

I think winds are intensified within craters on Mars, not reduced. For example, you might notice that a majority of dust devil tracks we see around the planet begin within craters. My thinking is that winds catch a crater wall and spin up into vortical forms. If conditions are right, these vorteces depart the craters and wander along the adjacent plains as dust devils.

In this case, you likely get the highest wind speeds along the circumference of Victoria, with the lag area of the winds encouraging the deposition of the dust that forms the central dune field. So, the most easily wind-eroded strata along the walls of Victoria would get fluffed off the walls (transported both out of the crater into the dark dust tails and into the central dune field), and the more-resistant rock strata become overhangs (or fallen overhangs). As Bill said, some overhangs form at the failure of the old rim along vertical joints and faults, while other overhangs simply slump onto the voids left below them and become "boat ramps".

What intrigues me is the evaporite layers, which we have seen are easily wind-eroded at ground level, seem to form the more resistant overhang layers on this rim. I'd be very interested to see what material is so much more easily eroded than the very friable, soft evaporite...

-the other Doug