Ooops! It appears a frog may have given its life for the conquest of space:

[url="http://www.nbcnews.com/science/frog-pops-nasa-photo-ladee-rocket-launch-did-it-croak-8C11134276"]

And the image:



-the other Doug

Oh, no doubt. I can well imagine that this is what makes sand traps more dangerous than rock fields -- the latter can be much more easily seen and avoided.

Truly, I'm not in any way questioning the abilities of the rovers or their excellent drivers. Just noting that we've seen places -- like the V2 landing site -- where trafficability would be lousy for just about any wheeled vehicle. We've actually been somewhat lucky (or at least better at estimating ground truth from orbital imagery) in that the three rover landing sites -- Gusev, Meridiani and Gale -- show considerably less dense boulder populations than we saw at either Viking site or at the Pathfinder site. Indeed, Meridiani has a remarkably low boulder density, making for generally great trafficability, the odd soft dust ripple notwithstanding...



-the other Doug

In no way... Although, if there was a chance that saying "yes" would magically cause a MER or an MSL to suddenly appear next to the V2 lander, just to take on the challenge, my answer would of course be different...




Oh, understood, and I can imagine a rover the size of MSL might even be able to make, oh, 5 or 10 meters a drive at a site as boulder-strewn as the V2 site, climbing over one half-meter-tall rock after another. Perhaps less than that for a MER-sized rover. I wasn't saying you couldn't drive one of these marvelous wheeled vehicles over difficult terrain, just that it would make for lousy trafficability -- your forward progress would be slow and painstaking.

Come to think of it, rocky terrain hasn't been the rover trap some might have imagined, has it? The only time the MERs have fallen into traps, it's been in drifts or pools of fine, unconsolidated powdered rock, not up against walls of hard, unscalable rock.

-the other Doug

I'll tell you one thing -- I doubt that you could have driven the MERs or MSL at, say, the Viking 2 landing site. Way too many blocks to work around at that location, at least for anything larger than a smallish toaster.

It just goes to show that, for rovers of MER and even MSL size, there is a lot of the Martian surface that is not easily trafficable.

-the other Doug

That thing leapt off the pad like there was something a-comin' after it and it didn't dare to look back...

-the other Doug

Thanks, Gerald! That far rim wall is just incredible in 3D -- reminds me of seeing the rise of the Rockies emerging from the horizon as you drive west through Kansas.

As impressive as these views are, I'm really looking forward to the panorama we will see from the side of Mt. Sharp of the Gale floor fading into the haze and, in the distance, the rim wall rearing up to enclose and overlook it all. I'm betting the rim wall is far clearer once we gain some altitude, and that the haze will appear to almost hug the ground below. We saw something of that effect from Spirit when she was atop Husband Hill, but I'm thinking the effect is going to be even more impressive from high on Mt. Sharp's flanks in another 18 to 24 months.

-the other Doug

Yes, it sure does. Considering the total distance traveled, it gives an extremely good idea of how the view would change over the course of a pleasant walk of a couple of kilometers from Cape York to Solander Point. I can just place myself there, strolling closer and closer to the Point.

Very nice work!

-the other Doug

Thanks, guys! Some very good ideas to chew on.

I *think* the original article I found was a news item in Sky and Telescope's online service. When I have a little time over the holiday weekend, I'll find it and link it.

Again, thanks!

-the other Doug

I've tried to ask this kind of question on one or two physics forums and have been soundly humiliated because I cannot arrive independently at the mathematical equations that define the inflation theory (i.e., "if you have to ask for explanations of the math in English, you are far too stupid to speak with us and should stop worrying your tiny little brain over matters that you, unlike us, can never hope to understand" -- that's darned near a direct quote). I'm kind of hoping one of our people here can point me to a source, or explain in English words, what is wrong with my issue, here.

It has to do with the fact that dark matter is apparently immune from being ingested into the supermassive black holes that occupy the centers of all the galaxies, as far as we can tell. A report in one of the popular science magazines from last year (IIRC) stated that this has been definitely proven -- that the derived distribution of dark matter and its derivedly-observed behavior when galaxies collide prove that dark matter is not attracted gravitationally to regular matter.

The article stated that this observation means we have to rethink all of our concepts of dark matter being composed of weakly interacting massive particles -- that any particle with mass must inevitably be attracted to other massive particles (and particularly to black holes), regardless of how weakly they interact.

I've seen nothing published since then. My basic curiosity is, how can dark matter affect regular matter gravitationally but not vice-versa? Anyone seen any theories about this, any publications you could point me towards? I find nothing in internet searches beyond this article I mentioned.

-the other Doug

I will point out that, on the Moon, the highland uplands correspond to the less dense (and therefore lower gravitational potential) areas of the lunar gravisphere, while the mare lowlands correspond to the more dense (and therefore higher gravitational potential) areas -- the mass concentrations, or mascons.

In the case of the Moon, the lighter material (mostly anorthositic melt) rose to the top of the crust. Denser mare lavas extruded later occupied the lower reaches, especially within the confines of large impact basins.

Just because a piece of the crust is pushed up, or is on top of the general mean level of the crust, doesn't necessarily mean (as it usually does on Earth) that there is a massive pile of dense rock forming the mountains or the uplands, with deep "roots" into the crust. As in the case of our Moon, sometimes the uplands and mountain ranges are higher because they are less dense and rose to the surface of a molten crust.

In the case of Titan, maybe the entire crust was once molten (i.e., in the liquid phases of its constituents) and the mountains and other highlands are just places where the lighter materials floated to the top? Denser materials may have since occupied the lowlands, creating what appears to be low-density windows in the crust where the lighter materials haven't been sunk under more dense stuff that was either extruded from below or rained down from above?

-the other Doug

Thanks for the cross-eyed view, Gerald. That is still the best way for me, personally, to see 3D images properly. I know YMMV applies to that, and that most people prefer the red-blue anaglyph format. I appreciate that you toss out a good x-eye every once in a while.

Yeah, the ground unit does rather look like conglomerate, doesn't it? Looking at the semi-embedded rounded pebbles and some of the completely exhumed lag deposit of rounded pebbles and cobbles really gives that impression. My eye actually went to the half-shadowed rock near the bottom of the field of view, which shows a conspicuous concave "crater" in the side facing the camera. I somehow doubt it's an impact feature -- looks more like where a nice rounded cobble has fallen out of the conglomerate matrix.

-Doug

Are you saying that we could have been seeing the shadow of Phobos passing over the terrain?

Cooool!!!

-the other Doug

Must it have been a dust cloud? The air at Gale has been getting clearer and less dusty lately, I thought.

What are the possibilities of either clouds or one of the larger-size dust devils casting these shadows?

-the other Doug

There seem to be two different camps among the Curiosity science team as to the benefits of imaging EDL hardware. We were first told that Curiosity would find a few good vantages from which to image EDL hardware as it moved back in the direction of Bradbury Landing. Then, when the route was obviously dipping way far away from the location of the EDL hardware, when asked why the route was moving along so far from the hardware as it was, we got an almost dismissive comment that "we've got all the information we need about the EDL hardware."

I can almost imagine one group of the planning team saying how much they wanted to see the EDL hardware, with another strongly opposed. Obviously, those who feel there is little to no value in imaging the hardware are in the driver's seat (so to speak). As befits a good, cohesive team, the discussions that occurred have been kept behind closed doors.

However, I would love to have been a fly on the wall during those discussions.

-the other Doug

I'm not sure how likely it would be to find granitic rocks on Mars -- my understanding is that most all terrestrial granites are a product of plate tectonics, formed by the interaction of the water in subducted sea floor materials interacting with the hot crust/mantle interface and enriching the basaltic mantle with the quartz and aluminous feldspathic grains found in granites. The theory I heard was that this melt would be significantly lighter than the basaltic mantle and would push up through cracks in the crust to form a granitic "basement" to the continental landmasses below which the sea floor is being subducted. (Of course, when I try to look up information about this theory, Wikipedia seems to think it's an outdated opinion and not in vogue these days...)

Now, if significant granite *were* to be found anywhere on Mars, it would be interesting to speculate on the process of its formation.

-the other Doug

Agreed. From an inherently low-resolution imaging system, you have teased out the best picture elements and created an absolutely beautiful view of something humans had never seen before -- a crescent Jupiter.

Excellent work, Ted.

-the other Doug

Yep -- sorry about the poor phrasing in re Mastcam, I've been in and out of the hospital over the past couple of months and sometimes my word choices while on heavy-duty painkillers could stand a little improvement. Of course, I was referring to the availability of both the M34 and M100 modes of Mastcam.

As for imaging the EDL hardware, the only reason I mention it is that during the telecon where the general plan for the post-conjunction wrap-up and Mt. Sharp traverse were discussed, it was stated (and if IIRC was noted on one of the powerpoint slides) that one of the goals for the early portion of the long traverse was to find vantages from which EDL hardware could be imaged. I guess that's why I've been a little surprised that the traverse route seems to be heading well south of both the landing site and the EDL hardware that is roughly "on the way" as we head towards the mountain. But, hey -- priorities change.

Also referring back to that telecon -- wasn't there some discussion of revisiting Hottah and perhaps doing some more involved work on characterizing the matrix of that conglomerate unit? We're obviously not heading anywhere close to Hottah, which again surprised me a bit, I guess. Are the managers thinking we'll likely find other examples of the "Hottah unit" elsewhere along the traverse path? Or do they think that the same or similar units were adequately analyzed back at Yellowknife Bay and its environs?

-the other Doug

MSL is in a different situation than Oppy. It has a zoom setting on Mastcam, so some very good information can be acquired without approaching really closely to any EDL hardware. All we need is a good vantage point from which to image it.

In my humble opinion, I think a survey of the damage caused by the impact and breakup of the descent stage is more applicable to future MSL-like operations than a view of the backshell and 'chute. If we re-use the skycrane approach on the next rover (as seems likely), it will be useful to know whether or not we need to change the flyaway maneuver to get a greater distance from the rover's landing point to the descent stage crash site, for instance.

Obviously, though, any survey of the descent stage crash site must be done from a distance. Don't want to approach that mess too closely.

-the other Doug

Phil -- one of the stated goals for the drive back towards the original landing site was to find vantages from which EDL hardware may be imaged to ascertain its condition and its interactions with the surface.

Looks like we're going quite a ways out of the way from the descent stage wreckage, though I imagine a nice ridge would let us see something of it using the Mastcam's highest zoom setting. But could you indicate the location of the heatshield and the backshell, if they are indeed within the confines of the current map image?

That would make it obvious when we're getting into position to be able to image the hardware.

-the other Doug

Gee -- almost everywhere else Oppy has been at Meridiani has had enough soil (or regolith, take your pick) to leave good, recognizable tracks, even in the absence of ripples/drifts. I wonder what processes are at work here in the Bay to strip a majority of the fines that you'd otherwise expect?

-the other Doug

In re the dark dunes, they remind me of El Dorado in Gusev. That dark dune field, while much smaller than the ones ringing Mt. Sharp, looked as dark from a distance and from above as the ones here in Gale. When we got really close to El Dorado, we found there is a thin layer of the ubiquitous red dust on the mini-dune ridges, but it's mostly just black basaltic dust.

I would imagine these dark dunes in Gale formed by a similar process as that which created El Dorado, an area that is wind-shadowed in such a way that the black basaltic grains are preferentially dropped from the general airborne dust entrainment. Or, maybe not exactly a wind shadow, more of a place where Mt. Sharp's effect on the winds causes the exact right kind of instability in the air that causes the preferential deposition.

The big difference between these extensive dune fields here at Gale and the El Dorado field in Gusev is that Mt. Sharp is a much bigger hill than Husband Hill was, so these dune fields are much larger and seem to show some differences in albedo (we'll know about textural differences when we get there), depending on how far away from Mt. Sharp you are (or maybe the angle of repose upon which the dunes formed; the two are sort of interrelated). Could be that the "edges" of the wind instability that causes the preferential deposition show a more well-mixed deposition? Again, something we will know more about when we get there.

In any event, we see this effect literally everywhere on Mars, be it influenced by mountains, crater rims or whatever causes the right kind of instability that causes the preferential deposition. It's certainly not unique to Gale.

-the other Doug

The dune fields are multi-toned, it shows up in the HiRISE images and shows up better in the Curiosity images (at least as far as the fine color delineations are concerned).

I also think we need to remember that the human eye tends to apply a contrasting color level to what is essentially gray if it is in contrast with a reddish color. It's been especially true on Mars that what may appear greenish or bluish is actually a pretty neutral gray, the eye seeing a bluish or greenish tint in the absence of the surrounding red.

My best guess is that the dune fields are primarily varying shades of gray, and when we're looking at them from a close-up vantage point we'll see a range of tones from light gray to a dark, almost black gray. (Of course, there is going to be at least a little of the ubiquitous red dust mixed in there, but not a whole lot, from the way it looks from a distance.)

-the other Doug

It is obvious from the HiRISE imagery that the dune field is multi-toned, and we see the exact same thing from a distance from Curiosity. However, I'm a little confused as to why a "fossilized" dune would appear more bluish than the darker, assumedly more actively recent dune structures.

If a fossilized dune is of a lighter color than more active dunes because of accumulation of the ubiquitous red surface dust, wouldn't that tend to make the fossilized dunes more reddish than bluish?

I'm wondering whether or not the apparent color difference may indicate a different mineral composition in the different structures within the dune field. Of course, we'll need to wait and see what we find when we get there -- MSL certainly has the tools and sensors required to make that determination once we get there.

-the other Doug

"I know you! You're that Martian landshark!"

"Only a rock, ma'am...."



-the other Doug

From the Sol 300 Mastcam pan:



COOOOOOKIE!!!!!!!!!

-the other Doug