The darkening in El Dorado isn't very long -- it likely was caused not be a dust devil, but by a seasonal change in the direction and speed of the local winds. At least, that's what I would suggest, barring any evidence that dust devils actually occur during mid-winter here in Gusev.

-the other Doug

The Viking 2 lander image of frost-covered ground labeled as "Brines on the Martian Surface as pictured by Mars Pathfinder in 1997"?????

-the other Doug

You also have to remember that the Surveyors used a solid-fuel rocket engine as the main braking engine. I'm not sure, but I'd bet that there are higher-performance fuels out there that would give you more Isp for the weight than the solid fuel they used. (IIRC, they used the solid motors because it was far easier, and more mass-effective, to simply drop the motor and its casing out of the Surveyor structure after it burned out than it would have been to build tanks, piping, valves, etc., to feed liquid fuels into a braking rocket.)

The motor, again IIRC, was only abotut the size of a basketball (albeit with a nozzle attached). I have something of a hard time believing that this engine was more than 500 kg in weight -- they must have used quite a bit of fuel to power the final-stage descent thrusters, which were completely useless in terms of doing the major braking. So, I guess the solid fuel system did end up saving enough weight to make the landings possible...

-the other Doug

Honestly, as much as I would *really* love to see some robotic lunar exploration in the pipeline, I don't think that robotic rovers are the best investment for what we need from the Moon at this point, scientifically.

What would be most useful in terms of unraveling the remaining mysteries of the Moon, IMHO, would be a fleet of small sample return missions. Something like the Luna 16 plan -- able to pull a core up from next to the lander and return it to Earth.

I think the most valuable science you could do at the Moon right now would be to get more samples back here that you could date. We need to be able to pin down the extent of the Late Heavy Bombardment and the range of ages of the maria, and while we have some decent ballpark figures, we don't know very well when all the various basins were emplaced. That information, and data on how long the Moon was volcanically active, can only really be derived from dating of samples. And since the current technology doesn't really let you date the samples in situ, we need to bring them back here.

Now, from an engineering standpoint, rovers make good sense. If you're planning on building a lunar base (or a lunar resort hotel), it would be great to send a bunch of robotic surveyors (small 's'). But except for the thrill of exploration, I don't see any other reasons to send rovers at present... *sigh*...

-the other Doug

Yes -- with the flicker gif I can make out the change in albedo. I kept looking in the area of the streak that is apparent in the subtraction image, but by opening each image separately and just moving from one browser window to another, I honestly couldn't see the albedo change. With the flicker gif, I can see the actual albedo change quite clearly, even without the third subtraction frame.

-the other Doug

I know the MERs were right on the edge of the mass limits... but, it seems to me, if there had been enough margin to do it, you could have placed a small weather station and a small, local transmitter on the lander base units. Have them communicate with the MERs via a low-power UHF signal, which would use the existing UHF equipment that the rovers use to communicate with Odyssey. It wouldn't have entailed a single extra gram of weight on the rovers themselves, only the weight of the weather sensors, transmitter and batteries (and/or solar cells) to power the rig on the lander base units.

I can imagine doing the whole thing in less than 10 kilos, deployment apparatus included. Would 10 kilos have blown the landers' mass budget?

-the other Doug

D'oh!!!!!

I knew Ulysses used Jupiter to swing itself into its vast out-of-plane orbit. I guess my mind just failed to connect them.

I blame it on too much LDS in college...

-the other... ummm... hold on, I'll remember it in a second...

The H ring seems much darker and less reflective than the E ring, even (or maybe especially) in this lighting. I'd think this would argue against it being a pure-ice ring. Perhaps it is formed of icy/rocky debris from impacts on Janus and Epimetheus? I guess my first impression is that it's more of a dust ring that an ice ring.

-the other Doug

Eighth? I only count six prior missions that went to Jupiter -- Pioneers 10 and 11, Voyagers 1 and 2, Galileo and Cassini. Unless you're counting Galileo's entry probe as a separate spacecraft, a concept I would take serious issue with.

If you're going to count the entry probe, you might as well make NH the ninth spacecraft to Jupiter, since Huygens passed by Jupiter while attached to Cassini... Heck, I sure wouldn't count Cassini/Huygens as two spacecraft that went to Saturn. It was one spacecraft which deployed an entry probe (this one to a moon of Saturn and not into Saturn itself), just as Galileo was a single spacecraft that deployed an entry probe.

For that matter, Deep Impact, to my mind, was a single spacecraft. It deployed an impactor, but the two were different parts of the same spacecraft that simply parted ways when the mission plan called for them to do so. Also, I'd say that the MER cruise stage, aeroshell and lander base were all one spacecraft.

In my book, the number of spacecraft "to Jupiter" is the number of spacecraft *launched* which flew by or went into orbit about the planet. Six prior launches equals six spacecraft, methinks...

Of ocurse, that's just my opinion. Your mileage may vary.

-the other Doug

I guess I'm missing something -- except for the minor sun angle changes, I can't see what you're talking about in the three image set. I see what appears to be a dark groove in the very-low-sun-angle image, but I can't identify it in any of the three images. Or any albedo change in them.

Maybe my eyes are just getting too old for this...

-the other Doug

I use IE at home and Firefox at work, and I frankly can't tell any difference between the two of them in terms of how they browse UMSF. Both work fine for me.

-the other Doug

Speechless, yes. I think the best way I could sum it up is in the old word-play sentence, somewhat altered:

Able was I ere I saw Victoria...



-the other Doug

Also, unless they've changed the rules recently, you can't get to within more than a couple of hundred yards of the stones at Stonehenge at any time of the year, let alone at solstice. It seems that everyone who used to visit the stone circle just had to chip a piece of stone off as a souvenir. At the rate the stones were being vandalized, there wouldn't have been much left of them in another few decades...

-the other Doug

NASA's official name for the vehicle is the Space Transportation System or STS. Hence the nomenclature of the flights -- STS-1 through STS-whatever. However, NASA refers to the vehicle as the Space Shuttle in its official documents, as well. And it identifies each of the orbiters as shuttles -- I could find literally thousands of NASA documents that refer to the Shuttle Atlantis, the Shuttle Discovery, the Shuttle Endeavour, etc., etc.

As Doug said, it is only when the stack is discussed that the individual elements are referred to as ET, SRB and Orbiter. Very, very occasionally, when referring solely to an orbiter, do you see even official NASA documents refer to it as such -- and even then, it's usually referred to as "the Shuttle Orbiter Atlantis," or some such.

-the other Doug

Hmmm... my main hobby is what I'm doing right now, playing at being an amateur planetary geologist and space exploration afficionado. UMSF is the best place in the Cosmos to do this, in my humble opinion.

Sports? Well, I'm 50 years old and still on the mend from a knee surgery I had six months ago (they take an awful long time to regain full mobility, unfortunately), so I don't play much in the way of sports. But I'm a pretty standard American sports fan, I guess. I like football (Chicago Bears fan), baseball (Chicago Cubs fan), and basketball (used to be a Chicago Bulls fan, back when they had Michael Jordan, but the Minnesota Timberwolves have been the only team from my new [for 11 years, now] home that I've been able to get excited about).

I'm not all that fond of professional hockey or European football (soccer, we call it) -- it's just what I was brought up with, I guess. I do enjoy watching Olympic hockey -- for some reason, it's a much more enjoyable game when the main point isn't waiting for the next major fight to break out...

-the other Doug

Also, remember that we don't have really good slope information from the MOC images. There are some interesting features right at the rim that could indicate albedo differences on ground that is still sloping up towards the rim drop-off, or could indicate that the drop-off has already begun at that point.

I imagine that the long drive "to the rim" will be designed to culminate at the last point where they are *certain* we are not descending into the crater's inner wall slope. Then Oppy will look ahead, see how much farther it has to go to reach the actual precipice, and make small drives to get to its first quick-and-dirty Navcam look-around point. Only then will they plan the drive to the first major Pancam panorama location.

So, while we may drive to within 5 or 10 meters of the rim by Friday, it might not be until next week sometime that we arrive in a position where we can see the crater floor.

-the other Doug

Wow!!!!!

It occurs to me that if we had gotten images from this vantage point early in the orbital phase of the mission, there would have been no doubt whatsoever that Enceladus is the source of the E ring. You can see the ring material flowing off of Enceladus and smoothing itself into the ring quite clearly.

Amazing, amazing images. As someone said nearly 40 years ago of a somewhat similar view of the Moon, it's worth the price of the trip.

-the other Doug

This comment reminds me very much of an exchange between Dave Scott, on the Moon, and Joe Allen, the CapCom back in Houston. It occurred just a few minutes after Scott and Irwin had discovered the "Genesis Rock," a piece of nearly pure plagioclase, at the rim of a small crater on the Appenine Front. Despite the excitement of the find, Allen was pressing the crew to move on to their next stop:

Scott: Hey, Joe, this crater is a gold mine!

Allen: And there might be diamonds in the next one, Dave.

So, yes -- Emma Dean may have some very good finds in it. But, as always, we have to remember that Victoria might have diamonds in it...

-the other Doug

Me, I'd go to Home Plate and start digging around the periphery to see if I could identify any evidence of hydrothermal vent processes.

And, as long as the person I'd like to share it with doesn't have to be alive today -- I'd have Carl Sagan along with me. I would really enjoy the sense of wonder in his eyes as we hiked around the Martian landscape...

-the other Doug

Actually, I was suggesting that the smaller spherical objects we're seeing here in the annulus are *not* hematitic concretions, and thus are entirely different in morphology and composition from the blueberries we saw in Eagle, in Endurance and on the plains. In this hypothesis, of what we are seeing here in the soils of the annulus, only the bodies that have been modified into conical shapes would be concretions. The smaller spherical bodies, while they resemble mini-concretions, would be (I'm suggesting) impact melt droplets.

-the other Doug

The "Hershey's kiss" berries in this MI view are not only conical, the cones are slightly faceted. However, I still have a hard time believing that this is due to aeolian erosion.

My main objection to this being aeolian erosion is that, if these kisses are hematitic concretions that have been eroded out of evaporite from Victoria ejecta, they ought to have been emplaced on the surface (and thus exposed to winds) *after* some, if not most, of the blueberries out on the plains. All other things being equal, the berries on the plains, having been exposed to winds for a longer period of time, ought to display a greater degree of erosional faceting.

They don't. In fact, the blueberries seen in the soils out on the plains (and in both Eagle and Endurance, for that matter) were remarkably spherical. I don't remember seeing a single concretion, up until this last series of MIs in the Victoria ejecta, which displayed obvious ventifact forms. These are the very first examples of this type of morphology in the blueberries (if that's what they are) that I can recall.

Of course, the key to the above statement is "all other things being equal." If these are acutally hematitic concretions, they would seem to have eroded out of Victoria ejecta made up of concretion-bearing evaporite, correct? But evaporite emplaced this close to the rim of a crater this big must have been awfully shocked. What do berries which erode out of *highly shocked* evaporite look like? Maybe they look like Hershey's kisses...

One thing bothers me, though. We're only 120 meters away from the rim of a crater that was created in an enormous translation of kinetic energy into thermal energy. It was big enough to dig a crater that was, originally, probably at least a half a kilometer wide and several hundred meters deep.

I have a hard time imagining how the ejecta emplaced only a couple of hundred meters, at most, away from the edge of the hole made by this powerful explosion could have been so relatively unaltered that it would look even remotely like the evaporite we saw out on the plains. If, in fact, these berries are hematitic concretions which formed exactly the same way those out on the plains formed, and if they were originally formed in the target rock into which the Victoria impactor struck, why have so many of them survived seemingly intact (if mysteriously eroded into little cones)?

And if the "kisses" are the same size as the concretions we saw out on the plains, then what are the mostly spherical bodies which, except for size, closely resemble the mostly-spherical plains berries? Are these also concretions? If so, why are they fairly uniform in size but only a fraction the size of the plains concretions? And if the kisses and smaller, rounder bodies are both concretions, why do they both exist? We're not seeing spectrum of sizes, here, that would suggest the result of erosional or shock processes -- we're seeing a small population of kisses, and much larger population of fairly uniformly-sized smaller, rounded bodies. Such a neat division of populations suggests differences not in erosional processes, but in formative processes. And in composition. In other words, I think it makes more sense to assume that the kisses and the small spheres have different compositions and/or formation histories.

Ah, but if only one of these two populations is made up of hematitic concretions, which one is it? Perhaps there is a clue in this most recent MI image -- there is a feature in the dust "above" the rock face that looks rather like a worm. But this 'worm' is exactly the same size, in planform, as the small spheres. It resembles the small spheres in almost all respects, except that it is a drawn-out blob instead of a spherical blob.

Perhaps this would suggest that it is the small spheres that were once molten? I can visualize a spray of impact melt droplets solidifying into spheres in the very thin air as they flew out of the crater (not enough air pressure to compress them into teardrop shapes), and that while most of them fell as individual, rounded drops, some of them would hit each other in mid-air and form into, among other forms, chains of drops that ended up looking like tiny little worm-forms.

In other words, could the small spheres be the impact melt we've been looking for?

One last thing -- this all assumes that the annulus we see around Victoria is primarily the erosional remnants of her ejecta blanket. However, if Victoria is indeed a once-covered-over crater that has been (or is being) exhumed, then the soil we're looking at maybe doesn't incorporate much at all from the original ejecta. Maybe we're just looking at the erosional remnants of the materials that covered Victoria, and its actual ejecta blanket is still buried and inaccessible to our eyes? Of course, if that's the case, you would expect these soils to look exactly like any other patch of blueberry-paving in Meridiani, and it most definitely looks different from the plains soils. So I tend to discard the once-buried-now-exhumed crater theory. (Besides, it looks like a sharp, fresh crater -- most of the exhumed craters I've seen on Mars look far older and more eroded than this.)

Well, that's my two cents worth, anyway...

-the other Doug

And I'll tell you, I *still* want to get over to those Twin Peaks and take a look at the big boulders that lie in the hollow between them.

That raises an interesting question. The rationale for the selection of both the Ares Valles and Chryse Planitia landing sites (MPF and Viking 1, respectively) was that each seems to lie in the midst of an ancient catastrophic outflow channel. The reasoning, as I understood it, was that these sites ought to 1) show signs of the water that once flowed there, and 2) have a lot of rocks on the surface that were transported there by the floods which created the outflow channels.

As far as I know, no significant insights about the former presence of water has ever come from either site -- certainly nothing like what we've seen at both Meridiani and Gusev. Seems those forces left far more subtle clues in the outflow channels than in places where water once pooled and groundwater rose to the surface. So, reasoning path number one seems to have been a bust.

And as for reasoning path number two -- yes, it's interesting to see a large variety of rocks. But they might have come from anywhere along the path of the ancient floods. Doesn't that really muddy the waters (so to speak) when it comes to geologic analysis? Without a context for where these rocks might have formed, don't we get a far-less-helpful set of results, in geological terms, than we would if we were exploring an area in which the surface rocks could mostly be traced back to processes that occurred in the local area?

-the other Doug

That's, um, sort of circular logic, isn't it? It's sort of like saying "The reason you see so many babies in this town is because this town has one of the busiest maternity wards in the world." Both sides of that equation reflect a result without recognizing a real cause.

-the other Doug

Only if you can program those 'basic' landers to send messages to the more sophisticated probes that say things like "Hey, you're doing a great job! And you look great, too!"



(FYI, the word that means 'adding to another's capabilities' is spelled 'complement.' A compliment is a remark designed to praise someone or something... )

-the other Doug

And Don, as to your last point, I strongly disagree. But everyone knows that by now, there's no point in my belaboring it any more... *sigh*...

-the other Doug