Well... the airlock will help keep the (still rather small, especially for four people) LSM main cabin somewhat cleaner than the LMs were. But there will still be significant tracking of dust into the LSAM main cabin. It's impossible to get all of it off of the suits, and nothing you do will keep you from tracking it in with you if you doff your suit in the airlock and then enter the main cabin.

The airlock will also get pretty filthy, after eight or nine EVAs, making the whole task even more difficult. And since -- for this to work in keeping the main cabin clean -- you're going to leave your dirty EVA suits in the airlock, you'll just end up getting yourself and your long johns dirty again when you have to perform cleaning and maintenance on the suits. After all, it took a considerable attention to cleaning and lubricating the suit seals after each and every EVA on the Apollo J missions to keep the suits working. And that was only to make it through 18 to 22 hours of EVAs.

When we start to build larger habitats on the Moon, we'll end up with double-lock systems, I'm sure -- an outer lock, where you leave your dirty suit, and an inner lock (more like a locker room) where you change out of your somewhat dirty liquid-cooled long johns, take a shower, and dress in clean clothes. The outer lock would get cleaned with high-pressure air jets and sonics, while you could just sweep and mop the locker room.

Of course, that's all a little beyond the capabilities of the CEV/LSAM system. But a guy can dream, ya know?

-the other Doug

As I recall, the ambiguous results of the Viking landers' life detection experiments were explained at the time by postulating that the surface soils are highly enriched with extremely oxidized clays (I seem to recall descriptions of clays enriched with peroxides).

Nearly identical results were seen at both V1 and V2 sites, so, assuming that the results are explained by what was called "exotic soil chemistry," this chemistry would have to be widespread on Mars.

We now have some very good elemental analyses of the Martian soils, both from orbit and ground-truth from the MER rovers. In these analyses, clays seem not at all widespread, only appearing in very, very old outcrops that were presumably laid down during a very short geological timeframe during which non-acidic water was common on the Martian surface.

Soils in the Viking landing sites would appear, from the more advanced sensors we've flown since Viking, to be basaltic with admixtures of ferrous sulphates. Not exactly the exotic chemistry required to explain the Viking results.

So, the million-dollar question seems to be: if the Viking experiments can only be explained by *either* biotic processes that do not involve what we always considered the pre-requisite organic molecules, *or* by ubiquitous exotic chemistry in the soils that we're simply not seeing with more advanced instruments, which theory are we forced to accept as fact?

If neither, then what theory *does* account for the Viking results?

-the other Doug

Myran -- in space, no one can hear you yell...

-the other Doug

Hmmm... I thought we had all been given the option to re-select, since the long wait at Purgatory II had invalidated our former selection criteria. On that basis, I selected Sol 998.

Y'all please update your lists accordingly...

-the other Doug

Awww... what if they descoped it? Just included a small sea on Dawn? That might work...



-the other Doug

Just 'cause I said I would...

Hopefully, though, this whole episode has made its point -- NASA isn't afraid to tell overbudget missions to stand down.

I just *really* wish we could get the magnetometer back on the beastie, though...

-the other Doug

No, I don't think it was a typo. I think they mean to say that the valley formed roughly 3.15 to 3.5 billion years ago, and that the active valley-forming processes acted over the course of 350 million years (which happens to be the interval between the beginning and ending dates of their overall estimate).

I can definitely understand how counting *differential* cratering abundances can give you the number of years it would take for a given landform to have developed. If our assumptions on the impact flux are correct, then the oldest portions of this valley have the right number of craters to be about 3.5 billion years old, while the most recently emplaced portions of the valley have the right number of craters to be about 3.15 billion years old. So, you can state that it took 350 million years for the valley to form.

At least, that's how I interpreted the article.

-the other Doug

I don't know about that, Alan -- instead of looking less cohesive, I get the impression (in this latest unintended trench, anyway) that the white (presumably salt) layer is *more* cohesive than the soil in which it's buried.

Notice that the light-toned-to-white material has left some sand-sized grains (and larger) along the wheel track, while the redder soils seem much finer, more like talc in their grain sizes.

It really looks to me like the salt deposits are somewhat more cohesive than the soils in which they are embedded.

-the other Doug

The problem is, we have no way of knowing how long Enceladus has been expelling mass, or at what mean rate. It's possible (though extremely unlikely) that it *never* had active geysers or plumes until about, say, 50 years ago. It's also possible (and more likely) that it's been venting for its entire lifetime. It's also possible (and probably most likely) that it has had epochs of geyser activity and epochs without -- we just happen to be visiting during an active epoch.

And we have no real way of knowing how long such epochs may last, or what percentage of the lifetime of Enceladus have been active epochs. Or how much mass it may have expelled during active epochs.

And... I seriously doubt Cassini has the ability to answer *any* of these questions.

Sure did a good job of raising them, though, didn't it?

-the other Doug

So, like, they're gonna crash it into, like, Lake Excellent, dude?

Excellent!!!! ((insert bad air guitar riff here))

-the Other S. Doug, Esq.

I'd like to point out one or two things...

First, one reason SpaceX is having a really hard time getting these test flights in the air and proving out their engineering is they keep having to kludge together fixes and workarounds based on the lack of liquid oxygen on their base island. If part of "cheap access to LEO" is based on choosing not to develop *required* elements of infrastructure (like an oxygen liquification plant on the same land mass as your launch site), then that element of "savings" is not really valid. It's just a *deferred* expense.

Second, from what little detail can be seen in the RealPlayer version of the launch video, I'll bet you any money that the thing failed because the jerry-rigged insulation blanket (that was supposed to be ripped off the rocket at launch, but wasn't) flew back against the motor housing (and into the engine plume) and ruptured a fuel line. If a NASA rocket had suffered a failure because some similar kludged-up fix had backfired, most of the people here urging patience with SpaceX's travails would be calling for the heads of the NASA managers who "ought to know better." What makes it OK for SpaceX *not* to know better? Is it because they're promising "cheap" access to space, so it's OK to cut corners?

Hey, I want SpaceX to succeed as much as anyone here. But I've seen this many times before -- people loudly proclaiming that *they* know how to provide cheap access to space, only to utterly fail to deliver. Those who have succeeded to even a small degree have done so only by using second-hand military hardware that has already been proven to function and already been fault-tested by its manufacturers.

I will call Scaled Composite's contributions to the field a success when they put something into orbit. It's one heck of a lot easier to do a stunt pop-up out of the sensible atmosphere, going relatively slowly, than it is to achieve orbit. So far, neither they nor SpaceX has shown me an ability to get anything as far as LEO, and the history of the industry tells me that no one has yet lived up to the vaporware they've tried to sell us.

I guess this has just been a really long-winded way of saying I'll believe it when I see it, and not a moment before...

-the other Doug

You're correct, Phil, though I note you're unable to specify which of the seven said it.

It was Wally Schirra, by the way.

-the other Doug

Ummm... directly over the vault where the formula for Hush-a-Boom was stored, I think.

"Now, there's something you don't see every day, Chauncy..."

-the other Doug

Guys... I hate to say it... but this shows once again that getting into orbit is *not* easy. It's actually rather difficult. And when you try to do it cheaply, you tend to fail. Spectacularly.

It's all a matter of the amount of energy required to get into orbit -- and the time frame in which you have to release that energy. A fully fueled 747, for example, carries enough energy to place the entire airplane into orbit. But it cannot release that energy quickly enough to achieve the necessary acceleration.

You not only have to provide enough energy to accelerate you to orbital velocity, you have to have a motor (or motors) that can release that energy fast enough to actually achieve the acceleration you need. If you try to do that with cheaply built or mass-produced parts, or with assemblies that have not been fault-tested to within an inch of their lives, you tend to get the results we just saw Falcon 1 achieve. And the manufacturing standards and fault testing required to assure success -- they just ain't cheap.

-the other Doug

Remember, when speaking of the general slope over distance and how that might affect what we're rolling over stratigraphically, that the surface may not have always reposed at the same slope that we see today.

As Aldo captured so well, this area seems to have seen repeated episodes of deposition, each involving long periods with high water tables and then undergoing evaporation and salt cementation.

When supported by a water table, such a landfill assumes a pretty flat surface. The deposited material fills in the uneven terrain that underlies it -- and on Mars after the LHB, most of the terrain was pretty uneven.

As the water table recedes, the loosely consolidated sand and cemented sandstone tends to contract and slump a bit. This allows subtle surface expressions of underlying terrain. Of course, buried terrain closest to the surface is expressed the most.

So, it's possible that ridges and depressions expressed faintly in the current topography reflect larger and more impressive terrain that lies beneath. In this case, except for minor amounts of deflation and additional deposition that may have occurred over the millennia, the overall surface can be considered a single, relatively flat unit that is draped over expressions of underlying topography.

Thus, when taking into account deflation and deposition that has occurred slowly since the great dry-out, any given stratigraphic level on the surface is likely to be within a few feet of the level at any other given point.

Or, in more basic terms -- take a lasagna and plop it down on top of a big meatball. The lasagna will have a bulge in its top (an expression of the underlying meatball), and as you traverse along the top of the lasagna you may find local variations in the thickness of the cheese and sauce layers atop the highest noodle layer. But you're ultimately traversing the same stratigraphic unit that you would have seen had the lasagna never been dropped onto the meatball.

-the other Doug

And, Doug -- after you finish your first shed, might you possibly be considering building a second shed?

Then we could call you "Douglas 'Two-Sheds' Ellison," you see...



-the other Doug

Great! This is a good discipline that needs a little more establishing, I think. Since impact processes seem to have dominated crustal development on *every* rocky or icy body (at some point in its lifetime, anyway), this is a discipline that's truly required if we're to understand planets very well.

-the other Doug -- Senior Member

You know, everyone involved in the Gemini program seemed to love that spacecraft -- including but not limited to the guys who flew it.

But Gemini showed a pretty large maturation curve during its manned flights. There were lessons learned during Mercury that took a while to incorporate into Gemini, not the least of which were manufacturing lessons. And if it seemed to take a while for McDonnell-Douglas to learn from its own mistakes, think of how much harder it was for North American Aviation to learn anything from Gemini as it designed and built Apollo.

However, there is an element of heightened danger in flying a Gemini spacecraft that far from home that I think most people underestimate. While Gemini was a much safer spacecraft to fly by the end of the program than it was at the beginning, it suffered from a far higher malfunction rate than the Apollo flights eventually logged.

For example, one reason NASA didn't attempt flights longer than three or four days after the Gemini V and Gemini VII marathons was that a majority of the attitude control system thrusters had failed by the time each of those long-duration flights concluded. On Gemini V, in fact, the thrusters were in such bad shape that the crew was told the activate the re-entry control system two orbits prior to retrofire, to ensure positive control when setting up retrofire attitude.

The Gemini fuel cell system was notoriously finnicky, and always seemed to totter on the brink of reliability without actually achieving it. They didn't produce potable water, either -- the water those cells produced was full of an organic sludge euphemistically called the "brown fuzzies" by the engineers. If the cells put out too much water (as happened on one flight), you had a serious problem, since the nasty fuel cell water was used to pressurize the potable water tank. On a lunar flyby, such a problem could lead to a waterlogged outbound crew and a really thirsty inbound crew... not to mention the need to perturb the outbound trajectory frequently with "Constellation Urion".

Finally, the Gemini wasn't designed to handle the thermal loads of constant sunlight for several days at a time. Granted, Apollo needed to do passive thermal control rolls, and Gemini could have done the same thing -- but these kinds of thermal effects hadn't been considered when Gemini was designed. This issue alone might have ended up killing the idea, had it gotten that far.

And remember, you'd have to dock with a much bigger propulsion module than a Centaur or a Titan transstage to do more than follow a figure-eight loop-around of the Moon with a Gemini. Yes, it would have been an historic moment, and the Russians fought hard (though ultimately unsuccessfully) to pull off this very type of mission. But compared to what Apollo was capable of, and *designed* to do, trying this stunt with a Gemini was simply an unjustifiable risk.

-the other Doug -- Senior Member

The MERs were truly not designed with the thought in mind that the exposed wire bundles would have to suffer through more than 800 thermal cycles as severe as those seen on Mars. Remember, right up until the girls just kept performing normally well past their design lifetimes, their builders and handlers expected to get 90 sols out of them. Anything beyond that would be gravy -- so they didn't take long-term survival into account in their design. At all.

I'm sure that there are tricks you can use (like using wire and insulation with the best low-temperature ductility and flexibility you can find, as well as designing your wiring paths to reduce to the bare minimum the amount of wire flexing you induce in normal operations) that the MSL designers will at least consider in trying to ensure their vehicle remains in perfect operating condition for at least one Martian year.

If they do their jobs as well as the MER designers did their jobs, we could see MSL last for several Martian years. But we need to build it, launch it, and get it safely down onto the Martian surface first.

Don't eat your peanuts before your bird flies, boys...

-the other Doug

(sung to the tune of the main theme from the film "Exodus"):

"There are
Some things
Man was not
Meant to know,
And songs
Man was not
Meant to sing.
And this is
one of them."

-the other Doug

I have often commented on how strongly I perceive the craters on Rhea to be arrayed in a variety of linear forms -- arcs and straight lines.

Look carefully at the plains between the larger craters in the image linked above. Near the terminator, they take on a positively furrowed or ridged appearance. Great expanses of the surface appear to be furrowed -- those in the right-center of the image (closest to the equator) all trend up-and-down in this image, while some furrowed terrain in the upper left portion of the crescent (a little farther from the terminator) appear to trend on a bottom-left-to-upper-right vector.

Rhea is displaying linear arrays of depressions at finer and finer levels. I insist that this must have some significance.

-the other Doug

Actually, I would think Hyperion would be a better target for such a small, low-energy impactor. We might find out someting about the reasons for the dark flooring of those craters by putting a small scratch into Hyperion -- more than we would find out by making a tiny little crater that we might not even be able to resolve on Mimas, Rhea or Dione, or even on Iapetus.

-the other Doug

True, to a point -- but the Big Lie theory of ideological control also calls for the repetition of the lie, over and over, until it's been heard and repeated so often that it's accepted without question...

Oh, and don't call those who legitimately disagree with you "slow" or "uneducated." Makes it sound more like you're pushing the Big Lie than it sounds like you're right.

-the other Doug

Oh, gee -- that reminds me of an sf story I once read. It was written in the late '40s, and had its plucky 22nd-century-spaceship-pilot-hero turning on his ship's electronics and waiting, "as man had been forced to wait since the dawn of the electronic age, for the vacuum tubes to warm up."



-the other Doug (who is old enough to remember those TV tube sales carts and the joys of finding a given tube to replace one that had blown out...)

Hmmm -- I'd think we would want to see ice and water from the outer solar system, to see what the oxygen isotope ratios are within it. Our understanding of the structure of the early solar nebula is limited at best -- we need a lot more data points in order to fully pin down origin locations within the nebula based on given isotope ratios.

-the other Doug