There is, however, a good reason for a lander to have descent imaging capabilities, especially if there is no HiRise-style camera orbiting its destination.

Context.

Granted, a Ranger-style series of images with steadily decreasing coverage isn't that much good for observing large trends and larger context. But if your eventual landing site is visible throughout the descent, then you have context imaging that lets you observe from a relatively low-resolution level (good for identifying large trends) all the way down to the finest detail visible from the surface.

I am convinced that the DIMES imaging was very, very useful in the determination of geological context on the MER landings. Similar imaging would have been useful for the Surveyor landings, I believe, and I think we missed out on something when the imaging was canceled.

-the other Doug

As I read that last one, what went through my mind was:

"Dust devils don't clean solar panels. People clean solar panels."

-the other Doug

Well -- for scientific purposes, it would be far more useful to catelogue Solar System bodies using several different criteria, such as size, mass, primary/secondary composition, current location and presumed location of origin. That's a six-criteria statement, which isn't all that hard to represent in some form of classification system.

But that's categorization for scientific purposes. As has been recognized here, there are also cultural purposes for such categorizations. And those criteria are far different. That's a point I've been trying to make for quite some time.

-the other Doug

Hmmm... when I load the page linked above, I see the entire solar system (at least as it's currently defined), but all of it appears in the width of my screen. The Sun and planets are all to scale, and rendered properly (not squished or anything), but the distance between them is most definitely not to scale. At all.

-the other Doug

Ah, but what would such megastructures look like from interstellar distances? Dyson seheres would block out the light from the stars they encompass, so unless you see one being completed (i.e, the star just goes out), we wouldn't see them in the first place. Gravitational effects that would say a star should be in a particular place, but is not visible, could be explained by a dark neutron star or a black hole. And, again, there are other, far more likely explanations (dust rings, planetary nebulae, etc.) for megastructures that only partially or occasionally block the light from stars.

I also seriously doubt that anyone at our present level of civilization could even begin to model what types of ultraviolet, infrared, microwave or even X-ray signatures to look for that would indicate manipulations on a Kardashev scale. And such manipulations are probably going to look an awful lot like similar natural processes that end with the products these proposed engineers are trying to achieve. (In other words, if you're building planets, you're probably creating a situation that looks, from the outside, a lot like natural planet accretion. The only thing that might be different from a "natural" accretion scenario would be the timeframe, and we don't have a good enough handle on how long the natural processes take to be able to tell, from interstellar distances, that anything we see is happening at an accelerated rate.)

So, while what you say makes sense, we really don't have either the detection capability to see such things definitively, nor the intelligence or the context to be able to nuance the tell-tale signs we need to be looking for.

-the other Doug

I'm not trying to rain on your parade, here, ngunn, but what in the world makes you think that a frozen ball like Titan, where people will almost definitely *never* travel themselves, will excite the imaginations of the general populace? If Mars, which is in almost all respects more Earth-like (at least you can see the Sun and stars from there), hasn't done it to the extent that we're ever likely to send people there, then why should a place where water is rock and propane is water be all that interesting?

I tihnk you're doing something we're all a little guilty of, here -- projecting your own extreme interest onto a populace that could simply care less...

-the other Doug

Gee, and here I thought we were well past sol xx, and well into sol xxx...



-the other Doug

edit -- darnit, Bill fixed his sol number. Ruined a perfectly good joke, too... *sigh*...

Well, OK -- though the Vela remnant is a lot more obvious and detectable than the bubbles we're talking about. The local bubble that we're currently within is cold, almost completely undetectable unless you cancel out *all* radiant energies from other stars, etc., and the hotter bubble pushing in on it is almost as difficult to detect.

We're not talking about pretty, quite dense (relative to the local bubbles) and quite detectable supernova remnants, here. We're talking about almost completely invisible currents of remnant gas and dust. Where they interact, and where they sit nearby other stars, they are so tenuous that the starlight completely obliterates any detectability. That's a far cry from the Vela nebula, which still visibly shines in reflected starlight.

We're also talking about bubbles that are hundreds of light years in diameter. How long does it take for a supernova remnant to expand that far? Only 20 or 30 million years? Expanding debris shells from supernovae are only accelerated at the very beginning, recall, and are subject to decelaration due to the pull of the neutron star / black hole supernova remnants. They may start expanding at near-relativistic speeds, but they slow down as time goes on.

I guess I'd like to see some numerical analyses on these things before pronouncing them relatively recent newcomers to this neighborhood of the Milky Way.

-the other Doug

Hmm... it would seem to me that, for the Apollo lunar crews, if you're going to wait until three years after the last member of a given crew has died, we're in for quite a wait. Assuming you want to commemorate whole crews at once.

The most reduced Apollo crew, IIRC, is 14's -- only Ed Mitchell remains alive of that threesome. Of all of the rest of the crews, either two or all three members are still among us:

Apollo 7 -- Schirra and Cunningham
Apollo 8 -- Borman, Lovell and Anders
Apollo 9 -- McDivitt, Scott and Schweickart
Apollo 10 -- Stafford, Young and Cernan
Apollo 11 -- Armstrong*, Aldrin* and Collins
Apollo 12 -- Gordon and Bean*
Apollo 13 -- Lovell and Haise
Apollo 14 -- Mitchell*
Apollo 15 -- Scott* and Worden
Apollo 16 -- Young*, Duke* and Matttingly
Apollo 17 -- Cernan* and Schmitt*

Those are the surviving members of the Apollo crews. Those deceased are (in flight order) Eisele, Conrad, Swigert, Shepard, Roosa, Irwin and Evans.

With repeats taken into account, 22 crewmen survive, while seven have died. Of the 12 men who walked on the Moon, nine (asterisked above) are still with us.

The youngest of the guys on the Apollo crews was, IIRC, Charlie Duke. He was 35 at the time Apollo 16 flew, so he would be 69 today. The rest of the guys are in their 70's now.

So, being a bit morbid, I guess it won't be more than another 10 years or so before most of the crews can be commemorated en masse. But it seems a shame that we can't commemorate Pete Conrad or Al Shepard yet.

If it were me, I would rename some of the small-scale features visited by the crews. For example, at Fra Mauro, we could rename North, Middle and South Triplet to Shepard, Mitchell and Roosa. At Hadley, Matthew, Mark and Luke could be renamed Scott, Worden and Irwin. That kind of thing.

Just my $.02...

-the other Doug

Yep -- if Bruce's information is correct, then this is the unmanned LSAM concept. It makes a great deal of sense; if you're going to develop an infrastructure, you ought to take as much advantage as possible of economics of scale. Use the same design over and over.

With that specification for the lander mass, I can't imagine anything else that could get it onto the Moon other than the CaLV.

-the other Doug

Hmmm... could the old, cool bubble be the actual source of the AL-26 enrichment our solar nebula received?

Be interesting if that enrichment happened in the middle of solar system development.

-the other Doug

Hiya, Jim.

No, this thing wouldn't fly on a CLV -- the stick isn't big enough for it. Remember, this is an unmanned version of the LSAM. It will need to fly on the Shuttle-derived heavy lift booster that will, in the manned flight profile, launch the LSAM and TLI stage. In these unmanned landings, they'll just go ahead and fire the TLI stage without waiting for a CEV to come up and man the thing.

That's why these unmanned landings will have such a cargo surplus -- they'll be flying, alone, with all the post-LEO delta-V available to manned mission, but without the additional mass of a lunar CEV and crew.

-the other Doug

I followed you exactly through your first two paragraphs, and lost you on the third.

Here (in the linked image) we see a number of these tiny dimple craters, all roughly alined with a linear feature and arc-shaped features which all seem obviously related to sapping.

If these features are pretty old, then the sapping could all have happened a long time ago and the surface dimples remain intact -- or perhaps are excavated as ancient dune faces are deflated.

At least, that lends more credence to the sapping, if we don't have to postulate a lot of recent activity resulting in subsurface voids. It could all have happened millions of years ago.

But, the image just screams at me that all of the small depressional features are products of sapping...

-the other Doug

Cue MBS (Martian Broadcasting System) commercial:

"After a long day exploring the mountains, canyons and deserts of Mars, your feet ache! Those pressure suit boots just don't provide the support you need!

"But with genuine Gusev Epsom Salts, your foot aches disappear! Just add a measured cup of Gusev Epsom Salts to a gallon of hot water, and soak those dogs 'till the aches melt away!

"That's Gusev Epsom Salts! Buy some today! (Price of the gallon of hot water, roughly 3000% of your annual recreational water ration, not included.)"

-the other Doug

You know, that's a good point -- Enceladus has geysers and Europa does not, at least not at present.

And yet, Europa's cratering record shows that its surface has been reworked pretty extensively over time -- there just isn't anything like the crater count that you find on, say, Callisto or portions of Ganymede.

On Enceladus, it's pretty obvious that the resurfacing is happening via the geyser activity. Older, more rugged terrain is being buried in massive "snowfalls" on Enceladus.

But on Europa, the relatively young surface isn't simply a visually homogenous covering layer of snow. It is a very complexly cracked surface that appears to have, at least at some pont, been a pretty thin covering over a large liquid ocean. As I understand it, it's hard to explain the cycloidal (I think that's the term) cracks if the ice layer has always been kilometers-thick.

But the Europan resurfacing *appears* to have had everything to do with repeated release of liquid water onto the surface and nothing to do with plume-deposited ice crystals. All slosh, no whoosh.

So, does this mean that Europa hasn't really seen geyser activity in the geologically recent past (i.e., since its last major resurfacing)?

And if so, what does the lack of such eruptions tell us about Europa?

-the other Doug

Well, I'm sure that Doug will observe a certain moderation in his application of these rules, since there are certainly many, many posts here (even in the past day or two) which have absolutely nothing to do with unmanned spaceflight, even by the most liberal reading of Doug's definition. Including one or two by Doug himself -- though, to be fair, while a picture of a drone rover in the Antarctic has nothing to do with UMSF, Doug *did* sort of tie it in by noting a resemblance (that I couldn't see) of the scene to Meridiani's plains. And he posted it in the "this has nothing to do with UMSF" forum, which, if you're going to ignore the rules about posting about things other than UMSF, is I guess the right place to put it...

In other words, I don't think Doug is planning to be generally unpleasant about all of this -- eh, Doug? I think we all trust you to be rational about it. And a good, general codification of the rules *has* been well received, I think.

We know you make sacrifices to keep this place as good as it is, Doug. Please don't ever think we don't appreciate it.

-the other Doug

I'm with you, Dan. Even though I always do a quick proof-read of my posts for typos before I hit the Submit button, I will, more often than I like to admit, find when reading the posted version there is some typo or other quick fix I need to make. I pop into Edit, make my one-keystroke fix, hit Submit, and run into the flood control barrier.

It's not a huge problem, but some of us do legitimately pour through the site pretty quickly...

-the other Doug

Here's an offbeat question:

Are the Enceladan plumes dense enough that they would provide any amount of braking to an Enceladus lander?

I can imagine a lander that spends a good amount of its descent trajectory using the friction of the plumes for deceleration. But this assumes that they provide enough density for a noticeable amount of braking.

-the other Doug

The research I've seen on this issue indicates that, even if you oxygenate your blood as well as possible (i.e., get yourself on the verge of hyperventilation), you can maintain consciousness in a vacuum or near-vacuum for anywhere from 15 to 30 seconds. Doing something strenuous that pulls the oxygen out of your blood faster (like running from one pressurized space to another) would tend to decrease your available time of consciousness.

So, in other words, the scene in 2001 *is* plausible, but sprinting on Mars for more than 20 or 30 feet probably isn't.

Someone should suggest this as a project for the Mythbusters, see if they can bust it or confirm it.

-the other Doug

With all of those powerful oxidants (perhaps peroxides) so ubiquitous in Martian soils, I'm wondering what will happen the first time some of that dust hits the mucous membranes of a human being's nose and mouth.

At any rate, with all those sulphates around, the dust will likely stink to high heaven. If you want to colonize Mars, you better be able to get used to the smell of rotten eggs...

-the other Doug

Actually, Richard, I would be more prepared to believe that Hellas *is* an impact basin that has been highly modified by, among other things, crustal subduction along fault lines created by the impact.

A thorough analysis of the height of the ridges around Hellas actually shows that there is more material in what appear to be the basin rings than would fit back into the basin itself. This could happen if the crust were being pushed up around Hellas by subduction. Or had been in the past.

All in all, the boundaries of Hellas are a pretty good place to look for ancient subduction zones in the Martian crust.

-the other Doug

And that's not all!

It's full of... candy-coated popcorn, peanuts and a prize!

(That's what you get with Cracker Jacks...)

-the other Doug

OK -- I think I understand what y'all are saying. I guess the absolute certainty with which the MER team, for example, comes out with statements like "these soils are ground-up basaltic dust with a small admixture of sulphate binding materials" made me think that they had identified the chemical composition of the soils pretty definitively -- and with absolutely no mention of the peroxides, etc., necessary for the old explanations of the Viking results.

So, the truth really is that the MER team states definitively what they know to be in the rocks and soils, but leaves out any references to what *else* might be in the rocks and soils? And they're making somewhat confident statements about the origins of the rocks and soils, when a whole suite of constituents -- those necessary to recreate the Viking results on chemical reactions alone -- aren't detected by their instruments and, so, aren't even discussed?

Is that what y'all are saying?

-the other Doug

...and as they take one down and pass it around,
their probe crashes onto an asteroid!



-the other Doug

I owned that model as a kid -- got it on my 13th birthday.

The box cover image is of the plastic model, not of the sfx model used in the film. And the lunar surface shown is something the Aurora people came up with. It's really not the kind of lunar characterization used in the movie.

-the other Doug