Have to watch out, though, or Oppy just might land on a Wicked Witch...

-the other Doug

It really was no miracle,
What happened was just this:
The Hills began to twitch,
The craters took a stitch,
And Spirit's panel hinges
Started to unhitch...
Just then, the witch,
To satisfy an itch,
Went riding on her broomstick,
Thumbing for a hitch!

-the other Doug

OK -- here's a gedankenexperiment.

You have God's Magic Eight-Ball. You can only ask it the following question: "How many planets does this particular star have?" It can only give you a number back.

What answer is more helpful to you -- four, 12, or 33,117?

A classification system that is *too* inclusive makes it less useful.

-the other Doug

Yeah -- looks an awful lot like welded ashflow tuff, doesn't it?

-the other Doug

But if you call it Terminus, we'll have to establish the First Foundation there, and that's just asking for a whole lot of problems down the road...

Seriously, Terminus would indicate a border, and I'm pretty certain that this new KBO is not the most outlying of the large KBOs out there. Let's save the distinction of the name Terminus for something that truly does mark a natural boundary.

-the other Doug

The problem with using low-thrust, long-burn propulsion systems to send people to the Moon is they don't get you going fast enough, quickly enough.

The van Allen belts are really dangerous -- if you stay there for very long. The Apollo astronauts who went to the Moon spent only a few hours passing through the radiation belts, and they were going at some of the highest speeds they would attain while they traversed the belts.

And they still got a measurable dose of radiation. Not even close to a critical dose, but measurable.

Now, an ion or electric propulsion system is a good idea -- it accelerates a spacecraft slowly, over time, but because the thrust continues for days and weeks, the accumulated acceleration is potentially enormous.

But any of those propulsion systems, if used to get you from LEO to the Moon, would continually create a larger and larger Earth orbit, taking weeks to accelerate to an orbit large enough to place the spacecraft into the Moon's gravisphere. And you would spend many, many days at a stretch passing through the van Allen belts. Over and over.

You would need some really *serious* radiation hardening to build that kind of vehicle. I don't think we know how to do that, yet. At least not well enough to commit a crew's lives to.

The same problem applies to using aerobraking to decelerate returning lunar spacecraft into Earth orbit, possibly to dock with the ISS. Aerobraking requires a lot of passes through the upper atmosphere, starting with a very large, very elliptical orbit and reducing a little speed on each pass to reduce the apogee a few hundred km on every pass, until you're in a position to establish a circular orbit at ISS altitudes.

And that orbit's apogee would slowly dip through the van Allen belts, over and over, and of course since the spacecraft slows down at apogee, it would spend very long hours on each aerobraking orbit traversing the hearts of the radiation belts.

For the foreseeable future, if we're going to fly men to the Moon and beyond, I think we need to use whatever it takes to build up a really fast exit from LEO, to minimize the time spent in the van Allen belts. Or else you risk damaging your spacecraft, not to mention your crew...

-the other Doug

If by "our locale," you mean Earth or the inner Solar System, you're right. But for the Solar System in general, I bet the impact that tilted Uranus on its side was a bigger, more violent event.

-the other Doug

I've read a lot of theories, most of them generated in the past 20 years or so, about how rings around the gas giants (and, at a larger scale, rings or clouds of small, unconsolidated bodies around stars) are formed. They seem pretty evenly divided between the idea that gravitational resonances broke apart larger bodies to create these rings, or that the same resonances have kept the ring bodies from accreting into larger bodies.

What is the current thinking on this issue? Is it the tear-em-down, the don't-let-em-accrete, or some steady-state combination of the two?

Just curious...

-the other Doug

Don't delude yourselves, guys -- there is a far larger percentage of the world's population out there who are terrified by the increasing complexity we can now see in the Universe, than are awe-struck and delighted.

One of the reasons so many people in this world retreat into incredibly narrow and limiting, but very well-defined, roles and world-views is because facing up to how complex the world *really* is scares the living daylights out of them.

Since scientists and like-minded individuals rarely, if ever, have to deal with those people in any context other than the extremely mundane, we tend to forget that they're out there. But they are, and they outnumber us hundreds to one. (Note that you'll rarely see one of these people at a lecture by an astrophysicist -- except perhaps to demonstrate against the "relentless march of science" as if it's a bad thing, or loudly proclaim that "your science is all false becasue my god told me so." Just Google up some discussions about Creationism and its teaching in American public schools, if you don't believe me.)

Not that we need, as a culture or as individuals, to hide from the ever-more-complex Universe that is unfolding before us. Just that we need to understand that a vast majority of the human populace is irrational and fears this trend towards complexity-beyond-their-ability-to-understand, and that we need to take that at least somewhat into account when we design classification systems.

(Of course, there is always that relatively small percentage of scientists who *glory* in making their classification systems as complex and unapproachable as possible, so that the average person out there will confuse the system with magic, and confuse the scientist with a magician... but those ego-maniacal scientests tend to be few and far between. I think most of them work for ESA, though... *sigh*...)

-the other Doug

I still recall watching that EVA live, and hearing Dave Scott saying "Guess what we just found. GUESS what we just found!"

-the other Doug

I've been enjoying the discussion, actually. It's obvious that human beings need to classify things into systems -- it's how we look at things. And whenever you get into defining rules for systems, you get into such wonderful discussions as this...

Alan, believe me when I say that I respect your opinion and your accomplishments. Quite a bit. I've also enjoyed how you have stuck to a single set of referents within the argument, no matter how many people have tried to place their own rules onto the system.

I still think there need to be more useful and handle-able subclassifications within the system for "popular consumption." But other than that, your logic holds sway, Alan.

-the other Doug

First off, the latest thinking is that the Moon actually still has a molten core -- either that, or it has a molten near-core mantle that allows the core to move within the Moon. Because orbital studies seem to show that the Moon's core rotates in a slightly different plane than the rest of the Moon does. So, either the core is still molten, or the core can move through a molten "sheath" relative to the rest of the Moon.

One of the more fascinating models of lunar composition right now says that the core is molten nickel-iron, surrounded by a solid layer of primitive chondritic material, covered with a now-solid mantle that only completely congealed about a billion years ago, and topped off with the battered and brecciated megaregolith of feldspathic highlands and basaltic maria.

As for basin fill compensation -- the Moon displays tectonic activity where basaltic lava flows have filled basins. The lava fill is actually heavier than the feldspathic rock of the crust onto which it was extruded, so after lava filled a basin, the rocks holding up the basin would sink under the weight. The whole thing reached an isostatic equilibrium after several hundred million years, but in the meantime great cracks (called graben) appeared where the centers of the circular maria sank and pulled themselves away from the fringes. Wrinkle ridges also appeared, as congealed lava surfaces piled into each other in rings around the heavier centers of the circular maria.

The graben and the wrinkle ridges are both genuine tectonic features. There are also some collapse features at antipodes to large basins that may represent tectonic actibity triggered by basin-forming impacts.

-the other Doug

OK -- fair enough. Though that *is* allowing a gravitational definition of real estate to affect the terminology...

Isn't there some theory out there that Triton was once a KBO that was later captured by Neptune? If that's the case, then you would say that Triton is a planetary body that was once a planet but is now a satellite?

I think the reason people are so energized over the classification issue is that most people have a need for a world around them that they can hold in their heads at one time. When we think of a city, for example, we think in sequential sequences of roughly ten-square-block areas that we can characterize in our minds "at once." We even give names to these small, handle-able chunks, calling them districts or neighborhoods. But we chop things into segments that we feel comfortable dealing with as single entities.

If you want people to feel like they have a place in a larger Universe, you need to give them relatively "small" chunks to deal with. Giving school kids ever-widening chunks (Earth as a planet, Earth/Moon System, Inner Solar System, Solar System) you keep the number of elements of each "chunk" under 10. That seems to be a good limit, since anything that gets a lot more complex is difficult for an average person to handle in one "chunk."

So, I think it is important to give people some kind of system that identifies a Solar System consisting of a number of objects (in the vicinty of 10 or so objects) that they can grasp in one "chunk." When you add thousands of objects, you need to add them "en masse," is with the Asteroid Belt, the Kuiper Belt, the Oort Cloud -- note that those are all singular, not plural, nounds. Otherwise, people begin to feel lost and overwhelmed by the sheer number of "things" they need to consider or account for within a given system.

(Note -- I'm not talking about the scientists and engineers, here, who are trained, or have an affinity, to think in different scales. I'm talking about your normal, salt-of-the-Earth kinds of people who make up 95% of the world's population...)

-the other Doug

So, is Titan a planet? Is Ganymede? Is Triton?

Or does real estate count, after all?

-the other Doug

If real estate doesn't matter and you classify planet vs. non-planet based solely on size and mass (i.e., is it big enough to have pulled itself into a ball), then what about a majority of the moons of the gas giants? Remember, real estate cannot be a factor in the equation.

Under the classification system that everything massive or large enough to pull itself into a sphere (more or less) is a planet, we have to admit Ceres, Vesta, the Galilean moons of Jupiter, many other Jovian moons, a lot of Saturnian moons, a lot of Uranian and Neptunian moons, plus possibly thousands of KBOs, all into the League of Planets.

Oh, and while it's not usually called a planet, our own Moon would have to be considered a planet, too.

If you're going to make an exception for bodies that orbit other planets to call them moons, then you're allowing real estate to enter the equation, and once you do that, you're simply applying arbitrary dividing lines...

-the other Doug

I would think the heavy-life unmanned Shuttle variants (remarkably like the old Shuttle-C variant designs) would keep the Shuttle contractors happy. And it'll keep the guys and gals who will fly the CEV a lot happier if they don't have to deal with a 50-G liftoff crunch.

That SRB launcher will likely take off like a model rocket -- SWOOOOOSH and it's suddenly ten miles up!

-the other Doug

And here I was going to ask you how many gigabytes the cat held... I guess, in the case of a cat, it's more like giganibbles.

-the other Doug

You can vary the nozzle and the burn cavity in a solid to change the thrust and the burn duration -- so, in theory, you *could* design the SRB to have a lower initial thrust-to-weight ratio. Of course, you'd be reducing the motor's ISP, too.

What the heck is wrong with using a Delta IV or an Atlas V for the CEV, anyway???

-the other Doug

Aw, shoot -- and here I had in mind a concept whereby these out-of-plane objects could be classified based on a certain degree of extra-solar composition. I had this image of the objects in the Kuiper Belt and Oort Cloud being condensed out of the interaction between the T-Tauri stage of the solar wind and the supernova remnant gasses and particles into which this energetic solar wind slammed... as such, they would be of a compositional mix between the solar nebula and the surrounding supernova nebula from which the Sun and its planetary nebula evolved.

Since the T-Tauri stage of the solar wind would have pushed out in all directions, it would have established a spherical structure around the Sun of the remnants of the interactions between the wind and whatever it pushed into and through on its way out. That would seem to be the perfect structure from which to derive the KBOs and OCOs, would explain why they occupy a space defining a spherical cloud around the Sun, and would suggest that these objects might be of somewhat different composition from the rest of the solar system.

Granted, all of this extrasolar material ought to similar to the materials derived from the planetary nebula, since the solar system was formed from a piece of the original supernova nebula. But it was my thinking that the extrasolar gasses and ices included in the KBOs and OCOs could let us characterize differences between the planetary nebula (from which the solar system was derived) and the surrounding supernova remnants. Isotopic abundance information would be extremely interesting, I bet...

But if all of these objects were originally formed from the planetary nebula disk and were later ejected into this spherical cloud, then my theory is non-applicable... darn it!

-the other Doug

Truthfully, I think that Pluto needs to be demoted to a KBO, and the rest of these objects need to be classified as KBOs. Regardless of size and mass. I think it's obvious that the KBOs, as a class, were formed rather differently from the rest of what we think of as planets -- most specifically, since they do not orbit in the plane of the ecliptic, they could not have been formed primarily from the solar nebula, since those nebulae always seem to array themselves in fairly thin disks.

I think that planets should be defined as objects that accreted directly from the solar nebular disk (defined by its orbital inclination) *and* that are larger than "X" in size and/or mass. Everything else, regardless of size and/or mass, should be defined as a KBO or an Oort cloud object (OCO).

So, simple rule -- formed from within the planetary disk = planet, formed outside of the disk = other.

-the other Doug

Shannon Lucid has been the wake-up CapCom every day so far during this flight. I had thought Lucid was retired.

She only seems to handle the first few minutes of the wake-up shift, and then hands off to the regular CapCom.

Anyone have any info as to why Lucid is doing this? Did the crew request it, or what?

-the other Doug

Personally, I think that we will find biogenesis processes on a variety of worlds and in a variety of non-planetary environments. But we will find that most of them have progressed only so far before they have run across some limiting factor that has arrested the process (or slowed it into virtual arrest) at very primitive levels.

For example, we can speculate all we want on the early biogenetic processes on Earth, but we *know* that Earth is a somewhat freakish exception in its overall climatic uniformity. The only reason the Earth does not have cyclic extremes of climate (as Mars does) is because our Moon keeps our rotational precessions from wandering all over the place -- our axial tilt is maintained by the Moon's gravitational influence. An Earthlike planet in another star system might develop exactly the way Earth did, with exactly the same range of elements and minerals and water and temperatures -- but without a large moon, its axial tilt would wander around and subject its surface to cyclic periods when one whole hemisphere never sees sunlight for thousands of years at a time.

That kind of thing might not stop biogenesis cold, but I bet it slows it down a lot. And that "progress" towards multi-cellular organisms might be wiped out every few hundreds of thousands of years when the climate changes and favors only the continued development of extremophiles that are so constrained by their adaptations to extreme environments that they are "blind alley" developments as far as complex life forms are concerned.

Frankly, I think the only Earthlike bodies we're going to find out there that have stable long-term climates will be moons of gas giants that have been dragged into their stars' habitable zones as their primaries migrate in toward their stars. And if it really *does* require a few billion years of "simmering" before multi-cellular organisms can arise from a soup of primitive single-cell organisms, then the limiting factor of climate stability might be the major constraint on "M"...

-the other Doug

I'm reminded of the lyric to the song "The Gambler" -- I should write up a whole lyric, but the line that springs to mind is:

"And somewhere in the darkness,
Ol' Spirit, she broke even..."

-the other Doug

Now, that is the first rock I've seen in any of the images from the MERs that looks like a crystalline rock. It's got a fine, almost sugary crystalline structure that becomes apparent along the end of the "point."

It almost looks granitic, doesn't it?

-the other Doug

The replay makes it pretty obvious that the debris that was shed came nowhere near the orbiter itself. But it was a pretty substantial piece of debris.

Bill Parsons, I think it was, made the point that we have never had good images of the shuttle stack from an on-the-tank POV after SRB sep. As he said (paraphrasing slightly, I'm sure), "this might be something that has happened on every flight, we really don't know. We've never seen the vehicle like this during this phase of flight before. This is all new data that we've never had before."

-the other Doug