A get-together would be marvelous -- but since we're scattered all across the planet, it's probably not very practical.

-the other Doug

As I understood it, JIMO/Prometheus was to use not an RTG but a full-fledged nuclear reactor. Is there a reason why that would require Pu-238, as opposed to the same fuel used by commercial nuclear power plants? I sort of thought that Pu-238 was mostly used for RTGs, because it's the most efficient at generating heat during decay.

-the other Doug

As I recall, the fastest an Apollo ever traversed the distance between Earth and Moon was about 56 hours -- and that was Apollo 8's homeward journey. (With no LM, they had more fuel remaining when it came to TEI, and they burned a little longer to get home a little sooner.) However, due to vagaries of trajectories, the Apollo 10 crew were the fastest, reaching a slightly higher velocity just prior to entry interface than any other Apollo crew ever managed.

-the other Doug

That is remarkable, Phil. It's the way I've always wanted to see that particular vista. And I'm struck by the fact that an Apollo J mission would have had no particular problem operating in such an area -- there are abundant patches of relatively flat terrain suitable for landing a LM, and I don't see any slopes that an LRV would have had problems with. It wouldn't have been any harder to carry out a J mission here than it was at, say, Descartes.

-the other Doug

Yeah, but I don't blame the women -- most of the time, those professors *force* those youg women to show them their theses, or they won't *let* them matriculate!

It's a sad commentary, but true...



-the other Doug

Much thanks, Doug! It looks fabulous, and I hope Steve puts it up in his office... I'm glad he knows just how much his "kids" have done for us all.



-the other Doug

That's what they're doing right now -- Spirit is perched on the south side of the summit, down the hill just a few feet, staring down to the bottom of the hill.

-the other Doug

That little movie captures the reality of what science fiction films have been speculatively presenting for more than a half a century.

Seeing the real thing at last, in such high definition realism, is immensely moving for me.

-the other Doug

So -- is the octopole signal alignment issue something that was observed and discussed out of the first year's observations? I've read a couple of articles on the subject, and I sort of got the notion that the octopole signal alignment measurements that are at issue had come out of the second year of observation...

I guess I'm wondering if this issue is something that might turn out later to be incorrect? Or are we looking at a serious weakness in the expanding universe (with massive dark matter) theory?

-the other Doug

Hmmm... well, the effect must be very, very minor (at least in the local solar-system neighborhood), or else the planets wouldn't orbit in such a way as to generally validate the inverse-square law of gravitation.

It *does* occur to me that the inverse-square law relates to the "classic" three physical dimensions, and cosmologists are always saying that as many as 19 physical dimensions *must* exist. As far as we can tell (since we cannot directly measure anything outside of the three dimensions that are apparent to us), gravitation doesn't propogate along any of these other physical dimensions. Perhaps this is an indication that it *does* and the effect we are seeing is actually a relation between some other physical dimension(s) and the three we can perceive? This would mean that the inverse-square law could be maintained; we're just applying that law to a dimension that is not obviously connected to the three we can see.

I think it's time to start contemplating how these extra dimensions that cosmologists believe must exist inter-relate with the Universe as we observe it. Rather than assuming that these dimensions simply collapsed and vanished as energy levels decreased shortly after the Big Bang, maybe they still exist and interact with such things as gravitation... However, I think it's too early to say that this effect happens near massive bodies, and it's definitely too early to start making mass itself a variable factor, relative to its distance from other masses.

-the other Doug

The amount of water vapor in the atmosphere is dependent on the air's temperature and pressure -- not vice-versa. If there was absolutely no water or ice on Mars, but everything else was the same, we would see the same air pressure patterns.

I think, instread of water, you meant to say that as frozen CO2 sublimates into the air, the air pressure rises. Since the process is always going on at both poles (sublimating in the summer hemisphere and freezing out in the winter hemisphere), Mars' overall air pressure doesn't rise commensurate with the amount of CO2 released at a given pole; but the air pressure across the entire planet does fluctuate between about 3 and 9 millibars, depending on where in the cycle you're looking.

Also, Mars' northern hemisphere is significantly lower than its southern, which means that the air pressure tends to be a little higher in the northern hemisphere. It's also easier for gaseous CO2 to migrate to the north pole as northern winter approaches than it is for the reverse to happen -- it's heading downhill when flowing towards the north pole. But that's a very minor effect. The north polar ice/CO2 cap grows larger than the south pole's, and maintains a larger remnant cap during its summer, because Mars is farthest from the Sun during northern summer and closest to the sun during southern summer. And its orbital eccentricity is far greater than that of the Earth, so the difference in insolation between aphelion and perihelion is far greater than that on Earth.

One interesting thing I read once -- Mars' night-time atmosphere is nearly always at 100% relative humidity. In other words, while the extremely thin air on Mars can only hold a tiny, tiny amount of water vapor, Mars' air holds all that it can hold at night. Which brings up interesting possibilities for barely-noticeable precipitation events.

-the other Doug

The Saturn V required between 11.5 and 12 minutes to place the TLI stage (full Apollo CSM/LM, SLA, S-IVB and remaining fuel) into a low earth orbit (about 150 km high). The shuttle places a somewhat lighter total payload into a somewhat higher orbit after roughly nine minutes.

Recall, too, that the Saturn V used higher-density RP-1 and not liquid hydrogen in its first stage -- this provided the necessary lift-off thrust to get the whole thing off the ground. While the Saturn's upper stages, which used hydrogen and oxygen, were more efficient than the first stage, they couildn't deliver the kind of massive lift-off thrust required of the first stage.

-the other Doug

Eclithping the thun???

You're dethpicable!



-the other Doug

I think that's the new DDU measurement system -- Dumbed-Down Units.

-the other Doug

These rocks have already been determined to be evaporites -- not just from some theory as to their formation, or the cracked appearance of the surfaces, but from fine details in their layering and from their very compositions. It would seem to me that evaporites would *have* to have been formed via dessication processes; it's inherent in the type of rock.

Why do we have to propose much less likely processes to account for the cracking of the evaporite layer, when we know for a fact that the rocks are evaporites and were formed by the evaporation of water from this area?

-the other Doug

I think the trick here is going to be in the sub-classifications. These sub-classes already exist in the "taxonomy" of a solar system -- we just need to tighten up the definitions.

Maybe a nice, tidy system such as this:

Planets -- bodies made spherical by self-gravitation and that orbit the Sun primarily (i.e., do not have another body as its orbital primary)

Rocky planets -- includes Earth, Venus, Mercury & Mars

Dwarf rocky planets -- includes Ceres, Vesta, any others to be discovered

Gas giant planets -- includes Jupiter and Saturn

Icy planets -- includes Uranus and Neptune

Dwarf icy planets -- includes Pluto and any other KBO / TNO that meets the initial requirement of being a planet in the first place

I guess you could call the "dwarf" varieties something else, like "minor planets" or "planetoids," but I like dwarf better. Not only is the term more in keeping with established astronomical nomenclature, but with the amount of gravitational adjustment their orbits have probably undergone, you could say that the Solar System is engaged in "dwarf tossing"...

-the other Doug

Which is a problem when you want to reference an acronym in a thread title. Just try putting something like MER, or NASA, or NEAR, or MRO, into a subject line here...

-the other Doug

The real problem lies in the fact that when intelligent people discuss such pseudo-scientific claptrap, it's usually with an eye towards how to take advantage of the situation, or how to copy the techniques in order to hoodwink the public over more prosaic matters. And thus, harm *can* be done.

However, since none of us seem to fall into either category (the easily duped, or those who are desperate to dupe others), the discussion in this forum really does do no harm.

-the other Doug

Nope -- they covered about 35 km, total odometry. Which was awfully impressive, regardless.

The entirety of LRV travel, from all three Apollo J missions, covered about 100 km.

-the other Doug

It is. But tedstryk is right -- and it's not just a phenomenon seen in the late 50s and early 60s. Particles & fields experimenters have historically had a bias that would have you believe that imagery is worthless -- after all, *anyone* can see things in visible light, but it takes their own special instruments (and their peculiar abilities to understand the results from those experiments) to understand everything *unseen* out there in the Universe.

I've spoken to people who are so antagonistic to imagery that they believe there should *never* have been a camera flown in space, period -- they just can't understand how anyone can gain any *important* data from images.

For an example of such anti-imagery prejudice, Pioneers 10 and 11 were originally designed without any imaging system whatsoever. Many of the people involved in the design of those probes went to their graves feeling that imaging on those probes was a waste of time and effort.

I feel comfortable saying that the anti-imaging prejudice is just plain wrong -- particles and fields sensors, for example, would *never* have discovered the basic truth about Io that non-scientific *navigation* images revealed. And nothing except imaging could have established the water-laid nature of the evaporite rocks at Meridiani. But the anti-imaging prejudice did exist, and still does exist to a certain extent.

-the other Doug

One of the greatest conundrums of exploring Mars via solar cell is that the times of highest planetary insolation (SH summer) are also the times of highest atmospheric tau, because the greater insolation drives greeater atmospheric instability, which kicks more dust into the air and raises tau.

And yes, I wouldn't be at all surprised if the prevailing winds at Gusev were to shift from southerly to northerly as SH fall and winter approach. On Mars, the seasonal variations see the *air itself* precipitating out and forming the polar caps, so the theoretical highest volume of gaseous air on the planet occurs when the total extent of both polar caps is at a minimum. Which ought to happen at the equinoxes. However, as one cap sublimates down and the other builds up, the CO2 that forms the caps *must* travel, as flowing air, from one pole to the other -- so that would tend to drive northerly winds as the northen polar cap forms and the southern sublimates, while the reverse should be true when the northern cap shrinks and the southern cap grows.

-the other Doug

Reports of cannibalism on the MER Teams are very overblown. This kind of thing hardly ever happens anymore on the New MER Teams...

Besides, I thought Pete had a gimpy leg...?



-the other Doug

Those dark "nodule"-like boulders are arrayed on the southern "rim" of the Ultreya depression, are they not? They could well be what remains of the contact with the dark material on the southern side of the Ultreya "crater".

If there is a deposit of dark material, it's likely that it's larger than just the tiny patch that happens to be exposed in the northern wall of Ultreya, after all.

As for Dragons -- when I see unequivocal evidence of thoat tracks on Mars, I'll start believing in Martian dragons...

-the other Doug

My own personal opinion, at this point, is that Ultreya represents an ancient impact into the land that now makes up the Columbia Hills. It's a roughly circular depression, and while there are several ways to make those on Mars, by far the most common is impact cratering.

The next question is, why is there so much dark material in this depression, and why does it seem to sweep out of a linear contact along the north-northwest edge of Ultreya? My best guess is that the Ultreya impact excavated a bed of very dark material (either a continuous bed that is also exposed a few other places in the Hills, or a relatively small dark deposit). Wind comes in to the depression, swirls around in a clockwise direction, and over millions of years has eroded the very dark dust from this contact and strewn it along feather-like arcs toward the east-southeast.

So, I am *really* looking forward to seeing the side of Ultreya that will remain obscured the longest... because that's where this contact appears to be located.

-the other Doug

Hmmm... I don't think I necessarily agree with the assessment that the image shows anything actively being blown out of the crater. If you'll notice, the two most obvious "lobes" are arrayed exactly radial to their origin point. If these were lobes of a geyser or even a windblown plume, I would expect them to begin to travel the same direction (downwind) when they got a short distance away from whatever physical feature was separating them. There is no sign that either feature is arrayed anything except radial to the origin point.

Also, while the two "plumes" located at about 3:30 and 4:30 (in clock-face angles) are the most visible, there are degraded remnants of very similar features at about 10, 11:30, 12:30 and 1:00 angles -- all exactly radial to the same origin point as the two prominent features at 3:30 and 4:30.

These may all have been created by windblown sediments, but it would appear to me that each of them would *have* to have been created during a time when the wind was blowing from a different direction than when any of the others were created. So, I've got to say, it's pretty obvious that these are all static features lying on the ground, that may well have been caused by dust plumes emanating from the crater, but I don't think any of them are actual dust plumes or geysers hanging in the air at the time the image was acquired.

-the other Doug