You are probably not aware that Huygens employs 35 small Radioisotope Heater Units for thermal support. In addition, the mission is designed in a way to avoid Huygens freezing: After the heat shield is released, Huygens will be descending under an 8 m diameter parachute for 15 min. After that, this large parachute will detatch, and a smaller one (3.2 m diameter) will be used to accelerate the descent. This is done for three reasons:

1. If the 8 m parachute is used for the whole descent, Huygens will drop very very slow and it will freeze. So the descent has to be accelerated.
2. If the 8 m parachute is used, the batteries wont last until Huygens reaches the lower atmoshere and touches on the surface. Observations of the lower atmosphere and the surface are very important and can't be neglected
3. Even if the batteries could last for a very long time, the descent would have been so slow that Cassini wolud have gone out of line of site, before Huygens reaches the lower atmosphere, so communications would have been impossible.

So, you can see that thermal issues are considered too (together with a lot more issues).

In any case I don't think that they would have been so stupid, that they wouldn't test and simulate the "thermal" part of the mission, during the testing on the Earth.

The Voyager data atmospheric occultation experiment & earth observationa have been used to create the atmosphere engineering model used for Huygens (Yelle model). There is uncertainty of course, but I have seen technical documents of Huygens and the have simulated the descent including all range of possibilities. Plus, after the new mission was implemented due to the doopler problem they experienced, they had the chance to perform one distant and two close flybys of Titan, before the Huygens descent. They are using data from these flybys to validate the atmospheric models and since everything is still going as planned, the Yelle model is probably confirmed.

No, that is one of the most important axioms in scientific inquiry: Don't fall in love with your theory.

I could write a book about how badly PIs have screwed up an investigation by working towards a specific goal or verification, rather than looking at the data objectively. If we should learn anything from the two shuttle disasters, it is that people with vested interests in budget, schedule and public relations make lousy engineers.

My favorite example, though, comes from a friend who worked a Bedouin site in Jordan. The PI had them counting layers of camel dung, certain he could predict the age of the stable by examining the straw strata. He came up with a number like 3000 BC, And managed to get funding for another year. (This in spite of the fact the worker bees kept telling him people tend to shovel out the stable more often than once a year.)

The second year included C-14 dating, which was a good thing, because it showed quite conclusively the bottom most layers were about 400 years old. Impressive, but the whole project was just a pile of dung. The Bedouin thought the whole adventure was comical.


It is impossible to eliminate bias. That is inherent in the scientific method. Yes, the PI’s can and should make their own assessments, but the papers presenting the data, and the theoretical interpretations should be separate, and in my opinion, not released concurrently.

Good, because that is one of my goals.

This is because I am aware of phenomena that cannot be explained in the context of current theory, and also of phenomena, (such as the anisotropy in the CMB), that can only be interpreted with unwieldy and unrealistic projections of current theory.

Only if it is irrational to suspect current theory is not complete. Once you accept the possibility not every aspect of GR should be canonized, then it is reasonable to ask the type of questions I have been asking.

My projection of the density of Titan is based upon a handicapped analysis of supernova events, and an very real attempt to model the rotational effects known as MOND and the Tully-Fisher Relationship. Virtually everyone will concede that if there is no dark matter, it is impossible to model the rotation of galaxies without new physics. I am simply saying since we have not been able to detect dark matter, we should be able to detect these gravimetric effects in our own solar system. This is a reasonable hypothesis based upon observations of the physical world.

We should not be so certain of our understanding of the physical world that we continue to write off anomalies in our space programs to poor design, instrumental errors and other unknown causes. I believe I have identified a physical error: an error in our understanding of physics.

When I look at the photos of Pheobe, I see ice and frozen methane and carbon dioxide on top of an earthy planet, not the other way around - I can compare the talus slopes in the craters of Pheobe with the slopes I can see in the snow outside my window this very moment, and state that this is the most reasonable conclusion. I think everyone should be looking at the photos and spectroscopic data with enough objectivity to include this possibility in their analysis. I hope the PI s can do that.

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jwj

It's ok not to know. We should try harder to find out.

Just a couple of comments...

Jerry, I think you might be missing Evan's point.

So, if we were truly objective, we'd see things your way?? Is that what you're saying??

Thank you. This is the type of information that is very helpful.

Does anyone know how closely the data have matched the model? Are the predictions of the thickness of the atmosphere near Titan's surface based upon direct observation or computational data extrapolated from the edge of atmosphere?

When the Jupiter probe fell like a rock, it was fairly easy to write this off as an atmospheric effect caused by billowing updrafts and down drafts. The outer atmosphere of Titan looks stratified.

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jwj

It's ok not to know. We should try harder to find out.

I will not waste my time refuting your statements but for this. The entire objective of the scientific method is to eliminate bias. That is why double blind studies are performed. It is not only possible but is the usual course of scientific investigation that experiments are performed in a way to eliminate bias. No matter what the investigator may expect to be the result, if the data indicate otherwise then it is the result. It is the case that many investigations had a presupposed outcome but the data indicated otherwise. This has resulted in some of the most significant discoveries made.

I have been trained in the scientific method since I was a child. I can make a study that is double blind even though I am the only person that handles the data. You do not appreciate how this works.

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When I am done here I think I will go create something from metal.

From http://www.planetary.org/news/2004/c...ults_1221.html :

But the most important result to come out of the second Titan encounter was the result of two occultation experiments performed by the UVIS team. An occultation experiment involves staring at a bright light source -- in this case, the bright stars Spica and Shaula -- and watching how the intensity of their light varies as they appear to cross behind a semitransparent target. Occultation experiments will be performed throughout the mission on the atmospheres of Titan and Saturn, as well as on Saturn's rings. UVIS is sensitive to ultraviolet wavelengths, so it probes the uppermost atmosphere, the region in which Huygens will be relying upon the friction between her heat shield and the atmosphere to brake.

Once the data came down from the spacecraft on Monday afternoon, Pacific time, the UVIS team worked around the clock in order to analyze what the flashes of light from Spica and Shaula meant for the vertical structure of the atmosphere. Early Thursday morning was a critical event for the Huygens mission, a "GO / NO-GO" meeting for the Probe Targeting Maneuver, a burst of Cassini's engines that will set the spacecraft on a collision course for Titan. If the atmospheric models proved wrong, the mission would be forced to scuttle the plans for a January descent for Huygens.

Fortunately, the calculated values for the density of Titan's atmosphere -- the most critical number -- came "within three percent of predictions," reported UVIS Principal Investigator Larry Esposito. Because of the near-perfect match between predictions and observations, "We got the green light to proceed for the next step," said Jean-Pierre Lebreton, Project Scientist for Huygens. "The UVIS team did a great job in analyzing the data within 24 hours. In a sense it's almost disappointing -- we did not have to change anything

Your not listening! I am not disparaging the scientific method, I am not question the analytical methods, and I am certainly not questioning the expertise of the talented engineering teams who have pushed our knowledge frontiers to the limit with this and other extraordinary missions.

What I am saying is we should be taking the data in hand at face value: We cannot explain the Pioneer acceleration with known physics. We can detect the rapid acceleration at the edges of galaxies, but not the Dark Matter postulated to explain it.

We don’t know why the Beagle crashed, why the Galileo probe plunged, or why the period of Saturn’s day seems to have shifted six minutes. I am telling you new physics are needed to explain these events.

If you use the scientific method properly, you eliminate all the possible causes, then you have a decision to make: Either you do not understand the application of known physics, or new physical law is manifesting itself. This is the one thing the scientific method cannot tell us, and I am here to tell you we have walked too far down a blind tunnel.

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jwj

It's ok not to know. We should try harder to find out.

Thanks :P , this is most definitely good news, because it means Huygens should survive vehicle entry - Hey, whether my prediction is correct or not, the best scenario is for Huygen to survive the complete mission and return as much data as possible!

(A good hypothesis is not defined by whether it is right or wrong, but by whether in the process of disproving or supporting the hypothesis, the body of scientific knowledge is increased. I have strung a long string of observations together, formulated a hypothesis, and made a prediction base upon this hypothesis. The more data, the better the odds are we will find definitive answers.)

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jwj

It's ok not to know. We should try harder to find out.

Strict adherance to the scientific method is how science advances.

I think that ordinary human error is the most logical and likely explanation for those events. Lifting the edge of the rug and peering under it will commonly find only dust.

And, by the way, would you please provide some justification for your statement about the "Galileo probe plunged". NASA or JPL would do fine.

A hypothesis is elevated to the status of theory by the ability to predict an outcome. This is an essential part of the scientific method. In the case of a prediction being correct it is not sufficient for the singular outcome to be predicted but the mechanism for that outcome must also be explained.

This goes to the core of what you have proposed. There are certainly things about the universe that we do not yet fully understand. Dark matter is currently predominant on the list of things we need to know more about. Your proposals are not based on any sort of logical construct within the science that we know and have proven to be correct.

It is an accepted fact the the General Therory of Relativity as well as Quantum Theory are not full and complete descriptions of how the universe works. This is self evident as neither can encompass the other.

Your proposals do not fit within the observed continium of scientific observation. Your mathematical recreations are no more significant than spelling "SHELL OIL" on a calculator.

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When I am done here I think I will go create something from metal.

You can't explain it with "known physics," I'd say, because you have repeatedly demsonstrated your lack of knowledge of such "known physics."
And, what has dark matter got to do with this probe, exactly.
You don't know why Beagle crashed. The Galileo probe was SUPPOSED to plunge. Jeeze n' Rice, Jerry...

#-o

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Feynman
>~~~~<
Science is a way of trying not to fool yourself. The first principle is that you must not fool yourself, and you are the easiest person to fool.

Religion is a culture of faith; science is a culture of doubt.

Jerry is right that the Galileo probe fell faster than was hoped, but it wasn't so much a suprise to the scientists studying it as a disappointment. The location chosen happened to be in a very rarefied part of Jupiter's atmosphere (as confirmed independently from abundance measurements taken from the probe). The probe "plunged" because the atmosphere was thinner than was expected.

Almost correct:

"Close to expectations"? NASA, what the hell does that mean? Close to the expected levels before or after the higher readings were taken at higher elevation? Close high or close low? What does deeper mean?

This is why I keep harping about NASA’s failure to separate HARD data from interpretive data. As near as I can tell, the HARD date consisted of Doppler and atmospheric pressure readings, although the pressure may have been determined by bumping the measured acceleration up against the drag coefficients. (I read this is how the ESA plans to determine the density of Titan’s atmosphere. If this is true, since they are assuming they know the acceleration due to gravity, and if this is wrong, they will underestimate the density of the lower atmosphere.)

Surprising Doppler readings should not be reported as "strong winds and turbulence." For all we know, the Jupiter probe was snagged in an alien net and hauled off to some breeding ground. It could also mean 'stronger' gravity.

…Not to mention the Russian failures on Mars, and the late deployment of the parachutes on both of the Viking Mars Missions.

Short version: Dark matter is close to where I started: I was looking for a solution for the DM and MOND effects, but also the curious rings that develop when supernovae explode. I was also looking at this in the context of the knee in the cosmic ray spectrum, an event known to be associated with certain types of supernovea. I realize that if we are seeing distant gravity wave events as electromagnetic images, and the electromagnetic field strength dictates the expansion and radiation profile of type II supernovae, everything falls into place.

Then I turned my attention to the solar system and said these equations should describe local behaviors as well, so I plugged the local densities in, and out pops the Huygens probe falling way too fast…just like every other mission into the distant solar system. Venus, though, in comparison is a piece of cake. Venus should be less dense than we think it is, which would explain why one of the Pioneer probes survived after landing, even though it was not expected to. Air braking was much easier on Venus as well. (They did not have the unexpected heating problems experienced air braking into Mars.)

Exactly. I think we have to back-up beyond Newton to fix the fundamental problem: G is not constant. G is not even G, G is governed by an ‘inertial’ potential This means, even though he is close on the mass-energy conversion factor, Einstein was wrong when he bent space and time. Somewhere between now and then we should have realized the speed of light (and all nuclear and chemical reactions) in an electromagnetic system is inversely proportional (via the Lorentz transform) to the total electromagnetic mass of the system.

We’ll see 8-[

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jwj

It's ok not to know. We should try harder to find out.

Yes, we will.

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When I am done here I think I will go create something from metal.

Well, I think "close to expectations" means "close to expectations". How could somebody explain this? It is so obvious...

Before or after the higher readings were taken? Obviously after... Since the higher readings were taken at the upper atmosphere and the probe was going down. What kind of questions is this? Does it have a scope?

Close high or close low? Doesn't matter, it was close.

What does deeper mean? Since the Galileo probe entered in the Jovian atmosphere... well, it fell... And when you fall you go deeper into the atmosphere. Come on...

If the knowledge about gravity was wrong, Cassini would have probably not been in Saturn right now...

No, it could not mean stronger gravity. The answer is just above. We know how gravity works and therefore if we eliminate the known effect of gravity on the probe's trajectory, we can attribute the rest to winds. That's all.

So what? Do you think that we have perfect understanding of the Martian atmosphere with just a few landing attempts? How do you expect scientist to have perfect knowledge on density and temperature profiles etc. about an atmosphere that has barely been studied? And on top of that, how do you expect them to understand the variabilllity of an atmosphere? You think is easy? NO! You think an atmospheric state is easily predictable? NO! You think that atmospheric densities are definded just by gravity? NO! What about winds, temperatures, latitude, topography, any other type of event that could disturb the atmosphere locally (dust storms)?

There are hundreds of reasons that an atmospheric state cannot be predicted. Especially for landers, where the accuracy in velocity has to be less (or not much more) than 1 m/sec during landing, those differences are much more important, but even more difficult to avoid. Maybe it is impossible. That is why the best thing that can be done, together with some good atmospheric physics, is a lot of statistics, so that margins on density profiles (that are the most important for landers), can be defined. In this case the necessary margins will be applied in mission design.

Now, I am not really sure whether any of these margins were available for the Russian landers (although you forget ot mention that Mars 3 landed within a dust storm), Viking, Pathfinder etc. Maybe they were available for Beagle, but you might know that Beagle had the worst mission design ever.

Plus, also don't forget that landers, orbiters etc are complex devices and they are required to perform difficult missions. There are numerous reasons that for example Polar Lander could have failed (it was so small, that even if everything went well, it could have tripped over if it landed on a small rock). As for the early Russian Mars landers &amp; orbiters, if you see the technology they used, you might understand what was the probable cause of failure...

You don't just fall when you are about to land. You also fall when you are in orbit. So according to you, both Cassini and Huygens, which have identical orbits currently, are in the wrong trajectory, since Saturn is also in the distant solar system... So, you are wrong. Because Cassini and Huygens are just where they supposed to be.

It was not expected, but it was not impossible. The pioneer probes were not just a thin piece of metal. Plus let me also remind you that Galileo worked for many more more years than expected, the MER rovers have worked for almost a year (not expected), the Cassini is already expected to have a 4 year extended mission, the Laser Reflectors on the Moon left by astronauts were designed for 10-year life, but they are still working, MGS is still working, NEAR landed on the asteroid while it was just an orbiter ,etc etc. In mission design, they are never optimistic. They always require a more than 90% propability that a mission will work. If they tell them "Well, the MER rovers have an 80% probability to survive more than one year", they wont make the 1-year survivability a goal of this mission (although the chances are good). Space missions deal with hundreds of millions of dollars/euros, and project managers and space agencies cannot give promises that are not almost sure that they could come true...

Well, air braking at Venus was done with Magellan at the end of the mission, as a technology/new technique demostration. It was not mission critical, as it was with MGS. If it was mission critical, they would have been much more concerned about the Maggellan instrument and system readings.

Plus, if you once say that densities on Mars are less than expected due to wrong understanding of gravity, and then you attribute the heating problems to this bad understanding, you are probably in a big confusion. Because lower densities would not cause unexpected heating problems. Only higher densities...

We don't have to wait for Huygens to see if Jerry is right or wrong. He is wrong. Physical laws apply everywhere and not just on a few landers, the Pioneers, or the outer planets. So his ideas should have applied everywhere (even at small scales). And they dont.

And even if Huygens doesn't send any data, this doesn't mean that Jerry was correct. Huygens is a very difficult mission. I know that there is tons of redundancy to make this mission work, but still there are always a lot of unknowns (technical and scientific), each one of these being very critical. Titan is still an unexplored planetary body. Its atmosphere is unique in the solar system.

From a technical point of view Huygens works perfectly. But all testing is based on simulated missions and scenarios. And simulations are just images of our thinking and current knowledge. So, everything should be expected, although I believe Huygens will work. But we have to be realistic. It is not an easy mission

But definately, this there is no danger due to mistaken understanding of gravity...

Correct. It would be one more data point, hopefully Huygens will survive entry and we will obtain good scientific measurments. Hopefully we will not be told “The atmosphere was thicker than we expected…there was strong turbulence…the clouds were thinner,… “. Numbers baby, that is what science is about!

Not true. The engineering margins are tight.

This is a statement of optimism, not of fact.

Can you explain how dark energy “works”? Can you explain where the energy comes from that is “pulling the universe apart”?

Can you successfully model the “Tuffs of Dark Matter” necessary