[X] My Assistant

[Guest_BruceMoomaw_*]

(1) From Lebreton (pg. 762): They still don't know why on earth Huygens was spinning backwards on its chute-line swivel during most of the descent: "Further detailed investigations of the aerodynamic interaction of the air flow with the probe under the parachute may be required to explain this behavior."

(2) From Owen (pg. 756): Since the near-surface winds are only about 1 meter/sec, "The challenge...is to find out whether such light winds can account for the observed wind-induced features on Titan's surface, or whether stronger gusts are required." (A reason to regret not including an anemometer.)

(3) From Fulchignoni (pg. 787): There really does seem to be fair evidence that Huygens detcted several radio bursts from distant lightning, but it's far from proven.

(4) From Niemann (pg. 782): There are still two different plausible theories for the origin of the methane that replenishes Titan's air: serpentinization reactions deep in its rocky core, or large amounts of methane clathrates stored in its icy crust (above the subsurface liquid water/ammonia layer) during Titan's original accretion.

(5) Niemann (pg. 781): The clash between the amount of nitrogen isotope fractionation found by the Infrared Space Observatory in Titan's HCN, and the considerably lesser degree of it found by Huygens' GCMS, is apparently because "photochemistry is strongly enriching the heavy isotope of nitrogen in HCN."

(6) Niemann (pg. 782): The only surface molecules identified so far that aren't in the atmosphere are ethane (firmly), and benzene, cyanogen and CO2 (tentatively). "Work is continuing to identify other constituents." He confirms that the high boiling points for all these substances suggests that there may indeed be a lot of them there. But he makes no mention of the identification of HCN and acetylene on the surface, such as Toby Owen mentioned in his June article in that Russian physics journal.

(7) Niemann (pg. 783): There's still a lot of GCMS analysis left to be done. "For example, heavy hydrocarbons with mole fractions less than 100 parts per billion may yet be identified in the enrichment cell data."

(8) Niemann (pg. 783): GCMS ion source 5 -- intended to allow CO to be measured -- did indeed fail early in the descent as Jason mentioned on his Titan blog (23.5 minutes into the descent, according to Jason). Niemann says that this happened at a moment when Huygens was being especially badly jostled by Titan's high-altitude wind shears.

(9) From Tomasko (pg. 765): Besides Huygens' backwards spin and high-altitude turbulence, yet another factor adding to the very serious problems in locating the precise orientations of the DISR images -- and thus putting them together properly -- was the fact that "Below about 35 km, the signal from the direct solar beam was lost by the Sun sensor owing to the unexpectedly low temperature of this detector." Also, the loss of radio channel A not only lost half the photos, but "several other low-altitude spectrometer measurements" (probably some of the rapid-fire ones at the very end of the descent).

(10) Tomasko (pg. 767): The famous "runway" -- one of the three dark features that is much too straight to be an ordinary riverbed -- actually splits a "bright lobate feature" which is therefore "a possible fissure-fed cryovolcanic flow." (I wonder whether the other two very straight apparent fissure features seen by Huygens show any sign of this.)

(11) No indication in Tomasko's article as to just how tall that row of "islands" in the middle of the dark mudflat -- divided by darker channels between them -- really are.

(12) Tomasko (pg. 770): "The DLVS [down-looking visible spectrometer] data clearly show that the highlands (high-albedo area)are redder than the lakebed (low-albedo area). Spectra of the lakebed just south of the coastline are less red than the highlands but clearly more red than the lakebed further away (that is, to the southeast). The data suggests that the brighter (redder) material of the hilly area may be of local origin, and is corrugated by rivers and drainage channels, and that the darker material (less red) is a substance that seems to be washed from the hills into the lakebed. It could be connected to the alteration of the highland terrain, either by precipitation, wind and/or cryoactivity. Additionally, it could indicate that the surface of the lowland area may be covered by different materials in regions that exhibit diverse morphology."

(13) Tomasko (pg. 771-2): The surface spectrum "is very unusual and has no known equivalent on any other object in the Solar System...

"We note the remarkable absence of other absorption features in the surface spectrum along with the 1,540 nm band. This is at odds with predictions that some specific chemical bonds, in particular C–H or C[3-bond]N, and possibly the individual bands of atmospherically abundant species, such as ethane (C2H6), acetylene (C2H2), propane (C3H8), ethylene (C2H4), hydrogen cyanide (HCN) and their polymers, would show up as signatures in the surface spectrum.

"The most intriguing feature in the surface spectrum is its quasilinear featureless ‘blue slope’ between 830 and 1,420 nm. As briefly illustrated in Fig. 15b, a featureless blue slope is not matched by any combination of laboratory spectra of ices and complex organics, including various types of tholins...

"Assessing the material responsible for the blue slope is a major challenge and also a prerequisite for a secure identification of the 1,540 nm band. If this band is indeed mostly due to water ice, an intimate mixing of this ice with a material displaying a strong ‘infrared-blue’ absorption would explain the absence of the weaker H2O bands at 1.04 and 1.25 microns in the surface spectrum, as demonstrated for several dark icy satellites, where these bands are hidden by the presence of an organic component (but neutral or reddish). Decreasing the water-ice grain size alone cannot suppress the 1.04- and 1.25-micron bands and at the same time maintain the apparent blue slope that is produced by large-grained water ice (considering only the continuum absorption between the infrared bands). To hide these weak water bands efficiently, the mixture would need to be ice and a material having a stronger and decreasing-with-wavelength infrared absorption." (This looks like the single most intriguing mystery dug up by Huygens -- again, what a pity we didn't have an attempt to do a direct GCMS analysis of the surface material.)

[remcook]

(6) Niemann (pg. 782): The only surface molecules identified so far that aren't in the atmosphere are ethane (firmly), and benzene, cynanogen and CO2 (tentatively). "Work is continuing to identify other constituents." He confirms that the high boiling points for all these substances suggests that there may indeed be a lot of them there. But he makes no mention of the idenfitication of HCN and acetylene on the surface, such as Toby Owen mentioned in his June article in that Russian physics journal.

I haven't had time or the state of mind to read the articles, but I assume that "that aren't in the atmosphere" means not detected by GCSM. They are quite clear in the infrared. But that's stratosphere as opposed to troposphere...

very interesting about the spectra of the surface material! looking forward to reading the articles on the boat back to holland

[The Messenger]

Great synopsis, Bruce.

A couple more:

http://www.esa.int/SPECIALS/Results_from_M...LKRULWFE_0.html
14)
"HASI found that in the upper part of the atmosphere, the temperature and density were both higher than expected. "
15)
"The temperature structure shows strong wave-like variations of 10-20 K about a mean of about 170 K. This, together with other evidence, indicates that Titan’s atmosphere has many different layers."

These layering effects seem rigidly at-odds with the intense wind-shear and buffeting, and I do have a tentative scenario:

The main parachute was sized to create a sufficient drag to allow the heat shield to spring free in Titanian gravity. The shear winds were unexpected, and if they caused the heat shield not to seperate on time (due to either ballistic loading, or by some mechanical hindrance), the heat shield may not have completely seperated, and simply been pushed aside by the DISR and other instruments as they emerged.

The Titan wind, striking this configuration from one direction, could have forced this unsymetric arrangement into backward rotation and with each rotation, jetted cold N2 into a small gap between the probe and the heat shield. If this happened, the temperature probe would have remained almost completely insulated before the instrument packages emerged, explaining both the high readings and the loosely periodic temperature swings. (This could be somewhat confirmed, if the periodic temperature variances correlate with the rotation rate of the probe.)

Edited to add:

Digging further, It looks like they are already looking at possible convection differentials causing apparent temperature differentials, possibly due to the design of the "Top Hat":

http://www.nature.com/nature/journal/v438/...ure04347-s7.doc

The effect of convection inside the open instrument (in particular the SSP “Top Hat” structure) will also require further analysis in order to be able to fully explain the thermal behaviour during the descent.

Is the 'top hat' on the top, or on the bottom of the probe?

[remcook]

SSP is at the bottom, so I guess that's what they mean

http://pssri.open.ac.uk/missions/mis-cas.htm

[The Messenger]

...And a couple more odd-ball things from the supplimental notes:

http://www.nature.com/nature/journal/v438/...ure04347-s7.doc

16) During entry, 'the heat shield and the back cover were predicted to reach up to 1700 °C and 275 °C respectively. However no heating effect was detected by the units mounted in the Descent Module'. On the other hand, during the descent, this same Descent Module cooled more rapidly than predicted. "Detailed post-flight analysis is ongoing to reconcile the measurements and the predictions."

17) "The ambiguity between contributions from zonal and meridional winds, at least near the surface, has essentially been resolved by a detailed comparison with wind drift data from the Descent Imager/Spectral Radiometer"

So the two teams did collaborate on the interpretation of the final moments of the descent, which is why Emily's graph indicates such a strong correlation.

[exoplanet]

Dear Bruce,

Thanks for your wonderful summary of the Huygens data. I would like to add a few comments to your synopsis for future discussion.

"(2) From Owen (pg. 756): Since the near-surface winds are only about 1 meter/sec, "The challenge...is to find out whether such light winds can account for the observed wind-induced features on Titan's surface, or whether stronger gusts are required." (A reason to regret not including an anemometer.)"

So good to hear that others have questions about how the low wind speed on the surface would be able to produce such large linear dunes.

"(3) From Fulchignoni (pg. 787): There really does seem to be fair evidence that Huygens detcted several radio bursts from distant lightning, but it's far from proven."

Could the lightning be detected this far away from the persistent storms at the south polar region?

"(6) Niemann (pg. 782): The only surface molecules identified so far that aren't in the atmosphere are ethane (firmly), and benzene, cyanogen and CO2 (tentatively). "Work is continuing to identify other constituents." He confirms that the high boiling points for all these substances suggests that there may indeed be a lot of them there. But he makes no mention of the identification of HCN and acetylene on the surface, such as Toby Owen mentioned in his June article in that Russian physics journal."

Acetylene has been confirmed by Cassini as a component of Titan's atmosphere. Since it is such a heavy molecule - why is it not showing up on the surface?

And the most astonishing and perhaps important result (IMO) . . .

"(13) Tomasko (pg. 771-2): The surface spectrum "is very unusual and has no known equivalent on any other object in the Solar System...

The most intriguing feature in the surface spectrum is its quasilinear featureless ‘blue slope’ between 830 and 1,420 nm. As briefly illustrated in Fig. 15b, a featureless blue slope is not matched by any combination of laboratory spectra of ices and complex organics, including various types of tholins..."

Possible complex sugars, amino acids, proteins?

[edstrick]

It's probably the red ink that will spill everywhere when they try to build and fly the Titan surface chemistry explorer!

[The Messenger]

It's probably the red ink that will spill everywhere when they try to build and fly the Titan surface chemistry explorer!

I don't care what color ink they use, as long as it happens, oh - and it would be nice if they checked out the bandwidth and on/off switches before launching.

Here is another something else I do not understand:

http://www.nature.com/nature/journal/v438/...ature04060.html

In addition to the above mentioned descent velocity, which slowly decreases with decreasing altitude, small, nearly constant, corrections must be applied for the effect of special relativity (- 7.5 Hz, where the minus sign means a red shift), as well as the effects of general relativity associated with the Sun (18.2 Hz), Saturn (- 0.7 Hz), Earth (1.4 Hz) and Titan (- 0.08 Hz). Propagation corrections to the Doppler measurements from the neutral and ionized intervening media (Titan, interplanetary, Earth) have been estimated and found to be negligible. Finally, a small correction of +10.0 Hz was applied to the absolute transmission frequency by requiring that Huygens remain stationary on Titan's surface after landing. This residual is within the error limits of the pre-launch unit-level calibration of +9.2 Hz determined for the specific DWE rubidium oscillator unit used to drive the Huygens channel A transmitter.

OK, how is 10 Hz 'within' a calibration of +9.2? What the hell is is a 'unit-level calibration of +9.2? Expected drift? bandwidth? measured mean?, three sigma?, spec tolerance?

Ten Hz is a lot of bending in an ultrastable oscillator - - wasn't it supposed to be stable to ~0.1ppb, not five? 10hz could mean there is a significant error in the landing location, or even in the science - this is of the same order of magnitude as the Pioneer anomalies. Ten hertz could mean Cassini might not even be able to track it. What am I missing?

[Guest_BruceMoomaw_*]

I can tell you, even at this point, that the results from the COMPLEX meeting show intense interest in a Titan follow-up mission -- and they MAY have found a way to fly a scientifically acceptable version for only a billion dollars (the quantity of cash which, as Sen. Dirksen said, eventually adds up to Real Money when you repeat it enough times). However, that cost figure is right now -- God knows how much that proposal would cost after they're actually done with it...

[edstrick]

"Ten Hz is a lot of bending in an ultrastable oscillator - - wasn't it supposed to be stable to ~0.1ppb, not five? "

My reading is that as built, the unit had a stable bias of about about 9.2 hz with unstated error bars on that measurement. The "ultrastable" bit is that during a given period, the output frequency is not allowed to VARY more than a certain tiny amount from the value at the start of the period.

Bruce: As I recall gravel-voiced Dirksen's quote went "A million dollars here, a million dollars there, sooner or later you're talking about real money." Since that was in the mid 60's, that was before the Johnson/Nixon/Ford/Carter inflation cycle, when a million dollars was still real money. Got your WIN (Whip Inflation Now) button?

[The Messenger]

"Ten Hz is a lot of bending in an ultrastable oscillator - - wasn't it supposed to be stable to ~0.1ppb, not five? "

My reading is that as built, the unit had a stable bias of about about 9.2 hz with unstated error bars on that measurement.  The "ultrastable" bit is that during a given period, the output frequency is not allowed to VARY more than a certain tiny amount from the value at the start of the period.

That's a reasonable interpretation, but I wish they were clearer. It is a strange way to state that the there was an off-the-floor bias of 9.2 Hz.

Wanna try another one:

Here:

Is the Fourier transform off the two rotational accelerometers:

http://www.nature.com/nature/journal/v438/...ure04347-s2.pdf

Now, it is a given that the rotational acceleration is very small and these probes are near the limits of sensitivity. For the first ~18 minutes, there is a fairly strong, even frequency of about 0.75 Hz, and a weaker harmonic at ~1.5 Hz.

After this, the signal is very noisy, but at ~ hour 10.6, a pair of 1Hz signals emerge and differentiate to 0.5 and 1Hz @ hour 11.

What I do not see, is how a rotational signal that started at 7Hz, slowed to zero, then went to -10Hz, and finally tailed off to zero was extracted from this data.

[edstrick]

Dunno. I've got to transfer the Nature PDF files to a winXP puter with acrobat reader 7 and print the suckers and sit down and READ them. Acrobat reader 6 on my net-configured win98se machine is increasingly unable to properly render current PDF files. (mumble... mumble) Version 7 doesn't install under win98.