[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.)

[edstrick]

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