[X] My Assistant

[Guest_AlexBlackwell_*]

The above-titled paper by Barnes et al. is being published online today in Geophysical Research Letters.

[volcanopele]

grr, even co-Authors would have to pay 9 bucks since I'm a "non-subscriber..."

I think I can dig up the corrected proof from my email if anyone has any questions.

[Guest_AlexBlackwell_*]

Though slightly off-topic, there's also an interesting paper by the VIMS team (Rodriguez et al.) about observations of the Huygens landing site. The paper is currently in press with Planetary and Space Science, and, if I'm not mistaken, some of the results were previewed at COSPAR or LPSC.

[volcanopele]

Though slightly off-topic, there's also an interesting paper by the VIMS team (Rodriguez et al.) about observations of the Huygens landing site. The paper is currently in press with Planetary and Space Science, and, if I'm not mistaken, some of the results were previewed at COSPAR or LPSC.

Thanks for the heads up. I like the last sentence of the abstract:

"The images show also a morphological structure that can be interpreted as a 150 km diameter impact crater with a central peak." Just goes to show how you have to be careful when interpreting albedo features. Let's just say it isn't an impact crater (or a volcano before anyone tries to jump in).

[remcook]

Jason, I can't access the article right now... Is this the same bright spot as here:

http://photojournal.jpl.nasa.gov/catalog/PIA07877

also, I would love to hear some general things about Titan's geology in layman's terms. My limited knowledge about Titan only starts above the tropopause... Can you point me to some good reference or paper? The only thing i've read is Ralph Lorentz's book...

[volcanopele]

No, that's Hotei Arcus. The study area can be seen in this ISS image:

http://photojournal.jpl.nasa.gov/catalog/PIA06192

And in this VIMS mosaic (the bright region at lower right, in SW Xanadu):

http://photojournal.jpl.nasa.gov/catalog/PIA06983

Now this paper describes a possible cryovolcanic flow, identified in VIMS and ISS data, in the western portion of Tui Regio. I have attached PIA06192 with the flows outlined in the paper highlighted. There are outlined based on their unique spectral signature compared to the surrounding terrain in southwestern Xanadu, and by their appearance in higher resolution ISS data from Tb (PIA06192 is from T3 last February). These features are identified as cryoflows based on their lobate structure, size (a landslide of this magnitude would require an altitude difference of 3km to for a deposit), and non-radiality (so it isn't ejecta from an impact crater). We also argue that "bluish" terrain in the VIMS data surrounding western Tui Regio is due an airfall deposit from this volcano. We argue that the ISS data suggests that the morphology of the flow is influence by pre-existing local topography, particularly a 60 km wide circular feature northwest of the flow source that maybe an impact crater.

Attached thumbnail(s)

 

[remcook]

thanks! any idea how the spectral differences translate to a difference in composition,e.g. more 'watery', or more 'tholiny', more ammonia, or more 'strange stuff that Huygens found'?

[volcanopele]

for those without access to GRL, the main author, Jason Barnes, has kindly put the paper on his website: http://c3po.barnesos.net/publications/papers/westTui.pdf

[ngunn]

for those without access to GRL, the main author, Jason Barnes, has kindly put the paper on his website: http://c3po.barnesos.net/publications/papers/westTui.pdf

Very useful - thanks to both Jasons!!

[ngunn]

Though slightly off-topic, there's also an interesting paper by the VIMS team (Rodriguez et al.) about observations of the Huygens landing site. The paper is currently in press with Planetary and Space Science, and, if I'm not mistaken, some of the results were previewed at COSPAR or LPSC.

I can't get this link to work. Any chance you (somebody?) could post the Rodriguez et. al. abstract?

[remcook]

I can't get this link to work. Any chance you (somebody?) could post the Rodriguez et. al. abstract?

this better? link

[ngunn]

this better?

Yes that's done it, thanks.

[Guest_AlexBlackwell_*]

Thanks for editing the link. Some forums have problems with the super-long URLs, which is why I used makeashorterlink.com to truncate it down to bite size. However, it appears that some people have problems accessing makeashorterlink.com, or that the site is frequently down, which defeats the whole purpose.

In any event, there's a newly posted VIMS preprint in Planetary and Space Science by Buratti et al.

[remcook]

Jason and Jason,

perhaps a stupid question: if the tendrils are from the volcano and their relative 5 um brightness correspond to their relative age, then what is the rest of Tui Regio (which, from the VIMS image, doesn't seem to be much different from the tendrils in composition) and why can't you use the same reasoning to say something about its relative age (but then it wouldn't be centred around the possible volcano)? Also, are there more tendrils on the east site of the regio?

[Jason W Barnes]

Jason and Jason,

perhaps a stupid question: if the tendrils are from the volcano and their relative 5 um brightness correspond to their relative age, then what is the rest of Tui Regio (which, from the VIMS image, doesn't seem to be much different from the tendrils in composition) and why can't you use the same reasoning to say something about its relative age (but then it wouldn't be centred around the possible volcano)? Also, are there more tendrils on the east site of the regio?

I didn't talk about eastern Tui Regio for two reasons: (1) both the VIMS and ISS data there are of significantly lower resolution, and (2) I wanted to keep the article concise enough to fit into a Letter. The east is even brighter, and is certainly interesting! Hopefully we'll get some higher resolution on it in the coming flybys.

- Jason

[The Messenger]

Thanks for the heads up. I like the last sentence of the abstract:

"The images show also a morphological structure that can be interpreted as a 150 km diameter impact crater with a central peak." Just goes to show how you have to be careful when interpreting albedo features. Let's just say it isn't an impact crater (or a volcano before anyone tries to jump in).

...And it is certainly not an oblisk Is there any spectroscopic data on this non-volcanic, non-impact roundish thingy? Huygens seems to have viewed it from many angles - ~ 15 degrees to more than 90 - or is there more than one of these 'wormholes' in the DISR images?

[volcanopele]

...And it is certainly not an oblisk Is there any spectroscopic data on this non-volcanic, non-impact roundish thingy? Huygens seems to have viewed it from many angles - ~ 15 degrees to more than 90 - or is there more than one of these 'wormholes' in the DISR images?

whoa there, DISR never saw this feature, it was way too far to the north and west.

In terms of what it is, it doesn't really look like anything special, just a dark region with a group of hills in the middle.

[The Messenger]

whoa there, DISR never saw this feature, it was way too far to the north and west.

In terms of what it is, it doesn't really look like anything special, just a dark region with a group of hills in the middle.

We report here on the analysis of VIMS images of the Huygens landing site acquired at TA and TB, with a spatial resolution ranging from 16 to14.4 km/pixel... Although pure water ice cannot be the only component exposed at Titan's surface, this area is consistent with a local enrichment in exposed water ice and seems to be consistent with DISR/Huygens images and spectra interpretations. The images show also a morphological structure that can be interpreted as a 150 km diameter impact crater with a central peak.

So the consistency they are talking about is in terms of signature, not a specific feature

[remcook]

More interesting surface results from VIMS: here

edit-this paper also deals with the apparent 'craters' mentioned by Jason: they also say they are not craters.

[Quintessence]

I remember reading a pdf form the LPI website called "Titan's Enigmatic 5-Micron-Bright Terrain" where it says that in the eastern Tui Region Eir Macula is located there and is basically related to the region.

Just a question could Eir Macula be repsonsible for the flow like features and could it still be active.

[remcook]

The flows discussed in the paper above are in a different regio, so the short answer would be 'no'. That spot in Tui Regio does show temporal variations, as also stated in the Nelson et al. paper mentioned in the previous post. This may possibly indicate active volcanism, but that needs to be researched more. It may also be something else. Interesting in any case!

[volcanopele]

edit-this paper also deals with the apparent 'craters' mentioned by Jason: they also say they are not craters.

hehe, well, I would take some of that with a big grain of salt I'm sure they looked at Guabonito, a fairly prominent circular feature near the boundary between Shangri-la and Xanadu. RADAR, at least from my prospective, confirmed our suspicion that it was an impact crater that has been almost completely buried by the equatorial sand seas.

BTW, they claimed that they thought the two circular features they looked at were palimpsets, which are just completely viscously relaxed impact craters. Again, I just think that a lot of these craters are getting filled in by sand (think Victoria on Mars, how a lot of it has been filled in by sand).

[remcook]

yes, that idea got mentioned as well

[remcook]

more surface goodies from VIMS at PSS:

here

Composition of Titan's surface from Cassini VIMS

T.B. McCorda, G.B. Hansenb, B.J. Burattic, R.N. Clarkd, D.P. Cruikshanke, E. D’Aversaf, C.A. Griffithg, E.K.H. Bainesc, R.H. Browng, C.M. Dalle Oree, h, G. Filacchionef, V. Formisanof, C.A. Hibbittsi, R. Jaumannj, J.I. Luninef, g, R.M. Nelsonc, C. Sotink and the Cassini VIMS Team

[The Messenger]

more surface goodies from VIMS at PSS:

here

Composition of Titan's surface from Cassini VIMS

T.B. McCorda, G.B. Hansenb, B.J. Burattic, R.N. Clarkd, D.P. Cruikshanke, E. D’Aversaf, C.A. Griffithg, E.K.H. Bainesc, R.H. Browng, C.M. Dalle Oree, h, G. Filacchionef, V. Formisanof, C.A. Hibbittsi, R. Jaumannj, J.I. Luninef, g, R.M. Nelsonc, C. Sotink and the Cassini VIMS Team

Our results show that the spectrum of water ice contaminated with a darker material matches the reflectance of the lower albedo Titan regions if the spectral slope from 2.71 to 2.79 μm in the poorly understood 2.8-μm methane window is ignored.

So, would that be a little water ice, no 'tholins', and darker material? What would it be if the 2.8um methane window is not ignored?

[remcook]

The fit of the water ice to the spectral windows is quite good even when this window is taken into account. The point they're making is that that window is actually two small sub-windows, very close to eachother, and the derived 'spectrum' of the surface between these two points has an opposite slope to water ice. However, it may be that that's just an artifact of the way they correct for the methane absorption in the atmosphere. Like they say - it's a poorly understood region in the methane spectrum. So if improved measurements of methane absorption in this region is obtained it may be that the slope is much more similar to water ice. All other windows seem to point that way.

[remcook]

...and more

here

Titan's surface albedo variations over a Titan season from near-infrared CFHT/FTS spectra

A. Negrão, A. Coustenis, E. Lellouch, J.-P. Maillard, P. Rannou, B. Schmitt, C.P. McKay and V. Boudon

[The Messenger]

...and more

here

Titan's surface albedo variations over a Titan season from near-infrared CFHT/FTS spectra

A. Negrão, A. Coustenis, E. Lellouch, J.-P. Maillard, P. Rannou, B. Schmitt, C.P. McKay and V. Boudon

Indeed, we find our data to be compatible with mixtures of water ice and tholin but have strong indication for the presence of an additional, as yet unidentified, component (or components) for which we offer a spectral description.

So, with one interpretation of the methane window slope the results are compatible with water-ice and 'tholins'; but in the other, the surface is compatible with water-ice, but not 'non-oxidized tholins'. In either case, there is unidentifiable, unknown spectra. I'm not sure how to characterized these reports - perhaps they are over-educated guesses: Are the researchers so certain of what they expect to see, that they are overlooking candidate molecules simply because they don't expect to find them? I understand the slopes are difficult to determine through the small spectral windows, but without a clue about what the 'unknown species' is, any qualification or quantification is iffy.

We know that what we are looking at has many of the physical properties of common silicates - sand. I would expect methane rain to transport ethane and other organics through a sandy silicate base - which would explain why ethane has not built up in large pools, other than perhaps in the polar regions. Are these research teams even considering the possibility that this is a very terrestrial surface?

[remcook]

The slope in the above paper, and all other papers except the mention of the slope of the two sub-windows near 2.8 um in McCord et al., are the slopes from one window to the next. For VIMS for instance, the "surface spectrum" is basically defined by 6 or 7 points, each at the position of a different methane window. The relative intesities of these points are then compared to spectra of e.g. water or tholin.

The Negrao et al. paper has much higher spectral resolution, but these are disc-averaged spectra. Also, they cannot yet fit the fine structure in the windows, but their point about the unidentified component refers to one very low point in the spectra for Titan's trailing side.

I think the story so far is (surprisingly):
dark material = water + perhaps little tholin
light material (Xanadu etc) = ???

About looking for different materials, here's a bit from McCord et al.:

"We also checked for matches with other material spectra. Obvious candidate materials are simple organics and cyanide molecules. We note, however, that many of these show considerable spectral structure in the 5-μm window region that is not seen in the Titan spectra (Fig. 12). We ran a comparison check of these Titan reflectances at the specific window wavelengths with the USGS spectral library (Clark et al., 2003 and Clark et al., 2005), including over 2000 spectra. Some interesting compounds that provide partial matches to Titan's normbrit and ddark spectra, when combined with a neutral absorber, are given in Table 8, including pyrene, decane, paraffin, and KCN. The long wavelength reflectances match Titan well, including the 2.79/2.71 μm reflectance ratio, but the 1.28-μm reflectance deviates from that derived here for Titan."