[X] My Assistant

[volcanopele]

This thread is intended as a discussion of Titan's surface features, possible analogs, wild ideas, etc. To get started, I am posting a list below of all relevent images along with observation request name so everyone is on the same page. The images to be released today will certainly provide plenty of fodder for discussion.

Pre-SOI
Approach Map
http://ciclops.lpl.arizona.edu/view.php?id=214

Reprocessed Approach Map
http://ciclops.lpl.arizona.edu/view.php?id=482

T0
SPOLEB
http://ciclops.lpl.arizona.edu/view.php?id=253

WIND002
http://ciclops.lpl.arizona.edu/view.php?id=252

Approach Map + SPOLEB
http://ciclops.lpl.arizona.edu/view.php?id=627

Ta
MOVIEB frame
http://ciclops.lpl.arizona.edu/view.php?id=515

LRMONITOR (unprocessed)
http://ciclops.lpl.arizona.edu/view.php?id=519

Ta MONITOR
http://ciclops.lpl.arizona.edu/view.php?id=575

Ta Early processing Montage
http://ciclops.lpl.arizona.edu/view.php?id=533

MEDRES002
http://ciclops.lpl.arizona.edu/view.php?id=541

HIRES frame showing Huygens landing site area
http://ciclops.lpl.arizona.edu/view.php?id=535

Tb

MOVIED
http://ciclops.lpl.arizona.edu/view.php?id=654

EUVFUV002
http://ciclops.lpl.arizona.edu/view.php?id=657

[Guest_Sunspot_*]

Cool, thanks for posting these.

Any more theories on what the dark areas might be? As large bodies of liquid seem to have fallen out of favour could we be seeing regions where the crust has pulled apart exposing darker material from below?

[volcanopele]

Here are some more. Hope you like them.

Ta

Ta_REGMAP
http://photojournal.jpl.nasa.gov/catalog/PIA06158

Tb

Tb_REGMAP
http://photojournal.jpl.nasa.gov/catalog/PIA06159

MOVIEC
http://photojournal.jpl.nasa.gov/catalog/PIA06154

[Guest_Sunspot_*]

Here are some more. Hope you like them.

Ta

Ta_REGMAP
http://photojournal.jpl.nasa.gov/catalog/PIA06158

Tb

Tb_REGMAP
http://photojournal.jpl.nasa.gov/catalog/PIA06159

MOVIEC
http://photojournal.jpl.nasa.gov/catalog/PIA06154

What a coincedence, I just found these images on the Cassini press release images page and not having seen them before was going to post links to them

[Guest_Sunspot_*]

So we maybe seeing the first evidence of impacts on Titan in the image below... which of the flybys will give us the best view of this hemisphere? Have scientists completely ruled out the possibilty that these dark areas could be liquid?

[volcanopele]

So we maybe seeing the first evidence of impacts on Titan in the image below... which of the flybys will give us the best view of this hemisphere? Have scientists completely ruled out the possibilty that these dark areas could be liquid?

In T3 we get a SAR swath over that multi-annulus structure. T4 I know we get coverage over the sub-Saturnian hemisphere.

[alan]

Whats the difference in brightness between the bright and dark areas. How does this compare to features on other moons, for example the difference between the mare and highlands on the moon or the bright and dark terrain on Ganymede.

[volcanopele]

Dark terrain: liquid or not? Well, based on the data returned from VIMS and ISS, the dark terrain seen in Ta and Tbis likely not liquid, or at least not all of if. However, this doesn't rule out smaller patches of liquid, perhaps like Sisi's cat from the Ta RADAR swath. In addition, the dark features seen in SPOLEB from T0 seem to be more consistent morphologically as bodies of liquid. Regarding the albedo difference, VIMS at 2 microns says that its an order of magnitude. ISS at 938 nm seems to show at 20-30% difference.

[volcanopele]

The order of magnitude could also come from comparing the brightest Titan terrain in SE Xanadu and the darkest terrain SE of Great Britain. Keep in mind that out side of the definied dark terrain and Xanadu, much of Titan is in shades of grey. But even then I don't think we are seeing an order of magnitude difference (by we, I mean ISS)

[Guest_Sunspot_*]

http://news.com.com/Tantalizing+clues+in+p..._3-5495111.html

Meanwhile, the "ocean" on Titan may not be. Instead of a liquid body of water, the dark mass seen on the surface of the Titan may be a viscous fluid flowing onto the white "coastline," Parco said. Then again, the viscous fluid could be flowing down from a higher altitude, like a glacier, onto the white mass.

Right now, researchers only have two-dimensional images. Often, scientists look at the images and analogize it to information they know about on Earth, such as island chains or coastlines, she said. Stronger conclusions may be possible with the availability later of images that are more precise, or stereoscopic images that include shadows or information on altitude.

Some typos in that artice lol...and I think they probably meant to say liquid methane.

[Guest_BruceMoomaw_*]

I'll stick by my earlier theory: it's been remarked on at two press conferences now that the dark streaks look very much as though they've been laid down by Titan's west-to-east winds -- and when you look at the bright "islands" in the middle of the darker area in that latest image, you see areas of an intermediate gray albedo consistently pointing downwind from the islands. (These are very clear to anyone, and they too were mentioned at Thursday's AGU press conference.)

I think the dark material has been, to a very great degree, wind-distributed. I think it consists largely -- and perhaps entirely -- of solid particles of dark organic smog, blown over the surface in the same way as Mars' fine dust, and thus tending to accumulate in low-lying parts of Titan's surface (and also resulting in gray "wakes" of reduced dark material in the leeward wind shadows of the higher-altitude bright "islands"). Dimitrov and Bar-Nun reported in the Feb. 2002 Icarus that their lab experiments indicated that Titan's solid smog particles are likely to be hard-surfaced and non-sticky, greatly increasing the extent to which they can be wind-blown even after landing.

The real question in my mind is how the slow rain of liquid ethane which is also supposed to be radiation-generated in Titan's upper atmosphere affects all this. Does it provide a further means by which the solid dark smog particles are washed off higher-altitude terrain? Does it mix with the smog particles to form a sludgy cryogenic mud (which -- due to the very low vapor pressure of liquid ethane in Titan's atmosphere -- would literally never dry out and harden)?

[volcanopele]

both are good possibilities, Bruce. However, one of my thoughts is that the bright stuff is the hardened particulates getting blown down wind. There are other possibilitites. Cool ones. The idea that the dark material is a high viscosity mix of particulates and ethane, or some gunk is one I like as well.

[alan]

This thread is intended as a discussion of Titan's surface features, possible analogs, wild ideas, etc.

I'll start with a wild idea. The dark area on Titan is a much larger version of these features on Europa

http://photojournal.jpl.nasa.gov/jpegMod/PIA02099_modest.jpg
http://photojournal.jpl.nasa.gov/jpegMod/PIA01125_modest.jpg
http://photojournal.jpl.nasa.gov/jpegMod/PIA01127_modest.jpg

It circles nearly all the way around the equator because it hapened before titan was tidally locked.

[NorbertGiesinger]

Why should Titan be tidally locked - what means it ???

It is in a quite eccentric orbit with e=0.029. As a consequence, there will be quite substantial tides with about 15.945 days full period and a magnitude for an ideal fluid sphere in the range of 20 meters or more.

There are tides on the "tidally locked" but eccenric orbiting earth moon, there are enormous tides on Jo with a very small forced eccentricity.

I have somme feeling that in recent months, the tidal influence is somewhat neglected..
If I remeber correctely, the late Carl Sagan made some (published) calculations, showing that a fluid surface must be 400 m or more deep in order to keep the tidal backreaction onto the eccentricity low.

I wonder why Titan has such a high eccentricity - it cannot be forcing of other moons - their mass is rather small.

[alan]

By not being tidally locked I meant while it was still rotating with respect to Saturn rather than rocking because of the eccentricity like it is now. The dark areas appear to be in a band around the equator, that seemed to be the simplest explanation. Like I said this is a wild idea.

[alan]

No other comments? I guess that idea was too "wild"

[alan]

I found something similar to the bright teardrop with the dark circle at one end
a volcano on Venus with a cometlike tail

[Guest_Sunspot_*]

There are lots of "Tear Drop" shaped islands on Mars too


http://wapi.isu.edu/geo_pgt/Mod09_Mars/str...ned_islands.htm

[volcanopele]

Alan, I don't think your idea is too wild. In fact, I favor a slightly modified version of it. The trails maybe wakes, not wind streaks. The tear shaped island maybe a wind streak or a volcano.

[alan]

I thought maybe I was thinking too big. Some of the "islands" in the dark area have sharp boundaries like icebergs. Many of them have jagged dark lines through them, some were refering to them as rivers, that look like fractures to me. Perhaps they were starting to break up when they froze in place, or cracked afterwards because of the tides.

[Guest_BruceMoomaw_*]

It was indeed pointed out by Carolyn Porco at Thursday's news conference that we still aren't even sure yet whether the white stuff or the dark stuff is the overlying particulates -- although in all the earlier articles I've seen on near-IR Titan photos taken from Earth, the dark stuff has been interpreted as hydrocarbons and the light stuff as exposed water (or water-ammonia) ice.

While most of those additional photos of Titan taken during the October flyby which JPL so mysteriously stuck up on the Raw Images pages last night are utterly useless (and, in fact, pitch black), there are a few very good ones taken by the wide angle camera from close range -- in fact, I think these are the best ISS photos of Titan I've seen so far. (See, for instance, the first one at http://saturn.jpl.nasa.gov/multimedia/imag...eiImageID=25980 ). One phenomenon that I think I'm starting to notice in them is that the dark stuff actually tends to center around only two clearly distinguishable albedo levels: one very dark and the other intermediate gray. If so, could the gray stuff be windblown solid smog by itself (perhaps frozen acetylene?), while the really dark stuff is liquid ethane as well? Or are my eyes deceiving me, so that there really is a gradual transition instead between different albedo levels in the darker areas?

By the way, JPL has also mysteriously yanked all the new photos of Dione off the Raw Images page and substituted some very long-range and utterly useless photos of it from the October Titan flyby period. I have no idea what they're up to. Maybe a black monolith turned up on Dione or something.

[Guest_BruceMoomaw_*]

As for Alan's idea -- that is, that the dark stuff has actually oozed up out of Titan's subsurface, as the dark stuff on Europa's surface did -- you still have to explain the streaky patterns and "wakes" on Titan, which have no Europan analog and still suggest wind distribution.

[alan]

If I remember 2001 right, the book not the movie, the monolith was on Iapetus. Trying to decide whether the light material is on top of the dark or vice versa is hard. Some of the bright "islands" appear to have gray trails leading from them. Then when you get to the edge of the dark area the dark material appears to extend inland in the "bays"

[alan]

The wakes could be from the dark material flowing toward low lying areas after it broke through the crust. The NE part of the dark area appears similar to estuaries, flooded river valleys. On Europa there are domes near the chaos areas, the dark material could flow out to nearby areas after the dome burst and collaped.

[alan]

Near the bottom of this image there is a dome with a crack through it. The area around is has sunk. Next to it there is some chaos terrain where the area around it which has sunk is flooded.
http://photojournal.jpl.nasa.gov/jpegMod/PIA00590_modest.jpg

[alan]

Something I've been reading that may apply to the annulus, possible crater to the NE

"Lorenz (1994) highlighted a fascinating implication for the effect of bedrock solubility in Titan's surface fluid on crater morphology. Lorenz demonstrated that craters should fill with liquid ethane to produce crater lakes, and that standard variations on crater shape (such as central peaks, multiple rings, and domed centres from viscous relaxation of the substrate could generate 'ring' and 'bullseye' lakes. Furthermore, an assessment of the magnitude and direction of tidal currents indicates that these rings and bullseyes could become smeared out to form 'horseshoes' oriented towards the anti-Saturn point (0°N, 180°E). In the event that neither chemical or mechanical erosion is equal to the task of smearing out these lakes we may observe some unusual drainage patterns as lakes break their banks along one margin and then drain back as tides rise and fall."

http://www.es.ucl.ac.uk/research/planetary...titan/chap7.htm

[Guest_Sunspot_*]

By the way, JPL has also mysteriously yanked all the new photos of Dione off the Raw Images page and substituted some very long-range and utterly useless photos of it from the October Titan flyby period.  I have no idea what they're up to.  Maybe a black monolith turned up on Dione or something.

Very weird, nearly 2 months worth of images have disappeared from the RAW image webpages.

[alan]

If the dark areas were a slushy material how would it be effected by the tides? Would it produce recognizable erosion patterns, or ridges along the margins?

[Guest_BruceMoomaw_*]

Flash: JPL has just restored all its new Cassini raw images. (They must be finished scrubbing the monolith off the Dione photos...)

[Guest_BruceMoomaw_*]

Alan: "If the dark areas were a slushy material how would it be affected by the tides? Would it produce recognizable erosion patterns, or ridges along the margins?"

Good question -- I presume it would depend on how viscous it is. I really don't think we're going to be able to reach ANY conclusions about this, even tentative, until the Huygens descent -- and even then it may take months of radar and high-resolution VIMS data afterwards to put the pieces of the puzzle together properly. About the one thing we can say with confidence is that the dark stuff -- or most of it -- is not your standard-style liquid dark hydrocarbon sea.

[alan]

Bruce, If the dark material is being blown around why are there no smaller dark areas? I was thinking of slushy material in the "seas" as a way of confining it, once it lands there it stays. Of course if there are slushy seas you would expect there to be a drainage network leading to it which I haven't seen yet. Do you have any other suggestions?

[alan]

I hope that if Huygens's land in windblown material if isn't too fluffy. I'd hate to have it land on the surface only to disappear into a "snowdrift"

[alan]

Chaos terrain or plate tectonics

[volcanopele]

alan, great minds think alike Seriously, the more I look at Titan as a whole, the more I see an active world, full of tectonism (and maybe even volcanism). A cross between Triton, Ganymede, Io, Europa, and Venus.

[alan]

"Contemporary volcanic activity ought to be rather easy to detect. The Cassini Visible and Infra-red Mapping Spectrometer (VIMS) will map parts of the surface through the atmospheric window at 5.1µm. An ammonia-water cryomagma at a peritectic temperature of 176K will emit twenty times more radiation at this wavelength than the surrounding landscape radiating at ~94K, contrasting quite strongly, particularly in images of the night hemisphere of Titan (Baines et al, 1992)."

Hmm that bright semicircle looks suspicious

http://photojournal.jpl.nasa.gov/jpegMod/PIA06154_modest.jpg

[volcanopele]

True, true. That bright semi-circle hasn't been seen by VIMS yet (the image you point to was just an ISS image at 938 nm, not 5.1 um). I'll need to check the T0 data to be sure.

[alan]

I thought it was a VIMS image, it had a grainy appearance like their earlier releases.

[alan]

and maybe even volcanism

Maybe you say, I suspose you can't come out and say so until you have definite proof. To me half of this image appears to be covered with lava flows, everything that isn't dark green in the colorized version.

http://photojournal.jpl.nasa.gov/jpegMod/PIA06992_modest.jpg

Tthe wrinkled area is interesting, it looks like the lava flowed slowly through two passes in a ridge, it cooled on the other side forming a crust which wrinkled as more built up behind it. Eventually it burst through another ridge to the right flooding the area beyond.

[alan]

Some lava flows on Venus and Io for comparison

Venus from Magellan using SAR

http://photojournal.jpl.nasa.gov/catalog/PIA00099
http://photojournal.jpl.nasa.gov/catalog/PIA00486
http://photojournal.jpl.nasa.gov/catalog/PIA00471
http://photojournal.jpl.nasa.gov/catalog/PIA00082

Io from Galileo

http://photojournal.jpl.nasa.gov/catalog/PIA02539
http://photojournal.jpl.nasa.gov/catalog/PIA02557
http://photojournal.jpl.nasa.gov/catalog/PIA02568
http://photojournal.jpl.nasa.gov/catalog/PIA02598

Enjoy

[alan]

If I'm linking to images of lava flows on a mars forum I should include some from mars too. Here are some from Mars Odyssey, THEMIS images

http://themis.asu.edu/zoom-20040805A.html
http://themis.asu.edu/zoom-20040622A.html
http://themis.asu.edu/zoom-20030731a.html
http://themis.asu.edu/zoom-20031117a.html

Some lava flows on Earth

http://visibleearth.nasa.gov/cgi-bin/viewrecord?1719
http://visibleearth.nasa.gov/cgi-bin/viewrecord?253
http://visibleearth.nasa.gov/cgi-bin/viewrecord?1577
http://visibleearth.nasa.gov/cgi-bin/viewrecord?1361

[Guest_Sunspot_*]

Plunge into an Alien World

http://www.space.com/scienceastronomy/tita...ies_041221.html

[alan]

VIMS from July, right image is at 5 microns, there are three bright spots, one is the clouds over the pole, one near the bright semicircle, and another near the center of the image. Hot spots or mid latitude clouds?

http://photojournal.jpl.nasa.gov/jpegMod/PIA06404_modest.jpg

[Guest_Sunspot_*]

http://news.bbc.co.uk/1/hi/sci/tech/4115251.stm

Titan probe gets early alarm call

The Huygens space probe will be woken up from its slumber four hours before its January descent into the smoggy atmosphere of Saturn's moon Titan.

Ground controllers are waking Huygens up earlier than originally planned to boost data transmission from the probe.

[alan]

Dammit Sunspot, I saw I saw alarm in bold thought something was wrong

[alan]

The dark area on Titan always looks like an ocean to me so I tried inverting the image, reversing white and black, to see if it wouldn't look like an ocean that way. Nope still looks like an ocean to me. Of course now I got something else stuck in my head, take a look at the southern portion of this image, tell me what you see.

[alan]

Anyone know what the opposite of a specular reflection would be called? What type of material would produce this effect?

[CosmicRocker]

Anyone know what the opposite of a specular reflection would be called?  What type of material would produce this effect?

I'm not sure, but specular reflections are usually described as mirror-like or directional, so one interpretation of the opposite of that might be diffuse reflection.

I suppose another way to consider an opposite might be no reflection at all, or a black body.

[alan]

I was looking at my inverted image and noticed it was brightest at the center, making the original darkest at the center, the opposite of what you would get for specular reflection. After thinking about it for a while I realized its probably just the result of the haze. At first I was thinking the dark surface could be something like velvet

[alan]

I've been thinking about how the area Cassini has been focusing on could be explained using plate tectonics as a model. In the northwest the cracks are oriented to parallel to the coastline. In the southeast they are orinted perpendicular to it. The dark area between them couldn't be spreading because they don't match. Some of the islands appear to be rotated so I'm thinking this could be an area where plates are sliding against each other like the Pacific plate against California. Don't know if this can be confirmed but its an interesting idea.

[imran]

Interesting article:

Titan: Many Lines of Evidence Converge on the Result That Titan is Puzzling
http://www.planetary.org/news/2004/cassini...sults_1221.html

[alan]

When I first inverted this image I thought Titan has icecaps!



Now that i've taken a second look at it I see that some features are visible through it but are softer and it has a diffuse boundary. It looks more like snow cover. It would explain why the rough features disappear away from the dark area, I thought they were related at first. It also creates an interesting possibility. In satellite images of the earth after a snowstorm you can still see bodies of water like in these images

http://www.gesource.ac.uk/worldguide/html/image_244.html
http://www.gesource.ac.uk/worldguide/html/image_218.html
http://visibleearth.nasa.gov/data/ev31/ev3...72175909_md.jpg
http://visibleearth.nasa.gov/data/ev50/ev5...99074181820.jpg

Because of this it may be easier to locate pools of liquid in the southern areas

[Guest_BruceMoomaw_*]

Alan: "Bruce: If the dark material is being blown around why are there no smaller dark areas? I was thinking of slushy material in the 'seas' as a way of confining it, once it lands there it stays. Of course if there are slushy seas you would expect there to be a drainage network leading to it which I haven't seen yet. Do you have any other suggestions?"

Well, there are -- there are detached horizontal streaks all over the place. One might ascribe them to liquid material accumulating inside tectonic grooves like those on Ganymede (and Saturn's smaller icy moons), but the post October-flyby press conference described them flatly as resembling streaks of windblown material deposited by west-to-east winds, as indicated by their shape.

HOWEVER: one very interesting new development. Athena Coustenis -- probably the leading expert on the pre-Cassini near-IR photos of Titan's surface taken by ground telescopes and Hubble -- says in a new interview ( http://www.space.com/scienceastronomy/tita...ies_041221.html ) that she's now quite certain that the light-colored parts of Titan's surface are NOT exposed water ice:

"Many people think the dark patches are hydrocarbon lakes, and the bright patches must be a solid material like ice. I think the dark areas could be hydrocarbon lakes, because their albedo -- their reflectivity -- is very low. But I don't think all the dark patches have to be hydrocarbon liquid, because water ice also is dark at infrared wavelengths.

"There are also intermediate regions where the bright and dark appear mixed. That could be slush, or mud, or something solid but with material in the pores. I like the idea of a porous surface, because even if the hydrocarbon lakes are there, they cannot account for the total amount of methane in the atmosphere. In my opinion, you're going to need a subsurface reservoir.

"I think the bright patches are only consistent with hydrocarbon ice. They cannot be water ice, because water ice is dark in two of the wavelengths we're looking at. But hydrocarbon ice is bright in all the wavelengths. So the bright regions could be plateaus or mountains with hydrocarbon ice on top. In order to get hydrocarbon ice, you have to have a mountain -- a high elevation -- and then the hydrocarbon can precipitate on top of that like snow."

If so, this could turn all my ideas topsy-turvy. I don't know what to think at this point; we'll have to wait for Huygens to get clearer ideas, apparently. (Frozen acetylene and its polymers -- which are thought to be by far the main solid component of Titan's smog -- is silver-white in color unless it has contaminants mixed in, but the latter can darken it dramatically.)

[alan]

So hydrocarbon ice is dark, I guess my snow cover idea may be wrong then. Perhaps the darkening to the south is cloud cover, would explain the lower contrast features. You can see the clouds are darker in the south in this image

http://ciclops.lpl.arizona.edu/view.php?id=651

but the boundary at the wrong latitude, maybe it shifted.

[David]

The dark area on Titan always looks like an ocean to me so I tried inverting the image, reversing white and black, to see if it wouldn't look like an ocean that way. Nope still looks like an ocean to me.

With the inverted brightness, the "ocean" reminds me of satellite pictures of the Sahara, with dark highlands emerging from beneath a sea of white sand.

[Decepticon]

Will cassini do any science during the Landing?

Or will she just listen to Huygens signal?

[djellison]

Will cassini do any science during the Landing?

Or will she just listen to Huygens signal?

Just listen. There's quite a lot of effort gone into making sure that it does nothing but get every bit of huygens data - it's the last of the critical manouvers - the previous two being SOI and the Per.Raiding manouver. - so there's lots of code gone to make sure it doesnt safe itself at any point.

Doug

[Mongo]

I would like to draw averyone's attention to a fantastic map of Titan's surface, incorporating information from each of Cassini's flybys to date:

http://laps.fsl.noaa.gov/albers/sos/saturn...cyl_041206b.jpg

This is from a very interesting site with various improved maps of solar system bodies:

http://laps.fsl.noaa.gov/albers/sos/sos.html

Bill

[Decepticon]

Umm yeah.... I posted that earlier in the other thred.

You should really give credit where its due.

[Mongo]

Right. Credit goes to Steve Albers: http://laps.fsl.noaa.gov/cgi/albers.homepage.cgi

[alan]

Question, if the dark areas in the global map are rift zones where the crust is spreading where is it going? It may be subducting near the north pole. Would this cause the pole to appear flattened?
http://saturn.jpl.nasa.gov/multimedia/imag...fm?imageID=1256

[David]

Question, if the dark areas in the global map are rift zones where the crust is spreading where is it going? It may be subducting near the north pole. Would this cause the pole to appear flattened?

I can't imagine that it would. If Titan is really 'flatter' at the pole, it would seem to be a much larger-scale effect than anything you could attribute to tectonics; this is, after all, a body that's larger than Mercury. Anyway, all we're seeing in that picture is atmosphere; the dimensions of the atmosphere need not exactly reflect the dimensions of the solid body. Perhaps the atmosphere is thinner at the pole for some reason.

[Guest_BruceMoomaw_*]

I presume that what we're seeing is simply that the top of the dense haze layer is lower at the north pole -- probably because that pole is in winter, whereas the south pole is being warmed more by the Sun and thus atmospheric convection from Titan's warmer troposphere is producing upward-streaming convection currents there. (This is already regarded as the explanation for the methane cloud cap at Titan's south pole. Right now, it's believed that the convection cycles of Titan's atmosphere extend clear between the poles, so that the north pole is seeing a downdraft -- but later this year, it should change into a two-cell Hadley circulation, with downdrafts at both poles and an updraft at the equator. There are two good new articles on this phenomenon, and its effect on Titan's cloud patterns, at http://www.gps.caltech.edu/~mbrown/papers/ps/temperate.pdf and http://www.gps.caltech.edu/~mbrown/papers/...onin_clouds.pdf .)

[alan]

I looked at the articles. The secondary peak in the insolation is responsible for the clouds at 40 degrees south. What causes the clouds to become darker north of there around 20 degrees south?
http://www.nasa.gov/mission_pages/cassini/...a/pia06152.html

[Guest_BruceMoomaw_*]

Actually, Roe's article said that it's only one possibility that the low-latitude clouds are due to that secondary insolation peak -- and added that, if this (rather than Titanian surface features) is their explanation, then some pretty complex meteorological processes must be going on at Titan, which might also explain the still lower-latitude darkening band you noted.

[volcanopele]

I looked at the articles. The secondary peak in the insolation is responsible for the clouds at 40 degrees south. What causes the clouds to become darker north of there around 20 degrees south?
http://www.nasa.gov/mission_pages/cassini/...a/pia06152.html

Don't forget, those are bands are in the stratosphere while the clouds are in the troposphere (and the mid-latitude clouds in the lower troposphere). In terms of what causes them, I prefer the venting possibility but freely admit the jury is still out.

[Guest_AlexBlackwell_*]

I presume that what we're seeing is simply that the top of the dense haze layer is lower at the north pole -- probably because that pole is in winter, whereas the south pole is being warmed more by the Sun and thus atmospheric convection from Titan's warmer troposphere is producing upward-streaming convection currents there.  (This is already regarded as the explanation for the methane cloud cap at Titan's south pole.  Right now, it's believed that the convection cycles of Titan's atmosphere extend clear between the poles, so that the north pole is seeing a downdraft -- but later this year, it should change into a two-cell Hadley circulation, with downdrafts at both poles and an updraft at the equator.  There are two good new articles on this phenomenon, and its effect on Titan's cloud patterns, at http://www.gps.caltech.edu/~mbrown/papers/ps/temperate.pdf and http://www.gps.caltech.edu/~mbrown/papers/...onin_clouds.pdf .)

I'm glad you found my December 28, 2004 post in the Yahoo! planetary_sciences group useful, Bruce. For others, below is the whole post (actually two posts combined):

==============================================

This press release, which is online at

http://pr.caltech.edu/media/Press_Releases/PR12627.html

refers to the Roe et al. paper from the January 1, 2005 issue of The Astrophysical Journal:

Discovery of temperate latitude clouds on Titan
Roe, H.G., A.H. Bouchez, C.A. Trujillo, E.L. Schaller, and M.E. Brown
Ap. J. 618, L49-L52 (2005).

~237 Kb PDF reprint available at
http://www.gps.caltech.edu/~mbrown/papers/ps/temperate.pdf

See also another paper in the same issue:

Statistics of Titan's south polar tropospheric clouds
A.H. Bouchez and M.E. Brown
Ap. J. 618, L53-L56, 2005.

~123 Kb PDF reprint available at
http://www.gps.caltech.edu/~mbrown/papers/...onin_clouds.pdf

[Guest_AlexBlackwell_*]

There's an interesting new preprint entitled "Titan's Wind and Unanticipated Temperature Asymmetry" on the LANL arXiv preprint server.

[David]

Maybe you say, I suspose you can't come out and say so until you have definite proof.  To me half of this image appears to be covered with lava flows, everything that isn't dark green in the colorized version.

http://photojournal.jpl.nasa.gov/jpegMod/PIA06992_modest.jpg

Having now seen what we've all seen from Huygens, I thought I'd go back to previous images, like the one above that alan posted. And now I'm seeing dendritic channels all over the place -- in this example, in the upper left and upper middle of the image. Why didn't I notice them before?

[alan]

Maybe you say, I suspose you can't come out and say so until you have definite proof.  To me half of this image appears to be covered with lava flows, everything that isn't dark green in the colorized version.

http://photojournal.jpl.nasa.gov/jpegMod/PIA06992_modest.jpg

Having now seen what we've all seen from Huygens, I thought I'd go back to previous images, like the one above that alan posted. And now I'm seeing dendritic channels all over the place -- in this example, in the upper left and upper middle of the image. Why didn't I notice them before?

Perhaps because you were told they probably weren't rivers?

[alan]

Someone called the mottled light areas in the sea reefs. I think they may be something similar: outcrops of harder material standing above the dark saturated soil. The bright points seen in some of them may be large boulders sitting on dry land. In this image there appear to be gullies between the brighter areas.

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[Sol]

Someone called the mottled light areas in the sea reefs. I think they may be something similar: outcrops of harder material standing above the dark saturated soil. The bright points seen in some of them may be large boulders sitting on dry land. In this image there appear to be gullies between the brighter areas.

Hi, just now joined this thread. I've read some speculation that the lighter areas are "ground fog," but I'm very skeptical. "Mottled" is a good word, IMO, to describe what we're seeing in the pics; in fact, I used that word myself in a different forum. Seems Titan's surface -- at least the portion we're privileged to see -- is a strange patchwork of dark-against-light and vice versa.

[Guest_Sunspot_*]

I think it's quite possible that the penetrometer struck one of those ice rocks as it hit the surface and continued on in to the ground. This would give the impression of a hard surface overlying a much softer one. John Zarnecki used phrases like "wets sand" or "clay" to describe it. Any hints from the other science intruments on what else they found on the surface?

[djellison]

That doesnt sound too likely given the shape of the impactor force curve they showed on BBC2 on the night of the landing...

It looked a BIT like this ( fuzzy, very tired memory )



The initial spike is indicatve of the 'crust' obviously - and wsa sharp and short.

The bulge afterwards is indicitive of something with fluid in it - compressable and squishy

I think if it went thru an ice-pebble, it's be a very different shape indeed

Doug

[Decepticon]

What if the "sea's" are frozen on top only? Just as the top of the great lakes frezze over during the winter.



Something like Europa.

Just a thought.

[Guest_BruceMoomaw_*]

That probably won't work -- because water, remember, is one of the very few substances in the Universe that actually decreases rather than increasing in density when it freezes. When methane and ethane freeze, they follow the more usual pattern of increasing in density, so that any frozen hydrocarbons will sink to the bottom of a body of liquid ones. It is possible that some kind of complex chemical reaction tends to make bodies of liquid hydrocarbons on Titan develop a "skin" of lighter-weight solid surface material, but it's hard to conceive of what such a reaction could possibly be. I still think that we're looking at a Titanian "playa" -- that is, a moist lakebed which is either periodically flooded before drying out or having its liquid sink into the underlying "soil", or which has liquid continuously flow into it at such a low rate that it never turns into anything more than a mudflat.

[OWW]

What about the white streaks in the dark areas? I've heard two different theories so far. They are either ridges sticking out of the 'mud' or clouds/fog hovering above the surface. Has anyone been able to make a 3D picture of one of these features?
Personally I doubt the cloud/fog theory is correct, because these features have cracks and pits in them. Maybe the radar results will clear this up.

[volcanopele]

What about the white streaks in the dark areas? I've heard two different theories so far. They are either ridges sticking out of the 'mud' or clouds/fog hovering above the surface. Has anyone been able to make a 3D picture of one of these features?
Personally I doubt the cloud/fog theory is correct, because these features have cracks and pits in them. Maybe the radar results will clear this up.

I seriously doubt the fog theory as well, my guess is that, at least in the Huygens landing site area, they are exposures of bed ice on the bottom of an old sea bed (now religated to the role of a flood basin)

[OWW]

But where did the 'flood' come from? Tides from the larger dark area to the east? Or liquid from seeping from the minature 'San Andreas faults' in the bright area?

[imran]

"One photo released Tuesday showed a large body of liquid - possibly liquid methane - jutting into what appeared to be rough, frozen terrain, with the probe appearing to be just meters (yards) from the shoreline."

Any idea what photo they are talking about?

[imran]

Never mind. They are probably referring to this photo:
http://www.esa.int/images/CH_landing_site_L.jpg

[Mongo]

Given that Titan's orbit has an eccentricity of 0.030, and its location in Saturn's gravity well, how big would any tides be? I am going to estimate how big they would be by comparing them to the tides on Earth.

Titan's average distance from Saturn is about 1,221,850 km, compared to 384,400 km between the Earth and its moon. Saturn's mass is 95.1 times that of the Earth, while Luna's mass is 0.012 times that of the Earth. Titan's surface gravity is 0.138 times that of Earth. Finally, Titan's diameter is 0.290 times that of Earth.

I am assuming that the height of a tide, all else being equal, is directly proportional to the ratio between the diameter of the object with the tide being raised, and the distance from the tide-raising object.

So the difference in ratios between the Titan/Saturn system and the Earth/Luna system, all else being equal, would make the tides on Titan 0.0912 times as high as those on Earth.

The difference in distances between Titan/Saturn and Earth/Luna, all else being equal, would make the tides on Titan 0.0990 times as high as those on Earth.

The difference in masses between Saturn and Luna, all else being equal, would make the tides on Titan 7925 times as high as those on Earth.

Finally, the difference in surface gravity between Titan and Earth, all else being equal, would make the tides on Titan 7.25 times as high as those on Earth.

Multiplying these together, I end up with tides on Titan being 518.76 times as high as those on Earth.

HOWEVER, Titan's rotation period is synchronous with its orbital period around Saturn. So the height of any tides at a given point on Titan's surface is not the difference between high and low tides, as is the case on Earth, but instead the difference between the height of the 'ocean' under the influence of the (stationary) tide at that point, and the height of the 'ocean' with no tide at all, multiplied by the eccentricity of Titan's orbit around Saturn, giving a maximum tide of 518.76 x 0.030 = 15.56 times as high as those on Earth.

I have no idea of how to allow for geographic features such as 'shorelines' (i.e. the Bay of Fundy on Earth), but it seems to me that the tides on Titan would be considerably larger than the tides on Earth.

So what was the state of the tide at the location where Huygens landed, at the time that it landed? Could it be that it landed at or near 'low tide', explaining the 'mud flats' and the possible flow of liquid past the lander?

Anybody with more knowledge of physics than me is free to correct my reasoning. :-)

Bill

[David]

Taking a tenth look at the global images of Titan, I notice (as I have before) that while most of the visible surface can be divided into light "land" and dark "sea" sections, there is a very considerable portion of it which is 'grayish'; this portion normally is clearly distinct from the 'land', separated by a sharp "shoreline", but merges insensibly into the "sea".

Taking as a conjecture that the "sea" really is a liquid reservoir, and that the gray areas are tidal flats, I have to conclude that tidal effects on Titan are quite massive -- that the sea sloshes around a great deal -- because the gray areas are very extensive and visible, much more so than comparable structures on earth.

(That would be consistent with Titan's surface not having a lot of variation in elevation, and no steep drop-offs close to the shoreline.)

[Mongo]

Taking a tenth look at the global images of Titan, I notice (as I have before) that while most of the visible surface can be divided into light "land" and dark "sea" sections, there is a very considerable portion of it which is 'grayish'; this portion normally is clearly distinct from the 'land', separated by a sharp "shoreline", but merges insensibly into the "sea".

I have certainly noticed this as well--it is one of the more obvious characteristics of the Titanian 'seas'.

When I saw the 'grey areas', I thought that the most likely explanation would be that suspended particles are being carried into the 'seas'. We can see this on Earth on satellite images of the mouths of the Amazon or Mississipi rivers, where the ocean is visibly turbid for long distances offshore. As time passes, the particles would gradually settle, resulting in the central areas of the 'seas' being much clearer--and hence darker--than the areas close to shore.

The reason that I think that this hypothesis is more likely than the tidal flat theory is the very fact that the 'grey areas' gradually merge into the 'dark areas'. If the 'grey areas' were in fact tidal flats, shouldn't the boundary between the 'grey areas' and the 'dark areas' be as sharp as the boundary between the 'white areas' and the 'grey areas'?

I do think that the intense tidal action--probably extending over a width of several km--would certainly mobilise a huge amount of sediment into the edges of the 'seas', in addition to whatever quantity is carried by the 'rivers'.

Bill

[Bill Harris]

Steep cliffs and a lot of relief implies tectonics at work; otherwise everything will try to erode down to base level. Unless there is some sort of "snowfall" depositing "ice" onto the land areas, like in our Antarctica.

The Titanian "earth" tides are strong enough to keep things stirred up; that may well be a major force behind any tectonics there, much like on Io. Is there any idea of the amount of tidal heating possible or the heatflow from Titan? Heat=hotspots=black-smokers=life.

--Bill

[alan]

A question about the colored surface images. Is surface orange or does it just look that way because the light is that color?

[lyford]

Steep cliffs and a lot of relief implies tectonics at work; otherwise everything will try to erode down to base level.  Unless there is some sort of "snowfall" depositing "ice" onto the land areas,  like in our Antarctica.

The Titanian "earth" tides are strong enough to keep things stirred up; that may well be a major force behind any tectonics there, much like on Io.  Is there any idea of the amount of tidal heating possible or the heatflow from Titan?  Heat=hotspots=black-smokers=life.

--Bill

I think this idea may be very fruitful - imagine a Titan wide Bay of Fundy...constantly swishing about material.

I do not know the densities of water ice and liquid ethane,and how they would react to each other, but maybe slurpee or icee isn't the right analogy - think frozen yogurt with toppings mixed in instead!

This could explain why the flyby images look to me like "stirred paint" at times, with light and dark intermingling chaotically.



But I know absolutely nothing and am just blindly speculating. Can someone hit me with a clue bat if I am way off?

[john_s]

Taking as a conjecture that the "sea" really is a liquid reservoir, and that the gray areas are tidal flats, I have to conclude that tidal effects on Titan are quite massive -- that the sea sloshes around a great deal -- because the gray areas are very extensive and visible, much more so than comparable structures on earth.

There's a limit to how extensive the tidal sloshing can be on Titan, over the long term. The fact that Titan's orbital eccentricity is significant means there's hasn't been too much tidal friction over the age of the solar system, as friction will circularize the orbit. Sloshing of seas over extensive tidal flats generates a lot of friction. There have been several published papers on the subject, starting with a Nature paper by Carl Sagan and Stan Dermott in 1984:

Sagan paper

[lyford]

Taking as a conjecture that the "sea" really is a liquid reservoir, and that the gray areas are tidal flats, I have to conclude that tidal effects on Titan are quite massive -- that the sea sloshes around a great deal -- because the gray areas are very extensive and visible, much more so than comparable structures on earth.

There's a limit to how extensive the tidal sloshing can be on Titan, over the long term. The fact that Titan's orbital eccentricity is significant means there's hasn't been too much tidal friction over the age of the solar system, as friction will circularize the orbit. Sloshing of seas over extensive tidal flats generates a lot of friction. There have been several published papers on the subject, starting with a Nature paper by Carl Sagan and Stan Dermott in 1984:

Sagan paper

Thanks for the info, John.

[Mongo]

There's a limit to how extensive the tidal sloshing can be on Titan, over the long term. The fact that Titan's orbital eccentricity is significant means there's hasn't been too much tidal friction over the age of the solar system, as friction will circularize the orbit. Sloshing of seas over extensive tidal flats generates a lot of friction. There have been several published papers on the subject, starting with a Nature paper by Carl Sagan and Stan Dermott in 1984:

As you can see, Sagan and Dermott themselves have repudiated that paper. In a paper published in 1995, they argue that a surface containing a number of disconnected hydrocarbon seas--much like what Cassini/Huygens has shown us--is also consistent with Titan's observed eccentricity.

Abstract of their paper: Tidal effects of disconnected hydrocarbon seas on Titan

[David]

As you can see, Sagan and Dermott themselves have repudiated that paper. In a paper published in 1995, they argue that a surface containing a number of disconnected hydrocarbon seas--much like what Cassini/Huygens has shown us--is also consistent with Titan's observed eccentricity.

I don't think that Sagan & Dermott's concept (either the earlier or the later one) is entirely consistent with what we see from Cassini. Certainly there is more "land" than "sea", but the "sea" looks pretty much connected over about 2/3 of the circumference of Titan. But it is also filled with lots of islands.

I also note that the "land" areas in the global mosaics are scored through with lots of dark features. It reminds me of parts of Finland or Canada, where there are long, parallel, glacial lakes profusely dotting the landscape (some parts of southeastern Finland are almost more lake than land).

There are still quite a few mysteries here. One I haven't seen any guessing on is: what are the branching light-colored structures? These are larger than the small, dark rivers, and similar features appear on a continental scale.

Another is: what's going on in the southern hemisphere? It appears to be contiguous with the "land", but is rather darker. Is that an artifact of the distance and angle of Cassini in making those images, or does the southern hemisphere have a very different type of terrain?

[Mongo]

One possibility for explaining Titan's orbital eccentricity, despite the evidence suggesting a connected 'ocean' over much of the northern hemisphere, is that Titan's eccentricity is pumped up by a near-resonance between Saturn and Jupiter.

Abstract of the 2004 paper: How Does Titan Retain a Finite Orbital Eccentricity?

Bill

[Guest_BruceMoomaw_*]

That Jupiter-Saturn orbital resonance has been proposed as the explanation for a lot of things -- including Saturn's axial tilt, and the Terminal Bombardment Period (as a result of the way the two planets supposedly kicked Uranus and Neptune into the outer System while the two bigger planets were actually passing through the 2-1 orbital resonance, so that the two smaller giants scatttered huge numbers of outer planetesimals into the inner System). Certainly there has got to be SOME major phenomenon to explain Titan's mysterious retention of eccentricity in tis orbit, when all the obvious factors suggest it should have vanished long ago.

[alan]

This area appears to have liquid pooled in it.

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