T42 Mission description now up.

http://saturn.jpl.nasa.gov/multimedia/prod...description.pdf

Imaging highlights:

• Last of the S hemisphere flyover sequence.
• Long VIMS stretch in "noodle mode" going into northern territory. ("noodle mode" gives a longer track, but is less accessible for us sitting in the cheap seats.)
• A VIMS "sit and stare" section
• ISS imaging of the area in N Belet and polar regions. (Hopefully a good look at the Dancing Monkey feature)

-Mike

Here is the Looking Ahead article: http://ciclops.org/view.php?id=4882

The Cassini-Huygens site just brought a smile to my face with this image:





A little humor never hurt anyone.

On a side note, the Enceladus press conference on NASA TV (Media channel) is about to start.

lovely layers (with detached haze the main one): http://saturn.jpl.nasa.gov/multimedia/imag...iImageID=146915

Mosaic of NAC images over Adiri, part of N Belet Cyclops, Sliced carrot of NW Shangri-La and the Dancing Monkey feature:

Click to view attachmentClick to view attachment

Boy, was this a challenge...

Is there a new seasonal haze layer developing? Most of these features were barely discernible. It took awhile to identify Adiri and the Sliced Carrot. The Dancing Monkey feature is almost obscured.

-Mike

T42 Dancing Monkey mosaic. (I think this is how they go together.)

It is really hard to tell if I got this right...

Click to view attachment

-Mike

Nice! A long distance shot received yesterday has a view of the rarely imaged part of Titan around 300 W longitude.

http://saturn.jpl.nasa.gov/multimedia/imag...iImageID=147170

Click to view attachmentClick to view attachment

In this image you can see NW Belet and a very suspicious looking inky dark stain on the surface just to the N.
And you can also see a few N polar clouds, too!!

-Mike

idle hands...

http://i225.photobucket.com/albums/dd78/al...ushjobsmall.jpg (flyby42rushjobmedium.jpg for medium)

various skews for interest

Nice enhancement of the clouds!

Those clouds don't seem very circumpolar. They don't follow the terminator very well and seem pretty straight.

It raises the possibility that the clouds may be orographically related. There are ridges up there that run roughly parallel and in the same orientation as the the cloud streaks. These ridges were observed in the T21 RADAR swath.

-Mike

Is that the toe-of-Italy shaped arm of the big northern lake just appearing to the left of the cloud?

Yes



Those clouds are too far to the north and west. Besides, these clouds are more than likely similar to the mid-latitude clouds in the south, which are also not orogenic.

Curiosity got the better of me....

So where are these clouds anyway? And with all that RADAR coverage up north, can we figure what kind of terrain is beneath them?

Click to view attachment

Here is a graphic showing the north polar RADAR swaths overlaid on a grid that shows the RADAR swath names and latitude and longitude. (At the very top right is just barely seen the T19 Swath).

Click to view attachment

Similar clouds were observed in the same location in PIA08365 as in images taken during T42. PIA08364 shows a ISS and RADAR images with an outline of the big north polar lake. (According to the catalog page, the ISS image was taken on February 25, 2007). That might indicate a long-lived cloud at this location or this may just be great place to make clouds.

Click to view attachment

Here is a graphic with the north polar RADAR swaths overlaid on PIA08366. The T30 RADAR Swath should have imaged some of the terrain that underlies the clouds.

Click to view attachment

Here is a graphic with the T30 RADAR Swath and the outline of the cloud. The dark section of lake was used to make the correct line-up.

Click to view attachmentClick to view attachment

Here is a graphic of the T30 RADAR swath showing the location of the clouds. Also a zoom region.

The terrain type is pretty non-descript, many blobby features, possibly some type of dried lakebed type terrain or it could be canyon or it could be plains as well. Who knows? There are some channel-like features barely discernable which seem to flow from left to right across the zoomed image. If there was any type of topographic rise parallel to the clouds, the channel-like features would need to cut through them. At the lower left in the zoomed image (zoomed further in the inset) there are bright streaks that may be aeolian deposits.

There are no obvious tectonic ridges in this area.

-Mike

The southern margins of the great lake could be an area where there is higher than average evaporation of methane from the surface, leading to cloud formation down-wind (???)

I believe the clouds coincide with the margin of the huge polar ethane/methane cloud beautifully imaged (PIA09171) by VIMS on 2/1/07. This polar cloud seems to be a persistent feature (although may change as Titan's north pole passes from winter to springtime) and was observed to reach to 62 degrees N latitude at all observed longitudes. Polar atmospheric weather/temperature conditions must be more important than surface topography in producing the clouds.
Speaking of topography, Planetary Photojournal has just put up a nice topographic map of a strip of the N polar region (PIA10353) covering that fascinating region with seas, islands and great rivers!

Welcome to UMSF, titanicrivers!

There were also clouds imaged in the southern hemisphere of Titan as well. An image of these can be found on the VIMS website: http://wwwvims.lpl.arizona.edu/whatsnew.html

There is also a cool movie as well from the T17 flyby. A few frames show apparent movement of the cloud features.

According to the captions the blue/white VIMS color in these images corresponds to liquid methane clouds at 10-30 km altitude. I would suspect that the clouds in the VIMS north polar image would be at the same altitude. (Anyone know?)

10-30 km altitude is pretty high up there. This is about the same level as polar stratospheric clouds (nacreous clouds) in Earth's atmosphere. From Wikipedia \Polar stratospheric cloud : "In the Northern hemisphere, the generation of lee waves by mountains may locally cool the lower stratosphere and lead to the formation of PSCs."

So even clouds at that altitude could feel the effects of topography.

I would add that a converging surface windfield on Titan possibly indicated by mid-latitude dune orientations might also cause enough of a "bump" in the atmosphere that it could trigger polar cloud formation. (See this post for possible evidence of converging surface winds in higher latitudes).

{BTW, does anyone know the location of the thicker knot of clouds in the PIA09171 image? When I tried to guesstimate using the terminator and the mission description I came up with a rough guess of [65N, 100W]}

-Mike

Keep in mind that the scale height of Titan atmosphere is greater than on Earth, so corresponding clouds would be higher up in Titan's atmosphere than they are on Earth. So the streak clouds ISS and VIMS see are equivalent to cumulus or stratocumulus clouds seen on Earth. Don't know what the altitude of the VIMS ethane cloud is/was, but I think it is also in the troposphere. also note that Titanian mountains are also lower in height than here on earth, so their effect on cloud formation would be reduced compared to Earth.

Topography might have some effect on cloud formation on Titan, but so far we haven't seen convincing evidence for it. The fact that most have preferred latitudinal bands and have similar morphologies despite differing cloud locations suggest that they are related to atmospheric circulation patterns.

titanicrivers, do you know if VIMS still sees the ethane polar cloud? We have been getting good data over the north polar region for a year now and we haven't see it (though that doesn't mean it isn't there, just that nothing is obscuring the surface at 938 nm over the north polar region).

The ethane cloud was between 30-50 km according to the paper, which is the upper edge of the troposphere. It is probably created by a different mechanism than the mid-latitude clouds though. The polar 'mammoth' cloud ( http://www.jpl.nasa.gov/news/news.cfm?release=2007-010 ) is an ethane cloud too, apparently.

A diagram cross-section of Titan's atmosphere can be seen here: http://upload.wikimedia.org/wikipedia/en/a...anAtmDetail.jpg

A more detailed figure is presented in the 20060926 CHARM presentation, freely available here (Warning: long download - it choked up my machine)

The little puffy clouds in the diagram are CH4 clouds, I assume the higher altitude stratiform clouds in the diagram would indicate the ethane clouds.

-Mike

Thanks for the welcome message!
I have been combing the VIMS images trying to see if the ethane cloud is present currently. I do not know. The north polar atmosphere is very active on most of the wide field np imaging in blue/violet/uv light mainly showing the banded pattern at high altitudes and dark 'polar hood' in visible light. What makes up the hood? Is it the big ethane cloud?
I did find an interesting article in Science on Titan's polar weather by Flasar.
I'll try to include part of it as an attachment as to me (not an atmospheric scientist at all!) it seems to provide an explanation for atmospheric cloud development at the edge (i.e. around 60-65 degrees N) of the descending air mass over the cold N pole. Made me wonder if relatively warmer air from mid N latitudes is moving up over the descending cold polar air producing methane clouds that are banded due to the super-rotation of Titan's atmosphere.Click to view attachment

The polar hood is thought to be a large concentration of haze particles at the pole, caused by the same mechanism as described by the Flasar overview (descending motion bringing enriched air to altitudes where you can see it). Lots of pretty pictures of the polar hood are on the cassini raw images site
http://saturn.jpl.nasa.gov/multimedia/imag...iImageID=147157
Note that in the troposphere, where this methane (?) cloud at the edge seems to be, is not necessarily that much colder at the poles than at a few latitudes lower. If I remember correctly, the ground temperature only changes by at most a few degrees over the globe and changes slowly with latitude .

Thanks for the reminder that many factors go into producing Titan's clouds. Roe et al (see excerpt below) in their discussion about the southern mid latitude clouds put forth the various mechanisms for the clouds they observed with Keck and other earth based telescopes. They did comment that south pole clouds had to do with ground warming-enhancing methane/ethane evaporation from the terrain. Not sure what kind of temperatures they were inferring. Perhaps in the north polar region there is the added methane/ethane evaporation from the substantial bodies of liquid there, the haze particle enrichment and the collision of air masses that all add together to produce the clouds.
"There are several ways to form clouds on Titan. These include:
- Wind blowing across a raised surface feature (such as a mountain). These are called "orographic clouds" and are often observed here on Earth (in Hawaii and along the west coast of the U.S.).
- Heating the surface. If the surface temperature is raised a few degrees this forces slightly stronger convection in the lowest layer of the atmosphere, which can lead to methane condensation and the formation of convective clouds. This is similar to what happens on Earth in the southwest United States during late summer when the sun heats the desert floor during the day and can generate huge thunderstorms. This is the mechanism thought to form the south polar clouds on Titan that we have been observing for several years.
- Circulation patterns that generate uplift regions. In regions where surface winds converge you get uplift (all that colliding air has to go somewhere). As the air is pushed upward it cools and this can trigger cloud formation. On Earth we see this type of phenomenon near the equator.
- Injecting methane. Titan's atmosphere near the surface is not usually saturated with methane, but if there is a mechanism that injects a bunch of gaseous methane into the lower atmosphere and saturates the atmosphere with methane, then clouds will form. "(source Geographic control of Titan's mid-latitude clouds
H.G. Roe, M.E. Brown, E.L. Schaller, A.H. Bouchez, & C.A. Trujillo)

On the orographic clouds...

The mention of clouds caused by high mountains is good for providing an example of the dramatic, but terrain can have big effects with much more subtle variation in terrain, too.

Columbus, OH and Pittsburgh, PA are roughly on the same windstreams. They are about 250 km apart, almost exactly east-west of one another, in an area where the winds almost always blow from the west.

Columbus has an elevation of 275 m. Pittsburgh's elevation is 372, with surrounding ridges reaching elevations of about 650 meters. That's a very subtle climb over that distance.

Columbus has 72 sunny days a year to Pittsburgh's 59. Columbus averages 137 days with precipitation to Pittsburgh's 152.

So I wouldn't discount the possibility of terrain, even inclinations that seem minor, having a significant role in cloud creation.

I speculate that the increased scale height of Titan also means that clouds originating low can survive to climb high.

On the other hand, big lakes can have much the same effect. Milwaukee, WI and Grand Rapids, MI are also close to one another on an east-west line, but with Lake Michigan lying between them. Milwaukee averages 125 days of precipitation to Grand Rapids' 144. Grand Rapids has 64 sunny days a year to Milwaukee's 90. So, just to compare two terrestrial cases, the lake has a bigger impact than the terrain.

Interesting. There's some topography and lakes around 65 N however the big ethane cloud covered the entire NP out to 65 N at all longitudes visible suggesting its not local ground conditions controlling it.
Re the mid southern latitude clouds is the consensus now that these are orographic clouds related to the mountain range near W0 and S lat 40? We are yet to see a radar pass over the highest part of those N-S trending peaks as far as I can fathom. Should be a priority for a SAR pass in the extended mission I hope.

The north polar ethane hood cloud VIMS sees might be related to the haze layer variations that ISS sees in the north.
No, it is not the consensus because those mountain chains may or may not exist. my bet is on not existing, or that those bright streaks are not mountains, anyway. Not to mention that we see other cloud systems at the same latitude but at a variety of different longitudes.

Click to view attachmentI was under the impression photos like attached were fairly strong evidence of a mountain chain. A sort of Titanic Tetons. (I suppose I should cancel my ski trip .... I was looking forward to that pristine ethane-methane powder!)

Well, let's just say there is disagreement about those. There are bright streaks in that area. The VIMS data suggest they are mountains based on apparent shading that seems consistent with them being topographic highs. However, ISS also sees many of these supposed shadows (ISS doesn't see topographic shading on Titan due to the higher atmospheric scattering at 938 nm, the wavelength ISS uses to see the surface) and see many bright and dark features in the region (that may look like shading at VIMS' lower resolution).

A few possible alternatives are that these are fresh fractures on Titan surface, with cleaner water ice/ammonia hydrates (akin to the fractures on Dione and Rhea) or these maybe fissures where such material has been extruded from the interior.

Hmm, if only there were a less ambiguous remote sensing technique that could probe
the surface while being unaffected by the atmosphere? Maybe you could even time
echos to measure heights directly - like sonar, but maybe with radio waves or
something...?

So, is this area going to be observed by SAR then such that it allows topography extraction? (like http://www.planetary.org/blog/article/00001385/ )

What kind of acoustical sensors are you suggesting for the next Titan probe?

Yes, but I don't think the whales would survive the trip.

That's what the situation needs. Heavily instrumented large aquatic mammals.

Or SAR.

(Trying to imagine designing a spacesuit for a sperm whale.)

(Trying to imagine persuading a whale to get into the suit.)

(Trying to imagine getting a whale into LEO, let alone landed in a Titanian sea...)

<BOOM!> (Head explodes.)

Yeah, gotta go with SAR, here, definitely...

If only we had Cptn. Kirk here, we wouldn't have to worry about things like these.

How about a dolphin? I'm sure a dolphin could produce higher resolution sonar imaging than this SAR you speak of.

(Trying to imagine teaching any given cetecean how to use zero-gee sanitary facilities.)

(Trying to imagine teaching one to describe sonar results in any fashion, let alone with scientific rigor.)

Nope. Still gotta go with SAR.

Now Flipper, squeak once if you see a mountain. Squeak twice if you see a lake. Squeak three times if you see dunes.

Okay, this has gotten too silly.

".....so long and thanks for all the fish!"

Cetacean EDL would be a bit of a challenge, and likely to alter the topology it was trying the measure (not to mention creating a new surface feature.) A bowl of petunias, on the other hand, wouldn't need a spacesuit. It's telemetry would be terser, though.

With frequent clouds in the area (and perhaps methane-ethane rain) and SAR's capability to show drainage patterns and lakes ONE radar pass centered on these potential mountain chains should go a long way to resolve any question as to their existence I would think. And a SECOND overlapping SAR pass might allow a USGS topo map to be constructed (like we now have up north, PIA10353) which should nail down their actual elevation.

"...Cetacean EDL would be a bit of a challenge,..."

They're already shaped <delphinids, that is> like a wingless shuttle.

Just glue a whole bunch of thermal tiles on the victim... then ... OUT THE AIRLOCK!

<you may shoot me now....>

Are there any planned SAR's of the possible mountain chain in the extended mission?

Click to view attachment
Well .......yes it appears so! I have cut a screen from the 'Tour Designers' a video post on the Cassini web site from several days ago. The extended mission tour selected has 26 Titan flybys and they are shown on the attached png file. I've added a red 'mountain' caret at the approximate location of the 'Titan Sierras'as they are located on the Titan Virtual Tour map which is in the right column of the Cassini home page. In fact it appears portions of many passes will cover the possible range presumably with several SAR at different angles so as to produce topographic maps. Nice!

These are spacecraft groundtracks of all the flybys. Only a fraction of those are planned for
radar, and it is not yet decided for all of those whether we are left -look, right-look (for which the
tracks give only a crude guide to location) or altimetry.

I am not sure we will get that particular mountain range or not - that's a detailed pointing design
issue that we will only get to closer to the time of the relevant pass (if there is a relevant pass).

But indeed the XM will give us much better coverage of the southern hemisphere which the nominal
mission has barely touched.

This is a composite of the primary mission and extended mission radar maps modified from Linda Spilker's OPAG presentation. The blue bands are primary mission tracks, the red are extended mission tracks.

Phil

Click to view attachment

Looks like there will be heavy coverage of the southern blandlands terrain. I really hope there is something discernible down there...
(although the swath terminii in NE Shangri-La might be pretty cool - hopefully it will still have high resolution)

The two swaths across Belet are interesting. Any idea when these occur?

Hmmm.... L.S. OPAG map of SAR coverage (centered closer to 180 deg longitude) suggests little coverage at the possible mountain range site (which lies closer to 300 deg longitude) on the left side of that map. May have to wait until the XXM!

I don't know about the Belet passes, but I think the southern passes might be interesting. The T7 SAR swath of Sept 2005 was one of my favorites showing rain dissected plains, Titan canyonlands with impressive rivers, a large delta and finally a probable shoreline of a partially drained lake. Suspect we'll see more of the same on some of the XM passes.Click to view attachment

I think anything over a basin gives a great contrast and allows a nice high contrast RADAR (and ISS, too) view of the actual surface. IMHO these give the easiest and most accessible information to try to tease out the intricacies of Titan. It's the lowest hanging fruit of a really difficult tree.

Regions outside the equatorial zones (30N-30S) that aren't basins or lakes may be covered by deposits and drifts of atmospheric organic schizzle that show low contrast and may be pretty much buried. It doesn't mean that they are totally boring, just that many of the features will be less easy to interpret. If stuff is indeed buried by a thick layer, then other cool techniques like radiometry, scatterometry, dielectric constant measurements, and VIMS might reveal a pretty uniform surface ("it all looks like schizzle, cap'n!".). [Ground penetrating RADAR, however, would be really useful here.]

The southern part of the T7 Swath dips into Mezzoramia Basin and shows pretty cool features. (Note that even these seem to have less contrast than areas in T8 Belet or T13 Xanadu Swaths.) But if you look at the northern section of T7, and the southernmost sectinion of T25, it's pretty bland in comparison; this might be typical. I worry that temperate zone SAR strips (or other experiments) outside the Mezzoramia basin might not be easy to figure out.

Heck, while I'm just glad that we have more Titan passes in the XM, I'm hoping that there is flexibility (given orbital constraints and other experiment needs) to allow more SAR coverage in the Equatorial zones in either the XM or XXM. (I'm also hoping that I'm totally wrong and that there are lots of cool and obvious features in the current plan). If there were a choice, I'd put my money on Equatorial zone imaging and go for the low hanging fruit.

-Mike

Some images from the April 26, 2008 Distant targeted flyby are down.

Click to view attachment

I tried to contrast-enhance and make a mosaic from two of the images. I'm not sure exactly what part of Titan we are looking at. Since there are no obvious dark zones, it must be in the high latitudes (either N or S). I'm guessing that the very subtle dark stain might be the N Polar Sea (Kraken Mare). Some high latitude clouds along the terminator might be visible.

-Mike

(Links to original images N00107967 and N00107965.)

Mike I would like to see your mosaic but that attachment doesn't seem to work.