[X] My Assistant

[titanicrivers]

A fascinating presentation by Roe and Brown on a April 2008 storm exploding over the tropics of Titan and followed for a month using the Gemini North telescope with adaptive optics.
Here's the link: http://www.nsf.gov/news/news_videos.jsp?cn...496&org=NSF

[volcanopele]

A few thoughts:

1) Mike Brown has a nice summary of their data on his blog: http://www.mikebrownsplanets.com/ . Very interesting description of the data, but his explanation for why this outburst of clouds formed.... Every time someone suggests cryovolcanism or venting or magic mountains as a reason why clouds form on Titan, God kills a kitten. Could those be reasons why, sure why not, but considering that we haven't even observed Titan in this way for an entire Saturnian year, we are aways off before we need to start coming up with unique reasons why cloud or storms systems form at certain locations. Let's get a handle on Titan's climate and how weather systems change over a Titan year before that.
2) Major Titan storms continue to avoid us....

[Jason W Barnes]

2) Major Titan storms continue to avoid us....

Agreed. Bad luck that this outburst occurred between Cassini flybys . . .

- VIMS Jason

[remcook]

....it is rather coincidental that this occurs around equinox, where surface heating occurs at ... the equator. (and dynamical models predict the start of the flipping over of the circulation pattern). Or is it? Hopefully we'll see some more clouds soon.

Edit: also note that the first detected clouds on Titan was also a massive cloud outburst, perhaps also in this tropics. This was in 1995, which happens to be close to equinox.

[rlorenz]

....it is rather coincidental that this occurs around equinox, where surface heating occurs at ... the equator. (and dynamical models predict the start of the flipping over of the circulation pattern). Or is it? Hopefully we'll see some more clouds soon.

Edit: also note that the first detected clouds on Titan was also a massive cloud outburst, perhaps also in this tropics. This was in 1995, which happens to be close to equinox.

The cloud observed by HST in October 1995 was around 40 deg North. This may or may not be the
same cloud system noted by Griffith spectroscopically (within a couple of weeks of the HST observation)
and her determination was that it covered 10% of the disk, which seems consistent with the HST pic.

[titanicrivers]

From a New Scientist article on the Titan Storm:“The team found that Titan appeared brighter on 13 April 2008, and on the following night, Mauna Kea's 8-metre Gemini North telescope revealed a large cloud centred some 30° south of Titan's equator.”

I wondered where exactly on Titan this storm developed. Using David Seal’s Solar System Simulator and the Celestia program and using the date of the first Gemini N. photo (April 14, 2008) one finds this storm amazingly close to Hotei Arcus !! (see graphic below)



Some thoughts:
1) Is it possible the postulated cryolava activity in this region influenced the storm’s development?
2) Did it rain on this region and if so could this have influenced the VIMS data collected before and after the storm event?
3) Are the clouds seen in the Hotei region on T44 (N00111091 taken on May 28, 2008 ) a remnant of the storm?
4) Were there any changes in the Hotei region (altered channels, playa like regions) that developed after April 2008?

[volcanopele]

Wow, I kept reading 2009, not 2008. Okay, yeah, now in the perspective, yes, we saw the remnants of that storm in T44. As far as if Hotei had an influence, possible, but I don't think we need to go that far just yet. Again, we barely have a handle on how Titan's climate changes with seasons. Until then, we can't be sure if this is just a season monsoon storm or a fluke as a result of cryovolcanic activity. Remember this same argument cropped up with the mid-latitude clouds...

[belleraphon1]

Wow is right if that area really matches the cloud burst...

I always get confused on what map coordinate conventions are being used..

See article in this link
http://www.skyandtelescope.com/news/53062642.html

Quote "The source region seems to be centered at 15° south, 250° west, where images from the Cassini orbiter show that the Titanian terrain is rather bland."

Using the published Titan maps from CASSINI, that would put the cloud over Belet?!

??Craig

[Juramike]

From the Nature article Figure 3, the primary outburst was located over the mass of unnamed southern bright terrain just S of the Belet sand sea on April 13-14, 2008.

The secondary outbursts then pulsed successively eastward and also pulsed down near the S Pole.

The second "biggie" outburst in this series was located S of Shangri-La.

According to the article there was a small thin elongated outburst along equatorial Xanadu on May 8, 2008. This also went over the Hotei Arcus region.

The T44 Cassini flyby on May 22, 2008 did see small clouds located over Hotei Arcus.
Here is a mosaic I put together (Xanadu thread, post 20)

Were the T44 clouds remnants of the May 8, 2008 clouds (itself a result of the intial pulse from S Belet?)
Or was it yet another pulse from the initial S Belet "cloud spasm"?

[titanicrivers]

I must confess not having the full Nature article and so not reading how the authors located the storm origin. However if the Gemini North photo I showed was taken in Hawaii (I used Hilo corrected UTC time of 8 pm on the 14th) and the solar system simulator (using the settings: Titan from Earth, 100% fov, view angle 0.0005) is correct then I'm having a hard time with the storm location for that image at least. Even on the 14th at 1 am Hilo time the simulator shows a similar view rotated about 15 degrees west.
Anybody know the accuracy of the simulator or some correction I failed to use?
The photo I used from Gemini was taken from the Caltech press release figure shown below:

A major storm erupts in the desert tropics of Titan.
[Credit: Emily Schaller et al./Gemini Observatory]

[Juramike]

The press release image above is Figure 2 in the Nature article.

From the full caption in the Nature article, the degree number in parantheses is the sub-Earth Titan longitude in degrees W.
The green box in the images is centered at the location of the original April 14 cloudburst (ca. -15S, 250W).

For reference, the midpoint of the southern edge of Belet is at about [-15S, 240W].

[titanicrivers]

Thanks Mike. Was there a UTC or Hawaii time specified for each image in Figure 2? (I made the assumption its was early am or early evening on the 14th Hawaii time)

[titanicrivers]

[quote name='Juramike' date='Aug 14 2009, 11:21 AM' post='144737']
The press release image above is Figure 2 in the Nature article.

From the full caption in the Nature article, the degree number in parantheses is the sub-Earth Titan longitude in degrees W.
The green box in the images is centered at the location of the original April 14 cloudburst (ca. -15S, 250W).

Wow! With the Solar System Simulator I was off by 160+ degrees with respect to the face of Titan seen from earth on 4/14/08. Is this a known inaccuracy of the simulator or did I goof up somewhere?

[Juramike]

Thanks Mike. Was there a UTC or Hawaii time specified for each image in Figure 2? (I made the assumption its was early am or early evening on the 14th Hawaii time)

Nope. But the date is UTC.

[HughFromAlice]

name='titanicrivers' date='Aug 13 2009, 07:11 AM' post='144664'] A fascinating presentation by Roe and Brown

Yes, fascinating. Thanks for posting. You guys have already posted key things on this, but one v. interesting area that they touched on was the likely effects of atmospheric waves analogous to Rossby waves.

On Titan, which rotates so slowly compared to Earth, there are no significant Coriolis forces. Mike Brown and Henry Roe noted that 'RW's propagate much better on Titan. The initial cloud outbreak was likely to have propogated powerful 'RW's all the way around Titan (none of the energy sapping meanders and shears that drop off our high and low weather systems) and was likely to have given rise to cloud formation at other latitudes (mostly in the same hemisphere). Most interestingly HR said "we think that what happen was..... the wave cycled around Titan and boosted it up (initial cloud mass) about 2 weeks later after the original event".

Also I read that just when (Dr) Emily Schaller completed in her Phd in April 08 - a large part of which dealt with the low amount of cloud cover on Titan - she became one of the first observers of this large cloud formation! She obviously has good timing in terms of completing things!

So, on Titan, it doesn't just 'rain' but pours.... again ... and again .... and again!