Cassini and Saturn's moons - Page 21

Kullat Nunu · #**601** (**permalink**) 11-April-2008, 05:44 PM

Titan's seas got names: They are now on known as Kraken Mare and Ligeia Mare. The large island in Kraken Mare is Mayda Insula.

mantiss · #**602** (**permalink**) 11-April-2008, 08:04 PM

Quote:

Originally Posted by Kullat Nunu

Titan's seas got names: They are now on known as Kraken Mare and Ligeia Mare. The large island in Kraken Mare is Mayda Insula.

So the old "Here be monsters" was true, Krakens, now that does make My day

ToSeek · #**603** (**permalink**) 20-May-2008, 03:20 PM

Mapping Icy Moons

Quote:

The Cassini Imaging Team's campaign to map the surfaces of Saturn's major icy moons continues, with the release of a cartographic atlas and an updated mosaic map of Dione.

AndreasJ · #**604** (**permalink**) 21-May-2008, 07:45 PM

So, apparently, Ligeia is the name of one of the sirens. I suspect I wasn't the only one who first thought of the Poe character ...

01101001 · #**605** (**permalink**) 08-July-2008, 05:23 AM

See the bands? Kinda like the familiar gas and ice giants? This is...

Titan.

Planetary Photojournal: Banded Moon

Quote:

This Cassini spacecraft view of Titan shows banding in the atmosphere of the moon's northern hemisphere.

Like the planet Venus, Titan's atmosphere rotates faster than its surface, a characteristic called "super rotation."

nutant gene 71 · #**606** (**permalink**) 08-July-2008, 08:07 PM

Does anybody really understand why some planets exhibit atmospheric Super-rotation? It somehow seems counter intuitive, unless the larger host’s (Sun for Venus, Saturn for Titan) tidal rotation transfer is somehow creating this effect. Impressive that Titan's atmosphere does this too.

indie85 · #**607** (**permalink**) 09-July-2008, 10:23 PM

Some things will always be a mystery.

ravens_cry · #**608** (**permalink**) 10-July-2008, 07:11 AM

Quote:

Originally Posted by indie85

Some things will always be a mystery.

Some things maybe, but I doubt this. Something would have to destroy or confine all mind, and all traces of mind to it's own planet for this to always be a mystery.We are humans, we want to know even if it goes boom in our face, and sometimes more so.

ToSeek · #**609** (**permalink**) 07-August-2008, 04:45 PM

Email from Carolyn Porco:

Quote:

Dear Friends and Colleagues,

Brace yourself, 'cause we're in for a wild ride.

Next Monday, Cassini will execute a flyby of Saturn's brightest moon, Enceladus, that has been carefully designed to return some of the most highly anticipated images of the entire mission: Extremely high resolution views of the warm surface vents on the famed south polar `tiger stripe' fractures from which Enceladus' towering jets are erupting. (See attached image.)

Because of its spectacular activity and the fascinating possible astrobiological implications of it, Enceladus has become a major target of investigation during Cassini's extended mission that began a little over a month ago. Seven very close flybys of this moon will be undertaken during the next two years, with close approach altitudes for some of them dipping as low as 25 km above the surface. Monday's flyby is the first.

To accomplish such high resolution imaging of specific surface locales from a platform moving 40,000 miles per hour relative to the surface, imaging scientists will be using an unusual image targeting technique equivalent to `skeet shooting'.

Online coverage here.

01101001 · #**610** (**permalink**) 11-August-2008, 06:06 AM

Planetary Society News: Cassini to Shoot Past Enceladus for Its Fifth Close Encounter

Quote:

[...] the main science goal of the August 11, 2008 flyby will be to acquire the highest-resolution-ever images of the south polar vents, along with detailed maps of the composition and temperature of the geologically active region.

[...]

If successful, the maneuver -- which is being referred to as "skeet shooting" by the Cassini science team -- will result in images of the south polar terrain with resolutions as high as eight meters per pixel. Many of the images are designed to look straight into the canyons of Enceladus' tiger stripes (formally known as sulci). Others are targeted specifically at unusually hot spots measured by Cassini's Composite Infrared Spectrometer (CIRS) during the previous flyby in March.

First event: Plume Observations
Sunday August 10 2340 PDT
Monday August 11 0240 EDT
Monday August 11 0640 UTC

Closest Approach
Monday August 11 1406 PDT
Monday August 11 1706 EDT
Monday August 11 2106 UTC

Timeline, times UTC

Quote:

August 11
06:40:19 Inbound low-resolution plume observations
12:06:19 Turn to point high-gain antenna at Earth for gravity studies
16:06:19 Optical remote sensing observations
19:36:19 Optical remote sensing observation
20:07:00 Cosmic Dust Analyzer (CDA) begins riding along with optical observations
20:26:19 Optical remote sensing observations
20:34:19 Turn to set up "skeet shoot"
20:36:25 Cassini Plasma Spectrometer
21:06:19 Closest Approach
21:07:19 Start "skeet shoot" imaging
21:10:09 End "skeet shoot," resume tracking Enceladus
21:34:49 Optical remote sensing observations
21:41:26 Enceladus passes into eclipse
21:48 Cassini passes through "Voyager-class" encounter distances of Mimas
21:56 and Daphnis
August 12
00:07:34 Eclipse ends
01:06:19 Optical remote sensing observations
02:06:19 Turn to Earth to broadcast data and perform gravity observations
12:42:19 Turn back to Enceladus
13:06:19 Optical remote sensing observations

See clocks and events at Real-time simulation by D Muller

16 hours to closest approach

01101001 · #**611** (**permalink**) 11-August-2008, 07:06 PM

NASA Cassini Blog (August 8, Carolyn Porco):

Quote:

In fact, there have only been a few times during this whole mission when I was more anxious and sleepless with anticipation than I am now [...]

This upcoming flyby holds that kind of fascination for me, because we have the chance of seeing those very special locales on the tiger stripe fractures that we now know are active, warm eruption vents and because of the daring targeting technique of `skeet shooting' that has been employed to make it happen. [...] We won't see such openings even in our highest resolution images, but maybe ... just maybe ... we might see other evidence of eruption, either something geologically unusual or banks of snow where icy particles in the jets fall back to the ground.

NASA Cassini Mission News: Cassini Prepares to Swoop by Saturn's Geyser-Spewing Moon

Quote:

"Our main goal is to get the most detailed images and remote sensing data ever of the geologically active features on Enceladus," said Paul Helfenstein, a Cassini imaging team associate at Cornell University in Ithaca, NY. "From this data we may learn more about how eruptions, tectonics, and seismic activity alter the moon's surface. We will get an unprecedented high-resolution view of the active area immediately following the closest approach."

Closest Approach
Monday August 11 1406 PDT
Monday August 11 1706 EDT
Monday August 11 2106 UTC

3 hours to closest approach

01101001 · #**612** (**permalink**) 12-August-2008, 05:09 PM

NASA Cassini Blog: Cassini Calls Home! (Todd Barber, Cassini Lead Propulsion Engineer)

Quote:

Hello from the "flip" side of Enceladus! I'm happy to report via this blog that the Deep Space Network in Canberra, Australia, locked onto Cassini's radio signal around 9:03 p.m. PDT on Monday, Aug. 11.

We've executed yet another successful flyby of Saturn's ice-geyser moon! Playback data has just begun streaming to our breathless scientists and engineers at JPL, and it will continue throughout the evening and into tomorrow morning. With the rest of you, I'm pumped up for the raw (unprocessed) images that will be posted Tuesday morning, Pacific Time. For the latest raw images, check here:
http://saturn.jpl.nasa.gov/multimedi...ges-list1.html

01101001 · #**613** (**permalink**) 12-August-2008, 11:41 PM

Emily Lakdawalla is building Cassini ISS images of Enceladus from the Rev 80 (August 11, 2008) Targeted Flyby that associates raw images with planned image sequences mapped onto a whole Enceladus. When the images are filled in, you'll be able to quickly tell the context of what you're looking at. Just a few have been downloaded as of this posting.

Cassini current raw images is beginning get some images from the flyby, like this:

(The line truncation, missing ends of alternate lines on the right of images, is normal and a way of getting something that is better than nothing. Raw Image FAQ)

Oh, here's a goood one:

Too bad it's an artist's impression.

ToSeek · #**614** (**permalink**) 13-August-2008, 12:20 AM

Some "skeet-shooting" images now up at CICLOPS.

01101001 · #**615** (**permalink**) 13-August-2008, 11:24 PM

So, what's the lump, the polyp, on Enceladus, in this raw image ID 165909, middle left side:

Quote:

N00118373.jpg was taken on August 11, 2008 and received on Earth August 12, 2008. The camera was pointing toward ENCELADUS at approximately 7,924 kilometers away, and the image was taken using the CL1 and UV3 filters. This image has not been validated or calibrated.

See also very similar, different filters: image ID 165910, image ID 165911, image ID 165912.

Emily Lakdawalla's cleaned up, rotated version

From the size of its shadow it's by far the tallest thing in the neighborhood.

Oh, the Planetary Society Weblog: More Enceladus image fun, asks, too:

Quote:

And then, on the extreme right edge -- what the heck is that?! Here's a slightly different view, exposing more of this odd feature. It's a weird, steep-sided, round-topped lump sitting on top of the terrain -- compare the length of the shadow that it casts to the other shadows in the image.

The entire image is on the order of 10 km by 10 km, so the blob would be very roughly a 1 km-long cylinder.

loglo · #**616** (**permalink**) 14-August-2008, 08:57 PM

It looks like it came out of the ground vertically and fell over to lay on top of the surrounding ground. Awesome photo, its a shame the "base" of polyp is still obscured by the interlacing. Will that be processed away eventually?

Swift · #**617** (**permalink**) 14-August-2008, 09:37 PM

I think its an empty coke bottle, buried in the sand, probably by one of those aliens with the beach buggies, that left all those tire marks behind.

ngc3314 · #**618** (**permalink**) 14-August-2008, 09:47 PM

Quote:

Originally Posted by loglo

It looks like it came out of the ground vertically and fell over to lay on top of the surrounding ground. Awesome photo, its a shame the "base" of polyp is still obscured by the interlacing. Will that be processed away eventually?

As I understand it, that interlacing effect is Cassini's way of doing data compression and maintaining high-frequency information. Each image is preallocated a certain amount of space, so they can plan long data sequences and not completely lose data. So if there is more detail than expected in some sense, it makes up for that by leaving out part of every other line. There are various ways to improve the appearance (like interpolation), but the actual data values are not there.

01101001 · #**619** (**permalink**) 16-August-2008, 01:55 AM

NASA Cassini-Huygens Mission News: Cassini Pinpoints Source of Jets on Saturn's Moon Enceladus

Quote:

One highly anticipated result of this flyby was finding the location within the fractures from which the jets blast icy particles, water vapor and trace organics into space. Scientists are now studying the nature and intensity of this process on Enceladus, and its effects on surrounding terrain. This information, coupled with observations by Cassini's other instruments, may answer the question of whether reservoirs of liquid water exist beneath the surface.

(large image)

Quote:

"There appears to have been extensive fallout of icy particles to the ground, along some of the fractures, even in areas that lie between two jet source locations, though any immediate effects of presently active jets are subtle," said Porco. Imaging scientists suggest that once warm vapor rises from underground to the cold surface through narrow channels, the icy particles may condense and seal off an active vent. New jets may then appear elsewhere along the same fracture.

Edit: Images also at Planetary Photojournal: Baghdad and Cairo Sulci on Enceladus and Damascus Sulcus on Enceladus.

borman · #**620** (**permalink**) 19-August-2008, 06:36 AM

The feature I find interesting is the large circular area centered just beneath VIII (hot zone B) that predates and lies beneath Cairo and possibly predates all the tiger stripes. It resembles a large impact crater possibly presenting a different thermal history from other impacts on the moon.

The image, while from an earlier pass, came up from a recent New Scientist reprise of current events: http://space.newscientist.com/data/i...4553-4_600.jpg

Another question is whether the 10 meter ice blocks can have a half life that can get them back to the formation time of the tiger stripes or whether they are constrained to more recent events. How old can these blocks be?

ToSeek · #**621** (**permalink**) 20-August-2008, 02:42 PM

Beautiful mosaic from the Enceladus encounter

Quote:

In an amazingly quick piece of work, the imaging team has already assembled the 8-frame mosaic captured by Cassini as it receded from its close encounter with Enceladus last week. This is a really difficult piece of work. There are 32 separate camera images in this mosaic -- 8 high-resolution images taken through a clear filter to get the detail, and 24 taken at half the resolution through ultraviolet, green, and infrared filters to get the color.

antoniseb · #**622** (**permalink**) 20-August-2008, 03:50 PM

Quote:

Originally Posted by ToSeek

Beautiful mosaic from the Enceladus encounter

That's a very nice image... I wish it were possible to actually see the vapors coming out of the cracks, but that's an unrealistic wish.

01101001 · #**623** (**permalink**) 20-August-2008, 04:09 PM

Quote:

Originally Posted by antoniseb

That's a very nice image... I wish it were possible to actually see the vapors coming out of the cracks, but that's an unrealistic wish.

Pull my finger.

Kullat Nunu · #**624** (**permalink**) 08-October-2008, 09:39 PM

Cassini flies within 25 kilometers of Enceladus tomorrow.

borman · #**625** (**permalink**) 08-October-2008, 11:50 PM

I wonder if onboard instuments can sort out if some of the particles monitored will have an isotope signature consistent with a radiogenic heat source for the plumes. If the tiger stripes are geologically young compared to underlying features, one must endeavor to discover what is the recent cause of the stripes and plumes that make the E-ring. Most of the theories that look to frictional or tidal influences or differentiation due to Al26 will eventually need to address the coincidence problem posed by young tiger stripes.

BigDon · #**626** (**permalink**) 09-October-2008, 03:18 AM

Quote:

Originally Posted by Kullat Nunu

Cassini flies within 25 kilometers of Enceladus tomorrow.

Thank you very much Mr. Nunu

I sort of dozed off concerning Cassini!

01101001 · #**627** (**permalink**) 09-October-2008, 04:37 AM

Planetary Society Weblog: Cassini flies within 25 kilometers of Enceladus tomorrow

Quote:

Enceladus-88 flyby (October 9, 2008) [Timeline]

In progress:

Quote:

[October 8 19:15:00 PDT; October 8 22:15:00 EDT; October 9 02:15:00 UTC]
Inbound Enceladus plume & neutral gas observations (ISS, UVIS prime)
As Cassini approaches over Enceladus' northern hemisphere, it will study the plumes, which should be fainly visible off the nightside limb. The observation lasts 4.25 hours.

Coming up next:

Quote:

[October 9 00:15:00 PDT; October 9 03:15:00 EDT; October 9 07:15:00 UTC]
Turn to Earth and downlink data
Cassini will clear its recorders in preparation for the flyby.

Closest approach
2008 October 09, 1207 PDT, Friday
2008 October 09, 1507 EDT, Friday
2008 October 09, 1907 UTC, Friday

15-1/2 hours to closest approach

01101001 · #**628** (**permalink**) 09-October-2008, 04:42 AM

Quote:

Originally Posted by borman

If the tiger stripes are geologically young compared to underlying features, one must endeavor to discover what is the recent cause of the stripes and plumes that make the E-ring.

I thought their youth was established.

NASA Cassini Mission News Release: Cassini Finds Enceladus Tiger Stripes are Really Cubs

Quote:

The Cassini spacecraft has discovered the long, cracked features dubbed "tiger stripes" on Saturn's icy moon Enceladus are very young -- between 10 and 1,000 years young.
[...]
"There appears to be a continual supply of fresh, crystalline ice at the tiger stripes, which could have been very recently resurfaced," said Dr. Bonnie Buratti. She is a team member of the Cassini visual and infrared mapping spectrometer at NASA's Jet Propulsion Laboratory, Pasadena, Calif. "Enceladus is constantly evolving and getting a makeover."
[...]
When ice comes out of the "hot" cracks, or "tiger stripes," at the south pole, it forms as fresh, crystalline ice. As the ice near the poles remains cold and undisturbed, it ages and converts to amorphous ice. Since this process is believed to take place over decades or less, the tiger stripes must be very young.

But, that's press release science. I can't say I've seen a paper that said the same -- nor have I looked for one. OK. I looked. Abstract for Photometric and spectral analysis of the distribution of crystalline and amorphous ices on Enceladus as seen by Cassini:

Quote:

These maps show the surface of Enceladus to be mostly crystalline, with a higher degree of crystallinity at the “tiger-stripe” cracks and a larger amorphous signature between these stripes. These results suggest recent geological activity at the “tiger stripe” cracks and an intriguing atmospheric environment over the south pole [...]

borman · #**629** (**permalink**) 09-October-2008, 02:47 PM

Thanks for looking up the references.

The issue of crystalline ice speaks to the age of the most recent eruptions of plumes from the stripes rather than the age of the stripes themselves. We know the ice is fresh now because Cassini has actually monitored plume activity. The short lifetime of crystalline ice in Saturn's high radiation environement is going to be significantly shorter than if Enceladus was nowhere near the planet. Even then the lifetime would only be about a million years as cosmic radiation serves to transform it into amorphous ice.

The issue of the actual age of the stripes, however, can not be determined from the age of crystal ice. All that can be sorted out is that it has been recently active from crystalline ice.

To constrain the age of the stripes themselves, one needs to constrain the age of features that underly and so predate the stripes. As mentioned in a post above, I found the "fingerprint-like" terrain beneath the stripes to be an interesting feature that itself might point to a limitation or constraint upon the age of the "fingerprint" terrain. This would then place an upper limit on the age of the Tiger Stripes themselves regardless of how recent the plumes were active. It is this age that could present a coincidence problem for many of the various theories presently put forth to address the heat or liquid ocean ideas. Why now, more recently, and not for billions of years? Certainly friction and tidal and any heat from differentiation would have made an imprint older than the stripes. They should have been there from the start and not a recent geological feature. They should predate the "fingerprint" terrain.

marsbug · #**630** (**permalink**) 09-October-2008, 03:12 PM

Borman, I'm not sure I follow you. The 'ocean' is purely speculative, but the fact that enceladus is warmer than it should be is a measured fact, not an idea. All the mechanisms put forward to explain this have holes in them. One of the most recurring ones being 'Why would this be active now?' as you point out.

Whatever we come up with to explain this needs to explain why the heat and geysers occur in this period of time, and it sounds a little like you've got an idea of your own....?

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