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View Full Version : Cassini takes first picture of Saturn



Superstring
2002-Nov-01, 09:10 PM
http://www.space.com/scienceastronomy/cassini_saturn_021101.html

In case some of you aren't familar with Cassini, it is a space probe that was launched in October 1997 and is set to orbit Saturn beginning on July 1, 2004. It should help boost our knowledge of Saturn and its moons. Personally I am eager to find out if Titan has an ethane ocean or not, and if Enceladus really has active icy volcanoes. The dark stuff on Iapetus is a mystery too.

Can't wait til Cassini goes into orbit. /phpBB/images/smiles/icon_smile.gif At least we know so far it is operating well, as the picture it just took proves it.

Jigsaw
2002-Nov-01, 10:07 PM
Ooooh, that is so cool and spooky, it looks just like a matte F/X painting...

DaveC
2002-Nov-01, 10:14 PM
On 2002-11-01 17:07, Jigsaw wrote:
Ooooh, that is so cool and spooky, it looks just like a matte F/X painting...


Well, space travel is impossible (radiation, you know) so the picture obviously is
fake. /phpBB/images/smiles/icon_smile.gif

Seriously, though, it's hard to believe it was so long ago that we got the last probe pictures of Saturn from Voyager 2 - 22 years back. I'm waiting eagerly for the high quality closeups in 2004 too!

Colt
2002-Nov-02, 12:54 AM
"The dark stuff on Iapetus is a mystery too."

I am just now reading The Lost World's Of 2001 by Arthur C. Clarke for the first time and today, I read a part where he explained why he selected Saturn as the mission's goal instead of Jupiter was because of the "dark stuff" on Iapetus.

Any relevant information at all to this "dark stuff" or to the moon would be most welcome, even pure speculation as to what it might be. Afterall, if Clarke thought it was that important, I want to know about it. /phpBB/images/smiles/icon_smile.gif -Colt

Superstring
2002-Nov-02, 01:41 AM
Hey Colt...the dark stuff on Iapetus has always interested me too. There are two widely accepted theories as to where the dark stuff came from.

Theory No. 1:

The first theory suggests that microscopic meteorite impacts constantly hit the moon Phoebe. This ejects a large amount of material from the dusty coating of Phoebe into space, due to the weak gravity on Phoebe. Saturnís strong gravitational pull causes the ejected dust to float inward. The majority of the dust is collected on the leading hemisphere of Iapetus. The volatile compounds within the surface of Iapetus, which was able to form being in the outer fringes of the proto-satellite nebula, causes a chemical reaction and turns the neutrally gray Phoebe material slightly more red.


Supporting Details of Theory No. 1:

Most of the dark material is concentrated on the leading hemisphere of Iapetus, a sign of cosmic debris collection. Also, the next moon in, Hyperion, appears to be coated all over in some sort of dust as well. Interestingly, it appears to be approximately the same color as the coat on Iapetus, though not quite as thick. The fact that Hyperion rotates chaotically can be explained for a coating all over, and along with being further inward, a less heavy one.

Theory No. 2:

The second theory is strikingly different than the first. This theory suggests that organic chemicals, such as methane and carbons, exist within the interior of Iapetus. These compounds once were, or still are, constantly oozing up from the interior onto the leading hemisphere.

Supporting Details of Theory No. 2:

Many of the craters on the icy side of Iapetus, but close to the border between the two, have the same form of black material in their floors. Also, the central peaks of some craters in the dark side are actually not covered in material. Furthermore, thin wisps of dark material are seen crisscrossing around the border between the two sides, filling into the craters in the icy half. All this indicates the material is concentrated in very low elevations, signal of volcanism.

I'm still doing some research as to which theory is really correct. They seem to be equally proven right and wrong, so we may not know the real truth until Cassini arrives.

Colt
2002-Nov-02, 07:10 AM
Thank you very much for the information. /phpBB/images/smiles/icon_smile.gif -Colt

David Hall
2002-Nov-02, 01:25 PM
I think the neatest thing about the photo is it's unusual angle. Only the Voyagers have heretofore sent back photos that show any of the night side.

And we have to wait another year and a half for the big rendevous? Aaarh! I can't wait!


That Iapetus contraversy is interesting. I'm leaning towards the first explanation myself. We can see a lot of the same kind of stuff around Jupiter (free dust and the like), so that seems like a natural explanation. Hypothesis number two requires several big leaps. First, there must be a layer of dark material under the surface of the icy body. Two, there must be some form of (volcanic?) activity to bring it to the surface. And, trickiest of all, there must be some explanation for why it primarily happens on one side. That's a lot of 'ifs' to put together.

There's probably some other explanation for the anomolies we see. Since the light side deposits are mostly evident in craters, perhaps the impactors that created them were from the same source? And the action that creates the central peaks might be an explanation as to why some of the dark-side ones aren't covered. Maybe also there was or is some kind of tenuous atmosphere (perhaps associated with occasional vulcanism) or other force that occasionally brings some material from the dark side to the light side?

In any case, it's a cool mystery. I can't wait to see what Cassini turns up. /phpBB/images/smiles/icon_smile.gif

Superstring
2002-Nov-02, 02:00 PM
On 2002-11-02 08:25, David Hall wrote:
That Iapetus contraversy is interesting. I'm leaning towards the first explanation myself. We can see a lot of the same kind of stuff around Jupiter (free dust and the like), so that seems like a natural explanation. Hypothesis number two requires several big leaps. First, there must be a layer of dark material under the surface of the icy body. Two, there must be some form of (volcanic?) activity to bring it to the surface. And, trickiest of all, there must be some explanation for why it primarily happens on one side. That's a lot of 'ifs' to put together.



Well, as shown in many of the other satellites, vulcanism is not really the exception; its the rule. Mercury, Venus, Earth, Moon, Mars, Io, Europa, Ganymede, Enceladus, Tethys, Dione, Titan?, Miranda, Ariel, Titania, Triton...ALL of these have or once had volcanism episodic activity. So it wouldn't be too hard for Iapetus to have volcanism, if it did.

That is pretty weird that all the stuff is on one side. However, while not as contrasting, our own moon has most of its ancient volcano plains on its Earth-facing side. The other half of the moon is almost 100% craters. So volcanic activity on one half is not out of the question, though with Iapetus it is so strikingly differed between the two hemeispheres its hard to accept.

Also, from what I can see the dark coating seems to be pretty thick, otherwise we would be able to see many large peek-a-boo spots everywehre. I find it hard to believe that ALL that stuff came from the small moon Phoebe. When micrometeorite impacts hit Phoebe, not all of the dust gets pulled inward by Saturn's gravity, but not all. Then, not all of that material hits Iapetus. I am not sure how long such a process would go on and how much it could accumulate on the coated moon (Iapetus). So this theory also has its doubts IMO.



On 2002-11-02 08:25, David Hall wrote:
There's probably some other explanation for the anomolies we see. Since the light side deposits are mostly evident in craters, perhaps the impactors that created them were from the same source? And the action that creates the central peaks might be an explanation as to why some of the dark-side ones aren't covered. Maybe also there was or is some kind of tenuous atmosphere (perhaps associated with occasional vulcanism) or other force that occasionally brings some material from the dark side to the light side?


That is an interesting hypothesis. In fact, being one of the furthest away from Saturn's primordal protosatellite nebula, a small atmosphere on Iapetus is not out of the question(not to mention the smoggy moon Titan which is nearby). But again, we won't find much evidence until the Cassini arrives.

-String

Argos
2002-Nov-02, 02:50 PM
The shadow of the rings cast on the northern hemisphere covers an area many times as large as Earth's. The shadow will last for a long time (months, few years - Earth time).

Thus, the overall absorption of Sun's radiation by the planet will fall dramatically. Don't this interfere in the atmospheric dynamics of Saturn to a very great extent?

<font size=-1>[ This Message was edited by: Argos on 2002-11-02 09:51 ]</font>

Colt
2002-Nov-02, 10:18 PM
Where might I be able to find some good images of Iapetus? Specifially showing the dark side. Clarke thought that this "oval" might have been created by the monolith with it at the center, why he picked it. Maybe Cassini will fly by and snap a picture of a black rectangular object sticking up from the very center of it. /phpBB/images/smiles/icon_biggrin.gif -Colt

Superstring
2002-Nov-03, 12:04 AM
Here Colt try these two links.

http://www.solarviews.com/eng/iapetus.htm
http://www.to-scorpio.com/iapetus.htm

These are the two best places I could find with good images of Iapetus. If you are looking for more, let me know. /phpBB/images/smiles/icon_wink.gif

harlequin
2002-Nov-04, 07:03 AM
What is really neat is that it is still over two years before Cassini actually reaches the Saturn system and it has already taken such a great photo. Imagine what it will take when it actually gets there!

David Hall
2002-Nov-04, 01:55 PM
It's interesting to see the angle of approach of Cassini. It's actually ahead of Saturn in it's orbit right now, and the two are converging on a fairly parallel course. They will meet at a single point that is ahead of them both right now.

Here's the current location of Cassini:
http://saturn.jpl.nasa.gov/operations/present-position.cfm

nebularain
2002-Nov-04, 03:25 PM
WoW! Neat link, David!

Anyway, here's another picture of Saturn from Cassini on today's APOD (http://antwrp.gsfc.nasa.gov/apod/ap021104.html) - it's the same picture, but flipped (I guess "flipped" is the right word?). I think it almost makes it look a little different when you first see it.

Colt
2002-Nov-04, 08:43 PM
Thanks guys. The irregular form of the dark stuff on Iapetus certainly seems to rule out artificiality, and point to one of the above given theories.

Is Cassini spinning or something? Just wondering why all of the images I have seen of Saturn seem to be at different angles.-Colt

Superstring
2002-Nov-05, 01:49 AM
Here's where Cassini is now, if anyone is interested.

http://www.jpl.nasa.gov/cassini/today/1.jpg</img>

I do believe Cassini is traveling with wobbling present, but I'm not sure if its actually spinning. Maybe you will find some more information regarding that at the JPL Cassini Homepage (http://saturn.jpl.nasa.gov/index.cfm). /phpBB/images/smiles/icon_wink.gif

-String

ToSeek
2003-Dec-05, 05:57 PM
Latest and greatest Saturn photo from Cassini (http://www.space.com/scienceastronomy/saturn_image_031205.html)

semi-sentient
2003-Dec-05, 06:26 PM
It will begin sending images regularly in February.

\:D/

Next year will be exciting indeed! Too bad we have to wait until 2005 to get the scoop on Titan.

TillEulenspiegel
2003-Dec-05, 10:17 PM
Amazing resoloution! gratz JPL. Anyone know if they use heat recovery from the fuel cell to keep the poor critter toasty in that cold galactic night?

PeteB
2003-Dec-06, 04:55 PM
Too bad we have to wait until 2005 to get the scoop on Titan.

Although the primary closeup investigation will be Huygens in January 2005, there will be some smaller scoops about Titan earlier than that from the orbiter. The diagram of the early orbits shows a 388,000 km flyby of Titan the day after SOI. Even though the Huygens landing site isnít in view as shown in the second link, the maximum resolution of the ISS narrow angle camera will be a little over 2 km/pixel if the atmosphere is sufficiently transparent for the near IR filters. So there may be at least some better information about the nature of the surface then. There will be much closer flybys on 10/26 and 12/13. Only the December one is shown but I think that the October encounter should be essentially the same geometry. One thing about the 12/13 still frame is that, to the best of my knowledge, the landing site is plotted wrong (my information is fourth hand from the Huygens operations manager at ESA). The longitude is right but the latitude should be about -10 deg, just south of the dark patch (methane lake ??)

http://solarsystem.dlr.de/PG/cassini/images/cassini_soi2tc.JPG
http://solarsystem.dlr.de/PG/cassini/


Also, about the earlier discussion on this thread about Iapetus - one of the things that fell out of the reconfiguration of the early orbits is an untargeted flyby as close as 64,000 km on December 31, 2004. This is a real plus since the targeted flyby at only about 1000 km wonít happen until September 2007. A QuickTime animation of this, and a massive animation of orbits of the entire 4 year mission (~40 minutes download on DSL), is shown at
http://solarsystem.dlr.de/PG/cassini/mission/orbit.shtml