APOD: Fresh Tiger Stripes on Saturns Enceladus (2014 Apr 06)

Comments and questions about the APOD on the main view screen.

APOD: Fresh Tiger Stripes on Saturns Enceladus (2014 Apr 06)

Postby APOD Robot » Sun Apr 06, 2014 4:10 am

Image Fresh Tiger Stripes on Saturns Enceladus

Explanation: Do underground oceans vent through the tiger stripes on Saturn's moon Enceladus? Long features dubbed tiger stripes are known to be spewing ice from the moon's icy interior into space, creating a cloud of fine ice particles over the moon's South Pole and creating Saturn's mysterious E-ring. Evidence for this has come from the robot Cassini spacecraft now orbiting Saturn. Pictured above, a high resolution image of Enceladus is shown from a close flyby. The unusual surface features dubbed tiger stripes are visible in false-color blue. Why Enceladus is active remains a mystery, as the neighboring moon Mimas, approximately the same size, appears quite dead. Most recently, an analysis of slight gravity deviations has given an independent indication of underground oceans. Such research is particularly interesting since such oceans would be candidates to contain life.

<< Previous APOD This Day in APOD Next APOD >>
User avatar
APOD Robot
Otto Posterman
 
Posts: 1898
Joined: Fri Dec 04, 2009 3:27 am

Re: APOD: Fresh Tiger Stripes on Saturns Enceladus (2014 Apr

Postby bystander » Sun Apr 06, 2014 4:27 am

I don't imagine you will dispute the fact that at present the stupid people
are in an absolutely overwhelming majority all the world over.
— Henrik Ibsen
User avatar
bystander
Apathetic Retiree
 
Posts: 12556
Joined: Mon Aug 28, 2006 2:06 pm
Location: Oklahoma

Re: APOD: Fresh Tiger Stripes on Saturns Enceladus (2014 Apr

Postby neufer » Sun Apr 06, 2014 7:10 am

http://en.wikipedia.org/wiki/Enceladus wrote:




:arrow: <<Model of the interior of Enceladus from 2006.

The inner, silicate core is represented in brown, whereas the outer, water-ice-rich mantle is represented in white.

The yellow and red colors in the mantle and core respectively represent a proposed diaper diapir under the south pole.>>
Art Neuendorffer
User avatar
neufer
Vacationer at Tralfamadore
 
Posts: 11631
Joined: Mon Jan 21, 2008 1:57 pm
Location: Alexandria, Virginia

Re: APOD: Fresh Tiger Stripes on Saturns Enceladus (2014 Apr

Postby Whiskybreath » Sun Apr 06, 2014 8:32 am

The entire feature to the left of this photograph is beguiling. It seems to be more mobile than the hemisphere to the right, and the meaning of the narrow band to the top, which opens out into the larger area - with what appear to be waves of material squashed between two masses of more dense or higher territory ... Could this be an ocean between continents, or shallower sea?
Whiskybreath
 

Re: APOD: Fresh Tiger Stripes on Saturns Enceladus (2014 Apr

Postby HellCat » Sun Apr 06, 2014 3:01 pm

And what about that surprisingly bright fracture on the lower left? Is it possible we're seeing a relatively recent layer of water ice? And what's the process that turns it from fresh-ice-blue to snow white?
PS - It's on the lower left in the high-res image...
HellCat
Ensign
 
Posts: 28
Joined: Wed Aug 05, 2009 1:30 am
Location: Cleveland, Ohio USA (Zulu -5)

Re: APOD: Fresh Tiger Stripes on Saturns Enceladus (2014 Apr

Postby BDanielMayfield » Sun Apr 06, 2014 5:40 pm

neufer wrote:
http://en.wikipedia.org/wiki/Enceladus wrote:




:arrow: <<Model of the interior of Enceladus from 2006.

The inner, silicate core is represented in brown, whereas the outer, water-ice-rich mantle is represented in white.

The yellow and red colors in the mantle and core respectively represent a proposed diaper diapir under the south pole.>>


See also http://www.skyandtelescope.com/news/Evi ... 29821.html

Neufer’s old diaper diapir idea might be all wet not wet enough, and overdue for a change. Compare the graphic image he provided with this fresh thinking as to why so much water spews forth from the bottom of this moon. This artist’s image is from April 3, 2014, also taken from the Wikipedia article on Enceladus:



Which view is right? I guess it Depends. :P

Bruce
"Happy are the peaceable ... "
BDanielMayfield
Don't bring me down
 
Posts: 876
Joined: Thu Aug 02, 2012 11:24 am
Location: South Texas
AKA: Bruce

Re: APOD: Fresh Tiger Stripes on Saturns Enceladus (2014 Apr

Postby LocalColor » Sun Apr 06, 2014 6:40 pm

Very interesting moon. The image shows many craters on one side and no craters on the other - as if it was a fresh "clean" surface. Poor Mimas looks all beat up.

PS - the dead parrot sketch was a blast from the past.
User avatar
LocalColor
Science Officer
 
Posts: 228
Joined: Sat Mar 31, 2012 9:11 pm
Location: Central Idaho, USA

Re: APOD: Fresh Tiger Stripes on Saturns Enceladus (2014 Apr

Postby neufer » Sun Apr 06, 2014 9:35 pm

BDanielMayfield wrote:
Which view is right? I guess it Depends.

And are the geysers always around the South Pole or is there incontinental drift?
Art Neuendorffer
User avatar
neufer
Vacationer at Tralfamadore
 
Posts: 11631
Joined: Mon Jan 21, 2008 1:57 pm
Location: Alexandria, Virginia

Re: APOD: Fresh Tiger Stripes on Saturns Enceladus (2014 Apr

Postby BDanielMayfield » Sun Apr 06, 2014 11:25 pm

neufer wrote:
BDanielMayfield wrote:
Which view is right? I guess it Depends.

And are the geysers always around the South Pole or is there incontinental drift?


The south polar hotspot area very likely is stationary, but much of the frozen crust of ice shifts position over time scales that may resemble those of continental motions of rock here on Earth. That would rework most of the surface over time, but still leave some ancient, heavily cratered surface regions. Even in areas where there is no liquid between the ice and the rocky core, the ice can still slowly move, like glaciers do here on Earth.

Note that the north polar area of Enceladus is more heavily cratered than the south. This moon therefore is suffering from deep-seated, long term bi-polar disorder. But is this a cause, or and effect? Could this moon be suffering shame because of it’s incontinent condition? The entire E ring around Saturn is evidence of its long term leakage.

Bruce
"Happy are the peaceable ... "
BDanielMayfield
Don't bring me down
 
Posts: 876
Joined: Thu Aug 02, 2012 11:24 am
Location: South Texas
AKA: Bruce

Re: APOD: Fresh Tiger Stripes on Saturns Enceladus (2014 Apr

Postby Nitpicker » Sun Apr 06, 2014 11:41 pm

Seems to me like there is little evidence to support one kind of structure over the other (diapir or a "sandwiched ocean"). There is evidence of southern geysers forming the E-ring, but that doesn't really tell us anything about the geological structure creating the geysers. I might have been less likely to recoil from the "sandwiched ocean" idea, if the image was not described as a cartoon, and south was not drawn at the bottom, making it look like a low point for water to drain.
User avatar
Nitpicker
Inverse Square
 
Posts: 1655
Joined: Fri Sep 20, 2013 2:39 am
Location: S27 E153

Re: APOD: Fresh Tiger Stripes on Saturns Enceladus (2014 Apr

Postby BDanielMayfield » Mon Apr 07, 2014 12:34 am

Nitpicker wrote:Seems to me like there is little evidence to support one kind of structure over the other (diapir or a "sandwiched ocean"). There is evidence of southern geysers forming the E-ring, but that doesn't really tell us anything about the geological structure creating the geysers. I might have been less likely to recoil from the "sandwiched ocean" idea, if the image was not described as a cartoon, and south was not drawn at the bottom, making it look like a low point for water to drain.

I think there IS evidence for the “sandwiched ocean” notion Nitpicker.
APOD Robot wrote:Most recently, an analysis of slight gravity deviations has given an independent indication of underground oceans.


And from the S&T article I referenced here's and explanation of that evidence:
So how do astronomers map the interior of a moon using only an orbiting spacecraft?

It all comes down to the subtle effect of gravity. We tend to think of the force of gravity on any planet as a constant. But in reality it varies depending on your global location and the composition of the planet under your feet. For example, Earth’s gravity measured at our equator is 9.788 m/sec2, whereas at one of the poles it may be as high as 9.838 m/sec2 (a difference of 0.5%).

“Gravity allows us to open a window into the interior of the moon,” said Iess. During three close flybys of Enceladus, Cassini measured variations in how the moon’s gravity pulled on the spacecraft. These variations revealed the large-scale characteristics of the moon’s surface and interior, including any mass anomalies — spots where there is an excess or lack of mass — typically due to a bulge or a basin, or even just a change in density.

While flying past Enceladus’s south pole, Cassini spotted a negative mass anomaly, likely due to a depression in the icy surface.

“When you look at the actual surface you see that, although there is indeed a depression, it is much larger than that needed to explain the gravity,” said coauthor David Stevenson (Caltech). In other words, there simply isn’t enough mass at the surface of the south pole to account for the gravitational field present there. So there has to be something more massive underneath the surface. “A natural way to do this is to have a layer of water, because water is more dense than ice.”


Thus this subsurface ocean idea does have some real evidence to back it up. So don't be so quick to flush it down the drain.

Bruce
"Happy are the peaceable ... "
BDanielMayfield
Don't bring me down
 
Posts: 876
Joined: Thu Aug 02, 2012 11:24 am
Location: South Texas
AKA: Bruce

Re: APOD: Fresh Tiger Stripes on Saturns Enceladus (2014 Apr

Postby Nitpicker » Mon Apr 07, 2014 12:52 am

I didn't say it had no evidence. I said there is little evidence to support one kind of structure over the other.
User avatar
Nitpicker
Inverse Square
 
Posts: 1655
Joined: Fri Sep 20, 2013 2:39 am
Location: S27 E153

Re: APOD: Fresh Tiger Stripes on Saturns Enceladus (2014 Apr

Postby BDanielMayfield » Mon Apr 07, 2014 1:28 am

Nitpicker wrote:I didn't say it had no evidence. I said there is little evidence to support one kind of structure over the other.


Understood. But by your first comment you were put off by how the illustration of the new concept was discribed as a "cartoon." I too was surprised by the use of that term for something that doesn't look a bit cartoonish. The use [of] "cartoon" is a bit demeaning, both to the artist and to the scientific theory it illustrates.

Bruce
Last edited by BDanielMayfield on Mon Apr 07, 2014 3:21 am, edited 1 time in total.
"Happy are the peaceable ... "
BDanielMayfield
Don't bring me down
 
Posts: 876
Joined: Thu Aug 02, 2012 11:24 am
Location: South Texas
AKA: Bruce

Re: APOD: Fresh Tiger Stripes on Saturns Enceladus (2014 Apr

Postby Nitpicker » Mon Apr 07, 2014 1:30 am

Yeah, that was more a criticism of the presentation, than the idea.
User avatar
Nitpicker
Inverse Square
 
Posts: 1655
Joined: Fri Sep 20, 2013 2:39 am
Location: S27 E153

Re: APOD: Fresh Tiger Stripes on Saturns Enceladus (2014 Apr

Postby DavidLeodis » Mon Apr 07, 2014 7:40 pm

The image was brought up through the "Pictured above" link where in its caption it stated the image was "a full-disk view of the anti-Saturn hemisphere on Enceladus". I take the "anti-Saturn" to mean the image shows a side of Enceladus that is not facing Saturn but does it also mean that side never shows its face to Saturn (like the far side of our Moon never faces the Earth). :?:
User avatar
DavidLeodis
Perceptatron
 
Posts: 839
Joined: Mon May 01, 2006 1:00 pm

Re: APOD: Fresh Tiger Stripes on Saturns Enceladus (2014 Apr

Postby neufer » Mon Apr 07, 2014 7:45 pm

DavidLeodis wrote:
The image was brought up through the "Pictured above" link where in its caption it stated the image was "a full-disk view of the anti-Saturn hemisphere on Enceladus". I take the "anti-Saturn" to mean the image shows a side of Enceladus that is not facing Saturn but does it also mean that side never shows its face to Saturn (like the far side of our Moon never faces the Earth). :?:

Yes,

Art Neuendorffer ("anti-Satur(atfordia)n"
User avatar
neufer
Vacationer at Tralfamadore
 
Posts: 11631
Joined: Mon Jan 21, 2008 1:57 pm
Location: Alexandria, Virginia

Re: APOD: Fresh Tiger Stripes on Saturns Enceladus (2014 Apr

Postby DavidLeodis » Mon Apr 07, 2014 9:16 pm

neufer wrote:
DavidLeodis wrote:
The image was brought up through the "Pictured above" link where in its caption it stated the image was "a full-disk view of the anti-Saturn hemisphere on Enceladus". I take the "anti-Saturn" to mean the image shows a side of Enceladus that is not facing Saturn but does it also mean that side never shows its face to Saturn (like the far side of our Moon never faces the Earth). :?:

Yes,

Art Neuendorffer ("anti-Satur(atfordia)n"


Thanks neufer for that clarification. :)
User avatar
DavidLeodis
Perceptatron
 
Posts: 839
Joined: Mon May 01, 2006 1:00 pm


Return to The Bridge: Discuss an Astronomy Picture of the Day

Who is online

Users browsing this forum: 360 Spider, Ahrefs [Bot], Yahoo [Bot] and 11 guests