CICLOPS: Cassini Imaging Central Laboratory for OPerationS

Jet Spots in Tiger Stripes
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Jet Spots in Tiger Stripes
PIA 10361

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Jet Spots in Tiger Stripes
PIA 10361

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  Heat radiating from the entire length of 150-kilometer (95-mile) long fractures is seen in this best-yet heat map of the active south polar region of Saturn's ice moon Enceladus. The warmest parts of the fractures tend to lie on locations of the plume jets identified in earlier images, shown in the annotated version with yellow stars. The measurements were obtained by the Cassini spacecraft’s Composite Infrared Spectrometer from the spacecraft’s close flyby of the moon on March 12, 2008.

Remarkably high temperatures, at least 180 Kelvin (minus 135 degrees Fahrenheit) were registered along the brightest fracture, named Damascus Sulcus, in the lower left portion of the image. For comparison, surface temperatures elsewhere in the south polar region of Enceladus are below 72 Kelvin (minus 330 degrees Fahrenheit).

Heat is escaping from Enceladus' interior along these warm fractures, dubbed "tiger stripes," which are also the source of the geysers that erupt from the polar region. The infrared radiation was mapped at wavelengths between 12 and 16 microns. The infrared data, shown in false color, are superimposed on a grayscale image mosaic of the south pole obtained by Cassini's cameras on July 14, 2005, during the previous close Enceladus flyby. Numbers on the map indicate latitude and longitude.

This new view shows that at least three of the south polar fractures are active along almost their full lengths--the fourth one, on the right, was only partially covered by this scan. The level of activity varies greatly along the fractures. The warmest parts of the fractures tend to lie on locations of the plume jets identified in earlier images. The main "tiger stripe" fractures are not the only sources of heat, however; additional warm spots are seen in the upper right part of the scan. The warm regions are probably concentrated within less than a few hundred meters (a few hundred yards) of the fractures, and their apparent width in this image results from the relatively low resolution of the infrared data.

This map was made by scanning the south pole during the period from 16 to 37 minutes after closest approach to Enceladus, at a distance between 14,000 and 32,000 kilometers (about 8,700 and 20,000 miles) as Cassini rapidly receded from its close (50-kilometer or 32-mile) flyby.

The Cassini-Huygens mission is a cooperative project of NASA, the European Space Agency and the Italian Space Agency. The Jet Propulsion Laboratory, a division of the California Institute of Technology in Pasadena, manages the mission for NASA's Science Mission Directorate, Washington, D.C. The Cassini orbiter was designed, developed and assembled at JPL. The composite infrared spectrometer team is based at NASA's Goddard Space Flight Center, Greenbelt, Md. The imaging team consists of scientists from the US, England, France, and Germany. The imaging operations center and team lead (Dr. C. Porco) are based at the Space Science Institute in Boulder, Colo.

Released: March 26, 2008 (PIA 10361)
Image/Caption Information

Alliance Member Comments
Tiger (Apr 19, 2008 at 4:29 PM):
I believe you are in middle or high school cmckay? Your have an awesome sense of chemistry and physics!
NeKto (Apr 17, 2008 at 6:11 PM):
Respected cmckay! you made an important point; that the non biological source for the hydrocarbons does not preclude biological activity. our wonderful little robot friend has given us a great deal of information to work with. with great teams like ciclops, jpl and others working on the data, i anticipate fascinating answers and more intriguing questions!
And Tiger, the most fundamental question the Saturn system poses to us is one i do not believe Cassinni can answer; that is the fundamental nature of gravity itself. i am confident that anyone on this forum agrees gravity exists. we know a lot about how it works, but what we know so far still cannot explain the complexities we see in the Saturn system. if i am not mistaken, human exploration of the Saturn system has generated more controversy in gravitational theory than anything else since the inseption of gravitational theory.
Tiger (Apr 13, 2008 at 4:43 PM):
Hi professor,I was just wondering if you there are mysreries about Saturn that cannot be solved...even with Cassini
cmckay (Apr 13, 2008 at 1:05 PM):

Yes, ethlyene (C2H2) is another C2 compound I should have listed. There is only one C1 but there are 3 C2 compounds. C typically has four bonds. In methane these all go to H. When there are 2 Cs then these two Cs can join with a single bond leaving three bonds for H for each carbon (ethane C2H6), double bond leaving 2 bonds for H for each carbon (ethlyene C2H4) or triple bond leaving only one bond for a H (acetylene- official name is ethyne, C2H2). Working this same logic there are many possible combinations of C3, even more C4 etc.

As I said, biogenic sources of CH4 tend not to also produce C2 and C3 compounds. A quick look at the spectrum from the INMS on the March 2008 flyby seems to show comparable levels of C2, C3 etc compared to C1. This would seem to suggest a non biological source of the methane. Even if true, this not rule out biology in the system, just says that the methane is not produced by methanogens.
NeKto (Apr 12, 2008 at 12:37 PM):
thank you cmckay. i was wondering what indicators could tell us about the source of the organic molecules. what you say about the mass spectrum makes sence to me. (i had forgotten how rare C2 hydrocarbons are in biomass!) it does lean toward non biological. So biological processes appear to be very unlikely as the energy source. that is the big riddle, where is the heat coming from? (by the way, you didn't mention C2H4)
Tiger (Apr 5, 2008 at 4:31 PM):
Thanks chris! You`re a genius!
cmckay (Apr 5, 2008 at 10:01 AM):
Tiger (Tyler) and others. A brief reminder about organic molecules might help explain what the INMS can do. The INMS detects the mass of individual molecules. Methane is the simplest organic molecule it has 1 carbon connected to 4 hydrogen atoms. Total mass is 16 mass units. The next more complex hydrocarbon is ethane with 2 carbons each connected to 3 hydrogens. Total mass is 30. Acetylene is a different hydrocarbon that also has 2 carbons but each one is connected only to one hydrogen. Total mass 26. As the number of carbon atoms an organic molecule has the number of possible different combinations becomes quite large. Looking at the number of molecules with one carbon atom sometimes called C1 (only methane, CH4) and comparing that to the number of atmosphere with two carbon atoms called C2 (ethane C2H6, acetylene C2H2) and comparing these to the C3 atoms (C3H6, C3H2 etc.) and C4, and C5. We see a series going from simple to complex. The INMS can measure up to total mass 100 so that would include benzene (C6H6 mass = 6X12+6=76) but not much more.

The relative concentration of C1 to C2,C3,C4 etc. may indicate a biological source. A biological source makes much more C1 than other. While non biological source tend to make them all. Quick look at the spectrum from the March flybe seems most consistent with a non-biological source.
carolyn (CICLOPS) (Apr 4, 2008 at 3:18 PM):
Yes, it can distinguish between molecules of different mass. How well it does at measuring the abundance of any molecule depends on how much of the molecule is present. See Chris McKay's comment about this in a diff't earlier thread.
Tiger (Apr 4, 2008 at 1:35 PM):
Then how come it can`t distinguish the real amount of carbons? You said earlier that there may be 3...or even 4 carbons.
carolyn (CICLOPS) (Apr 4, 2008 at 12:59 PM):
Tiger: This is not the way it works. The INMS instrument measures the mass of the molecules it collects. It can distinguish between molecules that contain one or two carbons by determining that one is heavier than the other. There is no `processing' of two carbons to make a single molecule. Nature does that!
Tiger (Apr 4, 2008 at 9:14 AM):
professor,this comment may not make any sense because I don`t really understand the situation about the methane and acetylene. Well, remember when you said that there may be more than 2 carbons of methane? According to my opinion,the way to know is to let the IMNS machine process the 2 carbons. If they make an atom,then there is only 2 carbons. But if they don`t make an atom,then there must be more existing carbons. So piece the carbons together until the results make sense. It`s like a puzzle.
carolyn (CICLOPS) (Mar 27, 2008 at 6:34 PM):
Harry....of course we are modeling such things. We want to figure out if it's possible, with all the evidence in hand, to determine the likelihood that we have liquid water beneath the surface somewhere. The resolution of the IR is much poorer than the resolution of the imaging data. So we don't know how wide really the hottest temps, along the tiger stripe fractures, are. If we assume the region that is hot is very narrow, you get hotter temps than if you assume it is wider. And heat conduction would make the warm temps spread out horizontally. But the heat coming from below would also be carried by the diffusion of vapor (which carries heat) upward.

Interesting, huh?
Harry (Mar 27, 2008 at 5:34 PM):
I expect that there will be a lot of post processing done on these overlapped infrared and visual images. Can you provide any rough idea of the differences in the spacial resolution of the infrared image with respect to the visual image? I presume that the region of higher surface temperature is wider than the visual "tiger strip" feature. Other than heat transfer of the vented material coming from the "tiger strip", the rest of the heat signature must come from thermal conduction of the surface "ice". I hope someone is modeling this heat transfer equation to formulate ideas of how deep "tiger strip" fissures are and possibly the ambient temperature of the subsurface heat source.

Again, great work! I am sure that interpretations of these features will take years to produce. Patience is a virtue that is a struggle to master. Harry from Houston.
MartinL (Mar 26, 2008 at 1:36 PM):
Hello, dear carolyne and all your kollegues, you are the greatest!
Your findings are so very interesting, that i look forward to all your newsletters. You all do a lot more than a good job, your work is fascinating and not possible without a great enthusiasm. I lift my hat in front of you!!
May be the force with you all the time!
best wishes from Stuttgart/ Germany to you all!!!

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