Has Cassini revealed the presence of life on Saturn's moon Enceladus

[spacestart.eu]

The Cassini probe may have already collected data that could reveal the presence of life on Saturn's moon Enceladus. A recent study led by Christopher McKay from NASA’s Ames Research Center in California reveals the moon holds an ocean of liquid water beneath its surface. This ocean could be a potential habitat for extraterrestrial life.



More info

[RGClark]

Thanks for that. Here's a more detailed discussion in New Scientist, with a link to the article in the journal Astrobiology available now free full text:

Cassini might hold secrets to life on Saturn moon.
"The Cassini probe may have already collected data that could reveal the presence of life on Saturn's moon Enceladus, a new study argues. But mission scientists say teasing out the subtle signature of life may prove difficult."
18:17 03 November 2008
http://space.newscientist.com/articl...turn-moon.html


Bob Clark

[01101001]

Here are some abstracts from the upcoming December AGU meeting that may have a bearing on the Enceladus’ organics discussion:

Enceladus Plume Composition

http://www.agu.org/cgi-bin/SFgate/SF...200&="P14A-01"

That one worked for me but many of these links are not working.

fm08: The following database is not available: /data/epubs/wai s/indexes/fm08/fm08
fm08: Search produced no result

Are they temporary results of database searches that have expired and been discarded?

(And, when you provide more stable URLs, why not make them active links so each reader interested doesn't have to play cut and paste?)

[borman]

That one worked for me but many of these links are not working.



Are they temporary results of database searches that have expired and been discarded?

(And, when you provide more stable URLs, why not make them active links so each reader interested doesn't have to play cut and paste?)

Usually the links are automatically shortened and functional when posted, such as in your repost of one of the links. Perhaps it is a quirk from quick-posting that prevents the auto-short linking.

I will try to resubmit the post this route to see if they will be auto-short-linked.

Sorry, no luck here. Cutting and pasting of the links isn't working here although I can load all abstracts from links from my browser correctly.
I notice that HTML is disabled.

Am I required to delete the post then?

[01101001]

(When I turned that single one into a functional link, I explicitly added the [URL="..."]...[/URL] tags. You can't always rely on the software to recognize a URL and make it an active link; I've never bothered to figure out why when it's so easy to work around.)

Am I required to delete the post then?

Looks like you did, but I think better would have been to just remove the bad links and maybe explain to the readers how they could visit the same abstracts you thought were important.

Those documents should have some kind of permanent location and URL so they can be referenced, but you'd probably have to do more work to present them. But, a brief visit to the AGU conference site indicates their database of abstracts fights friendly usage.

[borman]

(When I turned that single one into a functional link, I explicitly added the [URL="..."]...[/URL] tags. You can't always rely on the software to recognize a URL and make it an active link; I've never bothered to figure out why when it's so easy to work around.)



Looks like you did, but I think better would have been to just remove the bad links and maybe explain to the readers how they could visit the same abstracts you thought were important.

Those documents should have some kind of permanent location and URL so they can be referenced, but you'd probably have to do more work to present them. But, a brief visit to the AGU conference site indicates their database of abstracts fights friendly usage.

It appears they have redone the links to txt documents in the past couple days. I have cut repasted the new links and have included a couple extra abstracts as well.

Here are some abstracts from the upcoming December AGU meeting that may have a bearing on the Enceladus’ organics discussion:


Enceladus Plume Composition

http://www.agu.org/cgi-bin/SFgate/SF...m08%2ffm08.txt

Neutral Composition of Enceladus' Plume

http://www.agu.org/cgi-bin/SFgate/SF...m08%2ffm08.txt

Enceladusˇ¦ Gas Tori of Carbon-bearing and Nitrogen-bearing Molecules

http://www.agu.org/cgi-bin/SFgate/SF...m08%2ffm08.txt



Cassini CAPS-ELS observations of Enceladus's plume
http://www.agu.org/cgi-bin/SFgate/SF...m08%2ffm08.txt

Sodium Salts in Ice Grains from Enceladus' Plumes: Evidence for an Ocean below the Moon's Surface

http://www.agu.org/cgi-bin/SFgate/SF...m08%2ffm08.txt

On the formation of sodium bearing E ring ice grains on Enceladus.

http://www.agu.org/cgi-bin/SFgate/SF...m08%2ffm08.txt


On the Long-Term Abundance of Energetic Sodium Ions in Saturn's <20 Rs Magnetosphere
http://www.agu.org/cgi-bin/SFgate/SF...m08%2ffm08.txt


Regolith Growth and Darkening of Saturn's Ring Particles

http://www.agu.org/cgi-bin/SFgate/SF...m08%2ffm08.txt


Comment:
The question about Sodium is that it is found in the E-ring which is replenished by Enceladus. But does the E-ring also contain components derived elsewhere which might contribute to the Sodium signature. If the plume gives a Sodium signature of comparable strength to the E-ring, then the case is strengthened for a differentiated and ocean bearing Enceladus. Also, if Sodium is found, is it of sufficient concentration to distinguish Enceladus from what comes from a comet? Or do comets have subsurface oceans as well?

Habitability of Enceladus: Planetary Conditions for Life

http://www.agu.org/cgi-bin/SFgate/SF...m08%2ffm08.txt

Liquid Water vs. Hydrogen Cyanide on Enceladus

http://www.agu.org/cgi-bin/SFgate/SF...m08%2ffm08.txt


This one is interesting in that it suggests the presence of HCN with water may mean that the ocean is young.

Detecting a Subsurface Ocean From Periodic Orbits at Enceladus

http://www.agu.org/cgi-bin/SFgate/SF...m08%2ffm08.txt

Comparing Enceladus to Comets: Implications for Enceladus' Activity

http://www.agu.org/cgi-bin/SFgate/SF...m08%2ffm08.txt

Is Enceladus a Comet? A Cometary Perspective on Enceladus

http://www.agu.org/cgi-bin/SFgate/SF...m08%2ffm08.txt

TI: Saturn Magnetospheric Impact on Surface Molecular Chemistry and Astrobiological Potential of Enceladus

http://www.agu.org/cgi-bin/SFgate/SF...m08%2ffm08.txt

Photochemistry of Methane-water Ices

http://www.agu.org/cgi-bin/SFgate/SF...m08%2ffm08.txt

A Comparison of CAPS Composition Measurements of the Plasma near Enceladus with Predictions of a Chemical Model

http://www.agu.org/cgi-bin/SFgate/SF...m08%2ffm08.txt


The Plume Ionosphere of Enceladus as Seen by the Cassini Ion and Neutral Mass Spectrometer

http://www.agu.org/cgi-bin/SFgate/SF...m08%2ffm08.txt


Examining Enceladus' plume through observations and simulations

http://www.agu.org/cgi-bin/SFgate/SF...m08%2ffm08.txt

[timb]

Condensed version: no evidence for life.

[RGClark]

It appears they have redone the links to txt documents in the past couple days. I have cut repasted the new links and have included a couple extra abstracts as well.

Here are some abstracts from the upcoming December AGU meeting that may have a bearing on the Enceladus’ organics discussion:

...

Sodium Salts in Ice Grains from Enceladus' Plumes: Evidence for an Ocean below the Moon's Surface

http://www.agu.org/cgi-bin/SFgate/SF...m08%2ffm08.txt

On the formation of sodium bearing E ring ice grains on Enceladus.

http://www.agu.org/cgi-bin/SFgate/SF...m08%2ffm08.txt


On the Long-Term Abundance of Energetic Sodium Ions in Saturn's <20 Rs Magnetosphere
http://www.agu.org/cgi-bin/SFgate/SF...m08%2ffm08.txt


Regolith Growth and Darkening of Saturn's Ring Particles

http://www.agu.org/cgi-bin/SFgate/SF...m08%2ffm08.txt


Comment:
The question about Sodium is that it is found in the E-ring which is replenished by Enceladus. But does the E-ring also contain components derived elsewhere which might contribute to the Sodium signature. If the plume gives a Sodium signature of comparable strength to the E-ring, then the case is strengthened for a differentiated and ocean bearing Enceladus. Also, if Sodium is found, is it of sufficient concentration to distinguish Enceladus from what comes from a comet? Or do comets have subsurface oceans as well?

...

Thanks for all the interesting links.

The sodium ones are especially interesting because of a report last year that failed to find evidence for sodium and therefore concluded there was no subsurface ocean on Enceladus:

Updated: Sunday, 16 December 2007, 17:21 GMT
Sodium issue clouds Enceladus.
By Molly Bentley
http://news.bbc.co.uk/2/hi/science/nature/7145530.stm


Bob Clark

[borman]

Both the Sodium non-signal and HCN vs H2O papers begin to suggest a possible scenario I favored a couple years ago on another board.

The Sodium signal is based upon the idea that the moon has differentiated into a rocky core and an ice covering where short lived isotopes such as Al26 has assisted in the differentiation. No one has yet explained how an ocean between the core and ice covering could not be salty. For example, the ocean proposed to be beneath the icy surface of Europa is thought to be salty to explain the induced magnetic field that was monitored by Gallileo. But this differentiation with assistance of short lived isotopes must have taken place early in solar system history, some 4.5 Gya.

But the earlier observation did not see Sodium, so it could mean that the E-ring is made of more than one component rather than exclusively from Enceladus. To allow HCN to co-exist with water places a constraint that the ocean should only be around 5 million years old or younger. So the heat source would not have the benefit of either differentiation or short-lived isotopes if the HCN vs water abstract can be applied in this manner of constraint.

So if there is either an ocean or large lake under the surface of Enceladus, it may be of recent vintage. So I still consider it a viable hypothesis that the heat source is not indigenous to Enceladus. It may have been impacted by a fragment of a differentiated proto-planet from nearer its core where longer lived radio-isotopes may have collected prior to collision with another proto-planet. The presence of magnetic fields in some meteorites confirms that some planetismals did differentiate prior to collision. So some pieces nearer the core may have carried a higher proportion of longer-lived isotopes. If one of these shards struck Enceladus, it might provide some of the heat and energy to melt some of the ices without setting off a cascade to differentiation which would make the water salty. But the possibility of a sub-surface lake or ocean is not then ruled out because the moon is not differentiated by the normal route. The heat source like this may work to give the organics observed, but 5 million years seems to be a very short time to start biology within a very localised icy matrix that may not reach to the core of a moon that still may not be differentiated.

This might seem like a somewhat unique event, but then Enceladus is unique among the Saturn moons with its magnitude of venting.

[toothdust]

Condensed version: no evidence for life.

Optimistic condensed version: Great potential for life.

[Abbadon_2008]

Who knows? They might find Nemo. LOL!

[RGClark]

Nice article here describes the controversy over the sodium on Enceladus in more detail:

Saturn's moon may host an ocean.
By Ron Cowen
August 30th, 2008; Vol.174 #5
Enceladus' geysers could have delivered sodium from its underground ocean and into Saturn's E ring.
"Cassini researcher Roger Yelle of the University of Arizona has a different view. "The surface of Enceladus is not pure water ice. We just don't have a good idea of what the other components are," he notes. "There could be a small amount of sodium in the minerals in the surface layer." The sodium detected in the E ring could have come from that material on the moon's surface, rather than from its interior. "I don’t believe that you can say that the detection of sodium [in the E ring] implies that it came from a sub-surface ocean" on Enceladus, Yelle says. "So, let’s not run around crazy-like claiming the likely detection of life because sodium was found in dust particles in the Saturn system.”
"Another complicating factor is that studies from Earth, using large telescopes such as the Keck Observatory atop Hawaii’s Mauna Kea, have not found any sign of sodium in the E ring. Nick Schneider of the University of Colorado at Boulder reported the lack of sodium last December in San Francisco during a meeting of the American Geophysical Union.
"But such studies, notes Kempf, can only detect sodium in its gaseous form, not the solid sodium in the frozen ice particles. He maintains that the bulk of the sodium in the E ring lies in the solid phase recorded by Cassini’s cosmic dust analyzer."
http://sciencenews.org/view/generic/..._host_an_ocean

Bob Clark

[borman]

Another possibility to be considered is that the sodium on the surface arrived by implantation. Whatever is contaminating the E-ring with Sodium possibly complementing the contribution from Enceladus would likely also coat Enceladus as well since it too is in the E-ring.

[aurora]

Nice article on enceldus in this month's Sci Am.

I think it would be good to have a sample return mission. Something like the StarDust mission that returned samples from comets, could be done relatively cheaply without even having to land on the moon.

[Ilya]

Nice article on enceldus in this month's Sci Am.

Yes. I like this (quoting from memory):

"Europa has no active geysers that we know. To learn about its deep interior, we have to drill deep into Europa's interior -- an incredibly difficult project that will surely not happen in our lifetimes. On Enceladus you only have to fly through one of the plumes -- or land, look up, and stick your tongue out."

[borman]

The November 25th CHARM is out for Enceladus

http://saturn.jpl.nasa.gov/multimedi...HARM_encel.pdf

On page 48 it is noted that in the E-ring that there are 4 populations:

I) is pure water ice; II) is water ice with rocky or organic impurities; III) is Sodium rich water ice; IV) is iron rich non-water material.

It could be suggested that a source of contamination might derive from ring material around one of the other moons. Rhea will be visited in 2010. Perhaps the CDA can sample the material to see if there is an excess of Sodium or iron coming from either the ring or the dust cloud associated with the ring.

http://www.nasa.gov/home/hqnews/2008...ound_Rhea.html

[borman]

Methane to hydrocarbon ratios to test for support for biotic methane

A new paper suggests that 99.9 percent methane is more indicative of biotic methane than 90 to 99 percent methane where the 1 to 10 percent is made of non-methane hydrocarbons.

The Possible Origin and Persistence of Life on Enceladus and Detection of Biomarkers in the Plume

Abstract: http://www.liebertonline.com/doi/abs...ournalCode=ast

or
http://www.liebertonline.com/doi/pdf.../ast.2008.0265


Press release: The Possible Origin and Persistence of Life on Enceladus and Detection of Biomarkers in the Plume

http://www.spaceref.com/news/viewsr.html?pid=30293

[Abbadon_2008]

Does biotic methane indicate flatulent lifeforms?