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Saturn’s tiny moon Enceladus was the centre of attention for the Cassini spacecraft again last week, with beautiful new photos being released of the moon and its water vapour geysers erupting from the south pole. Some views show surface detail on the moon, some are of the geysers themselves and there is a very nice shot of Enceladus silhouetted against Saturn and its rings in the background. There is even a dual ultraviolet stellar occultation in which two of the stars in the belt of the constellation Orion are seen shining through the plumes! Even though these are still raw, unprocessed images, they again capture the beauty of Enceladus and the Saturnian system.
These new images were taken October 19, 2011 during the E-15 flyby, in which Cassini flew about 1,230 kilometres (765 miles) above the surface of Enceladus. The geysers can be seen in the image below, albeit these are not the closest views that Cassini has obtained. Still, it can be clearly seen how far they extend out from the moon, for a few hundred kilometres.
Some surface detail can be seen in the next image below, a hint of the geological complexity of this moon, most notably seen in the “tiger stripe” fissures at the south pole, where the geysers erupt from inside the moon, escaping to the vacuum of space outside, where the water vapour freezes and falls back to the surface of Enceladus as a form of snow. As some have suggested, Enceladus may be a good place for skiing (with the snow being a very fine powder, although the extremely low gravity would probably interfere too much…)!
Having a personal fascination with Enceladus, I was reminded of an older “Captain’s Log” entry on the CICLOPS web site (2006), by Cassini imaging team leader Carolyn Porco, after the initial discovery of the geysers. In part:
“Our detailed analyses of these images have led us to a remarkable conclusion, documented in a paper to be published in the journal SCIENCE tomorrow, that the jets are erupting from pockets of liquid water, possibly as close to the surface as ten meters… a surprising circumstance for a body so small and cold. Other Cassini instruments have found that the fractures on the surface and the plume itself contain simple organic materials, and that there is more heat on average emerging from the south polar terrain, per square meter, than from the Earth.
Gathering all the evidence and steeling ourselves for the “shockwave spread ’round the world”, we find ourselves staring at the distinct possibility that we may have on Enceladus subterranean environments capable of supporting life. We may have just stumbled upon the Holy Grail of modern day planetary exploration. It doesn’t get any more exciting than this.
A great deal more analysis and further exploration with Cassini must ensue before this implication becomes anything more than a suggestion. But at the moment, the prospects are staggering. Enceladus may have just taken center stage as the body in our solar system, outside the Earth, having the most easily accessible bodies of organic-rich water and, hence, significant biological potential.
Many years from now, it may well be that we and those who follow us will look back on these explorations of Saturn and take our discoveries on this otherwise cold little world to be the most wondrous of any we’ve ever made.
Future explorers of Saturn will have much to look forward to.”
A flyby of Enceladus to gather samples from these geysers is certainly a reasonable profile for a future mission to Saturn. Then either the spacecraft will need to have some molecular biological robotic lab to search for putative life or the sample will need to be sent back to Earth. The cost of this mission is certainly far less than deploying a robotic drilling system to the surface of Europa or similar ice moon.
I can say that I have certain hopes for life on these little moons. However, that is tempered by what I see as questions about the energetic flow in these bodies, and whether it is sufficient to really give temperature gradients sufficient to drive molecular processes found in biology.
LC
There is certainly many questions here. However, once sufficiently complex cells have been established the initial need for thermal gradients disappear.* There are many species getting energy from hydrogen, some of which survive on hydrogen released from background radioactive minerals alone. Remaining chemical gradients would be another hydrogen source.
“Perhaps most fascinating are the feeding habits of the new organisms. They depend not on sunlight, but on radiation from uranium ores for their existence. Radiation emanating from uranium minerals in or near the fracture allows for the formation of hydrogen gas from decomposition of water and formation of sulfate from decomposition of sulfur minerals. Hydrogen gas is highly energetic if it reacts with oxygen or other oxidants like sulfate and Firmicutes are able to harvest energy from the reaction of hydrogen and sulfate, allowing other microbes in the fracture community to use the chemical waste from the Firmicutes as food.”
Similar species utilize (actually prefer) a smidgen oxygen, which may be environmental in a water ocean without much of any photosynthesis around. Of course there is then the question of how much there is and how much the cells need.
I am assuming Enceladus minerals would have something like Earth residual radioactivity.** Another question would be if the hydrogen reaches the water, but since there seem to be contact with minerals (salt), I can’t see why not.
So yes, tempered hopes. But still hopes.
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* Some of these metabolisms have taken billion of years to evolve here, and have been evolved around an oxygenated chemistry in the last ~ 2.5 Ga. So while we can see the possibility, we don’t know the likelihood.
** Wikipedia tells of a theory for Enceladus which both results in the ocean responsible for the vents and a differentiated rocky core. That should ensure concentration of uranium ores I think.
The hydrogen or proton is the unit which is involved with cellular respiration. The question which might be asked is whether there are energy flow processes capable of producing by various means a proton. The proton is pumped through channel gates by mitochondria. Mitochondria are essentially prokaryotes within Eukaryotic cells. So the tidal induced energy flow or heating of Enceladus would have to be sufficient to have that chemical potential.
LC
what does it mean to be “raw, unprocessed” images? They look like normal snap shots. Is processing for bringing out details and such? Will processing intrinsically change them in some way?
Yes and no… they will still be available in their original format after they are ‘cleaned up’, cropped and reformatted. That way all of the data set will remain intact for future gens.
Go to the Cassini website to look at “raw, unprocessed images”. Many are fascinating.
Also, why do we never see any stars in any of these photos? Is there some filter or are the moons just so much brighter that the shutter speed is not enough for stars?
Basically, the background stars are much dimmer than the foreground object(s) imaged. The camera lens does not see background stars because the exposure is set to bring out details in foreground objects, which are much brighter.
This ‘photographic’ compensation is also present in the photo’s the astronauts took on the Moon. To the ‘under informed’ the lack of background stars was evidence that the images were NOT taken on the Moon. Stuart Robbins Phd., goes into a detailed discussion about this phenomena in one of the podcasts on his web page: Exposing PseudoAstronomy Podcast
Check this out at:
Episode 7 (BONUS): Live “Apollo Moon Hoax” Talk at Skepticamp
http://podcast.sjrdesign.net/