There's A Global Ocean Beneath The Surface Of Enceladus

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17 Sep 2015 18:22 #203061 by Akkarin
www.iflscience.com/cassinis-ocean-rg-editing

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The chances of life existing elsewhere in our Solar System have increased greatly because of this discovery!

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18 Sep 2015 07:49 #203120 by TheDude

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18 Sep 2015 11:12 #203126 by Gisteron
So the subsurface ocean has been known for at least as long as a year, though it was not confirmed that it is a global one until this month. At any rate, I am suspicious about the propositions of life formation, and here is why:
First, Enceladus, while rather dense, is a very small and very light object. Its surface g-acceleration is less than 1/85 that of earth's and it has an escape velocity that on our planet is well subsonic. Now that may be more or less irrelevant for most of bacterial life, at least considered on its own, but of course while those would be fascinating enough for the biologists, the rest of us are looking for something more multicellular, which brings me to another point: With a gravity so low, an atmosphere is nigh unthinkable. Now, again, water is enough to host molecule mobility, but water, especially subsurface water isn't good at letting sun rays through nor ought we expect the electrical stimulus that was the only way we ever could replicate natural amino acid generation - though maybe it is not indeed the only way. But you see the chances narrowing, don't you?

Finally, here is my biggest objection: Size and albedo. For this, let's do some math! :)

The sun has an electromagnetic emission rate of about 3.8*1026W.
Let's be generous in favour of Enceladus and round that up to P0=4*1026W. That'll make the math simpler, too.
Let us now be generous again and assume that between the sun and the Saturn subsystem there are no objects ever blocking the light. That is fair to assume, because any object in the way is negligibly small compared to the sun or the distance to it. I'm just pointing out this assumption for the sake of completeness.
So, effectively, all power the sun emits, by the time it reaches the Saturn system is distributed over a roughly spherical area with the radius equal to the average orbital distance of Saturn. That distance is the average distance of Enceladus to the sun, too, and we are assuming that Enceladus is never eclipsed by either Saturn or any of its fellow moons. We are being really generous here, saying Enceladus might as well be Saturn. So let's calculate that sphere's surface, 4[pi]r2 and let's again, for the sake of generosity, take the smallest distance Saturn ever has to the sun and round it down to something convenient rendering it r=1.35*1012m and therefore our Sun's power distributed over an area O=2.2*1025m2, again, underestimating the actual quantity here by about 5%.
At this distance it is fair to assume that the light rays are more or less parallel, so in order to identify the amount of power Enceladus receives we can assume it was a flat disc with the same diameter. Because we are being on a generous track today, we'll take the largest diameter of that moon, namely d=513200m. So our "catching" area is A=[pi]*d2/4=2.065*1011m2.
This means that with the power distributed over O, A is what actually captures any, so the power P out of the output power P0 we get is P=P0*A/O=3.8*1012W. Since Enceladus has an albedo of 99%, it keeps about a hundredth of that, so effectively it keeps as little as 3.8*1010W and much of that is probably absorbed by the ice long before it could reach the waters underneath.
For reference, earth being nine times closer to the sun, our O is eighty times smaller, and with our d being 25 times larger our A is 600 times larger and with our albedo being less than half of Enceladus', our net power gain is, speaking in orders of magnitude, about ten million times greater and we are well on the edge of the habitable zone.
I think Enceladus doesn't come close to meeting the energy demands life would have on it... But then I'd be excited to find out that and why I'm wrong, too, especially seeing how this would help us understand what it takes to form life to begin with and perhaps how it could have come to be on earth.

Better to leave questions unanswered than answers unquestioned

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20 Sep 2015 23:35 #203260 by Streen
I'll celebrate when I see a picture of an alien creature. The rest is just speculation.

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21 Sep 2015 19:57 #203314 by Akkarin

Gisteron wrote: Now that may be more or less irrelevant for most of bacterial life, at least considered on its own, but of course while those would be fascinating enough for the biologists, the rest of us are looking for something more multicellular


Hey, I'm not looking for anything multi-cellular :D though of course that would be pretty cool too.

Not sure why you did all the mathematics for how much energy Enceladus receives from the sun... Enceladus doesn't rely on the sun for energy, Enceladus gets most of its energy (at least the energy to keep it's ocean from freezing) from the gravity/friction interplay with Saturn so it's kind of a moot point.

The Earth would probably be a lifeless husk if it relied only on the sun for energy, it's the radioactive decay in the centre which helps keep the planet warm (beneath the surface) and the electromagnetic shielding necessary for an atmosphere of any use.

Enceladus not having an atmosphere also seems largely irrelevant, because we're not looking in Enceladus' atmosphere for signs of life but it's liquid oceans.

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22 Sep 2015 08:42 #203352 by Gisteron
Well is it then coincidence that Earth has next to no crust to speak of, barely enough to keep what's above from becoming what's beneath and often failing at that, too, while mars is rock solid so much that it pretty much has no magnetic field to speak of? I'm not much of an astronomer and haven't done my math on the two but intuitively it would seem that the sun is a very relevant factor in life on earth, arguably far more so than its hot mantles.

Now as for Enceladus, if the gravity interplay with Saturn was enough to keep something on that moon from freezing, one wonders why it has such a thick frozen crust. Gravity, on the other hand, and more specifically the pressure said crust exhibits on the waters beneath might just be a reason said waters don't freeze, though whether the temperatures are high enough to catalyze chemical reactions enough to form furtherly catalytic molecules remains to be seen. I was ignoring the influence of Saturn because I figured it negligible next to that of the sun and my layman's intuitions tell me that in a stable oscillating system where next to no mechanical energy is expended, next to no thermal energy can be generated from it either. I shall stand corrected if calculations reveal otherwise and feel free to present those so we can take a sum and see how much I was off and whether the difference is anywhere near great enough to warrant us expecting life of any recognizable type.

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22 Sep 2015 08:57 #203353 by Adder
I think Mar's lost its atmosphere because it lost its magnetosphere. Once the magnetosphere's shielding effect from our Suns solar wind ceased to exist, it literally blew out into space AFAIK... same could happen to us but Earth's inner core is much more massive from what I remember and considered unlikely to stop spinning around. Could be wrong, I aint no astronomer either
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25 Sep 2015 20:31 #203630 by Akkarin
Yes Mars has no atmosphere because it doesn't have a strong enough magnetic field. The reason it lacks a magnetic field is because it has cooled down too much, but the reason for that is because of the geometric relationship between the surface area and volume of a sphere.

Earth has a large enough radius, but Mars with its smaller radius means the proportion of volume to surface area is closer to 1:1 (in this instance I don't know if larger or smaller would have been the best adjective to describe it, I hope you get what I mean). Because of Mars' proportions there is less heat produced in its core and a greater opportunity for the heat to be radiated to the surface and lost. Hence it has cooled down much faster and largely solidified into a cold rock.

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