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Huge Ocean Confirmed Underneath Solar System's Largest Moon
sciencehabit writes The solar system's largest moon, Ganymede, in orbit around Jupiter, harbors an underground ocean containing more water than all the oceans on Earth, according to new observations by the Hubble Space Telescope. Ganymede now joins Jupiter's Europa and two moons of Saturn, Titan and Enceladus, as moons with subsurface oceans—and good places to look for life. Ceres, the largest object in the asteroid belt, may also have a subsurface ocean. The Hubble study suggests that the ocean can be no deeper than 330 kilometers below the surface.
Finally a reason to kick-start manned space exploration! Think of what can be learned! If there is life on these moons, then that means that it will also die. Dead plants means ocean floor sediment. That means there could be oil there! We now have a reason!
"Freedom in the USA is not the ability to do what you want. It is the ability to stop others from doing what THEY want"
Except it is not a solar radiation you need protecting against (Sun is very far), but Jupiter radiation. Unfortunately despite magnetosphere, Ganymede gets around 8 rem of radiation per day (http://en.wikipedia.org/wiki/Colonization_of_the_outer_Solar_System#Ganymede), which is bit too much for life as we know it. Fortunately, it is not going to be an issue 300km below the surface - but at that depth, you don't need magnetosphere anyway.
I think that biggest problem for life there would be availability of energy. 300km of crust is probably shielding external energy too well, so internal heat would be probably only viable source of that. Might be not enough to sustain life (or even more, to produce it randomly)
On the other hand, heat built up by tidal forcing of Jupiter will also not be able to escape easily, through such a thick crust. Remember that we have many deep-ocean creatures on earth, where there is no light, and the water is so cold that it is barely liquid. (zero to three degrees Celsius).
Actually, it has been estimated there are so many deep-ocean species, that bioluminescence might be the most common method of communication on earth.
I should add that we need to think better about how we want to think about early life, what's likely to lead to an evolutionary path.
On one hand, we have self replicators like the misfolded prions of BSE. Injected into a healthy human, a single misfolded prion can begin taking others in the person's body and misfolding them, leading to a catalytic cycle that spreads like a virus and eventually kills the person. One could conveive that if there were a wide range of "roughly prion-like" chemicals in some primordial soup, that their variations in folding could lead to evolutionary adaptation with time.
Is this reproduction some realistic sort of form of protolife? By far most people would say no. Prions are large, complex proteins; the concept of an early world containing large amounts of this exceedingly specific complex protein, or even proteins not exactly the same but still similar enough for reproduction, is exceedingly unlikely.
On the other hand, let's look at something like tin pest. Objects made of pure tin are stable at warmer temperatures, but at low temperatures they can develop something called "tin pest" where tiny spots break out, and then over the course of months expand and eat up the object, breaking it down into dust, like bacterial colonies spreading across a petri dish. This is a low-temperature stable allotrope of tin which catalyzes its own formation to reproduce itself.
Is this reproduction some realistic soft of form of protolife? By far, most people would say no. Contrary to prions, it's input is quite simple: plain, ordinary tin. It's easy to picture where this specific case or other natural cases like it could occur in some early world. But its problem is different: it's too specific. Tin pest seems unlikely to, say, mutate and start catalyzing the production of phospholipids or similar. It's just one self-catalytic reaction, with no real possibility for alterations.
The earliest forms of protolife surely lie somewhere on the spectrum in-between these two endpoints - not with such glaringly simple inputs as tin pest, such that your reaction is too simple to have any chance of it mutating without outright dying off, but not with inputs so complex as prions that you're unlikely to ever find significant quantities in nature. Surely the earliest forms were some sort of middle ground.
But what they were, specifically? This is totally and utterly unknown at this time.
"Are you hungry? I haven't eaten since later this afternoon." -- Primer
The four Galilean moons are interesting from an evolutionary POV.
Io - Molten sulphur on the surface, purple volcanoes all over it.
Europa - Deep water ocean, thin crust, very active plate tectonics.
Ganymede - Europa with a deep dish crust and cooler core.
Callisto - A rock.
So it would seem that gas giants may have their own "goldilocks zone" when they are orbiting in the colder regions of their host system. So the "average" solar system may have 3-4 "habitable zones" rather than just one.
And did you exchange a walk on part in the war for a lead role in a cage? - Pink Floyd.