Wonder if all that ammonia, lightning, water and other things going on might have lead to simple forms of life blowing around in the atmosphere, or if there's simply way too much blowing to allow that to develop? What's the current thinking?
Two of them are abundant carbon, nitrogen, oxygen, hydrogen and sulfur and a source of energy that will ensure that there is a continuous flux of compounds that are not very stable so they can take part in chemical reactions to generate complex molecules.
These 2 conditions might exist in the atmosphere of Jupiter, if lightning produces enough unstable molecules.
However, there is a 3rd prerequisite, the existence of inorganic catalysts, e.g. the sulfides of iron, cobalt and nickel. Other transitional metals might also work, but they are much less abundant, so they are unlikely to be used by life in the beginning.
The problem is that on Jupiter rocks with metallic minerals are found only very deep under the exterior part made only of light elements, at depths where the pressure and temperature might be to great for any life form.
So we do not know for sure, but it seems unlikely that life could have appeared on Jupiter or Saturn.
On the other hand, on the large satellites of Saturn and Jupiter, there are much more chances for a place with good conditions to exist, than in any other part of the Solar System besides Earth.
We don't know how those elements interact in high temperature/pressure/dynamic environments. Some compounds which are very stable here may be less so there. Some inorganic form of ice may behave in a very organic way under certain conditions - we just don't know - until we send a probe there.
Nobody knows, full stop. We can guess and conjecture about what should and should not be possible with respect to the origins of life, but really, we know very little. So it's not very meaningful.
We haven't observed abiogenesis and experiment/observation is the ultimate guide.
You have to remember just how _big_ Jupiter is. There's a lot of room for different environments and complex interactions. The only problem is it's quite far away and quite hard to get a good look at (especially the "internal" bits).
I've been confused about the "gas giants" since I first learned about them in gradeschool, but never really took it upon myself to dig into it deeply.
Whenever I think about planets, I think about a big rock you can land on, but if Jupiter and Saturn are made entirely of gas, landing on them is a non-sequitur, correct?
Do most planets start out as gas giants? Does the effect of gravity over epochs compress them into rocky planets? How should we think about them in terms of our solar system? In how we explore? In how we colonize?
When the solar system formed it began as a cloud of gas and dust. As the sun condensed out of the cloud the remaining gas and dust was drawn into orbit around it, forming a disk. Over time, larger rocks and pebbles in the disk accumulated the material around them during their orbit of the forming sun, like rolling snowballs getting larger and larger.
At some point during the formation of the sun, enough pressure builds up inside to allow ignition of its fusion fuel (mostly hydrogen). As the sun heats up it begins emitting radiation and the ejection of particles (solar wind). It’s this combination of stuff (light and particles) that pushes lighter gases out of the near orbital region (where the rocky planets formed). Those gases make their way out beyond the asteroid belt and get picked up by the forming gas giants. At the same time, the heavier dust and rocks don’t get pushed very far by the sun and instead get accumulated in the rocky inner planets.
This pattern is more or less consistent around all stars we see out there. Of course, it varies in strength based on the amount of radiation and particles emitted by the star and that is a complex topic all by itself. But I hope the basic picture I’ve given here is informative.
What causes the initial stage to form a disc (rather than a progressively more dense cloud/sphere/blob)? Just the rotation? (In which case, where’s the rotation come from?)
At the beginning there is no rotation. The cloud may start with roughly uniform density along with some momentum. Over time, this density becomes higher in the middle and lower around the outside. Everything in the cloud begins accelerating toward the place of higher density which forms into the sun while at the same time continuing in the direction according to its initial momentum. This is what causes rotation that leads to the formation of a disk. Any time you have momentum in a direction other than the local centre of mass (star, planet, etc), your path of travel curves into a circle (actually an ellipse, but that’s another topic: see Kepler’s laws).
Planets "start out" as a cloud of dust, rocks, and gas orbiting a young star which eventually coalesce into planets, lots of things go on which determine what kind of planet results.
Gas giants are indeed mostly gas and then gases liquefied and solidified by the very high pressures inside as you go down and eventually a bit of a rocky core.
If you were indestructible you would "land" on an ocean of liquid hydrogen, but because of the high pressures there won't necessarily be a well defined surface but a transition between gas-like qualities and liquid-like qualities. Go down and eventually you get to a solidified hydrogen, a few other things, and somewhat of a rocky core.
Jupiter and Saturn are not made entirely out of gas. They are made mostly out of atoms that form gases on earth.
For example, Jupiter is thought to have a solid core composed of solids twice as dense as earth's core. On top of this is a ocean of liquid metallic hydrogen. On top of that is the gas phase atmosphere.
Wonder if all that ammonia, lightning, water and other things going on might have lead to simple forms of life blowing around in the atmosphere, or if there's simply way too much blowing to allow that to develop? What's the current thinking?