#and that a lot of the puzzles with their internal structure and density are resolved through this disequilibrium synthesis

[togglesbloggle]

🔥The ice giants

Oh, this one's tricky. Do people have strong enough feelings about the ice giants for opinions about them to be unpopular? Even NASA doesn't care enough about them to send a spacecraft more than once in a blue moon. I think I'll try to weasel out of this one with the opinion 'all planets are interesting, even Neptune,' on the grounds that uninterestingness is itself the dominant opinion.

The midcentury explorations of the solar system were, in retrospect, kind of crushing for the human imagination. We went from totally unbounded speculations about the diversity of worlds- imagining robust ecosystems on Venus and Mars as late as the 50s and early 60s- to a series of photographs showing cratered, dead, atmosphere-less worlds. And 'realism' became accepting these photographs, building a story of the cosmos that is not just sterile but quite simple, treating the solar system as conforming closely to low-complexity models of planetary formation. Gravity collects micrometeorites and gas particles in planetoids and moons according to the ratios predicted by temperature and distance from the center of the accretion disk; terrestrial worlds close in, gas giants further out, ice giants further still. The planets sort themselves by density, with interior deformation or sortition based on thermal gradients, radioactive decay, magnetic forces; moons find a stable orbit or don't, and that's that.

But the thing is, once you actually get past that superficial Voyager flyby-photograph, these worlds all tend to have dramatic and exciting particularities of their own. Look at Pluto! Look at Titan! Look at Enceladus! Look at Ceres! Probably the most boring and well-studied planet I can think of is Mercury, and even that has cool stuff like solid ice at the surface.

Part of this is just noticing over time that the interface between planets and space (that is, their surface) is not always or even usually the most interesting part of them, and assumptions to the contrary are an understandable but misleading form of Earth-chauvinism.

And a larger share of it, I think, is just that once you get something substantially larger than an asteroid, the combined influence of so much volume, so much mass, and so much time just tends to amplify the variance of your system incredibly far beyond what you'd expect from your 'terrestrial, gas giant, ice giant' template. The model is actionably useful, don't get me wrong, and worlds rarely vary so much that they outright break their category. But nothing the size of a moon or planet is actually simple, and nothing on the scale of four billion years is actually stable. And so each of these things, no matter how straightforward the template, will gradually tilt and totter its way within an unfathomably large space of possibilities to something that is practically speaking unique, and which reveals something new about the cosmos that you can't find anywhere else.

If the ice giants seem simple, it's a reflection of our methods and our technological limits, not the planets themselves. We are, generally speaking, absolutely terrible about investigating gaseous worlds on their own terms- and maybe we simply don't have the right tools or the right questions yet to figure out what makes Neptune and Uranus special. But it's only a matter of time.

#my actual inside-baseball unpopular opinion is that I bet they have complex weather systems at certain characteristic depths #which have the potential to drive complex chemical synthesis #and that a lot of the puzzles with their internal structure and density are resolved through this disequilibrium synthesis #where the slowly changing chemistry alters the characteristic weather depths and vice versa