Sometimes I come across older astronomy and popular science books, and it's always interesting to ponder the way the outer planets were conceived/comprehended a century ago and well into recent times.

The "icy" models seem odd now but they haven't entirely gone away, as this article demonstrates.

The outer planets are really not "icy" at all, and they never were, at least not in any way we would commonly understand "ice." In fact, they are intensely hot (at least by our conception of "hot") a mere few dozens or hundreds of kilometers below the cloud tops, as descent into Jupiter has demonstrated. This situation was theoretically modeled long ago, but the earlier models of giant planets that were "ice" all the way down (at one time it was even argued that the cloud tops represented solid, ice, surfaces) still held great sway, so instead of dispensing with the "ice" models, "ice" was redefined.

Substances that would be frozen solid at the outer planets' distance from the sun (methane, ammonia, water, etc.) if they were not found in giant planet interiors were deemed to be "ices" -- even if they were under intense pressure that raised their temperatures exponentially and thus were not frozen at all. Thus, by definition, these substances were deemed to be "ices" no matter what their actual, physical state was.

Unfortunately, this subtle concept of planetary "ice" wasn't communicated very well to the public at large, to science writers, or to educators, who largely accepted the notion that the interiors of the outer planets were "icy" (meaning "cold" in the vernacular) because that's what planetary scientists said they were. But of course what they meant was that the interiors of these planets were very hot -- surface of the sun hot in the case of Jupiter, if not hotter -- and there was no cold, frozen methane or water whatsoever.

But in the article cited, that's not made clear at all. As written, in fact, it is nonsense. There is no "ice" at all at the core (or anywhere except the cloud tops and satellites) of the giant planets. Of course everyone in the planetary science field (and some science writers) now understands that "ice" when used by planetary scientists to describe the interiors of the outer planets does not mean "ice" as people commonly think of it. But laymen and some science writers don't seem to understand it.

And it's no wonder.

The question for planetary scientists is why they cling to this nonsensical notion of "icy" cores of giant planets? Is there not a better way to describe these cores that doesn't require specialized knowledge of an unorthodox definition of terms?

Just wondering.