What’s Inside Saturn?

What’s going on inside a gas giant?

Sending spacecraft in to investigate is a risky proposition—the deeper you go, the higher the heat and pressure, so you’d be burned up and/or crushed before you got far enough to record much.

But thanks to various probes and telescopes operating at safer depths, we know a good deal about the gas giants’ chemistry, heat patterns, and surface weather, as well as how these types of planets likely formed in the early days of the solar system.

One of the outstanding mysteries, however, is why gas giants such as Saturn seem to be giving off more light than they should based on the heat they’re getting from the sun.

In a new paper in this week’s PNAS, a team of scientists fed a bunch of observational data into some supercomputers and ran a couple different scenarios for density, temperature, and composition within Saturn.

Based on their results, we can now say with some certainty that, deep inside, Saturn is made of white and yellow Styrofoam.


—Picture by Kwei-Yu Chu, courtesy LLNL

Uh, wait a minute.

What this illustration is actually trying to tell us is that helium (yellow balls) is sinking through dense layers of hydrogen (white balls) thanks to Saturn’s extreme interior.

The idea is that all the extra brightness is coming from a process called phase separation.

Previous work had suggested that, at the staggeringly high temperatures inside Saturn, normally gaseous helium and hydrogen would be liquid metals, kinda like room-temperature mercury on Earth.

While physics says that the two liquids should repel like oil and water, we know they are both in there together, so the question is, exactly how well are they mixed?

Last year a team at UC Berkeley proposed that the two liquids can not only mix, but can merge into a bizarre metal alloy.

But the new study seems to like the more standard theory, which says that helium separates into a different phase than hydrogen and is raining down toward the core. Heat from friction during this process is what generates the excess energy we see.

In reality, we may never get a handle on what’s going on inside gas giants—we really don’t know what the center of the Earth looks like, and we live here.

Our best bet continues to be taking new, more detailed observations and feeding the data into new, faster-moving computers, then seeing which models fit the data—at least until we invent new ways of diving deeper so we can see for ourselves.

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