A scorching rocky planet is like a pot of boiling soup, except its lid is the atmosphere. Gases escape from the magma, wrap the world in a thick blanket, and in turn influence how quickly the celestial body cools. For GJ 1132 b, which orbits so close to its star that a year lasts just one and a half Earth days, this connection is especially important. Without accounting for gas exchange, you can't tell whether it will solidify within a billion years or remain a fiery ball.

The authors of the new study, for the first time, took into account that the melting temperature of rocks depends on oxidation: that is, on how much oxygen is in the mantle (the planet's rocky shell). Earlier models used Earth-like, oxygen-rich conditions, but that doesn't work for other planets. They found that if the mantle is made oxygen-poor, the depths solidify faster. However, a lava ocean persists on the surface for a long time, kept molten by a thick atmosphere of hydrogen and carbon monoxide. If the mantle is oxidized, like Earth's, the melt penetrates deeper, and the atmosphere is thinner, composed of water vapor and carbon dioxide.

The most surprising result: in volatile-rich systems, the difference in oxidation has almost no effect on solidification time. There, the total inventory of gases is what matters: it keeps the planet in a state of global magma ocean. It glows like a coal in a furnace for billions of years. This means that by observing the atmospheric composition, we can peer into the interiors of distant worlds and understand what they are made of.

And so this cosmic cauldron churns: gases rise from the depths, settle in the atmosphere, and in turn alter the planet's heat. GJ 1132 b reminds us that even a rocky sphere around a distant star lives its own complex life: it breathes, cools, and stores in its 'soup' a history we are only beginning to read.