Crustless world

This site has noted a few "lavaworlds" before - but by that, we intended possible lava pools on the crust. Wolf 437's planet isn't quite there yet; Gliese 1132's and LP 791-18's are more like Io. A true lavaworld means ... no crust. The entire surface is liquid rock, which should happen over 880 K. Ohio State is on it: more like 1700-2400 K (the release says between 2600 and 3860 degrees Fahrenheit).

That's for silica. Metal planets like GJ 367 b might melt at lower temperatures. But they're rare.

That silica-melt temperature-band is attained at 55 Cancri e.

Lava should bubble over rock; remember, water is an outlier in its density over Ice I. How is the surface molten, is now the question. OSU are talking layers of the mantle. Maybe there's only one layer, above the core (by analogy with our planets, its own thing - a metallic ball, liquid or solid or both). Or, maybe the melt sits atop a hard lower mantle. The third option is that the melt is on top, a solid middle mantle, and a liquid lower mantle. This might be because lava is more compressible than solid silica (which I didn't know). OSU think the latter two are more likely than a pure liquid mantle.

I do have to ask what the atmo will look like, considering escape-velocity of a superheated liquid sea passing energy to, what, nitrogen. And wouldn't most molecules, like, break down to ion plasma? Mind: if the atmosphere is thin enough, liquid doesn't transfer heat by convection. If by radiation, large-volume worlds leach out heat slower (and they're next to a star radiating that heat right back in there). Starflight "airless lava worlds" are... a thing.

Starflight had other problems. Lavaworlds all sit very close to their star so aren't wise to orbit. The delta-V cost alone is a problem for Mercury let alone 55 Cancri e.