An Earth with no Mantle or Crust? “Pretty Wild!”

Earth and planetary scientists are discovering ever more weird and wonderful sorts of exoplanets far beyond our solar system. Case in point: GJ 367b. First discovered in 2019, this planet, about three-quarters the size of Earth, is located nine parsecs or 31 light-years away in the constellation Vela.

An exceedingly dense planet, GJ 367b appears to be the “most metal-based planet yet” as reported by Kristine Lam (German Aerospace Center, Berlin) and colleagues in an article in the journal Science. It has an orbit of just 7.7 hours around the red dwarf star at the center of its solar system, and is it ever hot! It has a surface temperature estimated at 2,700°F or nearly the melting point of iron.

The planet is mostly iron, like the core of our own Earth, with just a thin layer of rock enveloping it and just a wisp of a gaseous atmosphere. Lam and her colleagues place it within a class of “extreme worlds.” It may have started like Earth, with a crust and mantle, but those outer layers seem to have been stripped away by collisions with space rocks or radiation from its sun. However it happened, all that’s left is a dense iron planet described by astronomer Lisa Dang (McGill University, Canada) as “pretty wild.”