Thstis the “toffee planets” hypothesis:
Super Earths—sometimes rocky exoplanets that are bigger than our pale blue dot but smaller than massive ice giants such as Neptune—have comparatively strong gravitational fields. Thanks to this extreme gravity, some scientists suspect, rocks on such worlds would flow far closer to the surface.
This arrangement would mean rocks that snap, fracture and break might only be found in thin veneers on these exoplanets’ crust. If these rocky super Earths have thick, Venus-like atmospheres or are especially close to their parent star, they might exhibit no familiarly brittle geology at their surface at all. Instead, says Paul Byrne, a planetary scientist at North Carolina State University and lead author of a study on the Super Earths, their surface rocks would be strangely malleable over long timescales, flowing a bit like the stretchy, sugary confections on offer in any earthly candy shop.Robin George Andrews, ““Toffee Planets” Hint at Earth’s Cosmic Rarity” at Scientific American
It could be worse:
Things have become even more complicated with the discovery by NASA’s Transiting Exoplanet Survey Satellite (TESS) of a brand-new confirmed rocky super Earth, HD 213885b. Byrne’s calculations suggest that this newfound world might be a toffee planet, with a brittle layer just more than two miles thick. The problem is that the radiation from HD 213885b’s parent star is akin to that of 55 Cancri e, another known rocky super Earth whose dayside is entirely molten.
“If HD 213885b is similarly hot, then any lack of rigidity at the surface won’t be from relatively higher surface gravity so much as the floor being lava,” Byrne says. It’s not quite a toffee planet, then, but something very close. Mayp1 be, he suggests, “fondue planets” are a thing, too.Robin George Andrews, ““Toffee Planets” Hint at Earth’s Cosmic Rarity” at Scientific American
Wherever you thought you were on that planet, you would soon be somewhere else. But it’s not really anywhere, is it? Advice: Stay home on solid Earth.
See also: Hugh Ross: The fine-tuning that enabled our life-friendly moon creates discomfort
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