Astrobiology Web summarized a Planetary Science Journal study on November 10, 2026, modeling how tidal circularization and atmospheric escape jointly shape TOI-2257 b, a transiting mini-Neptune.
The study modeled stellar tides, orbital tides, and atmospheric escape together. Tidal circularization is the process by which tides make an orbit more circular, and atmospheric escape is the loss of a planet’s atmosphere to space. It found TOI-2257 b sits near where those effects fade away, and the result held whether the planet formed with a hydrogen envelope or without one.
A rocky planet would not be expected to keep an eccentricity above 0.62 today, so a larger measurement would favor a gaseous composition.
The study found surface heat from tides would look much like Io’s in most cases, and none of the modeled scenarios gets hot enough to cause a runaway greenhouse. That keeps climate effects modest even with an eccentric orbit.
The authors say the results could help constrain mini-Neptune properties and show how the radius valley’s shape shifts with orbital eccentricity. A mini-Neptune is a planet smaller than Neptune but larger than Earth, and the radius valley is the gap between common super-Earth and mini-Neptune sizes.
The paper The Limits of Tidal Circularization and Atmospheric Escape for Mini-Neptunes and Super-Earths: The Case of TOI-2257 b appeared in the Planetary Science Journal.
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