ASTRO
In the literature: open
Is there a sharp boundary between airless and atmosphere-bearing planets?
In plain words
In the Solar System, bodies that are small or strongly heated have no air, and the dividing line follows a simple rule linking gravity and sunlight. Whether exoplanets follow the same line is untested.
Precise statement
Test whether atmosphere retention among rocky exoplanets follows the cosmic shoreline relation $I \text{ proportional to } v_{\mathrm{esc}}^4$ (I the cumulative XUV or bolometric instellation, v_esc the escape speed) proposed from Solar System bodies, and measure its location and width for M-dwarf and FGK hosts. The answer is the boundary in the $(v_{\mathrm{esc}}, I)$ plane with its scatter.
What would settle it
Atmosphere detections and non-detections for a sample of rocky planets spanning at least an order of magnitude in $v_{\mathrm{esc}}$ and instellation.
Related problems
- Special case of Can rocky planets around red dwarf stars keep atmospheres?