Editing Openai/6946e998-79f0-8007-9a65-19828450838d (section)

=== When you see labels like: ===
* “Recent Venus” inner edge
* “Runaway greenhouse” inner edge
* “Early Mars” outer edge

This does not mean:
* “Venus actually had liquid water recently,” nor
* “Mars actually had oceans early.”

Instead, these are names of flux benchmarks, chosen because Venus and Mars sit at those fluxes today (as measured in units of solar constant), and the models indicate transitions in Earth-like atmospheric behavior at those fluxes.

Example:
* The “recent Venus” inner HZ boundary: Defined as the stellar flux Venus receives today (~1.9× Earth flux). The assumption is if Earth were at that flux and had an Earth-like atmosphere, it would have lost surface water recently. This says nothing about Venus’s real history—it is purely a model reference point.
* The “early Mars” outer HZ boundary: Defined so that an Earth-like atmosphere could have kept early Mars wet if it had the right greenhouse conditions. Again, this says nothing firm about whether early Mars was ever consistently warm or had a dense atmosphere long-term.

So η⊕ simply counts planets whose stellar irradiance falls within this modeled HZ band.