Wolf 1069's Huronian planet

Yesterday the dreaming horseman found Kossakowski et al.'s Wolf 1069 article and commented.

The news is exciting. Unlike some stars we can mention, Wolf 1069 didn't flare during the observations and, best we've seen, it tends pretty quiet generally (so is old). At (barely!) triple-parallax 31.3 ly it follows Proxima Centauri b, Gliese/GJ 1061 d, Teegarden c, and GJ 1002 b and c in being HZ; especially since, unlike Proxima, it doesn't take flares. Out at 0.0672 ±0.0014 AU (the stellar mass is well-constrained so, Kepler helps) gets "incident flux" 0.652 ±0.029 S_⊕ not unlike GJ 1002 b's 0.67 "F_⊕". If that means irradiance, that's a bit more than Mars gets; closer to the ~70% S_⊕ for the Huronian Earth.

A 90.3 day periodicity is also pondered. The authors don't presently care, since - if that signal exists - it's of an obvious iceworld.

Whether the inner planet's orbit be tidally locked, or Mercurylike, is the question. It doesn't transit and we can't see it. If locked, the planet should be habitable at the circle of eternal noon (because its sun doesn't flare). If not, er. For other reasons than K2-415's reasons W1069 offers little constraint of planetary mass beyond that minimum 1.26 ±0.21 M_⊕. At least radius would force some density-rules. A waterworld or an iceworld is possible. Even hycean is possible: a large Hill-radius could explain why this planet is (so far as we know) innermost.

Let's be nice and assume <2 M_⊕.

The planet is close-enough the snowline that I have to suspect a formation with much water and hydrogen. I mean: it might have formed further in, with a Io-like planet inward of that, which planet has been eaten by the star and pushed this one further out. The paper speculates at a violent formation. But speculation is a harsh mistress.

I foresee a thick atmosphere rich in helium, argon, nitrogen - greenhouse gasses none of them. H₂O snows out around the rim; even CO₂ snows out the back of the ice. What CO₂ is left sunside is vulnerable to cyanobacteria. So what's left to warm the place, um. Nitrous oxides?

If a terrestrial world that habitable circle looks... small. I expect a high albedo (tholin-poor water ice) around it; and internally should be stormcloud around the ice. Definitely Huronian which, you'll recall, was snowball-Earth.

And I don't think this one is terrestrial. I think it owns more water than Earth owns. Also the ocean is probably saturated with ammonia; although, this (and salt of course) might allow more liquid water on the surface. Best case: thin ice at the central point of noonday.

It will get warmer but it's not going to get much warmer anytime soon.