Testing Sudarsky

One of the first essays on extrasolar speculation I recall reading was Sudarsky-Burrows' in 2000ish. Their papers proposed five classifications for gassy planets; here's the 2003 version. Unstated-assumption at least for II-III was that the planets collect volatiles out where's its cold and then migrate-in.

Our system's giants are all in the first set, ammoniac. If we had a giant drift toward Earth or Mars, ammonia would break down: thus type II is water-dominant and looks bright and cloudy, almost Earthlike. For Type III, inward of Venus, it's too hot for vapour: but since too big to lose their heavier compounds, such go cloudless - deep blue from Rayleigh, like I used to think for Neptune. Then over 900 K the clouds come back at Type IV because silicon-compounds and metals are melting. Let's don't visit a V.

I've already ranted about how much Kelvin sucks if we suspect I or II. But let's play along.

Venus gets 1.91 times the insolation we get so should be equilibrium at, what, 515 K. That is easily in the II range - for insolation. Venus is very cloudy but has no hydrogen over the clouds. The acids are simply heavier than the gasses it got (including water), so ride lower (given airpressure). Clouds annoy researchers because they reflect light and light is how we even into these things. I imagine clouds would also reflect light back up into the higher atmosphere; one more reason Venus' atmo over those clouds is as dry as it is.

So: we're testing the II/III/IV range now. I got this from SciDaily last weekend but the paper linked Gliese 9827, which I wanted into first. The papers are asking if the clouds form over or under the water. We can see water in Gliese 9827 - if it is vapour. If bundled into clouds, we won't.

GJ 9827 d despite getting Venus' insolation ... has water. I assume that planet has clouds too. But the clouds must be heavier, like Venus'. I wonder if the clouds are, likewise, acid.