We may never know the answers to these questions. Though it is currently possible to say something about the atmospheric composition of some close exoplanets, and that ability will be improved with better telescopes, the planets that Kepler observed during its mission are too far away to learn much about for the foreseeable future.
Well we just know so very little about planets around any star, excluding 8 planets circling around one out of ~1,000,000,000,000,000,000,000 stars in the observable universe.
> cloud-free, hydrogen-rich atmospheres were ruled out with high confidence. This means that there appears to be no clear, extended atmosphere around TRAPPIST-1 b
I will never not be amazed that we can read the atmospheric spectra of exoplanets.
The only thing reliable on this is the names of the planets, the distance away, the mass and the possibly the elements it possesses. We don't know much about how the planet looks at all or if its atmosphere is a death trap. I think its pretty misleading to show a beautiful earth-like terrain.
Our understanding of exoplanets is analogous to a 3 month old toddler exploring the world. It's _way_ too early to be making definitive statements about it.
I think is less surprising than the fact that Jupiter, and in fact all 4 big planets in our solar system, are actually just gas bubbles, and not actually not the rocky balls us ordinary people imagine as planets. That's right: they have no surface.
But what's giving it it's seemingly clear cutoff boundary? I have trouble imagining anything in the nothingness of space taking the role of the forces that shape our atmospheric clouds. It feels a bit as if it was some arbitrary artistic decision like that 2001 slit scan or the Solaris ocean. Then on the other hand of course it's amongst the few most "artistic" ones picked from all those super tiny projection viewports we have taken from the sphere of view directions, so perhaps we should not be all that surprised. It's not quite the level of unlikely discovering a planet populated by mattresses would be.
"We know a lot more about exoplanets now than we did in 2003. We're moving on to find out how many are in the Goldilocks zone, or how many contain water. Our idea of what to plug in is slowly getting better."
"Unfortunately", that's nailing down the one parameter that nobody has ever particularly questioned. There's some lines of thought that our solar system might be unusual in relevant ways, but nobody has ever seriously argued that the only planets in the galaxy are in our system, or anything related to that that would make that parameter small.
It's all the rest of the parameters where the mystery is.
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