I really appreciate the kind words,
StevenSpheres. Another possibility to expand out the range of textures are the possibility of transitional textures. Of course the insolation a planet receives, for the simple case of a non-inclined planet (which I assume we'll be assuming, lacking information to the contrary) scales with latitude,
φ as cos
φ. Consider a Sudarsky Class III planet just inward of the "habitable zone." You might imagine it would have water cloud condensation at its polar areas. So you could imagine a III-II transition texture, where the polar areas resemble a Sudarsky Class II planet, and the equatorial and tropical region are more Sudarsky Class III. We see something similar going on at Saturn, where the polar areas took on a more Uranus-like appearance. I believe this is from ammonia condensating out of the atmosphere at cooler temperatures but chemistry is
really not my thing so I'm very open to being shown otherwise.
SevenSpheres wrote:For Super-Earths/Neptunes, I'm not really sure what the textures should look like, but there are a lot of these planets and we need more than just the venuslike texture. Cold planets (<90K according to Andrew) would probably resemble Uranus and Neptune. Other planets might resemble their Jovian equivalents?
I strongly suspect that super-Earths / mini-Neptunes would look similar to, or identical to gas giant planets, but I don't know if the belt/zone structures do, and I don't know how to make an educated guess based on Juno-Jupiter or Cassini-Saturn data on the depths of the counterrotating atmospheric structure.
With super-Earth and mini-Neptune planets appearing to have H-He dominated upper atmospheres, the upper atmospheres of these planets may represent nothing more than higher-metallicity analogues to Jupiter and Saturn - or maybe not even higher metallicity,
see GJ 3470 (apologies for the link, I'm not at my main computer so I don't have the links to actual literature easily accessible).
Ultimately, venuslike.jpg seems to have been chosen for this task at a time when
a) It was not yet fully realized that the planets we now call super-Earths are actually low-density mini-ice giants. It made sense to consider GJ 581 c to be a giant terrestrial planet, pre-Kepler. We now know that these planets are not venus-like.
b) It was more important to distinguish the planet
visually from the gas giant planets that were known, to indicate that this is not a gas giant planet.
SevenSpheres wrote:Or if in the habitable zone, they might be panthalassas?
We need to understand that these mini-Neptunes likely have a range of pressure-temperature-water abundance profiles that would make such predictions about the phase state of water a bit outside our ability to confidently predict. The reason Neptune is not an ocean planet is because it is too hot and too dry (i.e., where the P-T parameter space allows it, the water abundance is too low), but you wouldn't know that just looking at its insolation, which is really all we have for these extrasolar planets. As you point out in your response to
fyr02, I do not think attempting to render ocean planets is advisable at this time, especially given how poorly such planets are understood, and the fact that not a single one has been confidently identified.
SevenSpheres wrote:Hot planets (interior to the habitable zone) would probably either lose their atmospheres like Mercury (these would have the asteroid texture) or have runaway greenhouse effects like Venus, with the mass cutoff being...somewhere between these two planets.
Okay, but where is that 'somewhere'? We know so little about this right now. M dwarfs, for example, require a lot of time to contract to their equilibrium Main Sequence stellar luminosity. Even planets in the "habitable zone" of such stars may have spent 100 Myr, or 1 Gyr for the coolest M dwarfs, being
interior to the HZ as the HZ slowly crept inward. There is a legitimate debate about whether or not terrestrial-mass planets in and inward of the habitable zone retain their atmospheres, or if outgassing of secondary atmospheres is a common thing, etc. Clearly there's a mass/insolation regime where planets hold onto their atmospheres, but it's not clear where that is. This is the kind of information that we will be answered by TESS, ground-based radial velocity surveys and JWST.
I would be very interested in revisiting this conversation in 2030 where we have a statistically interesting sample of extrasolar terrestrial-mass planets with atmospheric constraints.
SevenSpheres wrote:Edit: and this is my 100th post!
Congratulations!
Something I'd like to do for extrasolar planet night sides is to have a range of night side textures of increasing brightness, representing different temperatures. Some planets are efficient at heat redistribution to their night side, while others aren't. There's an interesting paper
here (Fourtney, et al. 2007) that has really guided a lot of my view on that sort of thing. More recently it was discovered that for a lot of hotter hot Jupiters, the night side temperatures tend to be roughly about the same up to a certain point where molecular hydrogen breaks down and the nightside temperature increases again (
Keating, et al.).
It will be interesting to see what ultimately comes out of the HST Panchromatic Survey (
lecture on the topic).
Joey P. wrote:Oh, I get it. But why don't we try making some good-quality textures out of poor-quality images, such as this one of 2M1207 b:
Because in that image, 2M1207b is an unresolved dot (in the infrared!), and the most you can get from it is a 2
n x
n image that is a uniform colour.
Exoplanet nerd. I maintain a monthly-updated exoplanet catalogue here:
https://celestiaproject.space/forum/viewtopic.php?f=23&t=18705
