Sulphur clouds on 51 Eri b?

View previous topic View next topic Go down

Sulphur clouds on 51 Eri b?

Post by Lazarus on 26th April 2016, 1:33 pm

Zahnle et al. "Photolytic Hazes in the Atmosphere of 51 Eri b"
http://arxiv.org/abs/1604.07388

51 Eri b seems to be right at the edge of where clouds of sulphur S8 may form. One of the factors that enables this is the low levels of ultraviolet received at its distance from the star, though there are a fair number of uncertainties in sulphur chemistry.

More interesting is that sulfur itself can be the photochemical cloud that we are looking for. We find that for a wide range of conditions the major photochemical product of sulfur in a planet like 51 Eri b is the ring molecule S8 , which typically forms at ∼10 mbars and extends up to 100 Ábars. The overall sulfur cycle is simple: H2S flows up and S8 and H2 flow down. In the cooler half of our models sulfur condenses to make a photochemical haze that, depending on particle size, can be optically thick, while in the warmer half of the models sulfur remains in the vapor phase. The sulfur vapor itself might also be optically important, especially at the interface between abyssal H2S and S8, where the latter thermally decomposes into a wide range of optically active molecules that are eventually hydrogenated to recombine H2S. The sulfur photochemistry we have discussed in this paper is quite general and ought to be found in a wide variety of worlds over a broad temperature range, both much cooler and much hotter than the 650-750 K range studied here, and will be present on planets where the UV irradiation is very weak. Sulfur clouds should be found in many of these. Whether 51 Eri b itself is cold enough for sulfur to condense cannot be answered until radiative transfer models incorporate sulfur vapors and sulfur clouds, which is a project beyond the scope of this paper, or until the yellow clouds are seen.

It's not the same as John Whatmough's sulphuric-acid cloud speculations (which don't make much sense for gas giants as the chemistry would be more hydrogen-rich than oxygen-rich), but if you want to justify some kind of yellow sulphur-based clouds on your gas giants, here you go.
avatar
Lazarus
dG star
dG star

Number of posts : 2894
Registration date : 2008-06-12

View user profile

Back to top Go down

Re: Sulphur clouds on 51 Eri b?

Post by Lazarus on 3rd January 2017, 6:56 pm

More on sulphur chemistry in giant planets. Seems like sulphur haze is likely for a lot of temperate gas giants, such planets may well be orange or red due to the significant effect of S8 on the geometric albedo.

Gao et al. "Sulfur Hazes in Giant Exoplanet Atmospheres: Impacts on Reflected Light Spectra"
https://arxiv.org/abs/1701.00318

avatar
Lazarus
dG star
dG star

Number of posts : 2894
Registration date : 2008-06-12

View user profile

Back to top Go down

View previous topic View next topic Back to top


 
Permissions in this forum:
You cannot reply to topics in this forum