Constraints on the microphysics of Pluto's photochemical haze from New Horizons observations

Fan, Siteng; Wong, Michael L.; Liang, Mao‐Chang; Shia, Run‐Lie; Kammer, Joshua A.; Yung, Yuk L.; Summers, M. E.; Gladstone, G. Randall; Young, L. A.; Ennico, Kimberly; Weaver, Harold A.; Stern, S. A.

doi:10.1016/j.icarus.2016.09.030

Cited by 80 publications

(82 citation statements)

References 38 publications

Supporting

Mentioning

Contrasting

Order By: Relevance

“…Non-ballistic collisions and rotation of aggregates could also reduce the fractal dimension down to D f ≈ 1.1 (Paszun & Dominik 2006). D f = 2 is often assumed in the studies of haze formation on Titan and Pluto (e.g., Lavvas et al 2010;Gao et al 2017b). Unless otherwise noted, we assume that aggregate-aggregate collisions dominate over aggregate-monomer collisions, adopting D f ≈ 2 and k 0 ≈ 1 ).…”

Section: Fractal Growthmentioning

confidence: 99%

Clouds of Fluffy Aggregates: How They Form in Exoplanetary Atmospheres and Influence Transmission Spectra

Ohno

Okuzumi

Tazaki

2020

ApJ

View full text Add to dashboard Cite

Transmission spectrum surveys have suggested the ubiquity of high-altitude clouds in exoplanetary atmospheres. Theoretical studies have investigated the formation processes of the high-altitude clouds; however, cloud particles have been commonly approximated as compact spheres, which is not always true for solid mineral particles that likely constitute exoplanetary clouds. Here, we investigate how the porosity of cloud particles evolve in exoplanetary atmospheres and influence the cloud vertical profiles. We first construct a porosity evolution model that takes into account the fractal aggregation and the compression of cloud particle aggregates. Using a cloud microphysical model coupled with the porosity model, we demonstrate that the particle internal density can significantly decrease during the cloud formation. As a result, fluffy-aggregate clouds ascend to altitude much higher than that for compact-sphere clouds assumed so far. We also examine how the fluffyaggregate clouds affect transmission spectra. We find that the clouds largely obscure the molecular features and produce a spectral slope originated by the scattering properties of aggregates. Finally, we compare the synthetic spectra with the observations of GJ1214 b and find that its flat spectrum could be explained if the atmospheric metallicity is sufficiently high (≥100× solar) and the monomer size is sufficiently small (r mon <1 µm). The high-metallicity atmosphere may offer the clues to explore the gas accretion processes onto past GJ1214b.

show abstract

Section: Fractal Growthmentioning

confidence: 99%

Clouds of Fluffy Aggregates: How They Form in Exoplanetary Atmospheres and Influence Transmission Spectra

Ohno

Okuzumi

Tazaki

2020

ApJ

View full text Add to dashboard Cite

show abstract

“…Although not a planet anymore, Pluto, as seen by the New Horizon spacecraft, is covered by layers of hazes (Gladstone et al 2016;West 2017), likely due to condensation of hydrocarbons and nitriles such as C 2 H 2 , C 2 H 4 , C 2 H 6 , and HCN (Gao et al 2017). We also have to mention Titan, since it has a unique and substantial atmosphere, with hydrocarbon and nitrile cloud types.…”

Section: A3 Condensation and Rainoutmentioning

confidence: 99%

From Cold to Hot Irradiated Gaseous Exoplanets: Fingerprints of Chemical Disequilibrium in Atmospheric Spectra

Molaverdikhani

Henning

Mollière

2019

ApJ

View full text Add to dashboard Cite

Almost all planetary atmospheres are affected by disequilibrium chemical processes. In this paper we introduce our recently developed Chemical Kinetic Model (ChemKM). We show that the results of our HD 189733b model are in good agreement with previously published results, except at µbar regime, where molecular diffusion and photochemistry are the dominant processes. We thus recommend careful consideration of these processes when abundances at the top of the atmosphere are desired. We also propose a new metric for a quantitative measure of quenching levels. By applying this metric, we find that quenching pressure decreases with the effective temperature of planets, but it also varies significantly with other atmospheric parameters such as [Fe/H], log(g), and C/O. In addition, we find that the "Methane Valley", a region between 800 and 1500 K where above a certain C/O threshold value a greater chance of CH 4 detection is expected, still exists after including the vertical mixing. The first robust CH 4 detection on an irradiated planet (HD 102195b) places this object within this region; supporting our prediction. We also investigate the detectability of disequilibrium spectral fingerprints by JWST, and suggest focusing on the targets with T eff between 1000 and 1800 K, orbiting around M-dwarfs, having low surface gravity but high metallicity and a C/O ratio value around unity. Finally, constructing Spitzer color-maps suggests that the main two color-populations are largely insensitive to the vertical mixing. Therefore any deviation of observational points from these populations are likely due to the presence of clouds and not disequilibrium processes. However, some cold planets (T eff <900 K) with very low C/O ratios (<0.25) show significant deviations; making these planets interesting cases for further investigation.

show abstract

“…Particle settling times depend strongly on size. For the 1 µm size range favored by observations of forward scattering, they are relatively short, in the range of Earth days to months (Cheng et al 2017;Gao et al 2017;Zhang et al 2017), though it may take of order a few Earth years for them to grow to that size before they settle out.…”

Section: Haze Production and Compositionmentioning

confidence: 99%

Pluto's haze as a surface material

Grundy

Bertrand

Binzel

et al. 2018

Icarus

Self Cite

View full text Add to dashboard Cite

Pluto's atmospheric haze settles out rapidly compared with geological timescales. It needs to be accounted for as a surface material, distinct from Pluto's icy bedrock and from the volatile ices that migrate via sublimation and condensation on seasonal timescales. This paper explores how a steady supply of atmospheric haze might affect three distinct provinces on Pluto. We pose the question of why they each look so different from one another if the same haze material is settling out onto all of them. Cthulhu is a more ancient region with comparatively little presentday geological activity, where the haze appears to simply accumulate over time. Sputnik Planitia is a very active region where glacial convection, as well as sublimation and condensation rapidly refresh the surface, hiding recently deposited haze from view. Lowell Regio is a region of intermediate age featuring very distinct coloration from the rest of Pluto. Using a simple model haze particle as a colorant, we are not able to match the colors in both Lowell Regio and Cthulhu. To account for their distinct colors, we propose that after arrival at Pluto's surface, haze particles may be less inert than might be supposed from the low surface temperatures. They must either interact with local materials and environments to produce distinct products in different regions, or else the supply of haze must be non-uniform in time and/or location, such that different products are delivered to different places.

show abstract

Constraints on the microphysics of Pluto's photochemical haze from New Horizons observations

Cited by 80 publications

References 38 publications

Clouds of Fluffy Aggregates: How They Form in Exoplanetary Atmospheres and Influence Transmission Spectra

Clouds of Fluffy Aggregates: How They Form in Exoplanetary Atmospheres and Influence Transmission Spectra

From Cold to Hot Irradiated Gaseous Exoplanets: Fingerprints of Chemical Disequilibrium in Atmospheric Spectra

Pluto's haze as a surface material

Contact Info

Product

Resources

About