Evidence for Possible Clouds in Pluto's Present Day Atmosphere

TL;DR

This study used New Horizons data to search for clouds in Pluto's current atmosphere and found it to be mostly cloud-free, with only a few possible cloud features observed under specific viewing conditions.

Contribution

First observational evidence indicating Pluto's atmosphere is largely free of discrete clouds, based on high-resolution flyby data.

Findings

Pluto's atmosphere is over 99% cloud-free by surface area.

A few potential clouds were observed only at high phase angles.

No clouds were detected in backscattering geometry images.

Abstract

Several trace constituents can reach saturation vapor pressure in Pluto's present day atmosphere. As such, we describe a search for discrete could features in Pluto's atmosphere using New Horizons data obtained on 14-15 July 2015, during the Pluto flyby closest approach. We report that Pluto's present day atmosphere is at least largely (>99% by surface area) free of discrete clouds. We also report a handful of features that may plausibly be clouds, all of which were detected obliquely and at high phase observing geometry. No cloud candidates were identified away from the terminators or in low phase (backscattering geometry) images.