The seasonal cycle of Titan's detached haze

TL;DR

This study analyzes Titan's detached haze over nearly half its seasonal cycle, revealing its disappearance and reappearance, which offers new insights into the atmospheric dynamics and haze formation mechanisms.

Contribution

It provides the first detailed observational record of the detached haze's seasonal cycle, including its disappearance and complex reappearance, challenging existing climate models.

Findings

Detached haze disappeared in 2012 and reappeared in 2016.

Reappearance occurred in two steps at different altitudes.

Observations constrain mechanisms controlling Titan's haze cycle.

Abstract

Titan's 'detached' haze, seen in Voyager images in 1980 and 1981 and monitored by the Cassini Imaging Science Subsystem (ISS), during the period 2004-2017, provides a measure of seasonal activity in Titan's mesosphere with observations over almost one half of Saturn's seasonal cycle. Here we report on retrieved haze extinction profiles that reveal a depleted layer that visually manifests as a thin layer detached from the main haze below. Our new measurements show the disappearance of the feature in 2012 and its reappearance in 2016, as well as details after the reappearance. These observations highlight the dynamical nature of the detached haze. The reappearance appears congruent but more complex than previously described by climate models. It occurs in two steps, first as haze reappearing at $450\pm20$ km and one year later at $510\pm20$ km. These new observations provide additional tight and valuable constraints about the underlying mechanisms, especially for Titan's mesosphere, that control Titan's haze cycle.