Observations of Titan's Detached Haze 2005 - 2017
Abstract
Spacecraft images and stellar occultation measurements of Titan throughout the UV-Visible range reveal a local maximum in brightness or extinction optical depth at altitudes from about 250 - 500 Km above Titan's surface. The appearance in images is of a distinct haze layer, 'detached' from and above the main haze that extends to the surface. We now know that the optical appearance can be attributed to a deficit in the haze density just below the apparent altitude of the detached haze. The detached haze was first seen in Voyager images in 1981 (K. Rages and J. Pollack, Icarus, 55, 50-62, 1983, doi: 10.1016/0019-1035(83)90049-0). With hundreds of images of Titan and several UV occultations observed by Cassini ISS and UVIS instruments we now have a time history of the haze over a significant fraction of a Titan year. These show seasonal behavior of the altitude and amplitude of the detached haze that has only been recognized in retrospect as likely due to the breakup of the meridional circulation near equinox in the stratosphere and mesosphere. Some details of the observations are still not adequately explained by models. The detached haze disappeared after mid-2012 and began to reappear weakly and intermittently in 2016. These observations drive new models for Titan's circulation and haze microphysics. Future observational work will focus on the latitude distribution of the haze morphology, probes to deeper layers via longer-wavelength observations, and details revealed at higher spatial resolution.
- Publication:
-
42nd COSPAR Scientific Assembly
- Pub Date:
- July 2018
- Bibcode:
- 2018cosp...42E3645W