Colloquium: Andrea Zorzi (Space Flight)
23 september 2019 14:00 - Locatie: Lecture Hall D, Faculty of Aerospace Engineering, Kluyverweg 1, Delft.
Long Term Evolution of Neptune's Atmosphere
We present an analysis of the temporal evolution of hazes on Neptune, as retrieved from HST images taken between 1994 and 2018. We see an increase in brightness in the F850LP/F845M filter from at least 1994 until 2009, followed by a decrease until today, both in a disk-averaged sense and from cloud-free regions only. A similar behavior occurs for F467M, which reaches a maximum disk-averaged I/F value in 2002. We performed radiative transfer modeling to identify changes in the atmospheric vertical structure that may give rise to these trends. We found that in 2002, all latitudes show a decrease in methane mixing ratio in the troposphere (0.03 as opposed to 0.05) and an upheaval of the top of the H2S ice cloud (2.6-3.0 bar), with the largest displacement (0.8 bar) for low cloud presence latitudes (65°S-50°S and 30°S-5°N). Today, southern lower hazes have descended to deeper pressure levels (3.6-4.1 bar).