Planetary Science Directorate


Upcoming SwRI Boulder Colloquia

Colloquia are normally on Tuesdays at 11:00 am in the 4th-floor conference room, except as indicated below in bold text.
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For questions or suggestions for speakers, please contact the SwRI colloquium organizers:
Derek Lamb, 720-208-7207 or derek(at)
Raluca Rufu, 303-226-0879 or raluca(at)
Julien Salmon, 720-208-7203 or julien(at)
Kelsi Singer, 303-226-5910 or ksinger(at)

To be added to the SwRI Boulder Colloquia email list, please contact Kelsi Singer, ksinger(at)

Tue Aug 18, 2020
In Web seminar
11:00 am Zarah Brown Arizona State University What’s heating Saturn’s thermosphere? Cassini Grand Finale observations show a connection between dynamics and heating.
Abstract: Like Jupiter, Neptune and Uranus, Saturn’s thermosphere is hundreds of degrees hotter than would be expected by solar heating alone. Enough energy is deposited into the auroral regions to heat the entire thermosphere, but previous models of Saturn’s thermosphere found that equatorward redistribution is prevented by Saturn’s strong Coriolis forces. Models that attempt to distinguish between contributing heating mechanisms are limited by the extent of the observations on which they are based. While a few high latitude observations had previously been made at Saturn’s thermosphere, the Cassini Grand Finale suite of stellar occultations provided the first concerted look at polar regions and cover lower latitudes as well. Analyzing these data along with previous observations taken in 2016 and 2017, has allowed us to create the first 2D snapshot of temperature with latitude and pressure in the thermosphere. I will present the observed temperatures, which peak at higher altitudes and lower latitudes and lead to a shallower gradient in gravitational potential. From these data we infer horizontal winds under an assumption of modified geostrophy. The inferred westward zonal jets are broader and extend to lower latitudes than predicted, supporting equatorward flow away from auroral latitudes in both hemispheres. I will discuss other interesting features of these data, including anomalously cool polar temperatures, a low latitude eastward jet and widespread evidence for gravity waves.