MCS Observations of the Initiation and Development of Large Regional
Dust Events on Mars
Abstract
Why do some Martian dust storms, in some Mars years, expand to reach
planet-encircling status, while the majority do not? In what ways do the
largest regional events differ from those that become global?
Comparisons of observations from these two categories of events may help
answer these questions. The dust storm season of 2018, which included a
global-scale dust event, was preceded by five successive dust storm
seasons in which only regional-scale events were observed. The recent
record thus presents an opportunity for making quantitative comparisons
between regional-scale and global-scale dust events. Observations by the
Mars Climate Sounder, on board the Mars Reconnaissance Orbiter
spacecraft, provide unique 4D information on temperatures and aerosol
loading of the Mars atmosphere, to altitudes of >80 km.
Available MCS observations span the past eight Mars years. We have
previously employed MCS observations to characterize the evolution in
latitude, longitude, and altitude of atmospheric dust clouds during the
initiation phase of the 2018 global event. Other atmospheric fields
provide complementary information. For instance, observed changes with
time in atmospheric ‘dynamical heating’ also help characterize the
response of the Mars atmosphere to added dust loading. In this process,
the atmosphere in regions far removed from the locations where dust is
lifted may be warmed by adiabatic compression within the descending
branches of Hadley-like meridional circulation cells. We will present
and interpret MCS observations of these and other phenomena for selected
large regional-scale dust events of Mars Years 29-33 (from 2009 through
2017), and draw comparisons with observations obtained during the 2018
global event. We will additionally explore the implications of the
results within the context of current hypotheses for the triggering of
the largest dust storms on sub-seasonal time scales.