A Survey of Venus' Windblown Ejecta Deposits Reveals Recent Resurfacing
and is Compatible with True Polar Wander
Abstract
Venus’s thick atmosphere rotates in the same direction as the solid
body, but ~60 times faster. This atmospheric superrotation
has produced dozens of windblown ejecta deposits (“parabolas”) on the
surface of Venus. The formation and modification of parabolas is an
interplay between impacts, aeolian erosion, and atmospheric dynamics. We
conducted a survey to explore the nature of these sedimentary surface
features and obtained three new results. Firstly, we observe trends in
parabolas’ morphology that shed light on how they are deposited and
eroded. Changes in the size and radar albedo of parabolas are likely
linked to the height and density (respectively) of ejecta plumes at time
of formation. Next, we discovered that parabolas show orientations
inconsistent with present atmospheric dynamics, and thus may record a
change in these dynamics or geologically recent true polar wander at a
rate of ~1° Myr-1. Lastly, we observe a definitive example
of a volcanically embayed parabola, which provides strong evidence for
large-scale geologic activity in the recent past. These results provide
important insights into the history and character of geologic processes
on Venus that will guide observations by upcoming missions. If true
polar wander is the cause of the anomalous parabola orientations, then
atmospheric superrotation has probably persisted for at least the age of
Venus’s surface. This mode of atmospheric circulation is unique to Venus
in the inner Solar System, but is likely common to terrestrial
exoplanets that are tidally locked in close orbits to their parent
stars.