Constraints on the Origin of the Martian Dichotomy From Southern Highlands Marsquakes

The Martian hemispheric dichotomy is delineated by significant differences in elevation and crustal thickness between the Northern Lowlands and Southern Highlands. Yet, its origin remains controversial. Here, we improve the signal-to-noise ratios and determine the locations of the low-frequency marsquakes recorded during the InSight mission. We find a new cluster of marsquakes in Terra Cimmeria, Southern Highlands, in addition to those previously located in Cerberus Fossae, Northern Lowlands. Using the spectral ratio method, we estimate the quality factor Q in the range 481–543 for Terra Cimmeria versus 800–2,000 determined for Cerberus Fossae. The attenuation difference might be linked to the temperature differences between the two hemispheres, along with more vigorous convection beneath the Southern Highlands. These seismological observations, together with geochronological constraints of giant impacts, reinforce the “endogenic” hypothesis that mantle convection causes the crustal dichotomy.