Mars's two distinct hemispheres caused by mantle convection not giant impacts, study claims

Mars has northern and southern hemispheres like Earth, but their defining characteristics are markedly different, a phenomenon known as Martian dichotomy. The Southern Highlands are older, higher in elevation and more cratered than the Northern Lowlands. The elevated terrain of the former acts as a natural barrier to airflow, resulting in varied wind patterns and contributing to localized weather phenomena.