Low-magnetic crust underlying South Province of Mars

► Impacts creating craters larger than 200 km can demagnetize the entire crust of Mars. ► Craters and QCDS larger than 200 km in South Province have no magnetic signatures. ► The crust underlying the South Province on Mars is not appreciably magnetized. ► No strong core dynamo existed within the first about 100 Myr of Mars history.