Paleointensity And Rock Magnetism Of Martian Nakhlite Meteorite Miller Range 03346: Evidence For Intense Small-Scale Crustal Magnetization On Mars

The martian dynamo's strength and duration are essential for understanding Mars' habitability and deep interior dynamics. Although most northern volcanic terranes were likely emplaced after the martian dynamo ceased, recent data from the InSight mission show stronger than predicted crustal fields. Studying young volcanic martian meteorites offers a precise, complementary method to characterize the strength of the martian crustal field and examine its implications for past dynamo activity. We present the first rock and paleomagnetic study of nine mutually oriented samples from the martian Nakhlite meteorite Miller Range (MIL) 03346, which is well-suited for paleomagnetic analysis due to its well-known age (1,368 +/- 83 Ma) and lack of significant aqueous, thermal, and shock overprinting. Rock magnetic analysis, including quantum diamond microscope imaging, showed that the natural remanent magnetization (NRM) is carried by Ti-magnetite crystals containing mu m-scale ilmenite exsolution lamellae, which can accurately record ancient magnetic fields. Demagnetization of the NRM revealed a high coercivity magnetization interpreted to date from the age of eruption based on its intensity, unidirectionality, and a passing fusion crust baked contact test. Paleointensities of four samples reveal a 5.1 +/- 1.5 mu T paleofield, representing the most reliable martian paleointensity estimates to-date and stronger than the 2 mu T surface fields measured by InSight. Modeling shows that the observed fields can be explained by an older subsurface magnetized layer without a late, active dynamo and support a deeply buried, highly magnetized crust in the northern hemisphere of Mars. These results provide corroborating evidence for strong, small-scale crustal fields on Mars.