Since 1998, the study of Mars' crustal remanent magnetism has advanced through data from orbiting spacecraft and surface assets, modeling of crustal sources, and meteorite studies. Mars Global Surveyor's magnetometer discovered strong magnetic anomalies, primarily in Mars' southern hemisphere, suggesting a past planetary dynamo. MAVEN's magnetometer has provided significantly more data at low altitudes, refining our understanding of the distribution and intensity of crustal fields.  From these data sets, several models of global magnetic field have been derived.  These models contain limited information about Mars crustal magnetism on scales smaller than the nominal MAVEN periapsis of ~150 km due to magnetic noise from non-crustal sources.  The Insight lander detected a strong, ~2000 nT crustal field at Elysium Planitia, ~10 times stronger than models predicted, underlining the limitations of orbital magnetic measurements.

Paleomagnetic studies of the Martian meteorite ALH84001 support the existence of a past Martian dynamo at radiometrically-determined ages of 4.0 and 3.9 Ga.  Lack of orbitally-detectable crustal magnetic fields within the large impact basins Hellas, Argyre, Isidis, and Utopia have been interpreted as evidence for a lack of a core dynamo following their formation at estimated ages of 3.9-4.1 Ga, an interpretation supported by the non-detection of crustal magnetic fields by the Chinese Zhurong rover at the surface in Utopia.  However, a) cooling in a rapidly reversing dynamo or a lack of magnetic minerals in the post-impact heated region above the Curie isotherm may account for these observations and b) these estimated basin ages likely have significant systematic errors.  Finally, magnetic measurements over small craters in Hesperian lava flows can be interpreted as evidence of a dynamo at 3.7 Ga.  Thus there is support in current data sets and modelling studies for a dynamo cessation after 3.9 Ga, either before or after the formation of the largest basins.

This sparse evidence emphasizes the need for future missions focusing on detailed, high-resolution near-surface magnetic surveys to overcome current limitations and advance our understanding of Mars' magnetic past.