New constraints on the dynamo timing and crustal magnetization on Mars from MAVEN observations

Crustal magnetic fields carry a wealth of information about planetary interiors. Crustal fields provide constraints on dynamo history and hence on the thermal evolution and interior composition of a planet. They tell us about characteristics of the subsurface layer in which the magnetic carriers responsible for the observed fields reside. Finally, they are a key to understanding planetary processes by which magnetization is gained, modified or lost. The martian crustal magnetic field was first detected with the fluxgate magnetometers on-board Mars Global Surveyor (MGS) operating from 1997-2006. The Mars Atmosphere and Volatile EvolutioN (MAVEN) Mission has been collecting data, since 2014. The night-side, near-periapsis portions of MAVEN orbits are particularly valuable for crustal field studies because they are sensitive to wavelengths shorter than 200 km and now provide global coverage with minimal external field contamination that was not available from MGS. We use MAVEN data to address some key questions regarding Mars' magnetic field, focusing on new evidence for the timing of the ancient dynamo field. Furthermore, we find evidence for magnetization that can be clearly tied to a datable surface unit of known thickness, allowing the magnitude of that magnetization to be well constrained. We revisit the magnetic signatures of basins and inferred magnetic field chronologies in the context of our new results.