title: Could giant basin-forming impacts have killed Martian dynamo?
abstract: The observed strong remanent crustal magnetization at the surface of Mars suggests an active dynamo in the past and ceased to exist around early to middle Noachian era, estimated by examining remagnetization strengths in extant and buried impact basins. We investigate whether the Martian dynamo could have been killed by these large basin-forming impacts, via numerical simulation of subcritical dynamos with impact-induced thermal heterogeneity across the core-mantle boundary. We find that subcritical dynamos are prone to the impacts centered on locations within 30° of the equator but can easily survive those at higher latitudes. Our results further suggest that magnetic timing places a strong constraint on postimpact polar reorientation, e.g., a minimum 16° polar reorientation is needed if Utopia is the dynamo killer.
authors.affiliation: Planetary Geodynamics Laboratory, NASA Goddard Space Flight Center Greenbelt, Maryland, USA.
authors.forename: W
authors.initials: W
authors.lastname: Kuang
authors.affiliation: Science Systems and Applications, Inc. Lanham, Maryland, USA.
authors.forename: W
authors.initials: W
authors.lastname: Jiang
authors.affiliation: Johns Hopkins University Applied Physics Laboratory Laurel, Maryland, USA.
authors.forename: J
authors.initials: J
authors.lastname: Roberts
authors.affiliation: Planetary Geodynamics Laboratory, NASA Goddard Space Flight Center Greenbelt, Maryland, USA.
authors.forename: H V
authors.initials: HV
authors.lastname: Frey
keywords: Martian dynamo; giant impacts; numerical simulation; thermal heterogeneity