The early martian evolution -- Constraints from basin formation ages

To link to full-text access for this article, visit this link: http://dx.doi.org/10.1016/j.icarus.2007.12.008 Byline: S.C. Werner Keywords: Mars; Cratering; Mars; surface; Moon; surfaces Abstract: Impact basin formation ages give insight into the early evolution of a planet. The martian basins Hellas, Isidis and Argyre provide an important time-marker for the cessation of the magnetic dynamo and the crustal thickness distribution, both established before 4 Ga ago. No martian surfaces are older than 4.15 Ga based on crater count statistics, and all are younger than the oldest lunar ones. I show that the heavy bombardment period on the Moon and Mars evolved similarly, but endogenic processes have removed the oldest martian basin record. The basin-forming projectile population appears to be different from the impactor population observed today in the inner Solar System. It is yet uncertain whether the heavy bombardment period is cataclysmic or characterized by the decaying flux of planetary formation. Author Affiliation: Geological Survey of Norway (NGU), Leiv Eirikssons vei 39, N-7491 Trondheim, Norway Article History: Received 16 January 2007; Revised 20 November 2007