The history of Mars' dynamo as revealed by modeling magnetic anomalies near Tyrrhenus Mons and Syrtis Major
Article first published online: 13 OCT 2012
©2012. American Geophysical Union. All Rights Reserved.
Journal of Geophysical Research: Planets (1991–2012)
Volume 117, Issue E10, October 2012
How to Cite
2012), The history of Mars' dynamo as revealed by modeling magnetic anomalies near Tyrrhenus Mons and Syrtis Major, J. Geophys. Res., 117, E10007, doi:10.1029/2012JE004099., , , , and (
- Issue published online: 13 OCT 2012
- Article first published online: 13 OCT 2012
- Manuscript Accepted: 6 SEP 2012
- Manuscript Revised: 31 AUG 2012
- Manuscript Received: 5 APR 2012
- NASA Graduate Student Researcher Program. Grant Number: NNG05GL93H
- National Science Foundation. Grant Number: 0909206
- Agence Nationale de la Recherche. Grant Number: ANR-08-JCJC-0126-01
 The lack of magnetic anomalies within the major impact basins (Hellas, Argyre, and Isidis) has led many investigators to the conclusion that Mars' dynamo shut down prior to the time when these basins formed (∼4.0 Ga). We test this hypothesis by analyzing gravity and magnetic anomalies in the regions surrounding Tyrrhenus Mons and Syrtis Major, two volcanoes that were active during the late Noachian and Hesperian. We model magnetic anomalies that are associated with gravity anomalies and generally find that sources located below Noachian surface units tend to favor paleopoles near the equator and sources located below Hesperian surface features favor paleopoles near the geographical poles, suggesting polar wander during the Noachian-Hesperian. Both paleopole clusters have positive and negative polarities, indicating reversals of the field during the Noachian and Hesperian. Magnetization of sources below Hesperian surfaces is evidence that the dynamo persisted beyond the formation of the major impact basins. The demagnetization associated with the volcanic construct of Syrtis Major implies dynamo cessation occurred while it was geologically active approximately 3.6 billion years ago. Timing of dynamo activity is fundamentally linked to Mars' climate via the stability of its atmosphere, and is coupled to the extent and duration of surface geologic activity. Thus, the dynamo history is key for understanding both when Mars was most geologically active and when it may have been most hospitable to life.