Regional Mapping of MAVEN Orbital Magnetometer Data: Implications for the Nature of Crustal Field Sources and the Duration of the Mars Dynamo

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Abstract
By implementing an alternate regional mapping approach that selects MAVEN orbit passes with periapses below 170 km within the region of interest and directly compares magnetometer data along adjacent tracks, more accurate regional maps of the Mars crustal magnetic field are constructed. Results for the Claritas Fossae region south of Tharsis show a more detailed correlation than previously found in Mars Global Surveyor (MGS) data between magnetic anomalies and areas of ancient magmatic activity and uplift. These anomaly sources are interpreted to consist of magmatic intrusions magnetized thermoremanently in an oxidizing, hydrothermal environment during early Mars history when the planetary dynamo was still active. Similarly, mapped anomalies near Olympus Mons are consistent with thermal demagnetization in the absence of a dynamo during the Late Hesperian and Amazonian epochs when its final eruptions occurred. Weak anomalies over the Syrtis Major calderas and the Tyrrhenus Mons caldera further support partial thermal demagnetization of the underlying older terrain. Hadriacus Mons has previously been reported to have a magnetization signature based on MGS electron reflectometry data. The regional mapping reported here confirms that anomalies extend southwestward from the Hadriacus Mons central caldera toward Hellas, following the direction of apparent pyroclastic flow deposits with model ages ranging from 3.7 to 3.9 Ga. If future lower‐altitude measurements demonstrate that these anomalies are indeed associated with the asymmetric flanks of Hadriacus Mons, it would follow that dynamo activity continued into the Late Noachian or Early Hesperian epochs.

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