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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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Title: Regional Mapping of MAVEN Orbital Magnetometer Data: Implications for the Nature of Crustal Field Sources and the Duration of the Mars Dynamo.
Authors: Hood, L. L.1 (AUTHOR) lon@lpl.arizona.edu, Matlock, T.1,2 (AUTHOR), Crown, D. A.3 (AUTHOR), Williams, D. A.4 (AUTHOR), Oliveira, J. S.5 (AUTHOR), Halekas, J.6 (AUTHOR), Langlais, B.7 (AUTHOR), Lillis, R.8 (AUTHOR)
Source: Journal of Geophysical Research. Planets. Jun2026, Vol. 131 Issue 6, p1-22. 22p.
Subject Terms: *Volcanoes, *Geomagnetism, Magnetic anomalies, Igneous intrusions, Magnetometers, Demagnetization
Company/Entity: United States. National Aeronautics & Space Administration
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. Plain Language Summary: Orbital data from the magnetometer onboard NASA's MAVEN spacecraft are used to construct regional maps of the crustal magnetic field of Mars, that is, the magnetic field that results from magnetized geological structures or rocks beneath the surface. The objective is to better understand the sources of the crustal fields and the duration of the internal dynamo field that magnetized them. The timing of dynamo activity is important because the global magnetic field may have helped to protect the early atmosphere, allowing an early warmer climate. A careful data selection method is employed, involving actual plotting and comparisons of data for orbits that pass over the same region at low altitudes and at different times during the mission. Results show that magmatic intrusions forming in a water‐rich environment are the most likely sources of the orbital magnetic anomalies. The crust was thermally demagnetized by later volcanic episodes, including those that formed the volcanoes of Tharsis. However, evidence is obtained for a crustal magnetic field extending along an outflow of volcanic material that has a relatively young estimated age of 3.7–3.9 Ga. Lower‐altitude measurements are needed to confirm whether this material is indeed the source of the magnetic anomaly. Key Points: An alternate method of data selection for producing regional maps of the Mars crustal magnetic field is described and implementedIn the Claritas Fossae region, a more detailed correlation is found of magnetic anomalies with areas of ancient magmatic activity and upliftAt Hadriacus Mons, anomalies extend southwestward along apparent pyroclastic flow deposits with a model age of 3.7–3.9 Ga [ABSTRACT FROM AUTHOR]
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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. Plain Language Summary: Orbital data from the magnetometer onboard NASA's MAVEN spacecraft are used to construct regional maps of the crustal magnetic field of Mars, that is, the magnetic field that results from magnetized geological structures or rocks beneath the surface. The objective is to better understand the sources of the crustal fields and the duration of the internal dynamo field that magnetized them. The timing of dynamo activity is important because the global magnetic field may have helped to protect the early atmosphere, allowing an early warmer climate. A careful data selection method is employed, involving actual plotting and comparisons of data for orbits that pass over the same region at low altitudes and at different times during the mission. Results show that magmatic intrusions forming in a water‐rich environment are the most likely sources of the orbital magnetic anomalies. The crust was thermally demagnetized by later volcanic episodes, including those that formed the volcanoes of Tharsis. However, evidence is obtained for a crustal magnetic field extending along an outflow of volcanic material that has a relatively young estimated age of 3.7–3.9 Ga. Lower‐altitude measurements are needed to confirm whether this material is indeed the source of the magnetic anomaly. Key Points: An alternate method of data selection for producing regional maps of the Mars crustal magnetic field is described and implementedIn the Claritas Fossae region, a more detailed correlation is found of magnetic anomalies with areas of ancient magmatic activity and upliftAt Hadriacus Mons, anomalies extend southwestward along apparent pyroclastic flow deposits with a model age of 3.7–3.9 Ga [ABSTRACT FROM AUTHOR]
ISSN:21699097
DOI:10.1029/2025JE009486