{"title":"Reconciling Mars InSight Results, Geoid, and Melt Evolution With 3D Spherical Models of Convection","authors":"J. P. Murphy, S. D. King","doi":"10.1029/2023JE008143","DOIUrl":null,"url":null,"abstract":"<p>We investigate the geodynamic and melting history of Mars using 3D spherical shell models of mantle convection, constrained by the recent InSight mission results. The Martian mantle must have produced sufficient melt to emplace the Tharsis rise by the end of the Noachian–requiring on the order of 1–3 × 10<sup>9</sup> km<sup>3</sup> of melt after accounting for limited (∼10%) melt extraction. Thereafter, melting declined; however, abundant evidence for limited geologically recent volcanism necessitates some present-day melt even in the cool mantle inferred from InSight data. We test models with two mantle activation energies and a range of crustal Heat Producing Element (HPE) enrichment factors and initial core-mantle boundary temperatures. We also test the effect of including a hemispheric (spherical harmonic degree-1) step in lithospheric thickness to model the Martian dichotomy. We find that a higher activation energy (350 kJ mol<sup>−1</sup>) rheology produces present-day geotherms consistent with InSight results, and crustal HPE enrichment factors of 5–10-times produce localized melting near or up to present-day. The 10-times crustal HPE enrichment is consistent with both InSight and geochemical results and also produces present-day geoid power spectra consistent with Mars. However, calculations that match the present-day geoid power spectra require more than 60% melt extraction to produce the Tharsis swell. The addition of a degree-1 hemispheric dichotomy, as an equatorial step in lithospheric thickness, does not significantly improve upon melt production or the geoid.</p>","PeriodicalId":16101,"journal":{"name":"Journal of Geophysical Research: Planets","volume":null,"pages":null},"PeriodicalIF":3.9000,"publicationDate":"2024-05-02","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"https://onlinelibrary.wiley.com/doi/epdf/10.1029/2023JE008143","citationCount":"0","resultStr":null,"platform":"Semanticscholar","paperid":null,"PeriodicalName":"Journal of Geophysical Research: Planets","FirstCategoryId":"89","ListUrlMain":"https://onlinelibrary.wiley.com/doi/10.1029/2023JE008143","RegionNum":1,"RegionCategory":"地球科学","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":null,"EPubDate":"","PubModel":"","JCR":"Q1","JCRName":"GEOCHEMISTRY & GEOPHYSICS","Score":null,"Total":0}
引用次数: 0
Abstract
We investigate the geodynamic and melting history of Mars using 3D spherical shell models of mantle convection, constrained by the recent InSight mission results. The Martian mantle must have produced sufficient melt to emplace the Tharsis rise by the end of the Noachian–requiring on the order of 1–3 × 109 km3 of melt after accounting for limited (∼10%) melt extraction. Thereafter, melting declined; however, abundant evidence for limited geologically recent volcanism necessitates some present-day melt even in the cool mantle inferred from InSight data. We test models with two mantle activation energies and a range of crustal Heat Producing Element (HPE) enrichment factors and initial core-mantle boundary temperatures. We also test the effect of including a hemispheric (spherical harmonic degree-1) step in lithospheric thickness to model the Martian dichotomy. We find that a higher activation energy (350 kJ mol−1) rheology produces present-day geotherms consistent with InSight results, and crustal HPE enrichment factors of 5–10-times produce localized melting near or up to present-day. The 10-times crustal HPE enrichment is consistent with both InSight and geochemical results and also produces present-day geoid power spectra consistent with Mars. However, calculations that match the present-day geoid power spectra require more than 60% melt extraction to produce the Tharsis swell. The addition of a degree-1 hemispheric dichotomy, as an equatorial step in lithospheric thickness, does not significantly improve upon melt production or the geoid.
期刊介绍:
The Journal of Geophysical Research Planets is dedicated to the publication of new and original research in the broad field of planetary science. Manuscripts concerning planetary geology, geophysics, geochemistry, atmospheres, and dynamics are appropriate for the journal when they increase knowledge about the processes that affect Solar System objects. Manuscripts concerning other planetary systems, exoplanets or Earth are welcome when presented in a comparative planetology perspective. Studies in the field of astrobiology will be considered when they have immediate consequences for the interpretation of planetary data. JGR: Planets does not publish manuscripts that deal with future missions and instrumentation, nor those that are primarily of an engineering interest. Instrument, calibration or data processing papers may be appropriate for the journal, but only when accompanied by scientific analysis and interpretation that increases understanding of the studied object. A manuscript that describes a new method or technique would be acceptable for JGR: Planets if it contained new and relevant scientific results obtained using the method. Review articles are generally not appropriate for JGR: Planets, but they may be considered if they form an integral part of a special issue.