The Study On Inner Structure Of Martian Volcanic And The Ancient Martian Magnetic-3D Inversion Of Magnetic Anomaly Of Volcanic Clusters In The Hellas Basin

Mars is a terrestrial planet that is the focus of deep-space exploration in the solar system.Now,Mars has no global magnetic field,but the stop time of the Martian magnetic field dynamo and the main characteristics of the ancient Martian magnetic field are still controversial.The remanent magnetization carried by the magnetized magmatic rocks below the Martian volcanoes records the intensity and direction of the Martian ancient dynamo field,which deserves careful study.The depth and volume of magma chambers of Martian volcanoes are of great significance for understanding the evolution of the crust-mantle system.This article analyzes the magnetic anomalies of Martian volcanoes to reveal the distribution of magnetized rock in the crust and the internal structure of the volcanoes;obtains the direction and intensity range of the ancient Martian magnetic field based on the comparison between the results from 3D amplitude inversion and 3D directional inversion;and infers the stop time of dynamo based on the surface age of the patera;according to the relationship between the magnetic latitude and the inclination of the dipole magnetic field,the magnetic pole positions in different age are obtained.This paper uses a high-resolution surface magnetic field model based on the orbital magnetic field measurement data of the Mars Global Surveyor(MGS)and Mars Atmosphere and Volatile Evolutio N(MAVEN)Missions.Three-dimensional magnetic anomaly modulus inversion and three-dimensional magnetic anomaly directional inversion were used to study the crustal magnetic anomaly on the southwest side of the Circum-Hellas Volcanic Province on Mars.This area has one of the oldest volcanic clusters on Mars,formed in Noachian to Hesperian around 3.7 Ga.In this paper,the 3D inversion of magnetic amplitude data is carried out on the magnetic anomaly caused by remanent magnetization.The inversion results show the3 D distribution of remanent magnetization under the four volcanoes on the southwest side of the Circum-Hellas Volcanic Province,indicating that there may be magma chambers at depth from 30 km to 60 km below the three volcanoes: Amphitrites,Peneus,and Pityusa.It is highly possible that there is no magma chamber below Malea patera.The maximum remanent magnetization below Amphitrites is 1 A/m,and the volume of the magma chamber is about 10 km.The remanent magnetization below Peneus volcano is 0.15 to 0.4 A/m,and the volume of the magma chamber is about 10 km.In order to simulate the magnetic environment of the rock,this paper compares the results of the 3D magnetic anomaly directional inversion and amplitude inversion.When the two results show the highest similarity,the corresponding magnetic inclination at the center of the Amphitrites,Peneus,volcanoes are about approximately 30°,-75°,and the related magnetic poles in dipole field are reversal;the intensity of the paleomagnetic field may be between 5000 and50000 n T.To sum up,our inversion supports an active Martian dynamo field at approximately 3.75 Ga,and the internal structure and volume of the Martian volcanoes are quite similar to those on Earth.