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Pressure effects on martian crustal magnetization near large impact basins
Author(s) -
KLETETSCHKA Gunther,
CONNERNEY John E. P.,
NESS Norman F.,
ACUÑA Mario H.
Publication year - 2004
Publication title -
meteoritics and planetary science
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 1.09
H-Index - 100
eISSN - 1945-5100
pISSN - 1086-9379
DOI - 10.1111/j.1945-5100.2004.tb00079.x
Subject(s) - geology , remanence , impact crater , crust , coercivity , demagnetizing field , thermoremanent magnetization , geophysics , magnetization , magnetite , martian , rock magnetism , magnetic anomaly , petrology , geochemistry , magnetic field , mars exploration program , condensed matter physics , astrobiology , paleontology , physics , quantum mechanics
— Martian crust endured several large meteoroid impacts subsequent to the demise of an early global magnetic field. Shock pressures associated with these impacts demagnetized parts of the crust, to an extent determined by shock resistance of magnetic materials in the crust. Impacts that form large basins generate pressures in excess of 1 GPa within a few crater radii of their impact sites. Crustal materials near the surface experience significantly reduced impact pressure, which varies with depth and distance from the impact point. We present new demagnetization experiments on magnetite (Fe 3 O 4 ), hematite (α‐Fe 2 O 3 ), and titanohematite (Fe 2‐x Ti x O 3 where x <0.2). Our measurements show that pressures of ˜1 GPa are sufficient to partially demagnetize all of these minerals. The efficiency of demagnetization by impact pressure is proportional to the logarithm of the minerals' magnetic coercivity. The impact pressure magnetic response from exsolved titanohematite samples is consistent with the magnetization decay near Prometheus impact basin and may point to an oxidized igneous rock in Terra Sirenum region at the time of acquisition of magnetic remanence. The remaining magnetic anomalies near large impact basins suggest moderate crustal coercivity. These anomalies point to titanomagnetite as a magnetic carrier and more reduced condition during crustal formation.