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Global Distribution of Crustal Magnetization Discovered by the Mars Global Surveyor MAG/ER Experiment

M. H. Acuña, J. E. P. Connerney, N. F., Ness, R. P. Lin, David Mitchell, C. W. Carlson, J. P. McFadden, K. A. Anderson, H. Rème,

Science · 1999 · 1.1K citations · 9 references

DOI

TL;DR

The Mars Global Surveyor MAG/ER instrument collected vector magnetic field data of the Martian crust during aerobraking and science‑phasing orbits at 100–200 km altitude. The observations reveal crustal magnetic sources of varying scale and strength, correlated with ancient highland craters, absent near large basins such as Hellas and Argyre—indicating early dynamo shutdown—and with strong moments up to 1.3 × 10¹⁷ A m² in Terra Sirenum that shape an asymmetric, time‑variable solar‑wind obstacle.

Abstract

Vector magnetic field observations of the martian crust were acquired by the Mars Global Surveyor (MGS) magnetic field experiment/electron reflectometer (MAG/ER) during the aerobraking and science phasing orbits, at altitudes between approximately 100 and 200 kilometers. Magnetic field sources of multiple scales, strength, and geometry were observed. There is a correlation between the location of the sources and the ancient cratered terrain of the martian highlands. The absence of crustal magnetism near large impact basins such as Hellas and Argyre implies cessation of internal dynamo action during the early Naochian epoch ( approximately 4 billion years ago). Sources with equivalent magnetic moments as large as 1.3 x 10(17) ampere-meter2 in the Terra Sirenum region contribute to the development of an asymmetrical, time-variable obstacle to solar wind flow around Mars.