Imaging Magnetization in Terrestrial and Extraterrestrial Rocks
Salle Lagrange gris, on March 4, 2:00 PM
Warning!Ancient magnetic fields may be recorded as remanent magnetization in terrestrial and extraterrestrial rocks at the time they formed. These records can provide invaluable information about the evolution of the Earth and the formation of the solar system. In most practical situations, however, magnetization distributions cannot be measured directly, and must be instead estimated from measurements of the magnetic field exterior to the rock. Scanning Magnetic Microscopy (SMM) is a recent technique that allows us to map the magnetic field above a thin geological sample with spatial resolution as high as a few thousandths of a millimeter and with magnetic moment sensitivity up to four orders of magnitude greater than that of commercial rock magnetometers. This has enabled us to analyze rocks that were previously inaccessible to standard paleomagnetic techniques. In this talk, we will briefly review the instrumentation utilized in SMM and the associated constraints imposed on the inverse problem for magnetization, in addition to discussing novel results obtained for the meteorites Allende, Semarkona and ALHA81001, as well as for Earth rocks.