Ground-truthing magnetic recording in meteorites

太阳系中的原始天体是否拥有内部产生的发电机，是理解早期行星形成的动力学和时间的根本制约因素。对几颗陨石的古强度研究表明，它们的宿主行星在当今地球磁场的数量级内具有磁场。古强度数据的解释在很大程度上依赖于磁性载体磁性的基本知识，例如单区到多区尺寸阈值或饱和磁化强度如何随颗粒尺寸变化，但对陨石中的一些主要磁记录器--铁-镍合金--的这些关键参数知之甚少。此外，大多数陨石在其历史上都经历了一定程度的冲击，但即使是非常小的应力对古强度数据的影响也鲜为人知。我们希望通过将Fe-Ni合金作为颗粒大小的函数进行磁性表征来填补这些空白，并确定绝对和相对古强度数据如何因应变水平低于岩石学上可观察到的水平(&lt；4-5 Gpa)而产生偏差。例如，我们的初步工作表明，0.6 Gpa的外加应力将使单域磁铁矿岩石的绝对古强度估计减少46%。一般而言，古烈度测定在测量精度和人力时间投入过多方面具有固有的缺点。我们打算通过扩展和改进我们的全自动磁性工作站Suhibar来克服这些限制。

Whether primordial bodies in the solar system possessed internally-generated dynamos is a fundamental constraint to understand the dynamics and timing of early planetary formation. Paleointensity studies on several meteorites reveal that their host planets possessed magnetic fields within an order-of magnitude of the present Earth’s field. Interpretation of paleointensity data relies heavily on fundamental knowledge of the magnetic properties of the magnetic carriers, such as the single to multidomain size threshold or how the saturation magnetization varies as a function of grain size, yet very little knowledge exists about these key parameters for some of the main magnetic recorders in meteorites: the iron-nickel alloys. Moreover, most meteorites have experienced some amount of shock during their histories, yet the consequence of even very small stresses on paleointensity data is poorly known.We wish to fill these gaps by magnetically characterizing Fe-Ni alloys as a function of grain size and by determining how absolute and relative paleointensity data are biased by strain levels lower than those petrologically observable (< 4-5 GPa). For example, our preliminary work shows that an imposed stress of 0.6 GPa will reduce absolute paleointensity estimates by 46% for single domain magnetite-bearing rocks. In general, paleointensity determinations possess inherent disadvantages regarding measurement precision and the inordinate amount of human time investment. We intend to overcome these limitations by extending and improving our fully automated magnetic workstation known as the SushiBar.