Contents – N through R Comprehensive Study of Hydrated IDPs: X-Ray Diffraction, IR Spectroscopy and Electron Microscopic Analysis

Fig. 1: X-ray diffraction patterns in a range of diffraction angle from 12 to 52° (2θ) of a hydrated IDP L2036E23. Introduction: Chondritic hydrated interplanetary dust particles (IDPs) comprise up to 50% of all IDPs collected in the stratosphere[1]. Although much is known about the mineralogy, chemistry and carbon abundance of hydrated IDPs [2-4] controversies still exist regarding their formation, history, and relationship to other primitive solar system materials. Hydrated IDPs are generally believed to be derived from asteroidal sources that have undergone some degree of aqueous alteration. However, the high C contents of hydrated IDPs (by 2 to 6X CI levels [3,4]) indicate that they are probably not derived from the same parent bodies sampled by the known chondritic meteorites. Methods: We report the comprehensive study of individual hydrated IDPs. The strong depletion in Ca [1] has been used as a diagnostic feature of hydrated IDPs. The particles are embedded in elemental sulfur or low-viscosity epoxy and ultramicrotomed thin sections are observed using a transmission electron microscope (TEM) equipped with an energy-dispersive X-ray detector (EDX) followed by other measurements including: 1) FTIR microspectroscopy to understand the significant constraints on the organic functionality and the nature of the C-bearing phases and 2) powder X-ray diffraction using a synchrotron X-ray source to understand the bulk mineralogy of the particles. Bulk Composition and Mineralogy: Hydrated IDPs are composed predominantly of smectite and/or serpen-tine phyllosilicates and usually contain minor anhy-drous grains as shown in Figure 1 from IDP L2036E23. L2036E23 exhibits distinctive intergrowth of smectite and serpentine that has been reported from the Orgueil CI chondrite [5], the Tagish Lake CI2 [6] and a hy-drated IDP [7]. Mg-Fe carbonates common in CI chondrites [8], Tagish Lake [9] and other hydrated IDPs [8,9] are also abundant in L2036E23. Magnetite is the major Fe-bearing phases in CI chondrites, whereas magnetite in L2036E23 is observed as a prominent rim in response to atmospheric entry heating. Tochilinite which is commonly intergrown with serpen-tine in CM matrices is observed in IDP L2006A5. Although the majority of hydrated IDPs have chemical compositions that resemble to CI and CM chondrites [1,2,5], there are mineralogical similarities to the fine-grained material in certain altered type-3 carbonaceous and ordinary chondrites [10,11]. Possible Parent Bodies: Reflectance spectra (380-850 nm) of most IDPs are similar to those of P-and D-class outer belt asteroids [12] as well as the Tagish Lake meteorite [13]. Extraterrestrial materials resembling …