Our main study area is in the north of Chile in the hyperarid core of the Atacama Desert. Two field campaigns were conducted, during February/March 2024 and during March/April 2025. In the field, we acquire data for pre-characterizing the soils and their environmental settings, e.g. through portable hand-held X-Ray Fluorescence (XRF) for elemental composition analyses; drone imaging for photogrammetry, geomorphology, and optical and infrared spectroscopy; Ground-Penetrating Radar (GPR) and Transient Electromagnetic (TEM) for shallow and deep subsurface mapping. We use several excavation methods to obtain million-year-old soil profiles including shovel & pickaxe, motorized dredger, excavator, and core drilling probe.
During the two campaigns, several 100 kg of sample material was collected. For deciphering the formation processes and age distribution of the exotic sediment profiles, we analyse the samples for 1) sedimentology, e.g. through sieving and leaching for grain-size analyses, 2) geochemistry, e.g. through X-Ray Fluorescence (XRF) and X-Ray Diffraction (XRD) for elemental and mineralogical composition, and 3) isotopes, e.g. through mass spectrometry (MS) for C, N, O stable isotope ratios of organic matter, carbonates, and nitrates as well as accelerator mass spectrometry (AMS) for depositional age dating with meteoric 10Be.
Micrometeorites are hand-picked from the previously leached and sieved sediment samples. Their identification is based the analysis of surface textures and composition using Scanning Electron Microscopy (SEM) and Energy-Dispersive X-ray spectroscopy (EDX). Their mineralogy is obtained with Electron MicroProbe Analysis (EMPA) from polished cross-sections. For estimating their heliocentric distance of origin in our Solar System, we analyse their content of cosmogenic radionuclides, which are produced in dust grains in space by irradiation from cosmic rays. Generally, longer travel times of the dust grains, lead to higher concentration of radionuclides. The measured concentrations are compared to a numerical model (MiMiTracer – Micrometeorites: Modelling irradiation and Transport of cosmic dust to earth) calculating the production of radionuclides in cosmic dust grains as they travel through space.
For the detection of past Supernova signatures, 60Fe is chemically extracted from the sediment samples and measured with AMS at the Heavy Ion Accelerator Facility (HIAF) at the Australian National University in Australia.
