Isotopic Composition of Solar Wind Calcium: First in Situ Measurementby CELIAS/MTOF on board SOHO

We present the first results of the Ca isotopic abundances derived from the high-resolution Mass Time-of-Flight (MTOF) spectrometer of the Charge, Element, and Isotope Analysis System (CELIAS) experiment on board the Solar and Heliospheric Observatory (SOHO). We obtain the isotopic ratios 40Ca/42Ca =128±47 and 40Ca/44Ca =50±8, consistent with terrestrial values. This is the first in situ determination of the solar wind calcium isotopic composition and is important for studies of stellar modeling and solar system formation since the present-day solar Ca isotopic abundances are unchanged from their original isotopic composition in the solar nebula.