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We consider the formation of solar infrared (2-6 micron) rovibrational bandsof carbon monoxide (CO) in CO5BOLD 3D convection models, with the aim to refineabundances of the heavy isotopes of carbon (13C) and oxygen (18O,17O), tocompare with direct capture measurements of solar wind light ions by theGenesis Discovery Mission. We find that previous, mainly 1D, analyses weresystematically biased toward lower isotopic ratios (e.g., R23= 12C/13C),suggesting an isotopically "heavy" Sun contrary to accepted fractionationprocesses thought to have operated in the primitive solar nebula. The new 3Dratios for 13C and 18O are: R23= 91.4 +/- 1.3 (Rsun= 89.2); and R68= 511 +/- 10(Rsun= 499), where the uncertainties are 1 sigma and "optimistic." We alsoobtained R67= 2738 +/- 118 (Rsun= 2632), but we caution that the observed12C17O features are extremely weak. The new solar ratios for the oxygenisotopes fall between the terrestrial values and those reported by Genesis(R68= 530, R6= 2798), although including both within 2 sigma error flags, andgo in the direction favoring recent theories for the oxygen isotope compositionof Ca-Al inclusions (CAI) in primitive meteorites. While not a major focus ofthis work, we derive an oxygen abundance of 603 +/- 9 ppm (relative tohydrogen; 8.78 on the logarithmic H= 12 scale). That the Sun likely is lighterthan the Earth, isotopically speaking, removes the necessity to invoke exoticfractionation processes during the early construction of the inner solarsystem.

Is the Sun Lighter than the Earth? Isotopic CO in the Photosphere, Viewed through the Lens of 3D Spectrum Synthesis