Vol. 662
10. Planets and planetary methods
Excessive D/H ratios in water and alkanes in comet 67P/Churyumov-Gerasimenko measured with Rosetta/ROSINA DFMS
Measurements of isotopic abundances in comets bear key data concerning the early Photo voltaic System’s composition and bodily situations. Because of its sensitivity and mass decision, the mass spectrometer ROSINA/DFMS onboard Rosetta had the aptitude to detect tens of recent atomic and molecular species in comet 67P/Churyumov-Gerasimenko and to measure isotopic ratios in lots of them. Right here, Müller et al. current two units of recent outcomes. First, they present that the D/H ratio in water, which is enhanced by an element 3.2 over the terrestrial worth, is unbiased of heliocentric distance, the extent of cometary exercise, and the space to the nucleus; the identical is true for the 16O/17O ratio. Extra remarkably, additionally they measured for the primary time in comets the D/H ratios in a set of alkanes (CH4, C2H6, C3H8, and C4H10). The inferred values are 4-5 occasions enhanced over the D/H ratio in water, however akin to its worth in a number of different carriers, essentially the most noteworthy one being within the natural refractory element of 67P mud. This implies that these natural molecules could also be inherited from the presolar molecular cloud, the place ionized radiation in chilly environments favored D/H fractionation, each in water and (differentially) in organics. In distinction, the 13C/12C ratio in 67P’s alkanes is discovered to be in keeping with the 13C/12C ratio on Earth and different planets, including additional proof for a “common” Photo voltaic System 13C/12C worth.
