open access

https://hdl.handle.net/2115/34717

Origin of Cometary Ices : Composition, Nuclear Spin Modifications, and Deuterium-to-Hydrogen Ratio in Cometary Molecules

日本語

2008-03-31

北海道大学低温科学研究所

Low Temperature Science

66

89-95

3章 惑星における氷の物理と化学

Recently we performed near-infrared high dispersion spectroscopic observations of two bright comets, C/2004 Q2 (Machholz) and a nucleus "B" of 73P/Schwassmann-Wachmann 3(SW3). The former was very bright and it allowed us to obtain very high-S/N ratio spectra. We extracted H2O and CH4 emission lines and determined nuclear spin temperatures of both molecules. The obtained temperatures are higher than the typical value for the Oort Cloud comets (～30K). Furthermore, we report a tentative detection of CH3D in comet Machholz. The D/H ratio in methane was consistent with the temperature range obtained from nuclear spin temperatures. On the other hand, in the case of break-up comet 73P/SW3, we also derived higher nuclear spin temperature than the typical Oort Cloud comets. We also found the similarity in chemical composition between fragments of the same comet. Fragments "B" and "C" of comet SW3 are very similar to each other from the viewpoint of chemistry. This fact indicates that the parent body of SW3 was quite homogeneous in chemical composition of ices.

紀要論文

Version of Record

1880-7593