High-dispersion Spectroscopic Observations Of 8P/Tuttle With VLT/CRIRES

We present near-infrared observations of organic molecules in comet 8P/Tuttle. Comet 8P/Tuttle is a Halley-type comet and its last perihelion was in early January 2008. Our observations were carried out on January 28 and February 4 using CRIRES (CRyogenic high-resolution InfraRed Echelle Spectrograph) at the Very Large Telescope (VLT). We used a 0.2" slit which provided a spectral resolving power of 80,000. We detected H[SUB]2[/SUB]O, OH, HCN, C[SUB]2[/SUB]H[SUB]2[/SUB] on Jan 28, and H[SUB]2[/SUB]O, OH, CH[SUB]4[/SUB], C[SUB]2[/SUB]H[SUB]6[/SUB], and CH[SUB]3[/SUB]OH on Feb 4. We find that 8P/Tuttle is depleted in HCN, C[SUB]2[/SUB]H[SUB]2[/SUB] and C[SUB]2[/SUB]H[SUB]6[/SUB] relative to H[SUB]2[/SUB]O compared with most other Oort cloud comets studied to date. Perhaps these depletions suggest that 8P/Tuttle formed in a different region from most Oort cloud comets, but it is also possible that the depletions are caused by repeated passages through the inner solar system.