The unusual volatile composition of the Halley-type comet 8P/Tuttle: Addressing the existence of an Inner Oort Cloud

TL;DR

This study analyzes the volatile composition of comet 8P/Tuttle, revealing no distinct chemical signature to confirm its origin from the inner Oort Cloud, challenging previous assumptions about comet formation regions.

Contribution

It provides the first detailed volatile composition analysis of 8P/Tuttle and compares it with other Halley-type comets to investigate their origins.

Findings

No common chemical characteristics found among Halley-type comets from different Oort Cloud regions.

Comet 8P/Tuttle's composition does not support a unique inner Oort Cloud origin.

Chemical gradients in the proto-planetary disk may not be preserved in comets.

Abstract

We measured organic volatiles (CH4, CH3OH, C2H6, H2CO), CO, and water in comet 8P/Tuttle, a comet from the Oort cloud reservoir now in a short-period Halley-type orbit. We compare its composition with two other comets in Halley-type orbits, and with comets of the "organics-normal" and "organics-depleted" classes. Chemical gradients are expected in the comet-forming region of the proto-planetary disk, and an individual comet should reflect its specific heritage. If Halley-type comets came from the inner Oort cloud as proposed, we see no common characteristics that could distinguish such comets from those that were stored in the outer Oort cloud.