Artist’s Concept of Comet 238P/Read

This illustration of Comet 238P/Read shows the main belt comet sublimating—its water ice vaporizing as its orbit approaches the Sun. This is significant, as the sublimation is what distinguishes comets from asteroids, creating their distinctive tail and hazy halo, or coma. It is especially important for Comet Read, as it is one of 16 identified main belt comets found in the asteroid belt, as opposed to the colder Kuiper Belt or Oort Cloud, more distant from the Sun. Comet Read was one of three comets used to define the class of main belt comets in 2006.

The James Webb Space Telescope’s detection of water vapor at Comet Read is a major benchmark in the study of main belt comets, and in the broader investigation of the origin of Earth’s abundant water. However, the fact that carbon dioxide was not detected in the sublimating material was a surprise that scientists will need to follow-up on to get a better understanding of the role main belt comets play in the history, and current state, of our solar system.