The James Webb Space Telescope made its second breakthrough observation in as many weeks. The researchers used the lab’s near-infrared camera to detect The first known occurrence of water vapor around a comet in the main asteroid belt, also known as a main belt comet. Scientists thought that comets could preserve water ice so close to the Sun, but until now there was no conclusive evidence. They typically expect comets to sit in the Kuiper Belt or Oort Cloud, both far from the Sun where ice persists.
However, the findings have created a new puzzle. Carbon dioxide typically represents about 10 percent of the volatiles in a comet, and Webb’s instruments detected none in Reed. The research team speculates that the CO2 dissipated over billions of years or that the reed formed in a relatively cold part of the solar system where CO2 was not present.
Reed was one of the first bodies used to establish the main belt comet category. The Webb Telescope is the first powerful instrument to study these comets in detail.
Further observations will be needed to understand whether the lack of reed CO2 is shared by a fluke or other main belt comets. Whether it is or not, team member Stephanie Milam suggests that a sample collection mission would be helpful in learning more about such comets. It’s certainly more practical than other journeys—the Kuiper Belt starts roughly at the edge of Neptune’s orbit, while the Oort Cloud is roughly two light-years away.