NASA’s James Webb Space Telescope has made another long-awaited scientific breakthrough, this time for solar system scientists studying the origins of Earth’s abundant water. Using Webb’s NIRSpec (Near Infrared Spectrograph), astronomers have confirmed for the first time the presence of gas – specifically water vapor – around a comet in the main asteroid belt, suggesting that the region may harbor water ice from the early Solar System. However, the successful detection of water brings with it a new mystery: unlike other comets, comet 238P/Read had no detectable carbon dioxide.

“Our water-soaked world, which is full of life and unique in the universe as we know it, is something mysterious – we’re not sure how all this water got here,” said Webb Project Associate Scientist Stephanie Milam. Planetary Studies. Co-author of the study reporting science and discovery. “Understanding the history of the distribution of water in the Solar System will help us understand other planetary systems and whether they are on their way to host an Earth-like planet,” she added.

Comet Reed is a main belt comet – an object in the main asteroid belt that periodically exhibits a halo or coma and a comet-like tail. The main belt comets themselves are a fairly new classification, and Comet Reed was one of the first three comets used to create the category. Before that, comets were thought to be in the Kuiper belt and the Oort cloud, beyond the orbit of Neptune, where their ice could be stored farther from the Sun. What gives comets their characteristic coma and the flowing tail that separates them from asteroids is the frozen material that evaporates as they approach the Sun. Scientists have long suspected that water ice could be stored in the warmer asteroid belt orbiting Jupiter, but conclusive evidence was elusive until Webb.

“In the past, we’ve seen main belt objects with all the characteristics of comets, but only with these precise Webb spectral data we can say yes, we can say that it was definitely water ice that created this effect,” said astronomer Michael Kelly. . University of Maryland, lead author of the study.

“Through Webb’s observations of Comet Reed, we can show that water ice from the early Solar System could be stored in the asteroid belt,” Kelly said.

The lost carbon dioxide was a bigger surprise. Typically, about 10 percent of the volatile matter in a comet is carbon dioxide, which can be easily evaporated by solar heat. The scientific group offers two possible explanations for the carbon dioxide deficiency. One possibility is that Comet Reed contained carbon dioxide during its formation but lost it due to high temperatures.

“A long stay in the asteroid belt can do this — carbon dioxide evaporates more easily than water ice and can leak out over billions of years,” Kelly said. In addition, he said Comet Reed may have formed in a particularly hot pocket of the Solar System where there is no carbon dioxide.

The next step is to take the research beyond Comet Reed to see how it compares to other main belt comets, says astronomer Heidi Hummel of the Association of Astronomical Research Universities (AURA), head of Solar System Guaranteed Time Webb Observations. Objects and co-author of the work. “These objects in the asteroid belt are small and faint, and with Webb we can finally see what’s happening to them and draw some conclusions. Don’t other main belt comets also have carbon dioxide? In any case, it will be interesting to learn,” said Hammel.

Co-author Milam envisions opportunities to bring research closer to home. “Now that Webb has confirmed that water is preserved as close as the asteroid belt, it will be interesting to follow up on this discovery with a sample collection mission and see what else main belt comets can tell us.” The research was published in the journal Nature.