Webb detects water vapour around a comet in main asteroid belt for first time

The James Webb Space Telescope, the largest and most powerful telescope ever launched into space, has detected water vapour around Comet 238P/Read in the main asteroid belt for the first time. This groundbreaking discovery proves that water from the primordial Solar System can be preserved as ice in that region, the researchers said.

"In the past we've seen objects in the main-belt with all the characteristics of comets, but only with this precise spectral data from Webb can we say yes, it's definitely water ice that is creating that effect," explained astronomer Michael Kelley of the University of Maryland, lead author of the study.

However, this remarkable discovery of water vapour presents an intriguing puzzle. Unlike most other comets, Comet Read did not have detectable carbon dioxide. The absence of carbon dioxide in this main-belt comet has emerged as a surprise for the scientific community.

Typically, carbon dioxide constitutes approximately 10 percent of the volatile material in a comet that can be easily vaporized by the heat of the Sun. Its scarcity in Comet Read raises questions about the unique circumstances and evolutionary processes surrounding this particular comet.

The team investigating Comet Read has put forth a potential explanation to account for the absence of carbon dioxide - the comet did have carbon dioxide during its formation. However, over time and due to warm temperatures, the carbon dioxide molecules have dissipated or escaped.

"Being in the asteroid-belt for a long time could do it – carbon dioxide vaporises more easily than water ice, and could percolate out over billions of years" Kelley said. Alternatively, he said, Comet Read may have formed in a particularly warm pocket of the Solar System, where no carbon dioxide was available.

Another possibility, according to him, is that Comet Read might have originated in a particularly warm pocket of the Solar System, where carbon dioxide might not have been available.

The next step is taking the research beyond Comet Read to see how other main-belt comets compare, says astronomer Heidi Hammel of the Association of Universities for Research in Astronomy (AURA), lead for Webb's Guaranteed Time Observations for Solar System objects and co-author of the study.

What are the origins of the water that has made life on Earth possible?🌎☄️The NASA/ESA/CSA James #Webb Space Telescope has enabled astronomers get one step closer to the answer by allowing them to detect water vapour around a comet in the main asteroid belt for the first time.… pic.twitter.com/y1DvQGi5sL

— ESA (@esa) May 15, 2023