James Webb Space Telescope discovers water around a mysterious comet

May 16, 2023  22:06

The James Webb Space Telescope (JWST) has achieved another scientific milestone as it spotted water vapor around a unique comet located in the main asteroid belt between Jupiter and Mars. This groundbreaking observation represents the first time that gas, specifically water vapor, has been detected surrounding a comet within the main asteroid belt. The discovery has significant implications as it suggests that Astronomer Michael Kelley, leading the research from the University of Maryland, highlighted the water in the early solar system could have been preserved as ice in this region.

significance of the precise spectral data obtained from the JWST, stating, "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 the JWST can we say 'yes,' it's definitely water ice that is creating that effect. With the JWST's observations of Comet Read, we can now demonstrate that water ice from the early solar system can be preserved in the asteroid belt."

According to Space.com, the detection of water vapor around Comet 238P/Read holds the potential to strengthen theories that water, an essential ingredient for life, was delivered to Earth from space through comets. However, this comet has also presented an intriguing mystery. The team was surprised to find a lack of carbon dioxide, a compound typically expected in comets, within Comet 238P/Read.


The absence of carbon dioxide was more unexpected than the discovery of water vapor since previous calculations indicated that it could constitute up to 10% of the volatile matter easily vaporized by the sun in comets. The research team proposed two possible explanations for the missing carbon dioxide. Firstly, the comet may have initially possessed carbon dioxide during its formation but lost it due to solar heating over billions of years. "Being in the asteroid belt for a long time could do it—carbon dioxide vaporizes more easily than water ice and could percolate out over billions of years," explained Kelley. Alternatively, it is possible that this main belt comet originated from a region in the solar system devoid of carbon dioxide.

The main asteroid belt, primarily inhabited by rocky bodies such as asteroids, occasionally hosts comet-like objects like Comet 238P/Read. These cometary bodies can be distinguished by periodic brightening caused by the presence of a halo of material or a coma surrounding them. Additionally, they can develop a characteristic tail of material. A comet's coma and tail arise from solid icy material undergoing sublimation, transforming directly into gas as comets approach the sun and heat up. The prevailing theory was that all comets originated from the Kuiper Belt beyond Neptune or the Oort Cloud, which exists at the outermost reaches of the solar system. These locations provide protection from solar radiation, enabling the preservation of water ice within comets. However, the closer proximity to the sun near Mars may not offer the same preservation conditions.


The designation of "main belt comet" is relatively recent, and Comet 238P/Read was one of three objects that contributed to the establishment of this comet family found closer to Earth. Astronomers were uncertain whether these icy bodies could retain frozen water, and this discovery provides the first conclusive evidence of their ability to do so. The ability to observe the comet in such detail is a remarkable achievement for the powerful JWST, marking the first confirmation of gas in a main-belt comet.

Stefanie Milam, research co-author and Webb Deputy Project Scientist for Planetary Science, emphasized the importance of understanding the distribution of water in the solar system, stating, "Our water-soaked world, teeming with life and unique in the universe as far as we know, is something of a mystery—we're not sure how all this water got here.

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