Water on Comet 238P in place where it seems it shouldn’t be
Researchers have made a major discovery about the origins of Earth’s water, using NASA’s James Webb Space Telescope. The telescope’s NIRSpec tool has confirmed that water vapor is present around a comet in the main asteroid belt, suggesting that water ice from the early solar system can be found there. This discovery has sparked a new question, however, as Comet 238P/Read does not contain detectable carbon dioxide, unlike other comets.
Stefanie Milam, Webb deputy project scientist for planetary science and a co-author on the study reporting the finding, said,
“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. Understanding the history of water distribution in the solar system will help us to understand other planetary systems, and if they could be on their way to hosting an Earth-like planet,” she added.
Comet Read is an intriguing object located in the main asteroid belt. It can display a halo or coma, as well as a tail, similar to that of a comet. This type of object is known as a main belt comet and is a relatively new classification. In fact, Comet Read was one of the first three comets to be classified as such.
Before the discovery of main belt comets, it was believed that comets could only be found in the Kuiper Belt and Oort Cloud, beyond the orbit of Neptune, where their ices could be preserved away from the Sun. However, scientists have since discovered that water ice can also be preserved in the warmer asteroid belt, inside the orbit of Jupiter, which has been confirmed by the Webb telescope. When comets approach the Sun, their frozen material vaporizes, resulting in the distinctive coma and streaming tail that sets them apart from asteroids.
“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. With Webb’s observations of Comet Read, we can now demonstrate that water ice from the early solar system can be preserved in the asteroid belt.”
But where is Comet Read’s carbon dioxide?
It was surprising to discover that there was a significant lack of carbon dioxide in Comet Read. Typically, about 10% of the volatile material in a comet that can be easily vaporized by the Sun’s heat is composed of carbon dioxide. The scientists proposed two possible explanations for the low amount of carbon dioxide. One possibility is that Comet Read had carbon dioxide during its formation, but it evaporated due to the high temperatures it has been subjected to.
“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. Alternatively, Comet Read may have formed in a particularly warm pocket of the solar system, where no carbon dioxide was available.?
Waiting for more opportunities
According to astronomer Heidi Hammel of the Association of Universities for Research in Astronomy (AURA), the next step is to expand the research beyond Comet Read and examine other main belt comets. Hammel is the lead for Webb’s Guaranteed Time Observations for solar system objects and a co-author of the study. With the powerful capabilities of Webb, Hammel believes they can finally shed some light on these small and faint objects in the asteroid belt and draw some conclusions. They are excited to discover if other main belt comets also lack carbon dioxide. Regardless of the outcome, it will be an exciting discovery.
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In-Article Image Credits
Comet 238P/Read via NASA by NASA, ESA, CSA, Mike Kelley (UMD) IMAGE PROCESSING: Henry Hsieh (PSI), Alyssa Pagan (STScI) with usage type - Public Domain. September 8, 2022Artist's Concept of Comet 238P/Read via NASA by NASA, ESA with usage type - Public Domain
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Artist's Concept of Comet 238P/Read via NASA by NASA, ESA with usage type - Public Domain
